September 2020 guide to the bright planets

Click the name of a planet to learn more about its visibility in September 2020: Jupiter, Saturn, Mars, Venus, Mercury

Try Stellarium for a precise view of the planets from your location.

Want precise planet rise and set times? Click here for recommended almanacs

Don’t miss the moon’s sweep past the red planet Mars on September 4, 5 and 6, 2020. Earth will pass between Mars and the sun in October, and, for a month or so, Mars will be even brighter than Jupiter. Mars is the planet to watch this month and next! Read more.

Watch for the waning crescent moon to shine in the vicinity of the brightest planet, Venus, before sunrise on September 13, 14 and 15, 2020. Read more.

Look for the waxing gibbous moon near the planets Jupiter and Saturn for several days, centered around September 24 and 25, 2020. Read more.

This chart is for the Southern Hemisphere, where people will enjoy the best evening apparition of Mercury for the year in September 2020. As seen from the Northern Hemisphere, Mercury will be deeply submerged in evening twilight and hard to see. Read more.

In late September and early October 2020, the Northern Hemisphere’s Harvest Moon shines in the vicinity of the brilliant red planet Mars! Read more.

Jupiter and Saturn are the planets to watch as darkness falls in September 2020. They are near one another on the sky’s dome, with Saturn following Jupiter westward across the sky from dusk/nightfall until well after midnight. A few months ago, in July 2020, these gas giant worlds, Jupiter and Saturn, reached their yearly opposition.

Earth – in its yearly orbit – swung between these outer worlds and the sun in July 2020. Thus we were closest to Jupiter and Saturn for the year in July. Jupiter and Saturn, in turn, shone at their brightest best and were out all night long.

Read more: Jupiter at opposition on July 13-14

Read more: Saturn at opposition on July 20

Jupiter and Saturn climb highest up for the night at early evening in early September, and at nightfall by the month’s end. Read more.

In some respects, though, September gives us a better month than July or August for viewing Jupiter and Saturn. That’s because these two worlds remain bright and beautiful throughout September, yet appear highest up for the night right around nightfall.

That’s good news for people with telescopes who don’t want to stay up late. It’s quite convenient to have Jupiter and Saturn highest up for the night as soon as darkness falls. Typically, the view of Jupiter’s four major moons and Saturn’s glorious rings through the telescope is sharper when these worlds are higher up than lower down. The thickness of the Earth’s atmosphere near the horizon tends to blur the view of Jupiter’s moon and Saturn’s rings.

Positions of Jupiter’s moons via Sky & Telescope

Look first for brilliant Jupiter; Saturn is the bright object immediately to Jupiter’s east. Although Saturn is easily as bright as a 1st-magnitude star – as bright as the brightest stars in our sky – the ringed planet can’t compete with the the king planet Jupiter, which outshines Saturn by some 14 times. After all, Jupiter ranks as the fourth brightest celestial object, after the sun, the moon and the planet Venus, respectively.

For the first time since the year 2000, Jupiter and Saturn will showcase their great conjunction in December 2020, for the closest Jupiter-Saturn conjunction since the year 1623. Astronomers use the word conjunction to describe meetings of planets and other objects on our sky’s dome. They use the term great conjunction to describe a meeting of the king planet Jupiter and golden Saturn. The last great Jupiter-Saturn conjunction was May 28, 2000. The next one will be December 21, 2020. But September 2020 presents a fine time to start watching these worlds.

Read more: Before 2020 ends, a great conjunction for Jupiter and Saturn

Watch for the moon in the neighborhood of Jupiter and Saturn for several days, centered on or near September 24.

Mars rises over your eastern horizon by early-to-mid evening, and is coming up earlier daily, heading for its own opposition on October 13, 2020. At that wondrous time, Mars will actually supplant Jupiter as the sky’s fourth-brightest celestial body, after the sun, moon, and the planet Venus. That will be something to see!

