August guide to the bright planets

Look for the bright waxing gibbous moon to be near the planet Saturn for several days, centered on or near August 2, 2017. Read more.

Three of the five bright planets – Jupiter, Saturn and Venus – are easy to see in August 2017. Bright Jupiter is the first “star” to pop into view at nightfall and stays out until mid-to-late evening. Golden Saturn is highest up at nightfall and stays out until late night. Brilliant Venus rises before the sun, shining in front of the constellation Gemini the Twins for most of the month. Meanwhile, Mercury will be hard to catch after sunset from northerly latitudes, yet fairly easy to spot from the Southern Hemisphere. And – for all of Earth – Mars sits deep in the glare of sunrise all month long, and probably won’t become visible in the morning sky until September 2017. Follow the links below to learn more about the planets in August 2017.

Jupiter brightest “star” in evening sky

Saturn out from dusk till late night

Venus, brilliant in east at morning dawn

Mars lost in the glare of sunrise

Mercury briefly visible after sunset

See 4 planets during the August 21 total solar eclipse

Like what EarthSky offers? Sign up for our free daily newsletter today!

Astronomy events, star parties, festivals, workshops

Visit a new EarthSky feature – Best Places to Stargaze – and add your fav.

The waxing crescent moon shines in the vicinity of Jupiter (and the star Spica) for several days, centered on or near August 25, 2017. Read more.

Jupiter brightest “star” in evening sky. Jupiter reached opposition on April 7. That is, it was opposite the sun as seen from Earth then and so was appearing in our sky all night. The giant planet came closest to Earth for 2017 one day later, on April 8. Although Jupiter shone at its brightest and best in April, it’ll still be the brightest starlike object in the evening sky! Overall, Jupiter beams as the fourth-brightest celestial body, after the sun, moon and Venus. In August, Jupiter shines at dusk and evening; meanwhile, Venus appears only in the predawn/dawn sky.

Click here for an almanac telling you Jupiter’s setting time and Venus’ rising time in your sky.

Watch for the moon to join up with Jupiter for several days, on August 23, August 24 and August 25. See the above sky chart. Wonderful sight!

From the Northern Hemisphere, Jupiter appears fairly low in the southwest to west as darkness falls; and from the Southern Hemisphere, Jupiter appears rather high up in the sky at nightfall. From all of Earth, Jupiter sinks in a westerly direction throughout the evening, as Earth spins under the sky. In early August, at mid-northern latitudes, Jupiter sets in the west around mid-evening (roughly 10 p.m. local time or 11 p.m. daylight-saving time); and by the month’s end, Jupiter sets around nightfall (about one and one-half hours after sunset).

Jupiter stays out longer after sunset at more southerly latitudes. At temperate latitudes in the Southern Hemisphere, Jupiter sets in the west at late evening in early August, and around mid-evening by the month’s end.

Jupiter shines in front of the constellation Virgo, near Virgo’s sole 1st-magnitude star, called Spica.

Fernando Roquel Torres in Caguas, Puerto Rico captured Jupiter, the Great Red Spot (GRS) and all 4 of its largest moons – the Galilean satellites – on the date of Jupiter’s 2017 opposition (April 7).

If you have binoculars or a telescope, it’s fairly easy to see Jupiter’s four major moons, which look like pinpricks of light all on or near the same plane. They are often called the Galilean moons to honor Galileo, who discovered these great Jovian moons in 1610. In their order from Jupiter, these moons are Io, Europa, Ganymede and Callisto.

These moons orbit Jupiter around the Jovian equator. In cycles of six years, we view Jupiter’s equator edge-on. So, in 2015, we were able to view a number of mutual events involving Jupiter’s moons, through high-powered telescopes. Starting in late 2016, Jupiter’s axis began tilting enough toward the sun and Earth so that the farthest of these four moons, Callisto, has not been passing in front of Jupiter or behind Jupiter, as seen from our vantage point. This will continue for a period of about three years, during which time Callisto is perpetually visible to those with telescopes, alternately swinging above and below Jupiter as seen from Earth.

Click here for a Jupiter’s moons almanac, courtesy of skyandtelescope.com.

James Martin in Albuquerque, New Mexico caught this wonderful photo of Saturn on its June 15, 2017 opposition.

Let the moon guide your eye to the planet Saturn and the star Antares on August 28, 29 and 30. Read more.

Saturn out from dusk till late night. Saturn reached its yearly opposition on June 15, 2017. At opposition, Saturn came closest to Earth for the year, shone brightest in our sky and stayed out all night. It was highest up at midnight (midway between sunset and sunrise).

In August 2017, Saturn shines higher in the sky at nightfall than it did in June or July. Moreover, Saturn transits – climbs its highest point for the night at dusk or early evening – a few hours earlier than it did in July 2017. So, if you’re not a night owl, August may actually present a better month for viewing Saturn, which is still shining at better than first-magnitude brightness.

Click here to find out Saturn’s transit time, when Saturn soars highest up for the night.

Look for Saturn as soon as darkness falls. It’s in the southern sky at dusk or nightfall as seen from Earth’s Northern Hemisphere, and high overhead at early evening as viewed from the Southern Hemisphere. Your best view of Saturn, from either the Northern or Southern Hemisphere, is around nightfall because that’s when Saturn is highest up for the night.

Be sure to let the moon guide you to Saturn (and the nearby star Antares) on August 2, and then again at the month’s end: August 28, August 29 and August 30.

Saturn, the farthest world that you can easily view with the eye alone, appears golden in color. It shines with a steady light.

Binoculars don’t reveal Saturn’s gorgeous rings, by the way, although binoculars will enhance Saturn’s color. To see the rings, you need a small telescope. A telescope will also reveal one or more of Saturn’s many moons, most notably Titan.

Saturn’s rings are inclined at nearly 27o from edge-on, exhibiting their northern face. In October 2017, the rings will open most widely for this year, displaying a maximum inclination of 27o.

As with so much in space (and on Earth), the appearance of Saturn’s rings from Earth is cyclical. In the year 2025, the rings will appear edge-on as seen from Earth. After that, we’ll begin to see the south side of Saturn’s rings, to increase to a maximum inclination of 27o by May 2032.

Click here for recommended almanacs; they can help you know when the planets rise, transit and set in your sky.

Jenney Disimon in Sabah, Borneo captured Venus before dawn.

The waning crescent moon swings close to the dazzling planet Venus on August 18 and 19. Read more.

Venus, brilliant in east at morning dawn Venus is always brilliant and beautiful, the brightest celestial body to light up our sky besides the sun and moon. If you’re an early bird, you can count on Venus to be your morning companion until nearly the end of 2017.

Venus reached a milestone as the morning “star” when it swung out to its greatest elongation from the sun on June 3, 2017. At this juncture, Venus was farthest from the sun on our sky’s dome, and the telescope showed Venus as half-illuminated in sunshine, like a first quarter moon. For the rest of the year, Venus will wax toward full phase.

Click here to know Venus’s present phase, remembering to select Venus as your object of interest.

Enjoy the picturesque coupling of the waning crescent moon and Venus in the eastern sky before sunrise on August 18 and August 19.

From mid-northern latitudes (U.S. and Europe), Venus rises about three hours before the sun throughout the month.

At temperate latitudes in the Southern Hemisphere (Australia and South Africa), Venus rises about two and one-half hours before sunup in early August. By the month’s end that’ll taper to about one and one-half hours.

Click here for an almanac giving rising times of Venus in your sky.

The chart below helps to illustrate why we sometimes see Venus in the evening, and sometimes before dawn.

Earth's and Venus' orbits

The Earth and Venus orbit the sun counterclockwise as seen from earthly north. When Venus is to the east (left) of the Earth-sun line, we see Venus as an evening “star” in the west after sunset. After Venus reaches its inferior conjunction, Venus then moves to the west (right) of the Earth-sun line, appearing as a morning “star” in the east before sunrise.

Mars, Mercury, Earth’s moon and the dwarf planet Ceres. Mars is smaller than Earth, but bigger than our moon. Image via NASA/JPL-Caltech/UCLA.

Mars lost in the glare of sunrise. Mars transitioned out of the evening sky and into the morning sky on July 27, 2017, at which juncture Mars was on the far side of the sun at what astronomers call superior conjunction.

Look for Mars to emerge in the east before dawn in mid-September or October 2017. The conjunction of Mars and Venus on October 5, 2017, will likely present the first view of Mars in the morning sky for many skywatchers.

Exactly one year after Mars’s superior conjunction on July 27, 2017, Mars will swing to opposition on July 27, 2018. This will be Mars’s best opposition since the historically close opposition on August 28, 2003. In fact, Mars will become the fourth-brightest heavenly body to light up the sky in July 2018, after the sun, moon and the planet Venus. It’s not often that Mars outshines Jupiter, normally the four-brightest celestial object.

Wow! Wonderful shot of Mercury – over the Chilean Andes – January 2017, from Yuri Beletsky Nightscapes.

Before sunrise on September 16, 2017, draw an imaginary line from the waning crescent moon through the dazzling planet Venus to find the planets Mercury and Mars in conjunction near the horizon. Binoculars may come in handy! Read more.

Mercury briefly visible after sunset. When we say Mercury is visible in the evening sky, we’re really talking about the Southern Hemisphere. For the Southern Hemisphere, the year’s best evening apparition of Mercury happened in July 2017, but the tail end of this favorable apparition extends into the first week or two in September.

Mercury is tricky. If you look too soon after sunset, Mercury will be obscured by evening twilight; if you look too late, it will have followed the sun beneath the horizon. Watch for Mercury low in the sky, and near the sunset point on the horizon, being mindful of Mercury’s setting time.

Throughout August, Mercury will move closer to the sunset day by day, and then will pass behind the sun at superior conjunction on August 26, 2017. At superior conjunction, Mercury leaves the evening sky to enter the morning sky. The Northern Hemisphere will enjoy a favorable morning apparition of Mercury in September 2017.

For a fun sky watching challenge, try to glimpse Mercury and Mars in the east just as nightfall is giving way to dawn on or near September 16. You may need binoculars to view Mars next to Mercury!

What do we mean by bright planet? By bright planet, we mean any solar system planet that is easily visible without an optical aid and that has been watched by our ancestors since time immemorial. In their outward order from the sun, the five bright planets are Mercury, Venus, Mars, Jupiter and Saturn. These planets actually do appear bright in our sky. They are typically as bright as – or brighter than – the brightest stars. Plus, these relatively nearby worlds tend to shine with a steadier light than the distant, twinkling stars. You can spot them, and come to know them as faithful friends, if you try.

From late January, and through mid-February, 5 bright planets were visible at once in the predawn sky. This image is from February 8, 2016. It's by Eliot Herman in Tucson, Arizona. View on Flickr.

This image is from February 8, 2016. It shows all 5 bright planets at once. Photo by our friend Eliot Herman in Tucson, Arizona.

Skywatcher, by Predrag Agatonovic.

Skywatcher, by Predrag Agatonovic.

Bottom line: In August 2017, two of the five bright planets are easy to see in the evening sky: Jupiter and Saturn. Venus is found exclusively in the morning sky. Mercury shifts over into morning sky whereas Mars is lost in the glare of sunrise.

Don’t miss anything. Subscribe to EarthSky News by email

Enjoy knowing where to look in the night sky? Please donate to help EarthSky keep going.



from EarthSky http://ift.tt/IJfHCr

Look for the bright waxing gibbous moon to be near the planet Saturn for several days, centered on or near August 2, 2017. Read more.

Three of the five bright planets – Jupiter, Saturn and Venus – are easy to see in August 2017. Bright Jupiter is the first “star” to pop into view at nightfall and stays out until mid-to-late evening. Golden Saturn is highest up at nightfall and stays out until late night. Brilliant Venus rises before the sun, shining in front of the constellation Gemini the Twins for most of the month. Meanwhile, Mercury will be hard to catch after sunset from northerly latitudes, yet fairly easy to spot from the Southern Hemisphere. And – for all of Earth – Mars sits deep in the glare of sunrise all month long, and probably won’t become visible in the morning sky until September 2017. Follow the links below to learn more about the planets in August 2017.

Jupiter brightest “star” in evening sky

Saturn out from dusk till late night

Venus, brilliant in east at morning dawn

Mars lost in the glare of sunrise

Mercury briefly visible after sunset

See 4 planets during the August 21 total solar eclipse

Like what EarthSky offers? Sign up for our free daily newsletter today!

Astronomy events, star parties, festivals, workshops

Visit a new EarthSky feature – Best Places to Stargaze – and add your fav.

