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

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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.

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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.



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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



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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