In September 2020, you’ll find Mars heading toward that dramatic brightening. This month, Mars is respectably bright, more brilliant even than a 1st-magnitude star, or one of the sky’s brightest stars. Earth is now rushing along in its smaller, faster orbit, gaining on Mars, the fourth planet outward from the sun. Throughout September and the first half of October, watch for Mars to brighten dramatically as Earth closes in on Mars, passing between it and the sun on October 13, 2020.

Around the world, Mars rises about 9 p.m. (10 p.m. daylight saving time) in early September. By the month’s end, Mars will be up around 7 p.m. (8 p.m. daylight saving time).

Let the waning moon help guide your eye to Mars for several days, centered on or near September 5.

View at EarthSky Community Photos. | From Paul Armstrong, who took this photo of Mars, Saturn and Jupiter on the morning of April 15, 2020, from Exmoor, U.K. Jupiter is at the upper right, Mars at center left, with Saturn between them. In May 2020, Jupiter and Saturn were closer together, whereas Mars was farther away from Jupiter and Saturn. Thanks, Paul!

Venus – the brightest planet – reached its greatest elongation from the sun in the morning sky on August 12 or 13 (depending upon your time zone). But dazzling Venus will remain bright and beautiful as a morning “star” for the rest of this year.

At mid-northern latitudes, Venus rises about 3 1/2 hours before the sun throughout September.

At and near the equator, Venus rises 3 hours before the sun in early September, decreasing to 2 1/2 hours near the month’s end.

At temperate latitudes in the Southern Hemisphere, Venus rises about 2 1/2 hours before the sun in early September, tapering to 1 3/4 hours by the month’s end.

Inferior conjunction – when Venus sweeps between the sun and Earth – happened on June 3, 2020. Some 10 weeks later, Venus reached its greatest elongation in the morning sky on August 13, 2020 (when its disk was about 50% illuminated by sunshine). In September 2020, Venus will start the month about 60% illuminated and then end the month about 71% illuminated. Image via UCLA.

Throughout September, Venus in its faster orbit around the sun will be going farther and farther away from Earth. As viewed through the telescope, Venus’ waxing gibbous phase will widen, yet its overall disk size will shrink. Venus’ disk is 60% illuminated in early September, and 71% illuminated by the month’s end; Venus’ angular diameter, on the other hand, will shrink to 80% of its initial size by late September.

Watch for the waning crescent moon to shine with Venus in the morning sky for several days, centered on or near September 14.

Mercury is an evening planet all month long, though only nominally so at northerly latitudes. September 2020 showcases the best evening apparition of Mercury for the year in the Southern Hemisphere. Mercury will be a whopping 25 degrees east of the sun from September 26 till October 7, 2020. and at its greatest elongation on October 1.

Read more: Mercury in the west after sunset

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: September 2020 presents 4 of the 5 bright solar system planets in the evening sky (Mercury only nominally so at northerly latitudes). Catch Jupiter and Saturn at nightfall, Mars at early evening, and Venus in the predawn/dawn 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.

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 September 2020: Jupiter, Saturn, Mars, Venus, Mercury

Try Stellarium for a precise view of the planets from your location.

Want precise planet rise and set times? Click here for recommended almanacs

Don’t miss the moon’s sweep past the red planet Mars on September 4, 5 and 6, 2020. Earth will pass between Mars and the sun in October, and, for a month or so, Mars will be even brighter than Jupiter. Mars is the planet to watch this month and next! Read more.

Watch for the waning crescent moon to shine in the vicinity of the brightest planet, Venus, before sunrise on September 13, 14 and 15, 2020. Read more.

Look for the waxing gibbous moon near the planets Jupiter and Saturn for several days, centered around September 24 and 25, 2020. Read more.

This chart is for the Southern Hemisphere, where people will enjoy the best evening apparition of Mercury for the year in September 2020. As seen from the Northern Hemisphere, Mercury will be deeply submerged in evening twilight and hard to see. Read more.

In late September and early October 2020, the Northern Hemisphere’s Harvest Moon shines in the vicinity of the brilliant red planet Mars! Read more.

