May guide to the bright planets

Click the name of a planet to learn more about its visibility in May 2019: Venus, Jupiter, Saturn, Mars and Mercury.

For far-northern latitudes, like Alaska, viewing the moon and Venus in late April and early May 2019 will be difficult because the pair will rise about the same time as the sun. Elsewhere in the Northern Hemisphere, the moon and Venus will be a fragile and beautiful sight in the dawn. Read more.

The Southern Hemisphere has the advantage for catching the moon, Venus and Mercury in late April and early May 2019. From there, they appear more directly above the sunrise. Read more.

Venus is the brightest planet, beaming in the east before sunrise all month long. Watch for the waning crescent moon to join up with Venus in the morning sky for a few days, centered on or near May 1 – and then again on June 1 (see June chart below).

From northerly latitudes, Venus sits low in the glare of morning twilight. The northern tropics and Southern Hemisphere enjoy a much better view of Venus. For all of us, Venus starts out the month at an elongation of 28 degrees west of the sun. It ends the month at 20 degrees west of the sun. Despite Venus being the same angular distance from the sun worldwide, Venus spends more time in the predawn sky at more southerly latitudes. That’s because the ecliptic – or path of the sun, moon and planets – appears more nearly vertical with respect to the sunrise horizon from southerly latitudes at this time of year.

In May, at mid-northern latitudes, Venus rises well after the beginning of astronomical twilight (dawn’s first light). At temperate latitudes in the Southern Hemisphere, Venus comes up before the advent of astronomical twilight all through May 2019.

Click here to find out when astronomical twilight comes to your sky, remembering to check the astronomical twilight box.

At mid-northern latitudes, Venus rises about one hour before sunrise throughout the month.

At temperate latitudes in the Southern Hemisphere, Venus rises about two hours before sunup in early May. By the month’s end that’ll decrease to about 1 1/2 hours.

Let the waning crescent moon serve as your guide to the planet Venus, centered on or near May 1 – and then again, on or near June 1. See the sky chart for the late May/early June below.

The waning crescent moon pairs up with the queen planet Venus on or near June 1. Read more.

Mercury, the innermost planet of the solar system, passes out of the morning sky and into the evening sky in May 2019. From the northern tropics and the Southern Hemisphere, Mercury might be visible for the first week or so of May. Northerly latitudes will have a tough time catching Mercury, even with binoculars.

On the other hand, in June 2019, Mercury will become a fine evening object from both the Northern and Southern Hemispheres.

If you live in the northern tropics or the Southern Hemisphere, watch for the moon to pair up with Mercury on or near May 3, as shown on the sky chart above. If you’re in the Northern Hemisphere on May 2, you’ll find the moon and Mercury exceedingly low in the sky before sunup; they might not be visible. See the chart below.

As viewed from the Northern Hemisphere, it’ll be quite a challenge to spot Mercury in late April and early May, 2019. This chart shows May 2, when the moon and Mercury will be beneath Venus. Will you see them? It’ll be tough!

Jupiter is the second-brightest planet after Venus, and this planet is now rising earlier in our sky, coming into view at late evening in early May, and by dusk/early evening in late May. Jupiter is now approaching its opposition to the sun – marking the middle of the best time of year to see it – and so you’ll want to view Jupiter in the coming weeks. Opposition itself comes on June 10, 2019. Around that time, Jupiter will shine at its brilliant best for the year. Click here for a recommended sky almanac telling you when Jupiter rises into your sky.

That bright ruddy star rather close to Jupiter is Antares, the brightest star in the constellation Scorpius the Scorpion. Although Jupiter shines in the vicinity of Antares throughout 2019, Jupiter can be seen to wander relative to this “fixed” star of the zodiac. This year, in the first three months of 2019, Jupiter was traveling eastward, away from Antares. But starting on April 10, 2019, Jupiter reversed course, moving toward Antares. For the following four months (April 10 to August 11, 2019), Jupiter will be traveling in retrograde (or westward), closing the gap between itself and the star Antares. Midway through this retrograde, Jupiter will reach opposition.

In early May from mid-northern latitudes, Jupiter rises at late evening, roughly 11 p.m. daylight time. By the month’s end, Jupiter rises around nightfall.

At the beginning of the month at temperate latitudes in the Southern Hemisphere, Jupiter comes up by mid-evening, around 8 to 9 p.m. By the month’s end, Jupiter rises around nightfall.

Jupiter comes up first in the nightly procession of three bright planets. Saturn follows Jupiter into the sky about two hours after Jupiter first appears, and then Venus makes its appearance low in the eastern sky at dawn.

Watch for the waning gibbous moon to swing by Jupiter on the evenings of May 19 and 20, as displayed on the sky chart below.

Look for the moon near the king planet Jupiter on May 19 and 20. Read more.

Saturn comes up up a few hours after Jupiter. Throughout May, Saturn and Jupiter rise earlier each day, both of them making their appearance about two hours earlier by the month’s end. Saturn, although as bright as a 1st-magnitude star, pales in contrast to Jupiter. Jupiter outshines Saturn by some 14 times.

From mid-northern latitudes, Saturn comes up around the midnight hour (1 a.m. daylight saving time) in early May. By the month’s end, Saturn rises by around 11 p.m. daylight saving time.

From temperate latitudes in the Southern Hemisphere, Saturn comes up around two hours before the midnight hour in early May. As a reminder, midnight in our usage means midway between sunset and sunrise. By the month’s end, Saturn will rise at or around 8 p.m.

Watch for the waning moon to be in the neighborhood of Saturn for several days, centered around May 22 or 23, as shown on the sky chart below.

Unless you’re a night owl, you might want to view the moon and Saturn in the predawn/dawn sky. Read more.

Mars is the only bright planet to come out at nightfall all month long. “Bright” might be an overstatement, as Mars has faded into 2nd-magnitude brightness. Even so, Mars stays out until after nightfall. Given a dark sky, you should be able to spot this world in your western at early evening.

Click here for recommended sky almanacs providing you with the setting times for Mars for your location.

Watch for the young crescent moon to shine in the vicinity of Mars for several evenings, centered on or near May 7. The moon’s proximity might provide you with your best opportunity to catch Mars in the evening sky for the rest of 2019. Day by day, this planet is slowly but surely fading, and sinking closer to the afterglow of sunset.

Use the young crescent moon to locate Mars in your western sky as darkness falls. .

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.

Skywatcher, by Predrag Agatonovic.

Bottom line: In May, Mars is the only bright planet to pop out at nightfall all month long. Jupiter rises in the east at mid-to-late evening, whereas Saturn follows Jupiter into the sky about two hours after Jupiter does. Venus sits low in the glare of morning twilight all month long. Mercury is pretty much unobservable from northerly latitudes. Click here for recommended almanacs; they can help you know when the planets rise and set in your sky.

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

Visit EarthSky’s Best Places to Stargaze, and recommend a place we can all enjoy. Zoom out for worldwide map.

Help EarthSky keep going! Donate now.

Post your planet photos at EarthSky Community Photos

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Click the name of a planet to learn more about its visibility in May 2019: Venus, Jupiter, Saturn, Mars and Mercury.

For far-northern latitudes, like Alaska, viewing the moon and Venus in late April and early May 2019 will be difficult because the pair will rise about the same time as the sun. Elsewhere in the Northern Hemisphere, the moon and Venus will be a fragile and beautiful sight in the dawn. Read more.

The Southern Hemisphere has the advantage for catching the moon, Venus and Mercury in late April and early May 2019. From there, they appear more directly above the sunrise. Read more.

Venus is the brightest planet, beaming in the east before sunrise all month long. Watch for the waning crescent moon to join up with Venus in the morning sky for a few days, centered on or near May 1 – and then again on June 1 (see June chart below).

From northerly latitudes, Venus sits low in the glare of morning twilight. The northern tropics and Southern Hemisphere enjoy a much better view of Venus. For all of us, Venus starts out the month at an elongation of 28 degrees west of the sun. It ends the month at 20 degrees west of the sun. Despite Venus being the same angular distance from the sun worldwide, Venus spends more time in the predawn sky at more southerly latitudes. That’s because the ecliptic – or path of the sun, moon and planets – appears more nearly vertical with respect to the sunrise horizon from southerly latitudes at this time of year.

In May, at mid-northern latitudes, Venus rises well after the beginning of astronomical twilight (dawn’s first light). At temperate latitudes in the Southern Hemisphere, Venus comes up before the advent of astronomical twilight all through May 2019.

Click here to find out when astronomical twilight comes to your sky, remembering to check the astronomical twilight box.

At mid-northern latitudes, Venus rises about one hour before sunrise throughout the month.

At temperate latitudes in the Southern Hemisphere, Venus rises about two hours before sunup in early May. By the month’s end that’ll decrease to about 1 1/2 hours.

Let the waning crescent moon serve as your guide to the planet Venus, centered on or near May 1 – and then again, on or near June 1. See the sky chart for the late May/early June below.

The waning crescent moon pairs up with the queen planet Venus on or near June 1. Read more.

Mercury, the innermost planet of the solar system, passes out of the morning sky and into the evening sky in May 2019. From the northern tropics and the Southern Hemisphere, Mercury might be visible for the first week or so of May. Northerly latitudes will have a tough time catching Mercury, even with binoculars.