The waxing crescent moon shines in the vicinity of Jupiter (and the star Spica) for several days, centered on or near August 25, 2017. Read more.

Jupiter brightest “star” in evening sky. Jupiter reached opposition on April 7. That is, it was opposite the sun as seen from Earth then and so was appearing in our sky all night. The giant planet came closest to Earth for 2017 one day later, on April 8. Although Jupiter shone at its brightest and best in April, it’ll still be the brightest starlike object in the evening sky! Overall, Jupiter beams as the fourth-brightest celestial body, after the sun, moon and Venus. In August, Jupiter shines at dusk and evening; meanwhile, Venus appears only in the predawn/dawn sky.

Click here for an almanac telling you Jupiter’s setting time and Venus’ rising time in your sky.

Watch for the moon to join up with Jupiter for several days, on August 23, August 24 and August 25. See the above sky chart. Wonderful sight!

From the Northern Hemisphere, Jupiter appears fairly low in the southwest to west as darkness falls; and from the Southern Hemisphere, Jupiter appears rather high up in the sky at nightfall. From all of Earth, Jupiter sinks in a westerly direction throughout the evening, as Earth spins under the sky. In early August, at mid-northern latitudes, Jupiter sets in the west around mid-evening (roughly 10 p.m. local time or 11 p.m. daylight-saving time); and by the month’s end, Jupiter sets around nightfall (about one and one-half hours after sunset).

Jupiter stays out longer after sunset at more southerly latitudes. At temperate latitudes in the Southern Hemisphere, Jupiter sets in the west at late evening in early August, and around mid-evening by the month’s end.

Jupiter shines in front of the constellation Virgo, near Virgo’s sole 1st-magnitude star, called Spica.

Fernando Roquel Torres in Caguas, Puerto Rico captured Jupiter, the Great Red Spot (GRS) and all 4 of its largest moons – the Galilean satellites – on the date of Jupiter’s 2017 opposition (April 7).

If you have binoculars or a telescope, it’s fairly easy to see Jupiter’s four major moons, which look like pinpricks of light all on or near the same plane. They are often called the Galilean moons to honor Galileo, who discovered these great Jovian moons in 1610. In their order from Jupiter, these moons are Io, Europa, Ganymede and Callisto.

These moons orbit Jupiter around the Jovian equator. In cycles of six years, we view Jupiter’s equator edge-on. So, in 2015, we were able to view a number of mutual events involving Jupiter’s moons, through high-powered telescopes. Starting in late 2016, Jupiter’s axis began tilting enough toward the sun and Earth so that the farthest of these four moons, Callisto, has not been passing in front of Jupiter or behind Jupiter, as seen from our vantage point. This will continue for a period of about three years, during which time Callisto is perpetually visible to those with telescopes, alternately swinging above and below Jupiter as seen from Earth.

Click here for a Jupiter’s moons almanac, courtesy of skyandtelescope.com.

James Martin in Albuquerque, New Mexico caught this wonderful photo of Saturn on its June 15, 2017 opposition.

Let the moon guide your eye to the planet Saturn and the star Antares on August 28, 29 and 30. Read more.

Saturn out from dusk till late night. Saturn reached its yearly opposition on June 15, 2017. At opposition, Saturn came closest to Earth for the year, shone brightest in our sky and stayed out all night. It was highest up at midnight (midway between sunset and sunrise).

In August 2017, Saturn shines higher in the sky at nightfall than it did in June or July. Moreover, Saturn transits – climbs its highest point for the night at dusk or early evening – a few hours earlier than it did in July 2017. So, if you’re not a night owl, August may actually present a better month for viewing Saturn, which is still shining at better than first-magnitude brightness.

Click here to find out Saturn’s transit time, when Saturn soars highest up for the night.

Look for Saturn as soon as darkness falls. It’s in the southern sky at dusk or nightfall as seen from Earth’s Northern Hemisphere, and high overhead at early evening as viewed from the Southern Hemisphere. Your best view of Saturn, from either the Northern or Southern Hemisphere, is around nightfall because that’s when Saturn is highest up for the night.

Be sure to let the moon guide you to Saturn (and the nearby star Antares) on August 2, and then again at the month’s end: August 28, August 29 and August 30.

Saturn, the farthest world that you can easily view with the eye alone, appears golden in color. It shines with a steady light.

Binoculars don’t reveal Saturn’s gorgeous rings, by the way, although binoculars will enhance Saturn’s color. To see the rings, you need a small telescope. A telescope will also reveal one or more of Saturn’s many moons, most notably Titan.

Saturn’s rings are inclined at nearly 27o from edge-on, exhibiting their northern face. In October 2017, the rings will open most widely for this year, displaying a maximum inclination of 27o.

As with so much in space (and on Earth), the appearance of Saturn’s rings from Earth is cyclical. In the year 2025, the rings will appear edge-on as seen from Earth. After that, we’ll begin to see the south side of Saturn’s rings, to increase to a maximum inclination of 27o by May 2032.

Click here for recommended almanacs; they can help you know when the planets rise, transit and set in your sky.

Jenney Disimon in Sabah, Borneo captured Venus before dawn.

The waning crescent moon swings close to the dazzling planet Venus on August 18 and 19. Read more.

Venus, brilliant in east at morning dawn Venus is always brilliant and beautiful, the brightest celestial body to light up our sky besides the sun and moon. If you’re an early bird, you can count on Venus to be your morning companion until nearly the end of 2017.

Venus reached a milestone as the morning “star” when it swung out to its greatest elongation from the sun on June 3, 2017. At this juncture, Venus was farthest from the sun on our sky’s dome, and the telescope showed Venus as half-illuminated in sunshine, like a first quarter moon. For the rest of the year, Venus will wax toward full phase.

Click here to know Venus’s present phase, remembering to select Venus as your object of interest.

Enjoy the picturesque coupling of the waning crescent moon and Venus in the eastern sky before sunrise on August 18 and August 19.

From mid-northern latitudes (U.S. and Europe), Venus rises about three hours before the sun throughout the month.

At temperate latitudes in the Southern Hemisphere (Australia and South Africa), Venus rises about two and one-half hours before sunup in early August. By the month’s end that’ll taper to about one and one-half hours.

Click here for an almanac giving rising times of Venus in your sky.

The chart below helps to illustrate why we sometimes see Venus in the evening, and sometimes before dawn.

Earth's and Venus' orbits

The Earth and Venus orbit the sun counterclockwise as seen from earthly north. When Venus is to the east (left) of the Earth-sun line, we see Venus as an evening “star” in the west after sunset. After Venus reaches its inferior conjunction, Venus then moves to the west (right) of the Earth-sun line, appearing as a morning “star” in the east before sunrise.

Mars, Mercury, Earth’s moon and the dwarf planet Ceres. Mars is smaller than Earth, but bigger than our moon. Image via NASA/JPL-Caltech/UCLA.

Mars lost in the glare of sunrise. Mars transitioned out of the evening sky and into the morning sky on July 27, 2017, at which juncture Mars was on the far side of the sun at what astronomers call superior conjunction.

Look for Mars to emerge in the east before dawn in mid-September or October 2017. The conjunction of Mars and Venus on October 5, 2017, will likely present the first view of Mars in the morning sky for many skywatchers.

Exactly one year after Mars’s superior conjunction on July 27, 2017, Mars will swing to opposition on July 27, 2018. This will be Mars’s best opposition since the historically close opposition on August 28, 2003. In fact, Mars will become the fourth-brightest heavenly body to light up the sky in July 2018, after the sun, moon and the planet Venus. It’s not often that Mars outshines Jupiter, normally the four-brightest celestial object.

Wow! Wonderful shot of Mercury – over the Chilean Andes – January 2017, from Yuri Beletsky Nightscapes.

Before sunrise on September 16, 2017, draw an imaginary line from the waning crescent moon through the dazzling planet Venus to find the planets Mercury and Mars in conjunction near the horizon. Binoculars may come in handy! Read more.

Mercury briefly visible after sunset. When we say Mercury is visible in the evening sky, we’re really talking about the Southern Hemisphere. For the Southern Hemisphere, the year’s best evening apparition of Mercury happened in July 2017, but the tail end of this favorable apparition extends into the first week or two in September.

Mercury is tricky. If you look too soon after sunset, Mercury will be obscured by evening twilight; if you look too late, it will have followed the sun beneath the horizon. Watch for Mercury low in the sky, and near the sunset point on the horizon, being mindful of Mercury’s setting time.

Throughout August, Mercury will move closer to the sunset day by day, and then will pass behind the sun at superior conjunction on August 26, 2017. At superior conjunction, Mercury leaves the evening sky to enter the morning sky. The Northern Hemisphere will enjoy a favorable morning apparition of Mercury in September 2017.

For a fun sky watching challenge, try to glimpse Mercury and Mars in the east just as nightfall is giving way to dawn on or near September 16. You may need binoculars to view Mars next to Mercury!

What do we mean by bright planet? By bright planet, we mean any solar system planet that is easily visible without an optical aid and that has been watched by our ancestors since time immemorial. In their outward order from the sun, the five bright planets are Mercury, Venus, Mars, Jupiter and Saturn. These planets actually do appear bright in our sky. They are typically as bright as – or brighter than – the brightest stars. Plus, these relatively nearby worlds tend to shine with a steadier light than the distant, twinkling stars. You can spot them, and come to know them as faithful friends, if you try.

From late January, and through mid-February, 5 bright planets were visible at once in the predawn sky. This image is from February 8, 2016. It's by Eliot Herman in Tucson, Arizona. View on Flickr.

This image is from February 8, 2016. It shows all 5 bright planets at once. Photo by our friend Eliot Herman in Tucson, Arizona.

Skywatcher, by Predrag Agatonovic.

Skywatcher, by Predrag Agatonovic.

Bottom line: In August 2017, two of the five bright planets are easy to see in the evening sky: Jupiter and Saturn. Venus is found exclusively in the morning sky. Mercury shifts over into morning sky whereas Mars is lost in the glare of sunrise.

Don’t miss anything. Subscribe to EarthSky News by email

Enjoy knowing where to look in the night sky? Please donate to help EarthSky keep going.



from EarthSky http://ift.tt/IJfHCr

Earth’s eclipses are special

You may have heard that the Earth is the only planet that experiences eclipses. That is not true. Granted, our eclipses are special, but hypothetical observers on other planets also could experience partial and total solar eclipses.

Generally speaking, an eclipse occurs when one astronomical body (such as a moon) passes in front of another (such as the Sun). Mercury and Venus, having no moons at all, never have eclipses of any kind.

venera13
Observers on the searing hot surface of Venus, would never directly experience an eclipse even if the planet had a moon, simply because it is constantly enveloped by thick clouds. The images here are from the Soviet Venera 13 lander, which landed on the surface of Venus on March 3, 1982. The perpetually cloud covered sky can be seen in the triangular wedged at the upper corners of each photo. Images courtesy of NASA/JPL/NSSDCA & Roscosmos.

But Martians, if they existed, would occasionally experience transits by the planet’s moons Deimos and Phobos.  Transits occur when the nearer body appears too small to cover the farther body. This is essentially a partial eclipse and geometrically equivalent to annular eclipses seen on Earth.

Observers, floating at cloud-top level on Jupiter, Saturn, Uranus or Neptune could experience total eclipses, too. Even far-off Plutonians would on quite rare occasion see a moon pass in front of the Sun from their distant dwarf world.

So if solar eclipses are not exclusive to Earth, why are they so special?

Not to stress the obvious, but there are observers on Earth to view eclipses, something no other planet in our Solar System can boast. Aside from that, the main reason is that the Sun and Moon appear roughly the same size in the sky, allowing particularly impressive total solar eclipses. During totality of a solar eclipse, the silhouette of the Moon leaves a gaping “black hole” in the sky, surrounded by the ghostly glow of the Sun’s outer atmosphere, the corona.

This fortuitous circumstance happens because although the Moon’s diameter is about 400 times smaller than the Sun’s, it also is about 400 times closer. That makes the Sun and Moon to appear roughly the same size in the sky, about a half-degree.  If the Moon were 10% closer, as it was about a billion years ago*, it would always appear appreciatively larger than the Sun, and some of the magic of today’s total solar eclipses would be lost.

If the Moon were 10% farther away, as it will be roughly a billion years in the future*, it would appear too small to completely cover the Sun’s disk, and we would never experience a total solar eclipse.

So while our eclipse experience on Earth today is virtually unrivaled anywhere in the Solar System, it is simply a temporary coincidence.