Jupiter and Saturn are the planets to watch as darkness falls in September 2020. They are near one another on the sky’s dome, with Saturn following Jupiter westward across the sky from dusk/nightfall until well after midnight. A few months ago, in July 2020, these gas giant worlds, Jupiter and Saturn, reached their yearly opposition.

Earth – in its yearly orbit – swung between these outer worlds and the sun in July 2020. Thus we were closest to Jupiter and Saturn for the year in July. Jupiter and Saturn, in turn, shone at their brightest best and were out all night long.

Read more: Jupiter at opposition on July 13-14

Read more: Saturn at opposition on July 20

Jupiter and Saturn climb highest up for the night at early evening in early September, and at nightfall by the month’s end. Read more.

In some respects, though, September gives us a better month than July or August for viewing Jupiter and Saturn. That’s because these two worlds remain bright and beautiful throughout September, yet appear highest up for the night right around nightfall.

That’s good news for people with telescopes who don’t want to stay up late. It’s quite convenient to have Jupiter and Saturn highest up for the night as soon as darkness falls. Typically, the view of Jupiter’s four major moons and Saturn’s glorious rings through the telescope is sharper when these worlds are higher up than lower down. The thickness of the Earth’s atmosphere near the horizon tends to blur the view of Jupiter’s moon and Saturn’s rings.

Positions of Jupiter’s moons via Sky & Telescope

Look first for brilliant Jupiter; Saturn is the bright object immediately to Jupiter’s east. Although Saturn is easily as bright as a 1st-magnitude star – as bright as the brightest stars in our sky – the ringed planet can’t compete with the the king planet Jupiter, which outshines Saturn by some 14 times. After all, Jupiter ranks as the fourth brightest celestial object, after the sun, the moon and the planet Venus, respectively.

For the first time since the year 2000, Jupiter and Saturn will showcase their great conjunction in December 2020, for the closest Jupiter-Saturn conjunction since the year 1623. Astronomers use the word conjunction to describe meetings of planets and other objects on our sky’s dome. They use the term great conjunction to describe a meeting of the king planet Jupiter and golden Saturn. The last great Jupiter-Saturn conjunction was May 28, 2000. The next one will be December 21, 2020. But September 2020 presents a fine time to start watching these worlds.

Read more: Before 2020 ends, a great conjunction for Jupiter and Saturn

Watch for the moon in the neighborhood of Jupiter and Saturn for several days, centered on or near September 24.

Mars rises over your eastern horizon by early-to-mid evening, and is coming up earlier daily, heading for its own opposition on October 13, 2020. At that wondrous time, Mars will actually supplant Jupiter as the sky’s fourth-brightest celestial body, after the sun, moon, and the planet Venus. That will be something to see!

In September 2020, you’ll find Mars heading toward that dramatic brightening. This month, Mars is respectably bright, more brilliant even than a 1st-magnitude star, or one of the sky’s brightest stars. Earth is now rushing along in its smaller, faster orbit, gaining on Mars, the fourth planet outward from the sun. Throughout September and the first half of October, watch for Mars to brighten dramatically as Earth closes in on Mars, passing between it and the sun on October 13, 2020.

Around the world, Mars rises about 9 p.m. (10 p.m. daylight saving time) in early September. By the month’s end, Mars will be up around 7 p.m. (8 p.m. daylight saving time).

Let the waning moon help guide your eye to Mars for several days, centered on or near September 5.

View at EarthSky Community Photos. | From Paul Armstrong, who took this photo of Mars, Saturn and Jupiter on the morning of April 15, 2020, from Exmoor, U.K. Jupiter is at the upper right, Mars at center left, with Saturn between them. In May 2020, Jupiter and Saturn were closer together, whereas Mars was farther away from Jupiter and Saturn. Thanks, Paul!

Venus – the brightest planet – reached its greatest elongation from the sun in the morning sky on August 12 or 13 (depending upon your time zone). But dazzling Venus will remain bright and beautiful as a morning “star” for the rest of this year.

At mid-northern latitudes, Venus rises about 3 1/2 hours before the sun throughout September.

At and near the equator, Venus rises 3 hours before the sun in early September, decreasing to 2 1/2 hours near the month’s end.