On the other hand, in June 2019, Mercury will become a fine evening object from both the Northern and Southern Hemispheres.

If you live in the northern tropics or the Southern Hemisphere, watch for the moon to pair up with Mercury on or near May 3, as shown on the sky chart above. If you’re in the Northern Hemisphere on May 2, you’ll find the moon and Mercury exceedingly low in the sky before sunup; they might not be visible. See the chart below.

As viewed from the Northern Hemisphere, it’ll be quite a challenge to spot Mercury in late April and early May, 2019. This chart shows May 2, when the moon and Mercury will be beneath Venus. Will you see them? It’ll be tough!

Jupiter is the second-brightest planet after Venus, and this planet is now rising earlier in our sky, coming into view at late evening in early May, and by dusk/early evening in late May. Jupiter is now approaching its opposition to the sun – marking the middle of the best time of year to see it – and so you’ll want to view Jupiter in the coming weeks. Opposition itself comes on June 10, 2019. Around that time, Jupiter will shine at its brilliant best for the year. Click here for a recommended sky almanac telling you when Jupiter rises into your sky.

That bright ruddy star rather close to Jupiter is Antares, the brightest star in the constellation Scorpius the Scorpion. Although Jupiter shines in the vicinity of Antares throughout 2019, Jupiter can be seen to wander relative to this “fixed” star of the zodiac. This year, in the first three months of 2019, Jupiter was traveling eastward, away from Antares. But starting on April 10, 2019, Jupiter reversed course, moving toward Antares. For the following four months (April 10 to August 11, 2019), Jupiter will be traveling in retrograde (or westward), closing the gap between itself and the star Antares. Midway through this retrograde, Jupiter will reach opposition.

In early May from mid-northern latitudes, Jupiter rises at late evening, roughly 11 p.m. daylight time. By the month’s end, Jupiter rises around nightfall.

At the beginning of the month at temperate latitudes in the Southern Hemisphere, Jupiter comes up by mid-evening, around 8 to 9 p.m. By the month’s end, Jupiter rises around nightfall.

Jupiter comes up first in the nightly procession of three bright planets. Saturn follows Jupiter into the sky about two hours after Jupiter first appears, and then Venus makes its appearance low in the eastern sky at dawn.

Watch for the waning gibbous moon to swing by Jupiter on the evenings of May 19 and 20, as displayed on the sky chart below.

Look for the moon near the king planet Jupiter on May 19 and 20. Read more.

Saturn comes up up a few hours after Jupiter. Throughout May, Saturn and Jupiter rise earlier each day, both of them making their appearance about two hours earlier by the month’s end. Saturn, although as bright as a 1st-magnitude star, pales in contrast to Jupiter. Jupiter outshines Saturn by some 14 times.

From mid-northern latitudes, Saturn comes up around the midnight hour (1 a.m. daylight saving time) in early May. By the month’s end, Saturn rises by around 11 p.m. daylight saving time.

From temperate latitudes in the Southern Hemisphere, Saturn comes up around two hours before the midnight hour in early May. As a reminder, midnight in our usage means midway between sunset and sunrise. By the month’s end, Saturn will rise at or around 8 p.m.

Watch for the waning moon to be in the neighborhood of Saturn for several days, centered around May 22 or 23, as shown on the sky chart below.

Unless you’re a night owl, you might want to view the moon and Saturn in the predawn/dawn sky. Read more.

Mars is the only bright planet to come out at nightfall all month long. “Bright” might be an overstatement, as Mars has faded into 2nd-magnitude brightness. Even so, Mars stays out until after nightfall. Given a dark sky, you should be able to spot this world in your western at early evening.

Click here for recommended sky almanacs providing you with the setting times for Mars for your location.

Watch for the young crescent moon to shine in the vicinity of Mars for several evenings, centered on or near May 7. The moon’s proximity might provide you with your best opportunity to catch Mars in the evening sky for the rest of 2019. Day by day, this planet is slowly but surely fading, and sinking closer to the afterglow of sunset.

Use the young crescent moon to locate Mars in your western sky as darkness falls. .

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.

Skywatcher, by Predrag Agatonovic.

Bottom line: In May, Mars is the only bright planet to pop out at nightfall all month long. Jupiter rises in the east at mid-to-late evening, whereas Saturn follows Jupiter into the sky about two hours after Jupiter does. Venus sits low in the glare of morning twilight all month long. Mercury is pretty much unobservable from northerly latitudes. Click here for recommended almanacs; they can help you know when the planets rise and set in your sky.

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

Visit EarthSky’s Best Places to Stargaze, and recommend a place we can all enjoy. Zoom out for worldwide map.

Help EarthSky keep going! Donate now.

Post your planet photos at EarthSky Community Photos

from EarthSky http://bit.ly/1YD00CF

Preparing for asteroid Apophis

This animation shows the distance between the Apophis asteroid and Earth at the time of the asteroid’s closest approach in 2029. The blue dots are manmade satellites orbiting our planet, and the pink represents the International Space Station. Image via NASA/JPL-Caltech.

Asteroid experts are meeting this week in College Park, Maryland at the 2019 Planetary Defense Conference. This conference brings together world experts to discuss:

… the threat to Earth posed by asteroids and comets and actions that might be taken to deflect a threatening object.

Yes. Movies and sci fi novels notwithstanding, professional astronomers really do talk of such things, as, over the past several decades, the potential threat to Earth from asteroid impacts has become better understood. One topic of high interest for the week is happening today (April 30, 2019). It’s a session on the 2029 passage of an asteroid known as 99942 Apophis. The scientists will be talking about a range of topics about asteroid Apophis including how to observe it when it passes Earth in 2029, as well as hypothetical missions we could send out to the asteroid. NASA wrote of this asteroid:

On April 13, 2029, a speck of light will streak across the sky, getting brighter and faster. At one point it will travel more than the width of the full moon within a minute and it will get as bright as the stars in the Little Dipper. But it won’t be a satellite or an airplane – it will be a 1,100-foot-wide (340-meter-wide) near-Earth asteroid called 99942 Apophis that will cruise harmlessly by Earth, about 19,000 miles (31,000 km) above the surface. That’s within the distance that some of our spacecraft that orbit Earth.

Asteroid Apophis – unfortunately named for an ancient Egyptian “lord of chaos” – has been known since 2004. It is a near-Earth object (NEO); that is, its orbit – which is less than one earthly year long – brings it near Earth periodically. This asteroid caused a brief period of concern shortly after its discovery in 2004. When relatively few observations of its orbit were in hand – and thus its orbit wasn’t known with much certainty – there was, for a time, a probability of up to 2.7% that it would hit Earth on April 13, 2029. That possibility became lower and lower as astronomers used both optical and radar telescopes to track Apophis over subsequent years, and got a better understanding of its orbit. A strike in 2029 was entirely ruled out during a 2013 pass of the asteroid. Still, in 2004, during its time of infamy as an asteroid that might strike Earth, Apophis set the record for the highest rating on the Torino scale, reaching level 4 on by the end of that year.

Astronomers discovered asteroid Apophis on June 19, 2004. At first, when its orbit was not well understood, there was brief concern it had the potential to strike Earth in this century. Image via UH/IA/NASA.

There was also brief talk of asteroid Apophis possibly striking Earth during its 2036 pass. However, the 2036 possibility has also been ruled out.

As of 2014, the diameter of Apophis is estimated to be approximately 1,210 ft (370 meters). That’s hardly a world-destroying size, but an asteroid of this size could obliterate a city. According to some estimates, an asteroid the size of Apophis can be expected to strike Earth about every 80,000 years. For comparison, the object that struck Earth during the 1908 Tunguska event had an estimated size of 200 to 620 feet (60 to 190 meters).

That’s why the 2029 pass of asteroid Apophis has such high interest for scientists. NASA said that, although scientists have spotted small asteroids, on the order of 5-10 meters, flying by Earth at a similar distance, asteroids the size of Apophis are far fewer in number and so do not pass this close to Earth as often.

During the April 30 discussion session at the Planetary Defense Conference, astronomers are gathering to discuss observation plans and science opportunities for the 2029 pass of asteroid Apophis. Marina Brozovic, a radar scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California, who works on radar observations of near-Earth objects (NEOs), said:

The Apophis close approach in 2029 will be an incredible opportunity for science. We’ll observe the asteroid with both optical and radar telescopes. With radar observations, we might be able to see surface details that are only a few meters in size.

They’ll also be trying to make a close-up study of the Apophis’ size, shape, composition and possibly even its interior. At this week’s conference, scientists will be discussing questions like:

– How will Earth’s gravity affect the asteroid as it passes by?

– Can we use Apophis’ flyby to learn about an asteroid’s interior?

– Should we send a spacecraft mission to Apophis?

A model of the shape of asteroid Apophis, generated from its light curve and assuming that all areas of the asteroid have a similar albedo and reflectivity, via the Database of Asteroid Models from Inversion Techniques (DAMIT) and and Wikimedia Commons.