Phobos_Sun_transit

In this image, Martian moon Phobos passes in front of the Sun as viewed by the Curiosity Rover on August 20, 2013. Click here for a short video on Wikimedia: http://ift.tt/2tSeDt6)

Elsewhere in the Solar System, the Moons of Mars, Phobos and Deimos, are too small and too far from the planet for anything but partial eclipses.

From the major moons of Jupiter, Saturn, Uranus and Neptune, the Sun appears so small that total eclipses occur. The major moons of these planets, however, appear considerably larger than the Sun, so the spectacular type of total eclipse visible from Earth is generally not possible. However,  a couple of moons of the outer planets, viewed from the top of the planet’s atmosphere, would appear roughly the same size as the Sun seen from the same location, but the moons  are irregular in shape. Jupiter’s moon Amalthea and Saturn’s moons Pandora and Prometheus are examples.

Sun seen near Charon

The image here is a simulation showing the approximate size of the Sun with Pluto’s large moon Charon, as seen by an observer on the surface of Pluto. To a real observer, however, the Sun would be dazzlingly bright and Charon would show up silhouetted as a black disk.

From Pluto, the Sun is little more than an intensely bright star. In fact, it is only about the same size as the planet Jupiter as viewed from Earth. But Pluto’s large moon Charon appears from Pluto nearly four times as large as Earth’s Moon from Earth. A solar eclipse from Pluto would be more like a lunar occultation of a star from Earth.

The same moons that cause solar eclipses also can experience them as well, so there are literally dozens of places in the Solar System where eclipses occur. As mentioned above, there also is a special eclipse-relative called a transit, in which another planet is seen to pass in front of the Sun. Mercurians could see no eclipses or transits, since it has no moon and there is no planet closer to the Sun. Observers on Venus would have no Moon to cause an eclipse, and while orbital geometry allows for transits of Mercury, none can be seen from the surface because of the thick, obscuring clouds.

Earth observers can view transits of both Mercury and Venus, the last being a transit of Venus on June 5, 2012). Lucky Martian observers can seen transits of Mercury, Venus and Earth. Arthur C. Clarke, famed science/science fiction writer, even wrote a short story, “Transit of Earth,” about the Earth crossing the solar disk as viewed from Mars on May 11, 1984. Although the story is fictional, and there were no human observers on Mars at the time, the transit actually occurred on that date. Mars Curiosity Rover’s robotic eyes observed a transit of Mercury in 2014, the first time ever that an transit has been “observed” from a planet other than Earth.

PIA18389_mercury_transit-640-640x350

The animated image here shows the planet Mercury transiting the Sun as viewed from the NASA/JPL Curiosity Mars Rover on June 3, 2014. The two prominent black dots are sunspots. (http://ift.tt/2vgEtu9)

Similar transit events can be seen from all the outer planets and moons, although increasing distance from the Sun makes them more rare.

While eclipses and transits can occur almost everywhere in the Solar System (Except from poor Mercury), the unique circumstances we have in the Earth-Moon system provides the most spectacular examples.


(*Note: these are simplistic estimations based on the Moon’s current recession rate from Earth. These can be taken only rough approximations because the rate varies over time.)

Jupiter occultation by Moon photo by Easy n – Easy n at Hebrew Wikipedia (Created by Easy n at Hebrew Wikipedia) [CC BY-SA 3.0 (http://ift.tt/HKkdTz)], via Wikimedia Commons



from EarthSky http://ift.tt/2vgo894

You may have heard that the Earth is the only planet that experiences eclipses. That is not true. Granted, our eclipses are special, but hypothetical observers on other planets also could experience partial and total solar eclipses.

Generally speaking, an eclipse occurs when one astronomical body (such as a moon) passes in front of another (such as the Sun). Mercury and Venus, having no moons at all, never have eclipses of any kind.

venera13
Observers on the searing hot surface of Venus, would never directly experience an eclipse even if the planet had a moon, simply because it is constantly enveloped by thick clouds. The images here are from the Soviet Venera 13 lander, which landed on the surface of Venus on March 3, 1982. The perpetually cloud covered sky can be seen in the triangular wedged at the upper corners of each photo. Images courtesy of NASA/JPL/NSSDCA & Roscosmos.

But Martians, if they existed, would occasionally experience transits by the planet’s moons Deimos and Phobos.  Transits occur when the nearer body appears too small to cover the farther body. This is essentially a partial eclipse and geometrically equivalent to annular eclipses seen on Earth.

Observers, floating at cloud-top level on Jupiter, Saturn, Uranus or Neptune could experience total eclipses, too. Even far-off Plutonians would on quite rare occasion see a moon pass in front of the Sun from their distant dwarf world.

So if solar eclipses are not exclusive to Earth, why are they so special?

Not to stress the obvious, but there are observers on Earth to view eclipses, something no other planet in our Solar System can boast. Aside from that, the main reason is that the Sun and Moon appear roughly the same size in the sky, allowing particularly impressive total solar eclipses. During totality of a solar eclipse, the silhouette of the Moon leaves a gaping “black hole” in the sky, surrounded by the ghostly glow of the Sun’s outer atmosphere, the corona.

This fortuitous circumstance happens because although the Moon’s diameter is about 400 times smaller than the Sun’s, it also is about 400 times closer. That makes the Sun and Moon to appear roughly the same size in the sky, about a half-degree.  If the Moon were 10% closer, as it was about a billion years ago*, it would always appear appreciatively larger than the Sun, and some of the magic of today’s total solar eclipses would be lost.

If the Moon were 10% farther away, as it will be roughly a billion years in the future*, it would appear too small to completely cover the Sun’s disk, and we would never experience a total solar eclipse.

So while our eclipse experience on Earth today is virtually unrivaled anywhere in the Solar System, it is simply a temporary coincidence.

Phobos_Sun_transit

In this image, Martian moon Phobos passes in front of the Sun as viewed by the Curiosity Rover on August 20, 2013. Click here for a short video on Wikimedia: http://ift.tt/2tSeDt6)

Elsewhere in the Solar System, the Moons of Mars, Phobos and Deimos, are too small and too far from the planet for anything but partial eclipses.

From the major moons of Jupiter, Saturn, Uranus and Neptune, the Sun appears so small that total eclipses occur. The major moons of these planets, however, appear considerably larger than the Sun, so the spectacular type of total eclipse visible from Earth is generally not possible. However,  a couple of moons of the outer planets, viewed from the top of the planet’s atmosphere, would appear roughly the same size as the Sun seen from the same location, but the moons  are irregular in shape. Jupiter’s moon Amalthea and Saturn’s moons Pandora and Prometheus are examples.

Sun seen near Charon

The image here is a simulation showing the approximate size of the Sun with Pluto’s large moon Charon, as seen by an observer on the surface of Pluto. To a real observer, however, the Sun would be dazzlingly bright and Charon would show up silhouetted as a black disk.

From Pluto, the Sun is little more than an intensely bright star. In fact, it is only about the same size as the planet Jupiter as viewed from Earth. But Pluto’s large moon Charon appears from Pluto nearly four times as large as Earth’s Moon from Earth. A solar eclipse from Pluto would be more like a lunar occultation of a star from Earth.

The same moons that cause solar eclipses also can experience them as well, so there are literally dozens of places in the Solar System where eclipses occur. As mentioned above, there also is a special eclipse-relative called a transit, in which another planet is seen to pass in front of the Sun. Mercurians could see no eclipses or transits, since it has no moon and there is no planet closer to the Sun. Observers on Venus would have no Moon to cause an eclipse, and while orbital geometry allows for transits of Mercury, none can be seen from the surface because of the thick, obscuring clouds.

Earth observers can view transits of both Mercury and Venus, the last being a transit of Venus on June 5, 2012). Lucky Martian observers can seen transits of Mercury, Venus and Earth. Arthur C. Clarke, famed science/science fiction writer, even wrote a short story, “Transit of Earth,” about the Earth crossing the solar disk as viewed from Mars on May 11, 1984. Although the story is fictional, and there were no human observers on Mars at the time, the transit actually occurred on that date. Mars Curiosity Rover’s robotic eyes observed a transit of Mercury in 2014, the first time ever that an transit has been “observed” from a planet other than Earth.

PIA18389_mercury_transit-640-640x350

The animated image here shows the planet Mercury transiting the Sun as viewed from the NASA/JPL Curiosity Mars Rover on June 3, 2014. The two prominent black dots are sunspots. (http://ift.tt/2vgEtu9)

Similar transit events can be seen from all the outer planets and moons, although increasing distance from the Sun makes them more rare.

While eclipses and transits can occur almost everywhere in the Solar System (Except from poor Mercury), the unique circumstances we have in the Earth-Moon system provides the most spectacular examples.


(*Note: these are simplistic estimations based on the Moon’s current recession rate from Earth. These can be taken only rough approximations because the rate varies over time.)

Jupiter occultation by Moon photo by Easy n – Easy n at Hebrew Wikipedia (Created by Easy n at Hebrew Wikipedia) [CC BY-SA 3.0 (http://ift.tt/HKkdTz)], via Wikimedia Commons



from EarthSky http://ift.tt/2vgo894

Walking your dog is good for your health (and your pet’s) [Life Lines]

A new study shows that walking your dog is good for your health. Here is a YouTube video summarizing the findings of the study:

Let’s not forget that walking your dog is also very good for your dog. According to PetMD, some benefits include weight control, keeping your dog limber, controlling destructive behaviors and hyperactivity, and of course building a bond between you and your pet.

If you have a cat however, it might be best to just let the cat walk you as demonstrated in this YouTube video:



from ScienceBlogs http://ift.tt/2wei9OZ

A new study shows that walking your dog is good for your health. Here is a YouTube video summarizing the findings of the study:

Let’s not forget that walking your dog is also very good for your dog. According to PetMD, some benefits include weight control, keeping your dog limber, controlling destructive behaviors and hyperactivity, and of course building a bond between you and your pet.

If you have a cat however, it might be best to just let the cat walk you as demonstrated in this YouTube video:



from ScienceBlogs http://ift.tt/2wei9OZ

Universe’s Largest Black Hole May Have An Explanation At Last (Synopsis) [Starts With A Bang]

“Ultramassive black holes — that is, black holes with masses exceeding 10 billion solar masses — are probably not rare; several and even dozens of these colossal black holes may exist.” -Julie Hlavacek-Larrondo

The largest black hole in the Universe was a shocker when it was first discovered. At 40 billion solar masses, it certainly is impressively large. Like other quasars and active galaxies, it has a luminous accretion disk that can be seen from a great distance. Like only a few, one of its two incredibly energetic, polar jets is pointed directly at Earth, creating a blazar, the brightest of all active galaxies.

When an active galaxy has one of its jets pointed directly at Earth, we observe an ultra-luminous phenomenon known as a blazar. These are the brightest objects seen in the entire Universe. Image credit: NASA / JPL.

But what makes this object, known as S5 0014+81, so special is that it got so big and massive so quickly. Its light comes to us from a time when the Universe was only 1.6 billion years old: just 12% of its current age. If this brilliant, massive object were located a mere 280 light years away, or ‘only’ 18 million times the Earth-Sun distance, it would shine as brightly as our life-giving star.

If this quasar were 18 million times as far away as our Sun (280 light years from Earth), it would shine as bright in the sky as our life-giving star does. Image credit: Wikimedia Commons user Alan 2988.

Come learn about the largest ultramassive black hole known in the Universe, what explains its existence, and how there might be an even more massive one out there for Mostly Mute Monday!



from ScienceBlogs http://ift.tt/2welm14

“Ultramassive black holes — that is, black holes with masses exceeding 10 billion solar masses — are probably not rare; several and even dozens of these colossal black holes may exist.” -Julie Hlavacek-Larrondo

The largest black hole in the Universe was a shocker when it was first discovered. At 40 billion solar masses, it certainly is impressively large. Like other quasars and active galaxies, it has a luminous accretion disk that can be seen from a great distance. Like only a few, one of its two incredibly energetic, polar jets is pointed directly at Earth, creating a blazar, the brightest of all active galaxies.

When an active galaxy has one of its jets pointed directly at Earth, we observe an ultra-luminous phenomenon known as a blazar. These are the brightest objects seen in the entire Universe. Image credit: NASA / JPL.

But what makes this object, known as S5 0014+81, so special is that it got so big and massive so quickly. Its light comes to us from a time when the Universe was only 1.6 billion years old: just 12% of its current age. If this brilliant, massive object were located a mere 280 light years away, or ‘only’ 18 million times the Earth-Sun distance, it would shine as brightly as our life-giving star.

If this quasar were 18 million times as far away as our Sun (280 light years from Earth), it would shine as bright in the sky as our life-giving star does. Image credit: Wikimedia Commons user Alan 2988.