At temperate latitudes in the Southern Hemisphere, Venus rises about 2 1/2 hours before the sun in early September, tapering to 1 3/4 hours by the month’s end.

Inferior conjunction – when Venus sweeps between the sun and Earth – happened on June 3, 2020. Some 10 weeks later, Venus reached its greatest elongation in the morning sky on August 13, 2020 (when its disk was about 50% illuminated by sunshine). In September 2020, Venus will start the month about 60% illuminated and then end the month about 71% illuminated. Image via UCLA.

Throughout September, Venus in its faster orbit around the sun will be going farther and farther away from Earth. As viewed through the telescope, Venus’ waxing gibbous phase will widen, yet its overall disk size will shrink. Venus’ disk is 60% illuminated in early September, and 71% illuminated by the month’s end; Venus’ angular diameter, on the other hand, will shrink to 80% of its initial size by late September.

Watch for the waning crescent moon to shine with Venus in the morning sky for several days, centered on or near September 14.

Mercury is an evening planet all month long, though only nominally so at northerly latitudes. September 2020 showcases the best evening apparition of Mercury for the year in the Southern Hemisphere. Mercury will be a whopping 25 degrees east of the sun from September 26 till October 7, 2020. and at its greatest elongation on October 1.

Read more: Mercury in the west after sunset

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: September 2020 presents 4 of the 5 bright solar system planets in the evening sky (Mercury only nominally so at northerly latitudes). Catch Jupiter and Saturn at nightfall, Mars at early evening, and Venus in the predawn/dawn 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.

Help EarthSky keep going! Donate now.

Post your planet photos at EarthSky Community Photos

from EarthSky https://ift.tt/1YD00CF

Asteroid 2011 ES4 will pass much closer than the moon on September 1

The orbit of asteroid 2011 ES4 (in white) is slightly similar to Earth’s (in blue) but inclined in relation to our planet’s orbit. The space rock completes an orbit around the sun every 416 days. It nearly intercepts our orbit on September 1, 2020, as seen in this illustration, via NASA/ JPL.

A healthy-sized chunk of space rock will pass closer than the moon on September 1, 2020. Although there is uncertainty in its orbit, scientists say it will not hit our planet. Asteroid 2011 ES4 is expected to pass at about 0.3 or 30% the Earth-moon distance. But it may pass farther, or as close as 0.19 lunar distances, since its orbit is still not completely defined. Our knowledge of this asteroid’s orbit might improve sometime today – or early tomorrow – if it is “recovered” via astronomers’ telescopes prior to closest approach.

The asteroid should pass closest around 16:12 UTC on September 1 (12:12 p.m. EDT; translate UTC to your time).

The asteroid has an estimated diameter of 72 to 161 feet (22 to 49 meters). That’s in the range of the Chelyabinsk meteor – around 17 meters (55 feet) in diameter – which swept through Earth’s atmosphere above Russia in February 2013, generating an enormous shock wave that broke windows in six Russian cities and caused some 1,500 people to seek medical treatment, mostly from flying glass.

Chelyabinsk meteor smoke trail, February 15, 2013. Image via Alex Alishevskikh., who caught it about a minute after the blast.

But back to asteroid 2011 ES4. The uncertainty about its orbit is due to the fact that observatories were able to track the space rock during only four days after it was detected on March 2, 2011, from the Mount Lemmon Survey in Arizona. After that, the asteroid became too faint to be observed.

Astronomers use an uncertainty scale from 0-9, in which 0 means the orbit is well known, and 9 means great uncertainty. Asteroid 2011 ES4 has an uncertainty of 7.  The uncertainty not only means it may pass farther or closer than expected, but also may cause it to occur a few hours earlier or later than expected.

Asteroid 2011 ES4 is classified as a Near-Earth Object (NEO). But it’s good to know that this Apollo-class asteroid is not classified as a Potentially Hazardous Asteroid. What’s the difference? A Potentially Hazardous Asteroid is defined as an object that passes relatively close to Earth, and also is large enough (more than 150 meters in diameter) to cause significant regional damage, were it to strike Earth.