Davide Farnocchia, an astronomer at JPL’s Center for Near Earth Objects Studies (CNEOS), who is co-chairing the April 30 session on Apophis with Brozovic, said:

We already know that the close encounter with Earth will change Apophis’ orbit, but our models also show the close approach could change the way this asteroid spins, and it is possible that there will be some surface changes, like small avalanches.

Paul Chodas, director of NASA’s Center for NEO Studies (CNEOS), said:

Apophis is a representative of about 2,000 currently known Potentially Hazardous Asteroids (PHAs). By observing Apophis during its 2029 flyby, we will gain important scientific knowledge that could one day be used for planetary defense.

NASA said that asteroid Apophis will look “like a moving star-like point of light” to earthly observers during the 2029 pass. It said the asteroid:

… will first become visible to the unaided eye in the night sky over the Southern Hemisphere, flying above Earth from the east coast to the west coast of Australia. It will be mid-morning on the East Coast of the United States when Apophis is above Australia. It will then cross the Indian Ocean, and by the afternoon in the eastern U.S. it will have crossed the equator, still moving west, above Africa. At closest approach, just before 6 p.m. EDT, Apophis will be over the Atlantic Ocean – and it will move so fast that it will cross the Atlantic in just an hour. By 7 p.m. EDT, the asteroid will have crossed over the United States.

Astronomers will be watching!

For more information about asteroids and near-Earth objects, visit: http://www.jpl.nasa.gov/asteroidwatch Updates about near-Earth objects are also available by following AsteroidWatch on Twitter at http://www.twitter.com/asteroidwatch.

Bottom line: Astronomers are meeting April 30, 2019 at the Planetary Defense Conference to discuss plans to observe asteroid 99942 Apophis, a relatively large asteroid that’ll sweep past Earth safely – but rather closely – a decade from now.

from EarthSky http://bit.ly/2GO6gpW

This animation shows the distance between the Apophis asteroid and Earth at the time of the asteroid’s closest approach in 2029. The blue dots are manmade satellites orbiting our planet, and the pink represents the International Space Station. Image via NASA/JPL-Caltech.

Asteroid experts are meeting this week in College Park, Maryland at the 2019 Planetary Defense Conference. This conference brings together world experts to discuss:

… the threat to Earth posed by asteroids and comets and actions that might be taken to deflect a threatening object.

Yes. Movies and sci fi novels notwithstanding, professional astronomers really do talk of such things, as, over the past several decades, the potential threat to Earth from asteroid impacts has become better understood. One topic of high interest for the week is happening today (April 30, 2019). It’s a session on the 2029 passage of an asteroid known as 99942 Apophis. The scientists will be talking about a range of topics about asteroid Apophis including how to observe it when it passes Earth in 2029, as well as hypothetical missions we could send out to the asteroid. NASA wrote of this asteroid:

On April 13, 2029, a speck of light will streak across the sky, getting brighter and faster. At one point it will travel more than the width of the full moon within a minute and it will get as bright as the stars in the Little Dipper. But it won’t be a satellite or an airplane – it will be a 1,100-foot-wide (340-meter-wide) near-Earth asteroid called 99942 Apophis that will cruise harmlessly by Earth, about 19,000 miles (31,000 km) above the surface. That’s within the distance that some of our spacecraft that orbit Earth.

Asteroid Apophis – unfortunately named for an ancient Egyptian “lord of chaos” – has been known since 2004. It is a near-Earth object (NEO); that is, its orbit – which is less than one earthly year long – brings it near Earth periodically. This asteroid caused a brief period of concern shortly after its discovery in 2004. When relatively few observations of its orbit were in hand – and thus its orbit wasn’t known with much certainty – there was, for a time, a probability of up to 2.7% that it would hit Earth on April 13, 2029. That possibility became lower and lower as astronomers used both optical and radar telescopes to track Apophis over subsequent years, and got a better understanding of its orbit. A strike in 2029 was entirely ruled out during a 2013 pass of the asteroid. Still, in 2004, during its time of infamy as an asteroid that might strike Earth, Apophis set the record for the highest rating on the Torino scale, reaching level 4 on by the end of that year.

Astronomers discovered asteroid Apophis on June 19, 2004. At first, when its orbit was not well understood, there was brief concern it had the potential to strike Earth in this century. Image via UH/IA/NASA.

There was also brief talk of asteroid Apophis possibly striking Earth during its 2036 pass. However, the 2036 possibility has also been ruled out.

As of 2014, the diameter of Apophis is estimated to be approximately 1,210 ft (370 meters). That’s hardly a world-destroying size, but an asteroid of this size could obliterate a city. According to some estimates, an asteroid the size of Apophis can be expected to strike Earth about every 80,000 years. For comparison, the object that struck Earth during the 1908 Tunguska event had an estimated size of 200 to 620 feet (60 to 190 meters).

That’s why the 2029 pass of asteroid Apophis has such high interest for scientists. NASA said that, although scientists have spotted small asteroids, on the order of 5-10 meters, flying by Earth at a similar distance, asteroids the size of Apophis are far fewer in number and so do not pass this close to Earth as often.

During the April 30 discussion session at the Planetary Defense Conference, astronomers are gathering to discuss observation plans and science opportunities for the 2029 pass of asteroid Apophis. Marina Brozovic, a radar scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California, who works on radar observations of near-Earth objects (NEOs), said:

The Apophis close approach in 2029 will be an incredible opportunity for science. We’ll observe the asteroid with both optical and radar telescopes. With radar observations, we might be able to see surface details that are only a few meters in size.

They’ll also be trying to make a close-up study of the Apophis’ size, shape, composition and possibly even its interior. At this week’s conference, scientists will be discussing questions like:

– How will Earth’s gravity affect the asteroid as it passes by?

– Can we use Apophis’ flyby to learn about an asteroid’s interior?

– Should we send a spacecraft mission to Apophis?

A model of the shape of asteroid Apophis, generated from its light curve and assuming that all areas of the asteroid have a similar albedo and reflectivity, via the Database of Asteroid Models from Inversion Techniques (DAMIT) and and Wikimedia Commons.

Davide Farnocchia, an astronomer at JPL’s Center for Near Earth Objects Studies (CNEOS), who is co-chairing the April 30 session on Apophis with Brozovic, said:

We already know that the close encounter with Earth will change Apophis’ orbit, but our models also show the close approach could change the way this asteroid spins, and it is possible that there will be some surface changes, like small avalanches.

Paul Chodas, director of NASA’s Center for NEO Studies (CNEOS), said:

Apophis is a representative of about 2,000 currently known Potentially Hazardous Asteroids (PHAs). By observing Apophis during its 2029 flyby, we will gain important scientific knowledge that could one day be used for planetary defense.

NASA said that asteroid Apophis will look “like a moving star-like point of light” to earthly observers during the 2029 pass. It said the asteroid:

… will first become visible to the unaided eye in the night sky over the Southern Hemisphere, flying above Earth from the east coast to the west coast of Australia. It will be mid-morning on the East Coast of the United States when Apophis is above Australia. It will then cross the Indian Ocean, and by the afternoon in the eastern U.S. it will have crossed the equator, still moving west, above Africa. At closest approach, just before 6 p.m. EDT, Apophis will be over the Atlantic Ocean – and it will move so fast that it will cross the Atlantic in just an hour. By 7 p.m. EDT, the asteroid will have crossed over the United States.

Astronomers will be watching!

For more information about asteroids and near-Earth objects, visit: http://www.jpl.nasa.gov/asteroidwatch Updates about near-Earth objects are also available by following AsteroidWatch on Twitter at http://www.twitter.com/asteroidwatch.

Bottom line: Astronomers are meeting April 30, 2019 at the Planetary Defense Conference to discuss plans to observe asteroid 99942 Apophis, a relatively large asteroid that’ll sweep past Earth safely – but rather closely – a decade from now.

from EarthSky http://bit.ly/2GO6gpW

Black hole’s gravity seen tugging on nearby space

V404 Cygni Black Hole Animation from ICRAR on Vimeo.

The National Radio Astronomy Observatory (NRAO) said on April 29, 2019, that astronomers have spied a relatively modest black hole, which nonetheless features jets of fast-moving material that are wobbling or precessing so fast their change in direction can be seen in only minutes. This sort of wobble – witnessed before among black hole jets, but not on such short timescales – happens in a way that requires an effect of Einstein’s general theory of relativity. It happens because, as the black hole spins, its powerful gravity is dragging along nearby space itself.

James Miller-Jones of Australia’s International Centre for Radio Astronomy Research led researchers in this study. He and his team employed the Very Long Baseline Array, a system of 10 radio telescopes located in various U.S. states and remotely operated from Socorro, New Mexico. They studied a black hole known as V404 Cygni, which isn’t a supermassive black hole lodged in the center of a galaxy, but just an ordinary nine-solar-mass black hole, located only 8,000 light-years from Earth in our Milky Way galaxy. NRAO said in a statement:

The black hole is drawing in material from a companion star with a mass about 70 percent that of our sun. As the material streams toward the black hole, it forms a rotating disk, called an accretion disk, surrounding the black hole.

In such systems, the disk becomes denser and hotter with decreasing distance from the black hole. Either the innermost portion of the disk or the black hole itself launches jets of material outward away from the disk. The astronomers said V404 Cygni’s jet material moves as fast as 60 percent of the speed of light.