Come learn about the largest ultramassive black hole known in the Universe, what explains its existence, and how there might be an even more massive one out there for Mostly Mute Monday!



from ScienceBlogs http://ift.tt/2welm14

Experimental Drone Transforms in Flight

The U.S. Army Research Laboratory is experimenting with a hybrid unmanned aerial vehicle that transforms in flight and gives Soldiers an advantage on the battlefield of the future.

from http://ift.tt/2hgH2XJ
The U.S. Army Research Laboratory is experimenting with a hybrid unmanned aerial vehicle that transforms in flight and gives Soldiers an advantage on the battlefield of the future.

from http://ift.tt/2hgH2XJ

M17 is the Omega Nebula

The Wide Field Imager on the 2.2-meter telescope at ESO’s La Silla Observatory in Chile captured this image of the rose-colored star-forming region Messier 17. Image via Messier-objects.com.

Barely visible to the unaided eye on a dark, moonless night, Messier 17 – aka the Omega Nebula = is best seen though binoculars or low power on a telescope. It’s very near another prominent nebula known as Messier 16, the Eagle Nebula, home nebula of the famous Pillars of Creation photograph. These two closely-knit patches of haze readily fit within the same binocular field of view. Follow the links below to learn more.

How to see M17

Science of the Omega Nebula

Competing nebulae

Flickr user Mike Durkin captured this image of M16 and M17.

Flickr user Mike Durkin captured this image of M16 and M17.

How to star-hop from the Teapot to Messier 16 and Messier 17

How to see M17. If you want to see deep-sky objects like this one, learn to recognize the constellation Sagittarius the Archer. It’s located in the direction to the center of our Milky Way galaxy; many beautiful star clusters and nebulae can be found in this part of the sky. Luckily, this constellation contains an easy-to-find star pattern, or asterism, in the shape of a teapot. From the legendary Teapot asterism in Sagittarius, it’s fairly easy to star-hop to the Omega Nebula and its companion nebula, M16.

From the Teapot, draw an imaginary line from the star Kaus Austrinus and pass just east (left) of the star Kaus Media to locate M16 and M17. These two nebulae are close together and located about one fist-width above the Teapot.

As seen from the Northern Hemisphere, the Teapot, M16 and M17 are summertime objects. They’re highest up when due south on late August evenings. At the same time, they’re wintertime objects from the Southern Hemisphere, where they’re found closer to overhead.

VLT Survey Telescope image of the star-forming region Messier 17. Credit European Southern Observatory. Read more about this image.

VLT Survey Telescope image of the star-forming region Messier 17. Image via European Southern Observatory. Read more about this image.

Science of the Omega Nebula. Like M16, M17 Omega Nebula is a vast interstellar cloud of dust and gas giving birth to young, hot suns. It spans some 15 light-years in diameter. The cloud of interstellar matter of which this nebula is a part is roughly 40 light-years in diameter and has a mass of 30,000 solar masses. The total mass of the Omega Nebula is an estimated 800 solar masses.

The distance to the M17 Omega Nebula isn’t known with precision. There is little doubt that it lies farther away than the more brilliant Great Orion Nebula, the star-forming nebula that’s visible to the unaided eye in January and February. When you look at either M16 or M17, you’re gazing at deep-sky wonders in the next spiral arm inward: the Sagittarius arm of the Milky Way galaxy.

The M17 Omega Nebula is thought to be around 5,000 light-years away. In contrast, the Orion Nebula resides within the Orion spiral arm (the same spiral arm as our solar system) at some 1,300 light-years distant. By the way, the local geometry of the Omega Nebula is similar to that of the Orion Nebula – except that the Omega Nebula is viewed edge-on rather than face-on.

The M17 Omega Nebula also goes by the name Swan Nebula or Horseshoe Nebula.

Messier objects in the direction of the constellation Sagittarius and its Teapot asterism, via Backyard-astro.com.

Competing nebulae. There are many glorious deep-sky objects in this region of the heavens. Two of the most famous patches of nebulosity – M8 and M20 – also vie for your attention, and couple up together within the same binocular field.

Like M16 and M17, this pair resides in the Sagittarius arm and is found by star-hopping from The Teapot. Judge for yourself which pair of stellar nurseries makes the bigger splash!

Bottom line: Barely visible to the unaided eye on a dark, moonless night, the Omega Nebula (Messier 17) is best seen through binoculars, or low power in a telescope. It’s one of our galaxy’s vast star-forming regions.



from EarthSky http://ift.tt/2hfuErf

The Wide Field Imager on the 2.2-meter telescope at ESO’s La Silla Observatory in Chile captured this image of the rose-colored star-forming region Messier 17. Image via Messier-objects.com.

Barely visible to the unaided eye on a dark, moonless night, Messier 17 – aka the Omega Nebula = is best seen though binoculars or low power on a telescope. It’s very near another prominent nebula known as Messier 16, the Eagle Nebula, home nebula of the famous Pillars of Creation photograph. These two closely-knit patches of haze readily fit within the same binocular field of view. Follow the links below to learn more.

How to see M17

Science of the Omega Nebula

Competing nebulae

Flickr user Mike Durkin captured this image of M16 and M17.

Flickr user Mike Durkin captured this image of M16 and M17.

How to star-hop from the Teapot to Messier 16 and Messier 17

How to see M17. If you want to see deep-sky objects like this one, learn to recognize the constellation Sagittarius the Archer. It’s located in the direction to the center of our Milky Way galaxy; many beautiful star clusters and nebulae can be found in this part of the sky. Luckily, this constellation contains an easy-to-find star pattern, or asterism, in the shape of a teapot. From the legendary Teapot asterism in Sagittarius, it’s fairly easy to star-hop to the Omega Nebula and its companion nebula, M16.

From the Teapot, draw an imaginary line from the star Kaus Austrinus and pass just east (left) of the star Kaus Media to locate M16 and M17. These two nebulae are close together and located about one fist-width above the Teapot.

As seen from the Northern Hemisphere, the Teapot, M16 and M17 are summertime objects. They’re highest up when due south on late August evenings. At the same time, they’re wintertime objects from the Southern Hemisphere, where they’re found closer to overhead.

VLT Survey Telescope image of the star-forming region Messier 17. Credit European Southern Observatory. Read more about this image.

VLT Survey Telescope image of the star-forming region Messier 17. Image via European Southern Observatory. Read more about this image.

Science of the Omega Nebula. Like M16, M17 Omega Nebula is a vast interstellar cloud of dust and gas giving birth to young, hot suns. It spans some 15 light-years in diameter. The cloud of interstellar matter of which this nebula is a part is roughly 40 light-years in diameter and has a mass of 30,000 solar masses. The total mass of the Omega Nebula is an estimated 800 solar masses.

The distance to the M17 Omega Nebula isn’t known with precision. There is little doubt that it lies farther away than the more brilliant Great Orion Nebula, the star-forming nebula that’s visible to the unaided eye in January and February. When you look at either M16 or M17, you’re gazing at deep-sky wonders in the next spiral arm inward: the Sagittarius arm of the Milky Way galaxy.

The M17 Omega Nebula is thought to be around 5,000 light-years away. In contrast, the Orion Nebula resides within the Orion spiral arm (the same spiral arm as our solar system) at some 1,300 light-years distant. By the way, the local geometry of the Omega Nebula is similar to that of the Orion Nebula – except that the Omega Nebula is viewed edge-on rather than face-on.

The M17 Omega Nebula also goes by the name Swan Nebula or Horseshoe Nebula.

Messier objects in the direction of the constellation Sagittarius and its Teapot asterism, via Backyard-astro.com.

Competing nebulae. There are many glorious deep-sky objects in this region of the heavens. Two of the most famous patches of nebulosity – M8 and M20 – also vie for your attention, and couple up together within the same binocular field.

Like M16 and M17, this pair resides in the Sagittarius arm and is found by star-hopping from The Teapot. Judge for yourself which pair of stellar nurseries makes the bigger splash!

Bottom line: Barely visible to the unaided eye on a dark, moonless night, the Omega Nebula (Messier 17) is best seen through binoculars, or low power in a telescope. It’s one of our galaxy’s vast star-forming regions.



from EarthSky http://ift.tt/2hfuErf

Storm moving in

Photo taken July 29, 2017 Niccole Kowalski of Apache Junction, Arizona.



from EarthSky http://ift.tt/2uPC6fM

Photo taken July 29, 2017 Niccole Kowalski of Apache Junction, Arizona.



from EarthSky http://ift.tt/2uPC6fM

Sun halo with 2 contrail shadows

Sun halo, contrail and 2 contrail shadows via Jüri Voit in Kuusalu, Estonia.

Descriptions on this page are made possible by Les Cowley’s great website, Atmospheric Optics

Click here to learn more about 22-degree sun halos

Click here for more photos of contrail shadows, and to learn more about them



from EarthSky http://ift.tt/2va5srz

Waxing gibbous moon this week

Image at top: Waxing gibbous moon via OMladyO in Switzerland.

Tonight – July 31, 2017 – and in the coming evenings, people will see a waxing gibbous moon in the evening sky. The half-lit first quarter moon just happened on Sunday, July 30. Waxing means we’re seeing more and more of the moon’s illuminated side, or day side. Gibbous means the moon’s disk appears to us now as more than 50% lit by sunshine. On July 31, the moon is barely more than 50% illuminated, but the moon will be rising later – appearing in the sky for more hours of the night – and appearing bigger and brighter each evening this week. Click here to know the moon’s present phase.

Full moon will come August 7 or 8, 2017, depending on your time zone. And thus, in 2017, the moon will all but obliterate the annual Perseid meteor shower. At the same time, the moon is now edging toward a lunar eclipse, then a solar eclipse. 

At this upcoming full moon, people from Earth’s Eastern Hemisphere can watch Earth’s dark shadow (umbra) darken the southern edge of the August 2017 full moon. Hence that part of the world will see a partial eclipse of the moon.

Click here to learn more about the August 7-8 lunar eclipse.

Earth’s dark shadow (umbra) clips the southern part of the moon on the night of August 7-8. The moon goes through the Earth’s shadow from west to east. This lunar eclipse is not visible from North America.

By the way, a lunar eclipse can only happen at full moon because that’s the only time Earth’s shadow can fall on the moon. More often than not, the full moon eludes the Earth’s shadow by swinging to the north or south of it, thereby missing being eclipsed. But not this month.

Why no eclipse every full and mew moon?

Three weeks from now, the the moon’s shadow will hit Earth at the August 21, 2017 new moon. The moon’s dark umbral shadow will cross the U.S. during daylight hours on August 21, to cause a total eclipse of the sun.

Total eclipse of sun: August 21, 2017

How to watch a solar eclipse safely

Best places to watch 2017 eclipse

How much traffic on eclipse day?

Path of the total solar eclipse – with partial eclipse percentages indicated – via GreatAmericanEclipse.com (used with permission). Click here to enter your zip code and learn more about the solar eclipse in your area.

For now, each day after sunset, you’ll see more of the moon’s disk as sunlit. Another way to say this is, you’ll see more of the moon’s day side. Meanwhile, the dark part of a waxing gibbous moon – the part we can’t see well at this moon phase, because it blends with the dark of our own night, or blue of our own day – is the moon’s night side. Just as on Earth, night on the moon happens to be that part of the moon submerged in the moon’s own shadow. How much of the moon’s night, or day, side is visible from Earth depends on the moon phase.

As the moon orbits Earth, its changing geometry with respect to the sun produces the characteristic phases. This composite image is a mosaic made from 25 individual photos of the moon and illustrates its phases over one synodic month. For complete details about this image, see Moon Phases Mosaic. Photo copyright Fred Espenak.

Bottom line: The waxing gibbous moon is waxing toward full moon on August 7-8, obliterating the annual meteors showers and edging toward a lunar eclipse, then a solar eclipse. 

Help support EarthSky! Visit the EarthSky store for to see the great selection of educational tools and team gear we have to offer.



from EarthSky http://ift.tt/2tQvXys

Image at top: Waxing gibbous moon via OMladyO in Switzerland.

Tonight – July 31, 2017 – and in the coming evenings, people will see a waxing gibbous moon in the evening sky. The half-lit first quarter moon just happened on Sunday, July 30. Waxing means we’re seeing more and more of the moon’s illuminated side, or day side. Gibbous means the moon’s disk appears to us now as more than 50% lit by sunshine. On July 31, the moon is barely more than 50% illuminated, but the moon will be rising later – appearing in the sky for more hours of the night – and appearing bigger and brighter each evening this week. Click here to know the moon’s present phase.