Thus you may see that asteroid 2011 ES4 has the potential to come rather close. And it’s a healthy size, bigger, for example, than the tiny (truck-sized) asteroid that swept just 2,000 miles (3,000 km) from Earth on August 16, 2020. Yet – as asteroids go – asteroid 2011 ES4 is still relatively small, not large enough to cause significant damage upon impact (and it is not expected to get close enough to enter our atmosphere, much less impact).

So – to all of you worriers – you may all breathe easily now.

Location of the Apollo asteroids compared to the orbits of the terrestrial planets of our solar system. Image via Wikimedia Commons.

If an asteroid as big as 2011 ES4 were to hit our planet, it wouldn’t be big enough to cause a major impact, much less an extinction-level event. However, a space rock with an average size of 98 ft (30 meters) in diameter, like this one, could cause a huge shock wave if it enters our atmosphere.

Fortunately, even with the margin of errors in calculations, asteroid 2011 ES4 should safely pass by Earth on September 1, 2020.

If asteroid 2011 ES4 is detected in the next few hours or days, it may at first be confused with a “new” asteroid, and get a temporary or provisional designation before models show it definitely has the same trajectory, indicating it’s in fact asteroid 2011 ES4 being “recovered” in our skies. After new observations are made, astronomers may be able to better define the space rock’s orbit.

We may see many news about close passes of asteroids, but most of those are about small space rocks. We don’t have to worry, because if a small asteroid hits our atmosphere, most of the space rock will disintegrate, and since Earth is around 70% covered by oceans, most events will occur over water, probably even unnoticed.

What about any big asteroid approaching Earth? Although there are many small asteroids whose orbit crosses the orbit of Earth, fortunately, there is no known big space rock with a dangerous orbit which poses a threat to our planet.

As part of nature, there will be, however, lots of other significant approaches in the future, including asteroid Apophis on April 13, 2029. That will be an exciting opportunity for scientists. And even for casual observers, the close approach of Apophis will be an amazing event, as the space rock may even be slightly visible to the unaided eye from some areas.

Bottom line: Asteroid 2011 ES4 is expected to pass at about 0.3 or 30% the Earth-moon distance on September 1, 2020. But it might pass farther, or as close as 0.19 lunar distances. The asteroid should pass closest around 16:12 UTC on September 1 (12:12 p.m. EDT; translate UTC to your time).

from EarthSky https://ift.tt/3lBHBsv

The orbit of asteroid 2011 ES4 (in white) is slightly similar to Earth’s (in blue) but inclined in relation to our planet’s orbit. The space rock completes an orbit around the sun every 416 days. It nearly intercepts our orbit on September 1, 2020, as seen in this illustration, via NASA/ JPL.

A healthy-sized chunk of space rock will pass closer than the moon on September 1, 2020. Although there is uncertainty in its orbit, scientists say it will not hit our planet. Asteroid 2011 ES4 is expected to pass at about 0.3 or 30% the Earth-moon distance. But it may pass farther, or as close as 0.19 lunar distances, since its orbit is still not completely defined. Our knowledge of this asteroid’s orbit might improve sometime today – or early tomorrow – if it is “recovered” via astronomers’ telescopes prior to closest approach.

The asteroid should pass closest around 16:12 UTC on September 1 (12:12 p.m. EDT; translate UTC to your time).

The asteroid has an estimated diameter of 72 to 161 feet (22 to 49 meters). That’s in the range of the Chelyabinsk meteor – around 17 meters (55 feet) in diameter – which swept through Earth’s atmosphere above Russia in February 2013, generating an enormous shock wave that broke windows in six Russian cities and caused some 1,500 people to seek medical treatment, mostly from flying glass.

Chelyabinsk meteor smoke trail, February 15, 2013. Image via Alex Alishevskikh., who caught it about a minute after the blast.

But back to asteroid 2011 ES4. The uncertainty about its orbit is due to the fact that observatories were able to track the space rock during only four days after it was detected on March 2, 2011, from the Mount Lemmon Survey in Arizona. After that, the asteroid became too faint to be observed.