These jets are precessing or wobbling so fast, the scientists said, that Einstein’s general theory of relativity is needed to explain them. According to Einstein, massive objects like black holes distort space and time. Further, when such a massive object is spinning, its gravitational influence pulls space and time around with it, an effect called frame-dragging. NRAO said:

In V404 Cygni, the black hole’s spin axis is misaligned from the plane of its orbit with the companion star. That causes the frame-dragging effect to warp the inner part of the disk, then pull the warped portion around with it. Since the jets originate from either the inner disk or the black hole, this changes the jet orientation, producing the wobbling observed with the Very Long Baseline Array.

Miller-Jones said:

This is the only mechanism we can think of that can explain the rapid precession we see in V404 Cygni. You can think of it like the wobble of a spinning top as it slows down, only in this case, the wobble is caused by Einstein’s general theory of relativity.

Artist’s concept of the inner accretion disk of black hole V404 Cygni. The entire accretion disk is about 10 million km (6.2 million miles) wide. The inner few thousand km are warped. That inner part also is puffed up by strong radiation pressure into a doughnut shape that wobbles, or precesses, like a rigid body. Image via NRAO.

Normally, astronomers will produce a single image of a system of this sort, using data collected over as much as several hours, like a long time-exposure photograph. The rapid direction changes of the jets of V404 Cygni meant these astronomers had to change their observation strategy. Team member Alex Tetarenko said:

These jets were changing so fast that in a four-hour image we saw just a blur.

To capture the jets’ rapid motion, the researchers made 103 individual images, each about 70 seconds long, then combined them to make a movie.

Team member Greg Sivakoff commented:

We were gobsmacked by what we saw in this system. It was completely unexpected. Finding this astronomical first has deepened our understanding of how black holes and galaxy formation can work. It tells us a little more about that big question: ‘How did we get here?’

He said the finding indicates that similar behavior might be found in other objects.

Read more about V404 Cygni, which came to astronomers’ attention via a 2015 outburst.

Artist’s concept of black hole V404 Cygni, on right. At left you see the normal star in orbit with the hole. Material from the star falls towards the black hole and spirals inwards in an accretion disk, with powerful jets being launched from the inner regions close to the black hole. Image via ICRAR/NRAO.

Bottom line: Jets of fast-moving material shot from the area surrounding a black hole are wobbling so fast that their change in direction can be seen in periods as short as minutes, and astronomers say it’s happening because the rotating black hole’s powerful gravitational pull is dragging nearby space itself along with it.

Source: Miller-Jones, Tetarenko, and Sivakoff, along with colleagues from around the world, are reporting their results in the scientific journal Nature.

Via NRAO

from EarthSky http://bit.ly/2UIFUuw

V404 Cygni Black Hole Animation from ICRAR on Vimeo.

The National Radio Astronomy Observatory (NRAO) said on April 29, 2019, that astronomers have spied a relatively modest black hole, which nonetheless features jets of fast-moving material that are wobbling or precessing so fast their change in direction can be seen in only minutes. This sort of wobble – witnessed before among black hole jets, but not on such short timescales – happens in a way that requires an effect of Einstein’s general theory of relativity. It happens because, as the black hole spins, its powerful gravity is dragging along nearby space itself.

James Miller-Jones of Australia’s International Centre for Radio Astronomy Research led researchers in this study. He and his team employed the Very Long Baseline Array, a system of 10 radio telescopes located in various U.S. states and remotely operated from Socorro, New Mexico. They studied a black hole known as V404 Cygni, which isn’t a supermassive black hole lodged in the center of a galaxy, but just an ordinary nine-solar-mass black hole, located only 8,000 light-years from Earth in our Milky Way galaxy. NRAO said in a statement:

The black hole is drawing in material from a companion star with a mass about 70 percent that of our sun. As the material streams toward the black hole, it forms a rotating disk, called an accretion disk, surrounding the black hole.

In such systems, the disk becomes denser and hotter with decreasing distance from the black hole. Either the innermost portion of the disk or the black hole itself launches jets of material outward away from the disk. The astronomers said V404 Cygni’s jet material moves as fast as 60 percent of the speed of light.

These jets are precessing or wobbling so fast, the scientists said, that Einstein’s general theory of relativity is needed to explain them. According to Einstein, massive objects like black holes distort space and time. Further, when such a massive object is spinning, its gravitational influence pulls space and time around with it, an effect called frame-dragging. NRAO said:

In V404 Cygni, the black hole’s spin axis is misaligned from the plane of its orbit with the companion star. That causes the frame-dragging effect to warp the inner part of the disk, then pull the warped portion around with it. Since the jets originate from either the inner disk or the black hole, this changes the jet orientation, producing the wobbling observed with the Very Long Baseline Array.

Miller-Jones said:

This is the only mechanism we can think of that can explain the rapid precession we see in V404 Cygni. You can think of it like the wobble of a spinning top as it slows down, only in this case, the wobble is caused by Einstein’s general theory of relativity.

Artist’s concept of the inner accretion disk of black hole V404 Cygni. The entire accretion disk is about 10 million km (6.2 million miles) wide. The inner few thousand km are warped. That inner part also is puffed up by strong radiation pressure into a doughnut shape that wobbles, or precesses, like a rigid body. Image via NRAO.

Normally, astronomers will produce a single image of a system of this sort, using data collected over as much as several hours, like a long time-exposure photograph. The rapid direction changes of the jets of V404 Cygni meant these astronomers had to change their observation strategy. Team member Alex Tetarenko said:

These jets were changing so fast that in a four-hour image we saw just a blur.

To capture the jets’ rapid motion, the researchers made 103 individual images, each about 70 seconds long, then combined them to make a movie.

Team member Greg Sivakoff commented:

We were gobsmacked by what we saw in this system. It was completely unexpected. Finding this astronomical first has deepened our understanding of how black holes and galaxy formation can work. It tells us a little more about that big question: ‘How did we get here?’

He said the finding indicates that similar behavior might be found in other objects.

Read more about V404 Cygni, which came to astronomers’ attention via a 2015 outburst.

Artist’s concept of black hole V404 Cygni, on right. At left you see the normal star in orbit with the hole. Material from the star falls towards the black hole and spirals inwards in an accretion disk, with powerful jets being launched from the inner regions close to the black hole. Image via ICRAR/NRAO.

Bottom line: Jets of fast-moving material shot from the area surrounding a black hole are wobbling so fast that their change in direction can be seen in periods as short as minutes, and astronomers say it’s happening because the rotating black hole’s powerful gravitational pull is dragging nearby space itself along with it.

Source: Miller-Jones, Tetarenko, and Sivakoff, along with colleagues from around the world, are reporting their results in the scientific journal Nature.

Via NRAO

from EarthSky http://bit.ly/2UIFUuw

The End Is Not Near, But If An 'Insect Apocalypse' Ever Happens, How Would We Know?

The End Is Not Near, But If An 'Insect Apocalypse' Ever Happens, How Would We Know?

Insects scuttle, chew and fly through the world around us. Humans rely on them to pollinate plants, prey on insects that we don’t get along with, and to be movers and shakers for Earth’s ecosystems. It’s hard to imagine a world without insects.

That’s why news reports in recent months warning of an “insect apocalypse” sparked widespread alarm. These articles, which were based on long-term insect collections and a review of past studies, suggested that people alive today will witness the indiscriminate extinction of insect-kind.

I study fungi that can be used to control harmful insects, such as pests that damage crops and mosquitoes that transmit malaria. In my world, reports of mass insect die-offs are big news. But while there clearly is reason to be concerned about certain insects, such as the endangered rusty patched bumble bee or the American burying beetle, in my view it isn’t yet possible to predict a looming insect apocalypse.

More than 1 million insects have been discovered and named, but many millions have yet to be described. It’s undeniable that Earth is becoming increasingly inhospitable to some insects – but nightmarish conditions for one may be heaven to another.

Put another way, there is no perfect environment for all insects. And human impacts on the environment, like climate change and land development, very well may hurt beneficial insects and help harmful ones.

Insects account for 75% of all the known species on Earth. What makes them so successful?

Insect declines

Around the world, entomologists are looking wistfully into empty nets, and car owners are increasingly unsettled by their pristine windshields. It does not take decades of data collection and a degree to notice that in a human lifetime, our teeming world teems less.

The first study to set off alarms was published in 2017 by entomologists in Germany, who reported that over 27 years the biomass of flying insects in their traps had declined by 75%. Another study from the Luquillo Long Term Ecological Research program site in the Puerto Rican rainforest reproduced an insect survey from the 1970s. It found that the biomass of arthropods – a large group of organisms that includes insects – had declined 10- to 60-fold in that time, and that lizards, frogs and birds that ate arthropods had also declined.

Underscoring this theme, in April 2019 two scholars published a review that synthesized over 70 reports of insect decline from around the world, and predicted mass insect extinctions within a human lifetime. They took a alarmist tone, and have been widely criticized for exaggerating their conclusions and selecting studies to review with the word “decline.”

Nonetheless, these researchers had no trouble finding studies to include in their review. Many scientists are currently analyzing the roles that climate change, land use, chemical pesticides and other factors have played in reported declines in many insect species.