Full moon will come August 7 or 8, 2017, depending on your time zone. And thus, in 2017, the moon will all but obliterate the annual Perseid meteor shower. At the same time, the moon is now edging toward a lunar eclipse, then a solar eclipse. 

At this upcoming full moon, people from Earth’s Eastern Hemisphere can watch Earth’s dark shadow (umbra) darken the southern edge of the August 2017 full moon. Hence that part of the world will see a partial eclipse of the moon.

Click here to learn more about the August 7-8 lunar eclipse.

Earth’s dark shadow (umbra) clips the southern part of the moon on the night of August 7-8. The moon goes through the Earth’s shadow from west to east. This lunar eclipse is not visible from North America.

By the way, a lunar eclipse can only happen at full moon because that’s the only time Earth’s shadow can fall on the moon. More often than not, the full moon eludes the Earth’s shadow by swinging to the north or south of it, thereby missing being eclipsed. But not this month.

Why no eclipse every full and mew moon?

Three weeks from now, the the moon’s shadow will hit Earth at the August 21, 2017 new moon. The moon’s dark umbral shadow will cross the U.S. during daylight hours on August 21, to cause a total eclipse of the sun.

Total eclipse of sun: August 21, 2017

How to watch a solar eclipse safely

Best places to watch 2017 eclipse

How much traffic on eclipse day?

Path of the total solar eclipse – with partial eclipse percentages indicated – via GreatAmericanEclipse.com (used with permission). Click here to enter your zip code and learn more about the solar eclipse in your area.

For now, each day after sunset, you’ll see more of the moon’s disk as sunlit. Another way to say this is, you’ll see more of the moon’s day side. Meanwhile, the dark part of a waxing gibbous moon – the part we can’t see well at this moon phase, because it blends with the dark of our own night, or blue of our own day – is the moon’s night side. Just as on Earth, night on the moon happens to be that part of the moon submerged in the moon’s own shadow. How much of the moon’s night, or day, side is visible from Earth depends on the moon phase.

As the moon orbits Earth, its changing geometry with respect to the sun produces the characteristic phases. This composite image is a mosaic made from 25 individual photos of the moon and illustrates its phases over one synodic month. For complete details about this image, see Moon Phases Mosaic. Photo copyright Fred Espenak.

Bottom line: The waxing gibbous moon is waxing toward full moon on August 7-8, obliterating the annual meteors showers and edging toward a lunar eclipse, then a solar eclipse. 

Help support EarthSky! Visit the EarthSky store for to see the great selection of educational tools and team gear we have to offer.



from EarthSky http://ift.tt/2tQvXys

IMRT: bending radiotherapy beams to spare healthy cells

Radiotherapy

This entry is part 3 of 3 in the series Radiotherapy

Part three of our new blog series on radiotherapy explores a type of radiotherapy treatment called IMRT. We cover what it is, how it’s already improved the lives of many patients and why this number will continue to grow.

A tumour is a 3D ball of cells, each with a unique shape and position in the body. This causes a problem for radiotherapy as some parts of the tumour may be closer to healthy tissues than others.

The stronger the radiotherapy beam the more damage it will do to normal cells, which increases side effects and the chance of scarring.

So radiotherapists have borrowed a trick from the theatre.

Just as leading actors get a strong spotlight on stage with the rest of the set lit less brightly, different parts of a tumour can get different intensities of radiotherapy.

The advanced technique that lets this happen is called intensity modulated radiotherapy (IMRT), where the intensity of radiation varies depending on which part of the treatment area it hits.

To each according to his needs

The crux of IMRT treatment is to give each part of the tumour enough radiation to kill it but to protect healthy cells at the same time.

This is done by using a bit of high-tech kit in the radiotherapy machine called a multileaf collimator. The radiation beam passes through metal leaves that slide to make different shapes.

The collimators movement is unique to each patient and controls the area exposed to radiation as well as the direction and intensity of the beam. This means that the precious, normal tissues get a much lower dose.

 

Credit: The NCI Hospital, Washington

 

Professor David Sebag-Montefiore, a Cancer Research UK radiotherapy expert from the University of Leeds, says the way IMRT is given is also improving.

When it first came about IMRT was given by using many beams, each from a different direction. The patient lay on the bed whilst the radiotherapy machine sat in fixed positions, pointing to the tumour in the middle.

The idea is that the beam hits the tumour at lots of different angles but doesn’t stay in contact with healthy cells for long, so they have an easier job of recovering. Because this process is repeated from lots of different angles, the radiation beam has great coverage of the tumour but spares the important organs and normal cells around it.

A more sophisticated way of receiving IMRT is becoming increasingly available. Now the most modern radiotherapy machines deliver radiation in a smooth arc around the patient, which shortens the time it takes to give the treatment.

IMRT in the clinic

During IMRT the radiotherapy machine is a great multitasker. It moves around the patient changing the shape of the beams and their intensity, depending on which area of the body it’s treating.

“The way the beams shape and intensity changes, means it can spare areas of the body that don’t need radiation. For example, when we treat tumours in the pelvis it avoids sensitive areas like major nerves or genitals.” says Sebag–Montefiore.

Sebag–Montefiore thinks developments in IMRT have significantly improved treatment options for patients and their quality of life.

“IMRT has dramatically changed our ability to treat some cancers more effectively. It’s a type of radiotherapy treatment that can offer much more individualised treatment and gives the right dose to the right target,” he says.

All tumours are different shapes and sizes, so each patient gets their own individual programme of radiation.

Transforming lives

“We used to operate on cancers of the head and neck and remove the tumours with surgery, but this is such a delicate area the operation would cause a lot of physical and psychological damage,” says Sebag–Montefiore.

With IMRT, just the tumour and a small area around it are exposed to radiation, reducing side effects and scarring.

IMRT is also improving quality of life for patients with anal cancer. With reproductive organs, the lower intestines and the bladder very near, operating is tricky.

“In anal cancer, surgery used to be thought of as the best treatment, but the whole back passage would be removed and a patient would have to use a colostomy bag for the rest of their life,” says Sebag–Montefiore.

IMRT has dramatically changed our ability to treat some cancers more effectively.

 – Professor David Sebag-Montefiore

But IMRT’s beams are so carefully controlled delicate nerves around the bladder and genital area get less radiation, so anal cancer can be cured with fewer side effects.

“Because of this, the standard of care has changed for this cancer from chemo and surgery to radiotherapy,” he says.

There are many trials underway testing the best ways to use IMRT for a variety of cancers.

For example, the PLATO trial is using IMRT to decide the best radiotherapy treatment for patients with anal cancer.

Researchers are also looking at whether IMRT could help really hard to treat cancers. The SCALOP2 trial is looking at the best radiotherapy dose to use in patients with pancreatic cancer that hasn’t spread and how best to combine it with drugs.

Professor Corrine Faivre-Finn thinks IMRT could be particularly useful in killing non-small cell lung cancer (NSCLC). She’s a Cancer Research UK expert in radiotherapy and is looking into the impact of IMRT on lung cancer at The Christie hospital in Manchester.

Her team looked back on nearly 9,000 lung cancer patients treated with IMRT between 2005 and 2015. They found that, as time went by, the number of patients that had radiotherapy treatment with the intention to cure increased each year. Before the introduction of IMRT in 2008, the number of patients given radiotherapy to cure was at 39 in 100 patients. But once it was fully available between 2009-2012 this number rose to 59 in 100.

“This means that IMRT has let us treat large volumes of tumours and tumours near organs that in the past we wouldn’t have been able to treat. We would have just given them end-of-life care or low doses of radiotherapy.” says Fairve-Finn.

But she adds that it’s not just survival that’s important.

“If you give a treatment like this you can control the disease for longer. This means less symptoms and so a better quality of life for the patient.”

Personalising treatment

Both Sebag–Montefiore and Faivre-Finn think patients will be having more and more personalised treatment plans using IMRT.

It’s clear that IMRT has already put on a pretty impressive show. In the case of lung cancer, it’s meant that larger, more developed tumours – previously thought too advanced to treat – can now be treated. It’s also changed practice for a number of cancer types.

And with further improvements on the way, IMRT could be set to take centre-stage in more treatment plans, for more cancer types in the future.

Gabi



from Cancer Research UK – Science blog http://ift.tt/2uPbkEd
Radiotherapy

This entry is part 3 of 3 in the series Radiotherapy

Part three of our new blog series on radiotherapy explores a type of radiotherapy treatment called IMRT. We cover what it is, how it’s already improved the lives of many patients and why this number will continue to grow.

A tumour is a 3D ball of cells, each with a unique shape and position in the body. This causes a problem for radiotherapy as some parts of the tumour may be closer to healthy tissues than others.

The stronger the radiotherapy beam the more damage it will do to normal cells, which increases side effects and the chance of scarring.

So radiotherapists have borrowed a trick from the theatre.

Just as leading actors get a strong spotlight on stage with the rest of the set lit less brightly, different parts of a tumour can get different intensities of radiotherapy.

The advanced technique that lets this happen is called intensity modulated radiotherapy (IMRT), where the intensity of radiation varies depending on which part of the treatment area it hits.

To each according to his needs

The crux of IMRT treatment is to give each part of the tumour enough radiation to kill it but to protect healthy cells at the same time.

This is done by using a bit of high-tech kit in the radiotherapy machine called a multileaf collimator. The radiation beam passes through metal leaves that slide to make different shapes.

The collimators movement is unique to each patient and controls the area exposed to radiation as well as the direction and intensity of the beam. This means that the precious, normal tissues get a much lower dose.

 

Credit: The NCI Hospital, Washington

 

Professor David Sebag-Montefiore, a Cancer Research UK radiotherapy expert from the University of Leeds, says the way IMRT is given is also improving.

When it first came about IMRT was given by using many beams, each from a different direction. The patient lay on the bed whilst the radiotherapy machine sat in fixed positions, pointing to the tumour in the middle.

The idea is that the beam hits the tumour at lots of different angles but doesn’t stay in contact with healthy cells for long, so they have an easier job of recovering. Because this process is repeated from lots of different angles, the radiation beam has great coverage of the tumour but spares the important organs and normal cells around it.

A more sophisticated way of receiving IMRT is becoming increasingly available. Now the most modern radiotherapy machines deliver radiation in a smooth arc around the patient, which shortens the time it takes to give the treatment.

IMRT in the clinic

During IMRT the radiotherapy machine is a great multitasker. It moves around the patient changing the shape of the beams and their intensity, depending on which area of the body it’s treating.

“The way the beams shape and intensity changes, means it can spare areas of the body that don’t need radiation. For example, when we treat tumours in the pelvis it avoids sensitive areas like major nerves or genitals.” says Sebag–Montefiore.

Sebag–Montefiore thinks developments in IMRT have significantly improved treatment options for patients and their quality of life.

“IMRT has dramatically changed our ability to treat some cancers more effectively. It’s a type of radiotherapy treatment that can offer much more individualised treatment and gives the right dose to the right target,” he says.

All tumours are different shapes and sizes, so each patient gets their own individual programme of radiation.

Transforming lives

“We used to operate on cancers of the head and neck and remove the tumours with surgery, but this is such a delicate area the operation would cause a lot of physical and psychological damage,” says Sebag–Montefiore.

With IMRT, just the tumour and a small area around it are exposed to radiation, reducing side effects and scarring.

IMRT is also improving quality of life for patients with anal cancer. With reproductive organs, the lower intestines and the bladder very near, operating is tricky.

“In anal cancer, surgery used to be thought of as the best treatment, but the whole back passage would be removed and a patient would have to use a colostomy bag for the rest of their life,” says Sebag–Montefiore.

IMRT has dramatically changed our ability to treat some cancers more effectively.

 – Professor David Sebag-Montefiore

But IMRT’s beams are so carefully controlled delicate nerves around the bladder and genital area get less radiation, so anal cancer can be cured with fewer side effects.

“Because of this, the standard of care has changed for this cancer from chemo and surgery to radiotherapy,” he says.

There are many trials underway testing the best ways to use IMRT for a variety of cancers.

For example, the PLATO trial is using IMRT to decide the best radiotherapy treatment for patients with anal cancer.

Researchers are also looking at whether IMRT could help really hard to treat cancers. The SCALOP2 trial is looking at the best radiotherapy dose to use in patients with pancreatic cancer that hasn’t spread and how best to combine it with drugs.

Professor Corrine Faivre-Finn thinks IMRT could be particularly useful in killing non-small cell lung cancer (NSCLC). She’s a Cancer Research UK expert in radiotherapy and is looking into the impact of IMRT on lung cancer at The Christie hospital in Manchester.