The Taylor’s checkerspot butterfly, once found throughout grasslands in the Pacific Northwest, was listed as endangered in 2013. The main cause is habitat loss, driven by development, tree encroachment and spread of invasive plants. USFWS/Ted Thomas, CC BY

The end is not near

These discussions are important, but they don’t mean an insect apocalypse is under way. Predicting insect decline is hard to do without a lot of effort and data.

To predict an apocalypse, entomologists worldwide will need to conduct careful large-scale studies that involve collecting, identifying and counting many different insects. There are very few insects for which scientists have enough data now to reliably predict how many individuals there will be from year to year, let alone confidently chart a decline in each species. Most of the insects for which this information exists are species that are important for agricultural or human health, such as managed honey bees or mosquitoes.

And human actions are shifting balances between insect species. As an example, the mosquitoes that are best at spreading pathogens that cause disease have evolved to thrive near us. Entomologists call them anthropophilic, which means they love people.

That love extends to human impacts on the land. Insects that flutter from flower to flower won’t be happy when developers bulldoze a meadow and scatter tires around, but human-biting mosquitoes will be buzzing with excitement.

What else is out there?

Entomologists are uniformly concerned about the fate of insects in today’s changing world. But I believe the responsible approach is to push back on fire-and-brimstone rhetoric until detailed, large-scale studies are completed. Until then, these same gaps in our knowledge also make it hard to rule out that significant declines in diverse insects are happening. These gaps must be filled to illuminate challenges that insects face, from the inconvenient to the apocalyptic.

When the majority of insects remain to be described, it’s hard to value them. But here’s one example: Insecticide use in pear groves in China’s Sichuan Province has caused such a decline in native pollinators that beekeepers will not lend their bees to these orchards. These farmers are forced to pollinate their trees by hand – an expensive and time-consuming process if you aren’t an insect.

Similarly, native natural enemies played invisible roles in slowing the spread of the invasive brown marmorated stink bug when it was introduced into Pennsylvania in the 1990s. They included wasps that lay their eggs inside of stink bug eggs, and predatory insects and spiders that eat stink bugs eggs for breakfast.

Pollination and predation are just the start. Some insects could be sources of new drugs or traditional dyes, while others inspire artists or just provide little moments of inimitable beauty.

With so many unanswered questions, it’s clear that there is a need for more funding for biodiversity research. It is no coincidence that recent studies reporting massive insect declines came from a Long-Term Ecological Research center that is publicly funded through the National Science Foundation and from a carefully curated collection made and maintained by entomologists.

This kind of work requires money, bold foresight and dedication to science over long periods of time. But it can produce insights into how our world is changing – and that knowledge will help us prepare for the future.

By Brian Lovett, PhD Candidate, University of Maryland. This article is republished from The Conversation under a Creative Commons license. Read the original article.Top image credit: Chris Luczkow, CC BY

The Conversation Mon, 04/29/2019 - 10:19

Categories

Environment

from ScienceBlogs - Where the world discusses science http://bit.ly/2VyMmbU

The End Is Not Near, But If An 'Insect Apocalypse' Ever Happens, How Would We Know?

Insects scuttle, chew and fly through the world around us. Humans rely on them to pollinate plants, prey on insects that we don’t get along with, and to be movers and shakers for Earth’s ecosystems. It’s hard to imagine a world without insects.

That’s why news reports in recent months warning of an “insect apocalypse” sparked widespread alarm. These articles, which were based on long-term insect collections and a review of past studies, suggested that people alive today will witness the indiscriminate extinction of insect-kind.

I study fungi that can be used to control harmful insects, such as pests that damage crops and mosquitoes that transmit malaria. In my world, reports of mass insect die-offs are big news. But while there clearly is reason to be concerned about certain insects, such as the endangered rusty patched bumble bee or the American burying beetle, in my view it isn’t yet possible to predict a looming insect apocalypse.

More than 1 million insects have been discovered and named, but many millions have yet to be described. It’s undeniable that Earth is becoming increasingly inhospitable to some insects – but nightmarish conditions for one may be heaven to another.

Put another way, there is no perfect environment for all insects. And human impacts on the environment, like climate change and land development, very well may hurt beneficial insects and help harmful ones.

Insects account for 75% of all the known species on Earth. What makes them so successful?

Insect declines

Around the world, entomologists are looking wistfully into empty nets, and car owners are increasingly unsettled by their pristine windshields. It does not take decades of data collection and a degree to notice that in a human lifetime, our teeming world teems less.

The first study to set off alarms was published in 2017 by entomologists in Germany, who reported that over 27 years the biomass of flying insects in their traps had declined by 75%. Another study from the Luquillo Long Term Ecological Research program site in the Puerto Rican rainforest reproduced an insect survey from the 1970s. It found that the biomass of arthropods – a large group of organisms that includes insects – had declined 10- to 60-fold in that time, and that lizards, frogs and birds that ate arthropods had also declined.

Underscoring this theme, in April 2019 two scholars published a review that synthesized over 70 reports of insect decline from around the world, and predicted mass insect extinctions within a human lifetime. They took a alarmist tone, and have been widely criticized for exaggerating their conclusions and selecting studies to review with the word “decline.”

Nonetheless, these researchers had no trouble finding studies to include in their review. Many scientists are currently analyzing the roles that climate change, land use, chemical pesticides and other factors have played in reported declines in many insect species.

The Taylor’s checkerspot butterfly, once found throughout grasslands in the Pacific Northwest, was listed as endangered in 2013. The main cause is habitat loss, driven by development, tree encroachment and spread of invasive plants. USFWS/Ted Thomas, CC BY

The end is not near

These discussions are important, but they don’t mean an insect apocalypse is under way. Predicting insect decline is hard to do without a lot of effort and data.

To predict an apocalypse, entomologists worldwide will need to conduct careful large-scale studies that involve collecting, identifying and counting many different insects. There are very few insects for which scientists have enough data now to reliably predict how many individuals there will be from year to year, let alone confidently chart a decline in each species. Most of the insects for which this information exists are species that are important for agricultural or human health, such as managed honey bees or mosquitoes.

And human actions are shifting balances between insect species. As an example, the mosquitoes that are best at spreading pathogens that cause disease have evolved to thrive near us. Entomologists call them anthropophilic, which means they love people.

That love extends to human impacts on the land. Insects that flutter from flower to flower won’t be happy when developers bulldoze a meadow and scatter tires around, but human-biting mosquitoes will be buzzing with excitement.

What else is out there?

Entomologists are uniformly concerned about the fate of insects in today’s changing world. But I believe the responsible approach is to push back on fire-and-brimstone rhetoric until detailed, large-scale studies are completed. Until then, these same gaps in our knowledge also make it hard to rule out that significant declines in diverse insects are happening. These gaps must be filled to illuminate challenges that insects face, from the inconvenient to the apocalyptic.

When the majority of insects remain to be described, it’s hard to value them. But here’s one example: Insecticide use in pear groves in China’s Sichuan Province has caused such a decline in native pollinators that beekeepers will not lend their bees to these orchards. These farmers are forced to pollinate their trees by hand – an expensive and time-consuming process if you aren’t an insect.

Similarly, native natural enemies played invisible roles in slowing the spread of the invasive brown marmorated stink bug when it was introduced into Pennsylvania in the 1990s. They included wasps that lay their eggs inside of stink bug eggs, and predatory insects and spiders that eat stink bugs eggs for breakfast.

Pollination and predation are just the start. Some insects could be sources of new drugs or traditional dyes, while others inspire artists or just provide little moments of inimitable beauty.

With so many unanswered questions, it’s clear that there is a need for more funding for biodiversity research. It is no coincidence that recent studies reporting massive insect declines came from a Long-Term Ecological Research center that is publicly funded through the National Science Foundation and from a carefully curated collection made and maintained by entomologists.

This kind of work requires money, bold foresight and dedication to science over long periods of time. But it can produce insights into how our world is changing – and that knowledge will help us prepare for the future.

By Brian Lovett, PhD Candidate, University of Maryland. This article is republished from The Conversation under a Creative Commons license. Read the original article.Top image credit: Chris Luczkow, CC BY

The Conversation Mon, 04/29/2019 - 10:19

Categories

Environment

from ScienceBlogs - Where the world discusses science http://bit.ly/2VyMmbU

You saw the 1st photo of a black hole? Now see its home galaxy

The 1st direct black hole photo came from a galaxy known as Messier 87. Here’s the galaxy’s image from the Spitzer Space Telescope, an infrared telescope launched in 2003 and still operating as of 2019. You can’t see the hole itself in this image, but you can see 2 massive jets of material (and their aftershocks), ejected from the disk of material rotating around the hole. Image via NASA/JPL-Caltech/IPAC.

Earlier this month, scientists unveiled the first-ever photo taken of a black hole. It was a phenomenal achievement, and that image of the hot, glowing donut-shaped ring of gas and dust – surrounding the black hole itself, which can’t be seen – will go down in history as one of the most epic photos in space science. You can thank the Event Horizon Telescope for this first black hole image; this international group worked for years to accomplish it. Now … want some context for the black hole image? The first several images on this page let us step back a bit, to see how the giant black hole – 6.5 billion times more massive than our sun – appears in relation to its host galaxy, Messier 87 (aka M87). It’s a great view!

NASA released the image above – from its orbiting Spitzer Space Telescope – on April 25, 2019. It shows the black hole’s galaxy in the infrared. Although neither the black hole nor its event horizon can be seen here, you can see two massive jets of material being ejected from the event horizon out into space at nearly the speed of light, just one indication of the power of the central black hole. You thought black holes suck in material with gravity so strong that even light can’t escape? That’s true. But other material can become trapped in the disk around a black hole’s event horizon, and later be ejected again back out into deep space.

M87 is very far away – 55 million light-years away from Earth – and has been studied for over 100 years, including by observatories such as the Hubble Space Telescope, the Chandra X-ray Observatory and NuSTAR. The jets were first seen back in 1918, although their connection to a giant black hole was completely unknown at the time. The jets were first noticed by astronomer Heber Curtis as “a curious straight ray” extending from the center of the galaxy. What was this odd feature?

Another version of the first image, also showing the location of the black hole between the two jets. Image via NASA/JPL-Caltech/IPAC/Event Horizon Telescope. Larger versions of these images, including wallpaper, are available via JPL.

Now, we know that the jets are composed of high-energy material that shoots out of a disk of material that spins rapidly around the black hole. The ejected material moves at incredible speed – almost the speed of light – and can be seen in visible light, infrared light, radio waves and X-rays.

One of the jets is quite prominent, but when the material in it hits the much sparser material in the interstellar medium (the space between the stars of the galaxy), it creates a huge shockwave that is even more visible. The shockwave can only be seen in infrared light and radio waves. This jet is moving almost directly toward Earth, which increases its apparent brightness. We can still see some of the length of the jet, however, since it is slightly offset from our line of sight. At one point, it looks like the jet curves downward a bit; according to scientists, this is where particles in the jet hit gas particles in the interstellar medium and slow down a little.

The image that captured people’s imaginations earlier this month – the first real photo of a giant black hole, in the center of galaxy M87. The dark region in the middle isn’t actually the black hole itself, but rather the shadow of the black hole on the bright ring of material. The black hole itself is smaller than the shadow and can’t be seen directly. The bright ring forms as light is bent around the black hole by the intense gravity. Image via Event Horizon Telescope.

The other jet is much fainter, since it is moving away from Earth, and just as fast as the other jet. This makes it virtually invisible in all wavelengths. But as with the first jet, the shockwave – which looks like an inverted letter C – is still clearly visible.

Understanding black holes has been a great challenge for astronomers and physicists over the past few decades, but they’ve been making great strides towards that goal. Once considered to be “exotic,” and still among the strangest objects ever discovered, supermassive black holes are now known to be located in the centers of many (if not most) galaxies, including our own, and an untold number of smaller black holes dot the universe. Studying black holes in the context of their galaxies – and having the ability to image them directly – are major steps towards understanding one of these incredible and bizarre phenomena.

Here’s a classic photo of the galaxy M87, from the Hubble Space Telescope. This image is a composite of visible and infrared observations, and shows the galaxy’s prominent blue plasma jet, streaming from the central black hole at nearly the speed of light. Image via NASA.

Close-up on M87’s jet. It stretches 1,500 parsecs (5,000 light-years) from the galaxy’s core. In this Hubble image, the blue jet contrasts with the yellow glow from the combined light of billions of unresolved stars and the point-like clusters of stars that make up this galaxy. Image via Wikimedia Commons.

Star chart showing M87 on the sky’s dome, via Stellarium/NASA. This chart represents the view from mid-northern latitudes around 10 p.m. in May. Want to get oriented? Find the stars Arcturus and Spica.

Bottom line: Astronomers have released some new images (first two images on this page) of the galaxy M87, home galaxy to the giant black hole whose image you saw a few weeks ago. The images show you the black hole in the context of its galaxy.

Via Jet Propulsion Laboratory

from EarthSky http://bit.ly/2Vy5cjj

The 1st direct black hole photo came from a galaxy known as Messier 87. Here’s the galaxy’s image from the Spitzer Space Telescope, an infrared telescope launched in 2003 and still operating as of 2019. You can’t see the hole itself in this image, but you can see 2 massive jets of material (and their aftershocks), ejected from the disk of material rotating around the hole. Image via NASA/JPL-Caltech/IPAC.

Earlier this month, scientists unveiled the first-ever photo taken of a black hole. It was a phenomenal achievement, and that image of the hot, glowing donut-shaped ring of gas and dust – surrounding the black hole itself, which can’t be seen – will go down in history as one of the most epic photos in space science. You can thank the Event Horizon Telescope for this first black hole image; this international group worked for years to accomplish it. Now … want some context for the black hole image? The first several images on this page let us step back a bit, to see how the giant black hole – 6.5 billion times more massive than our sun – appears in relation to its host galaxy, Messier 87 (aka M87). It’s a great view!

NASA released the image above – from its orbiting Spitzer Space Telescope – on April 25, 2019. It shows the black hole’s galaxy in the infrared. Although neither the black hole nor its event horizon can be seen here, you can see two massive jets of material being ejected from the event horizon out into space at nearly the speed of light, just one indication of the power of the central black hole. You thought black holes suck in material with gravity so strong that even light can’t escape? That’s true. But other material can become trapped in the disk around a black hole’s event horizon, and later be ejected again back out into deep space.

M87 is very far away – 55 million light-years away from Earth – and has been studied for over 100 years, including by observatories such as the Hubble Space Telescope, the Chandra X-ray Observatory and NuSTAR. The jets were first seen back in 1918, although their connection to a giant black hole was completely unknown at the time. The jets were first noticed by astronomer Heber Curtis as “a curious straight ray” extending from the center of the galaxy. What was this odd feature?

Another version of the first image, also showing the location of the black hole between the two jets. Image via NASA/JPL-Caltech/IPAC/Event Horizon Telescope. Larger versions of these images, including wallpaper, are available via JPL.

Now, we know that the jets are composed of high-energy material that shoots out of a disk of material that spins rapidly around the black hole. The ejected material moves at incredible speed – almost the speed of light – and can be seen in visible light, infrared light, radio waves and X-rays.

One of the jets is quite prominent, but when the material in it hits the much sparser material in the interstellar medium (the space between the stars of the galaxy), it creates a huge shockwave that is even more visible. The shockwave can only be seen in infrared light and radio waves. This jet is moving almost directly toward Earth, which increases its apparent brightness. We can still see some of the length of the jet, however, since it is slightly offset from our line of sight. At one point, it looks like the jet curves downward a bit; according to scientists, this is where particles in the jet hit gas particles in the interstellar medium and slow down a little.

The image that captured people’s imaginations earlier this month – the first real photo of a giant black hole, in the center of galaxy M87. The dark region in the middle isn’t actually the black hole itself, but rather the shadow of the black hole on the bright ring of material. The black hole itself is smaller than the shadow and can’t be seen directly. The bright ring forms as light is bent around the black hole by the intense gravity. Image via Event Horizon Telescope.

The other jet is much fainter, since it is moving away from Earth, and just as fast as the other jet. This makes it virtually invisible in all wavelengths. But as with the first jet, the shockwave – which looks like an inverted letter C – is still clearly visible.

Understanding black holes has been a great challenge for astronomers and physicists over the past few decades, but they’ve been making great strides towards that goal. Once considered to be “exotic,” and still among the strangest objects ever discovered, supermassive black holes are now known to be located in the centers of many (if not most) galaxies, including our own, and an untold number of smaller black holes dot the universe. Studying black holes in the context of their galaxies – and having the ability to image them directly – are major steps towards understanding one of these incredible and bizarre phenomena.

Here’s a classic photo of the galaxy M87, from the Hubble Space Telescope. This image is a composite of visible and infrared observations, and shows the galaxy’s prominent blue plasma jet, streaming from the central black hole at nearly the speed of light. Image via NASA.

Close-up on M87’s jet. It stretches 1,500 parsecs (5,000 light-years) from the galaxy’s core. In this Hubble image, the blue jet contrasts with the yellow glow from the combined light of billions of unresolved stars and the point-like clusters of stars that make up this galaxy. Image via Wikimedia Commons.

Star chart showing M87 on the sky’s dome, via Stellarium/NASA. This chart represents the view from mid-northern latitudes around 10 p.m. in May. Want to get oriented? Find the stars Arcturus and Spica.

Bottom line: Astronomers have released some new images (first two images on this page) of the galaxy M87, home galaxy to the giant black hole whose image you saw a few weeks ago. The images show you the black hole in the context of its galaxy.

Via Jet Propulsion Laboratory

from EarthSky http://bit.ly/2Vy5cjj

All you need to know: Eta Aquariid meteors

The 2013 Eta Aquariid meteor shower was fantastic as viewed from Earth’s Southern Hemisphere. Colin Legg of Australia created this composite of his experience. He wrote, “Composite of approximately 50 images containing 26 meteors, meteor train, 17% moon, zodiacal light and Pilbara desert.”