Her team looked back on nearly 9,000 lung cancer patients treated with IMRT between 2005 and 2015. They found that, as time went by, the number of patients that had radiotherapy treatment with the intention to cure increased each year. Before the introduction of IMRT in 2008, the number of patients given radiotherapy to cure was at 39 in 100 patients. But once it was fully available between 2009-2012 this number rose to 59 in 100.

“This means that IMRT has let us treat large volumes of tumours and tumours near organs that in the past we wouldn’t have been able to treat. We would have just given them end-of-life care or low doses of radiotherapy.” says Fairve-Finn.

But she adds that it’s not just survival that’s important.

“If you give a treatment like this you can control the disease for longer. This means less symptoms and so a better quality of life for the patient.”

Personalising treatment

Both Sebag–Montefiore and Faivre-Finn think patients will be having more and more personalised treatment plans using IMRT.

It’s clear that IMRT has already put on a pretty impressive show. In the case of lung cancer, it’s meant that larger, more developed tumours – previously thought too advanced to treat – can now be treated. It’s also changed practice for a number of cancer types.

And with further improvements on the way, IMRT could be set to take centre-stage in more treatment plans, for more cancer types in the future.

Gabi



from Cancer Research UK – Science blog http://ift.tt/2uPbkEd

Double Comments of the Week #170: From terraforming Mars to what is and isn’t expanding [Starts With A Bang]

“Someone once told me that time was a predator that stalked us all our lives. But I rather believe that time is a companion who goes with us on the journey and reminds us to cherish every moment because they’ll never come again. What we leave behind is not as important as how we’ve lived.” -Brannon Braga, Ronald D. Moore, and Rick Berman

After being away for last weekend, it’s time to take a look back at the past two weeks on Starts With A Bang! There’s been no shortage of stories, of news, or of scientific matters of interest, so let’s see what we’ve got:

Next week, I’ll be at two days of the official Star Trek convention in Las Vegas, on August 3rd and 4th, and the full schedule is now online! While the Perseids are coming up, followed by the total solar eclipse, there’s still a whole lot to do before then. You’ve had a lot to think about and a lot to say, so let’s get right into our comments of the week!

The particle tracks emanating from a high energy collision at the LHC in 2014. Although these collisions are plentiful and incredibly energetic, they have not yet yielded any compelling evidence of physics beyond the Standard Model. Image credit: Wikimedia Commons user Pcharito.

From Elle H.C. on a (non-)problem with the LHC: “…while the LHC is all about creating as much noise possible (luminosity)…”

Hang on. Are you contending that you can’t know what goes on in a proton-proton collision, because there are bunched of protons being fired at each other, multiple collisions happening, and therefore we can’t pull the signal out of the noise? Because although that certainly makes things more difficult, it’s not at all a cause for concern in these experiments. Colliding composite particles means we need to be able to tell the difference between a collision of interest and a glancing collision, noise, or other particles that find their way (or their daughter particles find a way) into the detectors.

But we know how to do that: we trigger on large transverse-momentum events. For those events, we record the entirety of the data, and can determine which particle tracks originated from which collision. If you’re not concerned with disrupting spacetime or creating a catastrophe at the LHC, then perhaps I’ve misunderstood what you’ve been contending for a long time.

Photo by Paul Ehrenfest, in December of 1925.

From Pentcho Valev on walking the walk: “No need to ban me – I’m leaving your blog.”

I’ll believe it when I see it. Your “leaving my blog” lasted for an even shorter duration than a Jay-Z retirement.

Once you cross the threshold to form a black hole, everything inside the event horizon crunches down to a singularity that is, at most, one-dimensional. No 3D structures can survive intact. Image credit: Ask The Van / UIUC Physics Department.

From Adam on falling into a black hole with a tether: “I’m not getting the Option C listed here. If a particle emits a force mediating particle, and the force mediating particle crosses or goes deeper into an event horizon, even if it hits some other particle in some random location, how’s the original particle going to know?
Am I missing something obvious? Is a return force mediating particle not required?”

Imagine you’re falling into a black hole. You know that once you cross the event horizon, nothing can get out. You also know that, with enough power, something that’s outside the event horizon, if you do it just right, can escape. There are also tidal forces at play, working to stretch (in the “towards-the-singularity” direction) and compress (in the “perpendicular-to-that-previous-direction” direction) that you just can’t avoid.

So what could possibly happen to you as you fall in? Or, if you prefer, as you, in your ship outside, try and deal with a tether that extends to an object that’s just fallen inside the event horizon?

The outside part can try and escape! If you try too hard, you’ll snap the tether. If you don’t try hard enough, you’ll be pulled in. And if you try just right — which means just hard enough that if you tried any harder, the tether will snap — then what? Well, the answer is that you’ll fall in as slowly as possible. In particular, the particles outside will continue to communicate (i.e., exchange forces) with the particles outside; the particles inside will communicate with the particles inside; and the particles just inside the event horizon will exchange forces with the particles that were outside the event horizon when those virtual particles were emitted, but by time those signals are received, those particles now must be inside the event horizon. Which means you really do only have two options: either you’ll be pulled in or the tether will snap. But you can continue to not have the tether snap if you fall in at the minimum possible rate, which is governed not by the material strength of the tether, but rather by the laws of relativity and causality. (And FYI, no, a “round-trip” force exchange isn’t necessary. One way exerts forces on both particles. That’s physics!)

A visualization of a black hole exhibiting quantum effects, which we’d need a quantum theory of gravity to understand what was happening near the singularity at the center. Image credit: University of Nottingham, via http://ift.tt/1tNDA2t.

From Denier on quantum gravity: “

Ethan: you are of the mindset that spacetime fabric is a thing, rather than nothingness itself. We can create visualizations of it; we can write down the laws that govern it; we can quantify the interrelationships of its various components. But it’s not a physical thing that you can poke holes in or tear apart

Denier: That sounds an awful lot like you’re declaring LQG to be fiction.”

Hold on! Saying “spacetime is a fabric” is true in General Relativity, which is our theory of gravity today. Space and/or time may be quantized or discrete at a fundamental level, but those scales at which we’d observe such effects are Planck-scale effects, something we don’t have any way of accessing with current or even envisioned future technology. LQG, or any discrete quantum theory of spacetime, could still be true, but it would have to reproduce classical GR in the low-energy limit.

I thought I said something to that effect when I first brought that up? Oh wait, I did! Here’s the rest of that quote:

But it’s not a physical thing that you can poke holes in or tear apart; it’s a mathematical structure that’s well-defined, and the conditions where that structure breaks down — Planck scales — are also well-defined. The LHC doesn’t reach those scales, so we’re positive that we’re fine. Your analogy isn’t applicable here.

QED, I think.

This movie shows the star VB 10 moving across the sky over a period of nine years. The blue ellipse shows the (magnified) orbit of the unconfirmed planet VB 10 b (red dot) and its movement relative to the star. Image credit: NASA / JPL-Caltech / Palomar.

From Michael Mooney on the (perceived?) invalidity of Special Relativity: “I’m still waiting for Ethan to disambiguate the difference between apparent length contraction (re: differences in what observers see) and actual physical shrinkage of physical objects as promoted by SR.”

You wrote three things that you addressed here as a “response to my challenge.” Only one was physics:

Regarding length contraction, It would take a clear disambiguation of the difference between *apparent* contraction (as seen/measured by various observers) and *actual physical shrinkage* as claimed in the pole- in- a- barn and the train- in- a- tunnel SR thought experiments… also applied to flattened planets (as seen by…) and contracted distances between stars, as per fast travelers with slow clocks.

If we had a way to travel close to the speed of light and take 3D measurements, we would be able to do exactly that. We’d be able to combine the effects of length contraction along with frame-of-reference motions of light-emitting objects (i.e., arrival times) to measure if length contraction is real. We can do this for individual particles (or bunches of particles) and confirm that special relativity’s predictions are right. We’ve done it for fields (they exhibit length contraction at high speeds, like the electric field of an electron). But we haven’t been able to do this for large, composite, macroscopic objects because of practical constraints. But there’s no reason to believe that the physics is any different.

Your other two things that you wrote, however, complained about ontology. As a physicist, I’m not really interested in your (or my, or anyone’s) inability to wrap your head around a physical interpretation/visualization/ontology of what these well-defined entities actually are. You are of the mindset that such a definition is nonsense and incomplete and insufficient. You are entitled to your own opinion, but, like I said, I don’t find it interesting enough to even have a conversation about; it’s not physics, nor is it physically interesting. You are going to disagree and ask me to respond, and I will tell you that I won’t. Why not? Because I don’t waste my time explaining myself to someone who’s committed to misunderstanding me. And in this, you are.

The flow of a dried-up riverbed is an unmistakable signature of a water-rich past on Mars. With the right terraforming work, perhaps it could be habitable once again! Image credit: ESA/DLR/FU Berlin (G. Neukum).

From Frank on terraforming Mars: “Only possibility I see is if we can modify orbits of large asteroids and comets someday to collide with Mars to add both mass and water, and also make its orbit come closer to Sun.”

Wait, and you thought bringing material to Mars the old-fashioned way was difficult? How much mass do you plan on adding? Because the entire asteroid belt is 0.5% the mass of Mars. You want to bring Mars closer to the Sun? How are you going to dissipate all that orbital energy? I think the bigger lesson is that if you add just atmosphere and then water, you get a world that works, as is, for hundreds of millions of years. That’s pretty good!

Mars, the red planet, has no magnetic field to protect it from the solar wind, meaning that it loses its atmosphere in a way that Earth doesn’t. But the timescale over which Mars will lose an Earth-like atmosphere needs to be calculated. Image credit: NASA / GSFC.

From Steve Blackband on the same topic: “So a magnetic field not needed to maintain the atmosphere. Cool.
However there is still the issue of radiation exposure without one, unless you live underground or under a dome.”

Radiation exposure is an interesting question. While I may do lousy on Mars, someone who grew up in a radiation-rich environment would likely be fine. Somehow, if you grow up in a radiation-rich natural environment, you don’t suffer the same ill-effects that someone who grew up in a more typical Earth environment would when exposed to such radiation.

The most radioactive inhabited location on Earth is the city of Ramsar in Iran, and here’s the deal (from Wikipedia) on that:

Ramsar’s Talesh Mahalleh district is the most radioactive inhabited area known on Earth, due to nearby hot springs and building materials originating from them.[8] A combined population of 2,000 residents from this district and other high radiation neighbourhoods receive an average radiation dose of 10 mGy per year, ten times more than the ICRP recommended limit for exposure to the public from artificial sources.[9] Record levels were found in a house where the effective radiation dose due to external radiation was 131 mSv/a, and the committed dose from radon was 72 mSv/a.[10] This unique case is over 80 times higher than the world average background radiation.

People don’t die or get cancer as expected. You might have “zero-generation” problems with radioactivity on Mars, but I have a feeling that the surviving colonists are going to wind up just fine.

32 images of the 2016 eclipse were combined in order to produce this composite, showcasing not only the corona and the plasma loops above the photosphere with stars in the background, but also with the Moon’s surface illuminated by Earthshine. Image credit: Don Sabers, Ron Royer, Miloslav Druckmuller.

From Ragtag Media on a great list of eclipse apps: “It’s all about the apps:
http://ift.tt/2twl5s5

This is beautiful, and worth sharing. Also, if you haven’t caught it, did you know I just did a new podcast on the upcoming eclipse?

Have a listen; it’s worth it!

If these three different regions of space never had time to thermalize, share information or transmit signals to one another, then why are they all the same temperature? Image credit: E. Siegel / Beyond The Galaxy.

From eric on the horizon problem: “Can’t the horizon problem be solved by the notion of these causally separated locations obeying the same laws of physics?”

As Michael Kelsey said, the problem isn’t that the laws of physics are the same; the problem is that different regions of the Universe are the exact same temperature despite being millions of light years apart! But if that’s too hard, think about it in this other fashion: the Big Bang must have occurred at the exact same moment with the exact same initial conditions everywhere. How exact is exact? For the temperature fluctuations we see, the “bang” must have occurred in all locations with the same energy separated by timescales of no less than about 10^-33 seconds.

Over millions of light years, how can you make anything line up to that incredible degree of precision? I don’t think you can, not without invoking some “the initial conditions were just finely-tuned like that.” And maybe they were… but that’s the essence of the horizon problem.

Binary stars with planets around them are common, but if the world containing Westeros orbited a binary planet, particularly if those planets were much more massive than it itself, physics can give us the orbits we need. Image credit: Stuart Littlefair / University of Sheffield.