In 2019, the forecast calls for the greatest number of Eta Aquariid meteors to fall before dawn on (or near) May 5. However, this shower has a rather broad maximum, so the day before or after may be just as good. Fortunately, the new moon on May 4 will provide inky black skies for this year’s Eta Aquariid meteor shower. This shower favors the Southern Hemisphere, ranking as one of the finest showers of the year – in a year when no moon obscures the show. At mid-northern latitudes, these meteors don’t fall so abundantly – and the early morning twilight interferes at northerly latitudes.

Why more Eta Aquariid meteors in the Southern Hemisphere?

Halley’s Comet is the source of the Eta Aquariid meteor shower.

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Meteor captured over Mount Bromo, an active volcano in Indonesia, during the 2013 Eta Aquariid shower. Photo by Justin Ng of Singapore. See more photos by Justin Ng.

When and how should I watch the Eta Aquariids? The 2019 Eta Aquariid meteor shower is expected to produce the greatest number of meteors in the wee hours before dawn on May 5. However, the broad peak of the Eta Aquariid shower may present a decent showing of meteors during the predawn hours on May 4 and May 6, too. And in fact the shower extends much beyond these dates on either side. Writing for the International Meteor Organization on May 1, 2017, Robert Lunsford pointed out:

… There is no sharp peak for this shower, but rather a plateau of good rates that last approximately one week centered on May 6.

In general, the best time to watch these fast and often bright meteors is in the early morning hours, before the onset of morning twilight. Don’t know when twilight begins in your part of the world? Try this link and remember to check the astronomical twilight box.

Give yourself at least an hour of viewing time for watching any meteor shower. Meteors tend to come in spurts that are interspersed by lulls. Also, it can take as long as 20 minutes for your eyes to adapt to the dark.

You need no special equipment to watch a meteor shower, but a little luck always helps. Meteor watching is a lot like fishing. Sometimes you catch a good number of them and sometimes you don’t.

Radiant point of Eta Aquariid meteor shower. It’s in the constellation Aquarius, in the southeast before dawn on May mornings, as seen from mid-northern latitudes.

A Y-shaped asterism called the Water Jar marks the radiant of the Eta Aquariid meteor shower. It’s noticeable, if your sky is dark.

Radiant point of the Eta Aquariid shower. If you trace the paths of the Eta Aquariid meteors backward, they all seem to radiate from a certain point in front of the constellation Aquarius the Water Bearer. This point on the sky’s dome is called the radiant of the meteor shower, which nearly aligns with the faint star Eta Aquarii. Hence, this meteor shower is named in honor of this star.

Eta Aquarii is one of the four stars making up the Y-shaped Water Jar asterism in the northern part of Aquarius. If you can find the Water Jar in the constellation Aquarius, you’ve as good as located the radiant point for the Eta Aquariid meteors. The alignment of the radiant and the star is of course coincidental. Eta Aquarii is some 170 light-years away – trillons upon trillions of miles away – while the Eta Aquariid meteors burn up about 60 miles (100 km) above Earth’s surface.

Meteor shower radiants are sometimes misunderstood by casual meteor-watchers. You don’t need to know where they are to watch a meteor shower. That’s because the meteors fly every which way across the sky, in front of numerous constellations. However, the higher a shower’s radiant appears in your sky, the more meteors you’re likely to see. For the Eta Aquariids, the radiant soars highest in the nighttime sky just before dawn. That’s why you can expect to see the most meteors in the wee morning hours.

You can see some Eta Aquariid meteors in late evening, before the radiant rises into your sky. In fact, late evening is the best time to see earthgrazers, meteors that make exceptionally long streaks across your sky. As the radiant rises higher – that is, as the hours of the night tick away to dawn – you’ll see shorter meteors, but more meteors.

No special equipment is needed to watch a meteor shower. Find a dark, open sky away from artificial lights, and sprawl out on a reclining lawn chair.

How many meteors should I expect to see? In a dark sky, especially at more southerly latitudes, the Eta Aquariids can produce up to 20 to 40 meteors per hour. From mid-northern latitudes, you might only see about 10 meteors per hour.

Halley’s Comet, the parent of the May Eta Aquariid and October Orionid meteor showers. Image vuia NASA Blueshift. Dust from this comet will streak the nighttime as Eta Aquariid meteors on the mornings of May 5 and 6.

Halley’s Comet is the source of the Eta Aquariid meteor shower. Every year, our planet Earth crosses the orbital path of Halley’s Comet in late April and May, so bits and pieces from this comet light up the nighttime as Eta Aquariid meteors. This shower is said to be active from April 19 to May 20, although Earth plows most deeply into this stream of comet debris around May 5 or 6.

The comet dust smashes into Earth’s upper atmosphere at nearly 150,000 miles per hour (240,000 kilometers per hour). Roughly half of these swift-moving meteors leave persistent trains – ionized gas trails that glow for a few seconds after the meteor has passed.

Our planet also crosses the orbital path of Halley’s Comet at the other end of the year, giving rise to the Orionid meteor shower, which is usually at its best in the predawn hours on or near October 21.

Bottom line: What’s a good meteor shower for the Southern Hemisphere? It’s usually the Eta Aquariid shower on the mornings of May 5 and 6. This year, 2019, the new moon on May 4 guarantees dark skies for this year’s presentation.

EarthSky’s meteor shower guide for 2019

from EarthSky http://bit.ly/1pRgiL8

The 2013 Eta Aquariid meteor shower was fantastic as viewed from Earth’s Southern Hemisphere. Colin Legg of Australia created this composite of his experience. He wrote, “Composite of approximately 50 images containing 26 meteors, meteor train, 17% moon, zodiacal light and Pilbara desert.”

In 2019, the forecast calls for the greatest number of Eta Aquariid meteors to fall before dawn on (or near) May 5. However, this shower has a rather broad maximum, so the day before or after may be just as good. Fortunately, the new moon on May 4 will provide inky black skies for this year’s Eta Aquariid meteor shower. This shower favors the Southern Hemisphere, ranking as one of the finest showers of the year – in a year when no moon obscures the show. At mid-northern latitudes, these meteors don’t fall so abundantly – and the early morning twilight interferes at northerly latitudes.

Why more Eta Aquariid meteors in the Southern Hemisphere?

Halley’s Comet is the source of the Eta Aquariid meteor shower.

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Meteor captured over Mount Bromo, an active volcano in Indonesia, during the 2013 Eta Aquariid shower. Photo by Justin Ng of Singapore. See more photos by Justin Ng.

When and how should I watch the Eta Aquariids? The 2019 Eta Aquariid meteor shower is expected to produce the greatest number of meteors in the wee hours before dawn on May 5. However, the broad peak of the Eta Aquariid shower may present a decent showing of meteors during the predawn hours on May 4 and May 6, too. And in fact the shower extends much beyond these dates on either side. Writing for the International Meteor Organization on May 1, 2017, Robert Lunsford pointed out:

… There is no sharp peak for this shower, but rather a plateau of good rates that last approximately one week centered on May 6.

In general, the best time to watch these fast and often bright meteors is in the early morning hours, before the onset of morning twilight. Don’t know when twilight begins in your part of the world? Try this link and remember to check the astronomical twilight box.

Give yourself at least an hour of viewing time for watching any meteor shower. Meteors tend to come in spurts that are interspersed by lulls. Also, it can take as long as 20 minutes for your eyes to adapt to the dark.

You need no special equipment to watch a meteor shower, but a little luck always helps. Meteor watching is a lot like fishing. Sometimes you catch a good number of them and sometimes you don’t.

Radiant point of Eta Aquariid meteor shower. It’s in the constellation Aquarius, in the southeast before dawn on May mornings, as seen from mid-northern latitudes.

A Y-shaped asterism called the Water Jar marks the radiant of the Eta Aquariid meteor shower. It’s noticeable, if your sky is dark.

Radiant point of the Eta Aquariid shower. If you trace the paths of the Eta Aquariid meteors backward, they all seem to radiate from a certain point in front of the constellation Aquarius the Water Bearer. This point on the sky’s dome is called the radiant of the meteor shower, which nearly aligns with the faint star Eta Aquarii. Hence, this meteor shower is named in honor of this star.

Eta Aquarii is one of the four stars making up the Y-shaped Water Jar asterism in the northern part of Aquarius. If you can find the Water Jar in the constellation Aquarius, you’ve as good as located the radiant point for the Eta Aquariid meteors. The alignment of the radiant and the star is of course coincidental. Eta Aquarii is some 170 light-years away – trillons upon trillions of miles away – while the Eta Aquariid meteors burn up about 60 miles (100 km) above Earth’s surface.

Meteor shower radiants are sometimes misunderstood by casual meteor-watchers. You don’t need to know where they are to watch a meteor shower. That’s because the meteors fly every which way across the sky, in front of numerous constellations. However, the higher a shower’s radiant appears in your sky, the more meteors you’re likely to see. For the Eta Aquariids, the radiant soars highest in the nighttime sky just before dawn. That’s why you can expect to see the most meteors in the wee morning hours.

You can see some Eta Aquariid meteors in late evening, before the radiant rises into your sky. In fact, late evening is the best time to see earthgrazers, meteors that make exceptionally long streaks across your sky. As the radiant rises higher – that is, as the hours of the night tick away to dawn – you’ll see shorter meteors, but more meteors.