Binary stars with planets around them are common, but if the world containing Westeros orbited a binary planet, particularly if those planets were much more massive than it itself, physics can give us the orbits we need. Image credit: Stuart Littlefair / University of Sheffield.

From Sinisa Lazarek on the science of the Game of Thrones homeworld: “Would there be dragons?”

Physics will only get you so far, Sinisa. I can get you a world with chaotic rotations and seasons… but as far as exobiology, I don’t think our science is there yet. Someday, perhaps.

Also, I noticed the arrival of jimbob on this post. This is a science blog, not a bible study group. He is now banned.

The Voyager 2 spacecraft took this color photo of Neptune’s moon Triton on Aug. 24 1989, at a range of 330,000 miles. The image was made from pictures taken through the green, violet and ultraviolet filters. Image credit: NASA / JPL.

From Pawel on the possibility of life on Triton: “I cannot find any information on “black smokers” volcanoes on Triton. Sure, there is volcanic activity there, but what makes them similar to black smokers?”

Well, if you google “black smokers triton” you’ll find that there’s the Triton grill which can be used for smoking food, and that won’t help you much. But Voyager 2 was remarkable in the science it collected. Yes, it found a mostly nitrogen atmosphere with some methane, where the methane was indirect evidence of volcanic activity. It has evidence of resurfacing, so that’s more evidence of geological activity. And the presence of methane is different in different parts of the world, indicating a seasonal component — seasonal heating from the Sun — as well.

But we are absolutely certain that Triton is volcanically active. Along with Earth, Io, and Venus, only Triton also exhibits surefire volcanic activity. (This is likely due to tidal forces from Neptune.) But there’s also this:

Image credit: Voyager 2.

Those dark spots and streaks? Volcanic activity. As the New York Times reported back in 1989:

One of the pictures showed a five-mile-high, geyser-like plume of dark material erupting from the icy surface of Triton, the blue and pink moon that all but stole the show from its planet when the Voyager spacecraft had its rendezvous with Neptune last August.

The discovery, scientists said, confirmed the hypothesis advanced immediately after the Voyager encounter that explosive volcanoes probably fueled by liquid nitrogen accounted for much of the rugged terrain on Triton. This meant that Triton is only the third object in the solar system, after Earth and Jupiter’s moon Io, known to have active volcanoes.

You can find more about it in the 1999 book, Satellites of the Outer Planets, by David A. Rothery.

The fabric of the Universe, spacetime, is a tricky concept to understand. But, thanks to Einstein's general relativity, we're up to the challenge. Image credit: Pixabay user JohnsonMartin.

The fabric of the Universe, spacetime, is a tricky concept to understand. But, thanks to Einstein’s general relativity, we’re up to the challenge. Image credit: Pixabay user JohnsonMartin.

From CFT on mathematical constructs: “Nothing actually moves in a mathematical construct like space time, It can’t even accommodate an impulse to motion, so the entire idea of it somehow affecting physical reality is quite pointless Platonistic hand waving.”

You know that there are many mathematical spacetime constructs; Einstein’s General Relativity was hardly the only one. The reason Einstein’s formalism is remarkable, though, is because it accurately describes our observed, physical reality. That’s all you need for physics. Mathematics is like taking the square root of 4. You get multiple answers: it could be +2 or it could be -2. Mathematics gives you all the possibilities a setup can admit. Physics? It has one answer, and that answer gives us our physical reality. If you can’t wrap your head around it, you can either listen to the (dissatisfactory) analogies that people who are educated in it make, or you can go and become educated about it yourself. Enjoy the Christoffel symbols!

Look, it’s everyone’s favorite lunar Rover! The angles of the shadows on the Moon and the illuminated portion of the Earth in the sky clearly don’t line up. Also, the dog is photoshopped. Image credit: NASA / manipulator unknown.

From Steve on fake astro pictures: “Its such a sad sad sad reflection of the ignorance in this nation regarding science and education that you felt it necessary to tell the audience that the dog digging on the moon (without a dogsuit) is photoshopped in.
And that I felt it necessary to add ‘without a dogsuit’…”

You are aware that there are many people who don’t even believe humans landed on the Moon. They also think it was a hoax perpetrated by the American government, and that there was some sort of secret “staged area” where the Moon landings took place. So when you show them a picture like this, it jibes with their worldview. It confirms their belief, and so they’re likely to dig in deeper. This may happen frequently in your own life, depending on who you encounter and what issues you speak about.

For me, I prefer to just watch the Rammstein video that gave the best “how to fake a Moon-like video” I think I’ve ever seen.

From dean on the climate science issue: “All true, but as denialists know, all they have to do is repeat their lies and let them sit. It’s quick and doesn’t require any science but they do seem like common sense statements to most people.. They know refuting them takes time and longer explanations that will lose the attention of people. Not promising.”

You know, I am not a climate scientist. And I’m not really qualified to do climate science research. Which is why I ran my article past three separate Ph.D. climate scientists (technically, two climate scientists and one climatologist), all of whom vetted it and approved of all of my points.

But they made a separate point, one that I thought was quite important: their goal is to mislead. Their goal is to manufacture debate and uncertainty. Their goal is not to get the science right, nor to consider the full suite of evidence. Their goal is to keep the status quo in place. And perhaps if I keep taking the, “we have to all agree on the facts before we can discuss policy,” then all they have to do is keep muddying the facts and they win. So maybe I need to take a different line of argument if I want to make a difference.

I’m thinking on this.

The size, wavelength and temperature/energy scales that correspond to various parts of the electromagnetic spectrum. Image credit: NASA and Wikimedia Commons user Inductiveload.

From Pentcho Valev on Einstein: “Spacetime is a consequence of Einstein’s constant-speed-of-light postulate, and this postulate is OBVIOUSLY false.”

I’ll tell you what: show me one measurement from any reference frame that indicates that the speed of light in a vacuum is not exactly 299,792,458 meters per second (I even gave you the value!), and we can talk about your ideas. Also, you’re going to love yesterday’s Ask Ethan when you get to it… but you have to read it. Writing your own “wall of text” (as other commenters have rightly called it) is equivalent to promoting your own pet theories and nonsense here. If that’s all you have to write about, get your own blog, because if you don’t knock it off, you won’t be welcome here any longer.

Last chance to behave!

While most of the sky will darken in a total eclipse, there are portions during a total eclipse that will remain bright, as the Moon’s shadow is smaller than your view of the entire 360-degree horizon. Image credit: Luc Janet.

And finally, to end this on a high note, here’s Alan G. on… I don’t really know, but it doesn’t really matter: “Can’t wait to pop the corn and pop the top for reading these Sunday night. This is gonna be epic, and the start is not disappointing…”

There’s always a lot to say, think, and reason out, and if you’re curious about the Universe, I hope this blog (and even the forum) gives you something interesting to ponder. There’s some amazing stuff going on in the Universe all the time, and I hope to see you continue on this journey with me. Have a great rest-of-your-weekend, everyone!

 



from ScienceBlogs http://ift.tt/2tUSYo3

“Someone once told me that time was a predator that stalked us all our lives. But I rather believe that time is a companion who goes with us on the journey and reminds us to cherish every moment because they’ll never come again. What we leave behind is not as important as how we’ve lived.” -Brannon Braga, Ronald D. Moore, and Rick Berman

After being away for last weekend, it’s time to take a look back at the past two weeks on Starts With A Bang! There’s been no shortage of stories, of news, or of scientific matters of interest, so let’s see what we’ve got:

Next week, I’ll be at two days of the official Star Trek convention in Las Vegas, on August 3rd and 4th, and the full schedule is now online! While the Perseids are coming up, followed by the total solar eclipse, there’s still a whole lot to do before then. You’ve had a lot to think about and a lot to say, so let’s get right into our comments of the week!

The particle tracks emanating from a high energy collision at the LHC in 2014. Although these collisions are plentiful and incredibly energetic, they have not yet yielded any compelling evidence of physics beyond the Standard Model. Image credit: Wikimedia Commons user Pcharito.

From Elle H.C. on a (non-)problem with the LHC: “…while the LHC is all about creating as much noise possible (luminosity)…”

Hang on. Are you contending that you can’t know what goes on in a proton-proton collision, because there are bunched of protons being fired at each other, multiple collisions happening, and therefore we can’t pull the signal out of the noise? Because although that certainly makes things more difficult, it’s not at all a cause for concern in these experiments. Colliding composite particles means we need to be able to tell the difference between a collision of interest and a glancing collision, noise, or other particles that find their way (or their daughter particles find a way) into the detectors.

But we know how to do that: we trigger on large transverse-momentum events. For those events, we record the entirety of the data, and can determine which particle tracks originated from which collision. If you’re not concerned with disrupting spacetime or creating a catastrophe at the LHC, then perhaps I’ve misunderstood what you’ve been contending for a long time.

Photo by Paul Ehrenfest, in December of 1925.

From Pentcho Valev on walking the walk: “No need to ban me – I’m leaving your blog.”

I’ll believe it when I see it. Your “leaving my blog” lasted for an even shorter duration than a Jay-Z retirement.

Once you cross the threshold to form a black hole, everything inside the event horizon crunches down to a singularity that is, at most, one-dimensional. No 3D structures can survive intact. Image credit: Ask The Van / UIUC Physics Department.

From Adam on falling into a black hole with a tether: “I’m not getting the Option C listed here. If a particle emits a force mediating particle, and the force mediating particle crosses or goes deeper into an event horizon, even if it hits some other particle in some random location, how’s the original particle going to know?
Am I missing something obvious? Is a return force mediating particle not required?”

Imagine you’re falling into a black hole. You know that once you cross the event horizon, nothing can get out. You also know that, with enough power, something that’s outside the event horizon, if you do it just right, can escape. There are also tidal forces at play, working to stretch (in the “towards-the-singularity” direction) and compress (in the “perpendicular-to-that-previous-direction” direction) that you just can’t avoid.

So what could possibly happen to you as you fall in? Or, if you prefer, as you, in your ship outside, try and deal with a tether that extends to an object that’s just fallen inside the event horizon?

The outside part can try and escape! If you try too hard, you’ll snap the tether. If you don’t try hard enough, you’ll be pulled in. And if you try just right — which means just hard enough that if you tried any harder, the tether will snap — then what? Well, the answer is that you’ll fall in as slowly as possible. In particular, the particles outside will continue to communicate (i.e., exchange forces) with the particles outside; the particles inside will communicate with the particles inside; and the particles just inside the event horizon will exchange forces with the particles that were outside the event horizon when those virtual particles were emitted, but by time those signals are received, those particles now must be inside the event horizon. Which means you really do only have two options: either you’ll be pulled in or the tether will snap. But you can continue to not have the tether snap if you fall in at the minimum possible rate, which is governed not by the material strength of the tether, but rather by the laws of relativity and causality. (And FYI, no, a “round-trip” force exchange isn’t necessary. One way exerts forces on both particles. That’s physics!)

A visualization of a black hole exhibiting quantum effects, which we’d need a quantum theory of gravity to understand what was happening near the singularity at the center. Image credit: University of Nottingham, via http://ift.tt/1tNDA2t.

From Denier on quantum gravity: “

Ethan: you are of the mindset that spacetime fabric is a thing, rather than nothingness itself. We can create visualizations of it; we can write down the laws that govern it; we can quantify the interrelationships of its various components. But it’s not a physical thing that you can poke holes in or tear apart

Denier: That sounds an awful lot like you’re declaring LQG to be fiction.”

Hold on! Saying “spacetime is a fabric” is true in General Relativity, which is our theory of gravity today. Space and/or time may be quantized or discrete at a fundamental level, but those scales at which we’d observe such effects are Planck-scale effects, something we don’t have any way of accessing with current or even envisioned future technology. LQG, or any discrete quantum theory of spacetime, could still be true, but it would have to reproduce classical GR in the low-energy limit.

I thought I said something to that effect when I first brought that up? Oh wait, I did! Here’s the rest of that quote:

But it’s not a physical thing that you can poke holes in or tear apart; it’s a mathematical structure that’s well-defined, and the conditions where that structure breaks down — Planck scales — are also well-defined. The LHC doesn’t reach those scales, so we’re positive that we’re fine. Your analogy isn’t applicable here.

QED, I think.

This movie shows the star VB 10 moving across the sky over a period of nine years. The blue ellipse shows the (magnified) orbit of the unconfirmed planet VB 10 b (red dot) and its movement relative to the star. Image credit: NASA / JPL-Caltech / Palomar.

From Michael Mooney on the (perceived?) invalidity of Special Relativity: “I’m still waiting for Ethan to disambiguate the difference between apparent length contraction (re: differences in what observers see) and actual physical shrinkage of physical objects as promoted by SR.”

You wrote three things that you addressed here as a “response to my challenge.” Only one was physics:

Regarding length contraction, It would take a clear disambiguation of the difference between *apparent* contraction (as seen/measured by various observers) and *actual physical shrinkage* as claimed in the pole- in- a- barn and the train- in- a- tunnel SR thought experiments… also applied to flattened planets (as seen by…) and contracted distances between stars, as per fast travelers with slow clocks.

If we had a way to travel close to the speed of light and take 3D measurements, we would be able to do exactly that. We’d be able to combine the effects of length contraction along with frame-of-reference motions of light-emitting objects (i.e., arrival times) to measure if length contraction is real. We can do this for individual particles (or bunches of particles) and confirm that special relativity’s predictions are right. We’ve done it for fields (they exhibit length contraction at high speeds, like the electric field of an electron). But we haven’t been able to do this for large, composite, macroscopic objects because of practical constraints. But there’s no reason to believe that the physics is any different.

Your other two things that you wrote, however, complained about ontology. As a physicist, I’m not really interested in your (or my, or anyone’s) inability to wrap your head around a physical interpretation/visualization/ontology of what these well-defined entities actually are. You are of the mindset that such a definition is nonsense and incomplete and insufficient. You are entitled to your own opinion, but, like I said, I don’t find it interesting enough to even have a conversation about; it’s not physics, nor is it physically interesting. You are going to disagree and ask me to respond, and I will tell you that I won’t. Why not? Because I don’t waste my time explaining myself to someone who’s committed to misunderstanding me. And in this, you are.

The flow of a dried-up riverbed is an unmistakable signature of a water-rich past on Mars. With the right terraforming work, perhaps it could be habitable once again! Image credit: ESA/DLR/FU Berlin (G. Neukum).

From Frank on terraforming Mars: “Only possibility I see is if we can modify orbits of large asteroids and comets someday to collide with Mars to add both mass and water, and also make its orbit come closer to Sun.”

Wait, and you thought bringing material to Mars the old-fashioned way was difficult? How much mass do you plan on adding? Because the entire asteroid belt is 0.5% the mass of Mars. You want to bring Mars closer to the Sun? How are you going to dissipate all that orbital energy? I think the bigger lesson is that if you add just atmosphere and then water, you get a world that works, as is, for hundreds of millions of years. That’s pretty good!

Mars, the red planet, has no magnetic field to protect it from the solar wind, meaning that it loses its atmosphere in a way that Earth doesn’t. But the timescale over which Mars will lose an Earth-like atmosphere needs to be calculated. Image credit: NASA / GSFC.

From Steve Blackband on the same topic: “So a magnetic field not needed to maintain the atmosphere. Cool.
However there is still the issue of radiation exposure without one, unless you live underground or under a dome.”

Radiation exposure is an interesting question. While I may do lousy on Mars, someone who grew up in a radiation-rich environment would likely be fine. Somehow, if you grow up in a radiation-rich natural environment, you don’t suffer the same ill-effects that someone who grew up in a more typical Earth environment would when exposed to such radiation.

The most radioactive inhabited location on Earth is the city of Ramsar in Iran, and here’s the deal (from Wikipedia) on that:

Ramsar’s Talesh Mahalleh district is the most radioactive inhabited area known on Earth, due to nearby hot springs and building materials originating from them.[8] A combined population of 2,000 residents from this district and other high radiation neighbourhoods receive an average radiation dose of 10 mGy per year, ten times more than the ICRP recommended limit for exposure to the public from artificial sources.[9] Record levels were found in a house where the effective radiation dose due to external radiation was 131 mSv/a, and the committed dose from radon was 72 mSv/a.[10] This unique case is over 80 times higher than the world average background radiation.

People don’t die or get cancer as expected. You might have “zero-generation” problems with radioactivity on Mars, but I have a feeling that the surviving colonists are going to wind up just fine.

32 images of the 2016 eclipse were combined in order to produce this composite, showcasing not only the corona and the plasma loops above the photosphere with stars in the background, but also with the Moon’s surface illuminated by Earthshine. Image credit: Don Sabers, Ron Royer, Miloslav Druckmuller.

From Ragtag Media on a great list of eclipse apps: “It’s all about the apps:
http://ift.tt/2twl5s5

This is beautiful, and worth sharing. Also, if you haven’t caught it, did you know I just did a new podcast on the upcoming eclipse?

Have a listen; it’s worth it!

If these three different regions of space never had time to thermalize, share information or transmit signals to one another, then why are they all the same temperature? Image credit: E. Siegel / Beyond The Galaxy.

From eric on the horizon problem: “Can’t the horizon problem be solved by the notion of these causally separated locations obeying the same laws of physics?”

As Michael Kelsey said, the problem isn’t that the laws of physics are the same; the problem is that different regions of the Universe are the exact same temperature despite being millions of light years apart! But if that’s too hard, think about it in this other fashion: the Big Bang must have occurred at the exact same moment with the exact same initial conditions everywhere. How exact is exact? For the temperature fluctuations we see, the “bang” must have occurred in all locations with the same energy separated by timescales of no less than about 10^-33 seconds.

Over millions of light years, how can you make anything line up to that incredible degree of precision? I don’t think you can, not without invoking some “the initial conditions were just finely-tuned like that.” And maybe they were… but that’s the essence of the horizon problem.

Binary stars with planets around them are common, but if the world containing Westeros orbited a binary planet, particularly if those planets were much more massive than it itself, physics can give us the orbits we need. Image credit: Stuart Littlefair / University of Sheffield.

Binary stars with planets around them are common, but if the world containing Westeros orbited a binary planet, particularly if those planets were much more massive than it itself, physics can give us the orbits we need. Image credit: Stuart Littlefair / University of Sheffield.

From Sinisa Lazarek on the science of the Game of Thrones homeworld: “Would there be dragons?”

Physics will only get you so far, Sinisa. I can get you a world with chaotic rotations and seasons… but as far as exobiology, I don’t think our science is there yet. Someday, perhaps.

Also, I noticed the arrival of jimbob on this post. This is a science blog, not a bible study group. He is now banned.

The Voyager 2 spacecraft took this color photo of Neptune’s moon Triton on Aug. 24 1989, at a range of 330,000 miles. The image was made from pictures taken through the green, violet and ultraviolet filters. Image credit: NASA / JPL.

From Pawel on the possibility of life on Triton: “I cannot find any information on “black smokers” volcanoes on Triton. Sure, there is volcanic activity there, but what makes them similar to black smokers?”

Well, if you google “black smokers triton” you’ll find that there’s the Triton grill which can be used for smoking food, and that won’t help you much. But Voyager 2 was remarkable in the science it collected. Yes, it found a mostly nitrogen atmosphere with some methane, where the methane was indirect evidence of volcanic activity. It has evidence of resurfacing, so that’s more evidence of geological activity. And the presence of methane is different in different parts of the world, indicating a seasonal component — seasonal heating from the Sun — as well.

But we are absolutely certain that Triton is volcanically active. Along with Earth, Io, and Venus, only Triton also exhibits surefire volcanic activity. (This is likely due to tidal forces from Neptune.) But there’s also this:

Image credit: Voyager 2.

Those dark spots and streaks? Volcanic activity. As the New York Times reported back in 1989:

One of the pictures showed a five-mile-high, geyser-like plume of dark material erupting from the icy surface of Triton, the blue and pink moon that all but stole the show from its planet when the Voyager spacecraft had its rendezvous with Neptune last August.

The discovery, scientists said, confirmed the hypothesis advanced immediately after the Voyager encounter that explosive volcanoes probably fueled by liquid nitrogen accounted for much of the rugged terrain on Triton. This meant that Triton is only the third object in the solar system, after Earth and Jupiter’s moon Io, known to have active volcanoes.

You can find more about it in the 1999 book, Satellites of the Outer Planets, by David A. Rothery.

The fabric of the Universe, spacetime, is a tricky concept to understand. But, thanks to Einstein's general relativity, we're up to the challenge. Image credit: Pixabay user JohnsonMartin.

The fabric of the Universe, spacetime, is a tricky concept to understand. But, thanks to Einstein’s general relativity, we’re up to the challenge. Image credit: Pixabay user JohnsonMartin.

From CFT on mathematical constructs: “Nothing actually moves in a mathematical construct like space time, It can’t even accommodate an impulse to motion, so the entire idea of it somehow affecting physical reality is quite pointless Platonistic hand waving.”

You know that there are many mathematical spacetime constructs; Einstein’s General Relativity was hardly the only one. The reason Einstein’s formalism is remarkable, though, is because it accurately describes our observed, physical reality. That’s all you need for physics. Mathematics is like taking the square root of 4. You get multiple answers: it could be +2 or it could be -2. Mathematics gives you all the possibilities a setup can admit. Physics? It has one answer, and that answer gives us our physical reality. If you can’t wrap your head around it, you can either listen to the (dissatisfactory) analogies that people who are educated in it make, or you can go and become educated about it yourself. Enjoy the Christoffel symbols!

Look, it’s everyone’s favorite lunar Rover! The angles of the shadows on the Moon and the illuminated portion of the Earth in the sky clearly don’t line up. Also, the dog is photoshopped. Image credit: NASA / manipulator unknown.

From Steve on fake astro pictures: “Its such a sad sad sad reflection of the ignorance in this nation regarding science and education that you felt it necessary to tell the audience that the dog digging on the moon (without a dogsuit) is photoshopped in.
And that I felt it necessary to add ‘without a dogsuit’…”

You are aware that there are many people who don’t even believe humans landed on the Moon. They also think it was a hoax perpetrated by the American government, and that there was some sort of secret “staged area” where the Moon landings took place. So when you show them a picture like this, it jibes with their worldview. It confirms their belief, and so they’re likely to dig in deeper. This may happen frequently in your own life, depending on who you encounter and what issues you speak about.

For me, I prefer to just watch the Rammstein video that gave the best “how to fake a Moon-like video” I think I’ve ever seen.

From dean on the climate science issue: “All true, but as denialists know, all they have to do is repeat their lies and let them sit. It’s quick and doesn’t require any science but they do seem like common sense statements to most people.. They know refuting them takes time and longer explanations that will lose the attention of people. Not promising.”

You know, I am not a climate scientist. And I’m not really qualified to do climate science research. Which is why I ran my article past three separate Ph.D. climate scientists (technically, two climate scientists and one climatologist), all of whom vetted it and approved of all of my points.

But they made a separate point, one that I thought was quite important: their goal is to mislead. Their goal is to manufacture debate and uncertainty. Their goal is not to get the science right, nor to consider the full suite of evidence. Their goal is to keep the status quo in place. And perhaps if I keep taking the, “we have to all agree on the facts before we can discuss policy,” then all they have to do is keep muddying the facts and they win. So maybe I need to take a different line of argument if I want to make a difference.

I’m thinking on this.

The size, wavelength and temperature/energy scales that correspond to various parts of the electromagnetic spectrum. Image credit: NASA and Wikimedia Commons user Inductiveload.

From Pentcho Valev on Einstein: “Spacetime is a consequence of Einstein’s constant-speed-of-light postulate, and this postulate is OBVIOUSLY false.”

I’ll tell you what: show me one measurement from any reference frame that indicates that the speed of light in a vacuum is not exactly 299,792,458 meters per second (I even gave you the value!), and we can talk about your ideas. Also, you’re going to love yesterday’s Ask Ethan when you get to it… but you have to read it. Writing your own “wall of text” (as other commenters have rightly called it) is equivalent to promoting your own pet theories and nonsense here. If that’s all you have to write about, get your own blog, because if you don’t knock it off, you won’t be welcome here any longer.

Last chance to behave!

While most of the sky will darken in a total eclipse, there are portions during a total eclipse that will remain bright, as the Moon’s shadow is smaller than your view of the entire 360-degree horizon. Image credit: Luc Janet.

And finally, to end this on a high note, here’s Alan G. on… I don’t really know, but it doesn’t really matter: “Can’t wait to pop the corn and pop the top for reading these Sunday night. This is gonna be epic, and the start is not disappointing…”

There’s always a lot to say, think, and reason out, and if you’re curious about the Universe, I hope this blog (and even the forum) gives you something interesting to ponder. There’s some amazing stuff going on in the Universe all the time, and I hope to see you continue on this journey with me. Have a great rest-of-your-weekend, everyone!

 



from ScienceBlogs http://ift.tt/2tUSYo3