No special equipment is needed to watch a meteor shower. Find a dark, open sky away from artificial lights, and sprawl out on a reclining lawn chair.

How many meteors should I expect to see? In a dark sky, especially at more southerly latitudes, the Eta Aquariids can produce up to 20 to 40 meteors per hour. From mid-northern latitudes, you might only see about 10 meteors per hour.

Halley’s Comet, the parent of the May Eta Aquariid and October Orionid meteor showers. Image vuia NASA Blueshift. Dust from this comet will streak the nighttime as Eta Aquariid meteors on the mornings of May 5 and 6.

Halley’s Comet is the source of the Eta Aquariid meteor shower. Every year, our planet Earth crosses the orbital path of Halley’s Comet in late April and May, so bits and pieces from this comet light up the nighttime as Eta Aquariid meteors. This shower is said to be active from April 19 to May 20, although Earth plows most deeply into this stream of comet debris around May 5 or 6.

The comet dust smashes into Earth’s upper atmosphere at nearly 150,000 miles per hour (240,000 kilometers per hour). Roughly half of these swift-moving meteors leave persistent trains – ionized gas trails that glow for a few seconds after the meteor has passed.

Our planet also crosses the orbital path of Halley’s Comet at the other end of the year, giving rise to the Orionid meteor shower, which is usually at its best in the predawn hours on or near October 21.

Bottom line: What’s a good meteor shower for the Southern Hemisphere? It’s usually the Eta Aquariid shower on the mornings of May 5 and 6. This year, 2019, the new moon on May 4 guarantees dark skies for this year’s presentation.

EarthSky’s meteor shower guide for 2019

from EarthSky http://bit.ly/1pRgiL8

What’s on the far side of the moon?

The far side looks a lot like the near side. Image via NASA’s Scientific Visualization Studio.

By Wayne Schlingman, The Ohio State University

Looking up at the silvery orb of the moon, you might recognize familiar shadows and shapes on its face from one night to the next. You see the same view of the moon our early ancestors did as it lighted their way after sundown.

Only one side of the spherical moon is ever visible from Earth – it wasn’t until 1959 when the Soviet Spacecraft Luna 3 orbited the moon and sent pictures home that human beings were able to see the “far side” of the moon for the first time.

Comparison of humanity’s first glimpse of the lunar far side and the same view thanks to LRO data 50 years later. Image via NASA’s Goddard Space Flight Center Scientific Visualization Studio

A phenomenon called tidal locking is responsible for the consistent view. The Earth and its moon are in close proximity and thus exert significant gravitational forces on each other. These tidal forces slow the rotations of both bodies. They locked the moon’s rotation in sync with its orbital period relatively soon after it formed – as a product of a collision between a Mars-sized object and the proto-Earth, 100 million years after the solar system coalesced.

The moon’s orbital period and rotational period are the same length of time.

Now the moon takes one trip around the Earth in the same amount of time it takes to make one rotation around its own axis: about 28 days. From Earth, we always see the same face of the moon; from the moon, the Earth stands still in the sky.

The near side of the moon is well studied because we can see it. The astronauts landed on the near side of the moon so they could communicate with NASA here on Earth. All of the samples from the Apollo missions are from the near side.

Buzz Aldrin descends from the lunar module to the surface of the moon on July 20, 1969. Image via NASA.

Although the far side of the moon isn’t visible from our vantage point, and with all due respect to Pink Floyd, it is not accurate to call it the dark side of the moon. All sides of the moon experience night and day just like we do here on Earth. All sides have equal amounts of day and night over the course of a single month. A lunar day lasts about two Earth weeks.

With modern satellites, astronomers have completely mapped the lunar surface. A Chinese mission, Chang’e 4, is currently exploring the Aitken Basin on the far side of the moon — the first such mission ever landed there. Researchers hope Chang’e 4 will help answer questions about the crater’s surface features and test whether things can grow in lunar soil. A privately funded Israeli mission, Beresheet, started as a mission to compete for the Google Lunar X Prize. Despite crashing during an attempted landing earlier this month, the Beresheet team still won the Moon Shot Award.

Being shielded from civilization means the far side of the moon is “radio dark.” There, researchers can measure weak signals from the universe that would otherwise be drowned out. Chang’e 4, for instance, will be able to observe low-frequency radio light coming from the sun or beyond that’s impossible to detect here on the Earth due to human activity, such as TV and radio broadcasts and other forms of communication signals. Low-frequency radio peers back in time to the very first stars and the very first black holes, giving astronomers a greater understanding of how the structures of the universe began forming.

Arrows indicate position of Chang’e 4 lander on the floor of the moon’s Von Kármán crater. The sharp crater behind and to the left of the landing site is 12,800 feet (3,900 meters) across and 1,970 feet (600 meters) deep. Image via NASA/GSFC/Arizona State University.

Rover missions also investigate all sides of the moon as space scientists prepare for future human missions, looking to the moon’s resources to help humanity get to Mars. For instance, water – discovered by NASA’s LCROSS satellite beneath the moon’s north and south poles in 2009 – can be broken up into hydrogen and oxygen and used for fuel and breathing.

Researchers are getting closer to exploring the moon’s polar craters, some of which have never seen the light of day – literally. They are deep and in just the right place to never have the sun shine onto the crater floor. There are certainly dark parts of the moon, but the whole far side isn’t one of them.

Wayne Schlingman, Director of the Arne Slettebak Planetarium, The Ohio State University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Bottom line: What is on the far side of the moon?

from EarthSky http://bit.ly/2Lethb8

The far side looks a lot like the near side. Image via NASA’s Scientific Visualization Studio.

By Wayne Schlingman, The Ohio State University

Looking up at the silvery orb of the moon, you might recognize familiar shadows and shapes on its face from one night to the next. You see the same view of the moon our early ancestors did as it lighted their way after sundown.

Only one side of the spherical moon is ever visible from Earth – it wasn’t until 1959 when the Soviet Spacecraft Luna 3 orbited the moon and sent pictures home that human beings were able to see the “far side” of the moon for the first time.

Comparison of humanity’s first glimpse of the lunar far side and the same view thanks to LRO data 50 years later. Image via NASA’s Goddard Space Flight Center Scientific Visualization Studio

A phenomenon called tidal locking is responsible for the consistent view. The Earth and its moon are in close proximity and thus exert significant gravitational forces on each other. These tidal forces slow the rotations of both bodies. They locked the moon’s rotation in sync with its orbital period relatively soon after it formed – as a product of a collision between a Mars-sized object and the proto-Earth, 100 million years after the solar system coalesced.

The moon’s orbital period and rotational period are the same length of time.

Now the moon takes one trip around the Earth in the same amount of time it takes to make one rotation around its own axis: about 28 days. From Earth, we always see the same face of the moon; from the moon, the Earth stands still in the sky.

The near side of the moon is well studied because we can see it. The astronauts landed on the near side of the moon so they could communicate with NASA here on Earth. All of the samples from the Apollo missions are from the near side.

Buzz Aldrin descends from the lunar module to the surface of the moon on July 20, 1969. Image via NASA.

Although the far side of the moon isn’t visible from our vantage point, and with all due respect to Pink Floyd, it is not accurate to call it the dark side of the moon. All sides of the moon experience night and day just like we do here on Earth. All sides have equal amounts of day and night over the course of a single month. A lunar day lasts about two Earth weeks.

With modern satellites, astronomers have completely mapped the lunar surface. A Chinese mission, Chang’e 4, is currently exploring the Aitken Basin on the far side of the moon — the first such mission ever landed there. Researchers hope Chang’e 4 will help answer questions about the crater’s surface features and test whether things can grow in lunar soil. A privately funded Israeli mission, Beresheet, started as a mission to compete for the Google Lunar X Prize. Despite crashing during an attempted landing earlier this month, the Beresheet team still won the Moon Shot Award.

Being shielded from civilization means the far side of the moon is “radio dark.” There, researchers can measure weak signals from the universe that would otherwise be drowned out. Chang’e 4, for instance, will be able to observe low-frequency radio light coming from the sun or beyond that’s impossible to detect here on the Earth due to human activity, such as TV and radio broadcasts and other forms of communication signals. Low-frequency radio peers back in time to the very first stars and the very first black holes, giving astronomers a greater understanding of how the structures of the universe began forming.

Arrows indicate position of Chang’e 4 lander on the floor of the moon’s Von Kármán crater. The sharp crater behind and to the left of the landing site is 12,800 feet (3,900 meters) across and 1,970 feet (600 meters) deep. Image via NASA/GSFC/Arizona State University.

Rover missions also investigate all sides of the moon as space scientists prepare for future human missions, looking to the moon’s resources to help humanity get to Mars. For instance, water – discovered by NASA’s LCROSS satellite beneath the moon’s north and south poles in 2009 – can be broken up into hydrogen and oxygen and used for fuel and breathing.

Researchers are getting closer to exploring the moon’s polar craters, some of which have never seen the light of day – literally. They are deep and in just the right place to never have the sun shine onto the crater floor. There are certainly dark parts of the moon, but the whole far side isn’t one of them.

Wayne Schlingman, Director of the Arne Slettebak Planetarium, The Ohio State University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Bottom line: What is on the far side of the moon?

from EarthSky http://bit.ly/2Lethb8