Astronomers use an uncertainty scale from 0-9, in which 0 means the orbit is well known, and 9 means great uncertainty. Asteroid 2011 ES4 has an uncertainty of 7.  The uncertainty not only means it may pass farther or closer than expected, but also may cause it to occur a few hours earlier or later than expected.

Asteroid 2011 ES4 is classified as a Near-Earth Object (NEO). But it’s good to know that this Apollo-class asteroid is not classified as a Potentially Hazardous Asteroid. What’s the difference? A Potentially Hazardous Asteroid is defined as an object that passes relatively close to Earth, and also is large enough (more than 150 meters in diameter) to cause significant regional damage, were it to strike Earth.

Thus you may see that asteroid 2011 ES4 has the potential to come rather close. And it’s a healthy size, bigger, for example, than the tiny (truck-sized) asteroid that swept just 2,000 miles (3,000 km) from Earth on August 16, 2020. Yet – as asteroids go – asteroid 2011 ES4 is still relatively small, not large enough to cause significant damage upon impact (and it is not expected to get close enough to enter our atmosphere, much less impact).

So – to all of you worriers – you may all breathe easily now.

Location of the Apollo asteroids compared to the orbits of the terrestrial planets of our solar system. Image via Wikimedia Commons.

If an asteroid as big as 2011 ES4 were to hit our planet, it wouldn’t be big enough to cause a major impact, much less an extinction-level event. However, a space rock with an average size of 98 ft (30 meters) in diameter, like this one, could cause a huge shock wave if it enters our atmosphere.

Fortunately, even with the margin of errors in calculations, asteroid 2011 ES4 should safely pass by Earth on September 1, 2020.

If asteroid 2011 ES4 is detected in the next few hours or days, it may at first be confused with a “new” asteroid, and get a temporary or provisional designation before models show it definitely has the same trajectory, indicating it’s in fact asteroid 2011 ES4 being “recovered” in our skies. After new observations are made, astronomers may be able to better define the space rock’s orbit.

We may see many news about close passes of asteroids, but most of those are about small space rocks. We don’t have to worry, because if a small asteroid hits our atmosphere, most of the space rock will disintegrate, and since Earth is around 70% covered by oceans, most events will occur over water, probably even unnoticed.

What about any big asteroid approaching Earth? Although there are many small asteroids whose orbit crosses the orbit of Earth, fortunately, there is no known big space rock with a dangerous orbit which poses a threat to our planet.

As part of nature, there will be, however, lots of other significant approaches in the future, including asteroid Apophis on April 13, 2029. That will be an exciting opportunity for scientists. And even for casual observers, the close approach of Apophis will be an amazing event, as the space rock may even be slightly visible to the unaided eye from some areas.

Bottom line: Asteroid 2011 ES4 is expected to pass at about 0.3 or 30% the Earth-moon distance on September 1, 2020. But it might pass farther, or as close as 0.19 lunar distances. The asteroid should pass closest around 16:12 UTC on September 1 (12:12 p.m. EDT; translate UTC to your time).

from EarthSky https://ift.tt/3lBHBsv

Sun halo with birds

View at EarthSky Community Photos. | Jayesh Jayesh J of Vadodara, Gujarat, India caught this beautiful 22-degree halo around the sun on August 29, 2020. Thank you, Jayesh!

Read more: What makes a halo around the sun or moon?

from EarthSky https://ift.tt/3lvhbs5

View at EarthSky Community Photos. | Jayesh Jayesh J of Vadodara, Gujarat, India caught this beautiful 22-degree halo around the sun on August 29, 2020. Thank you, Jayesh!

Read more: What makes a halo around the sun or moon?

from EarthSky https://ift.tt/3lvhbs5

Repeating fast radio burst wakes up again right on schedule

The location of the host galaxy of FRB 121102. Image via Gemini Observatory/ AURA/ NSF/ NRC/ Phys.org.

A repeating fast radio burst (FRB) has woken up again just when scientists had predicted it would, scientists in China have reported. This news supports earlier observations that the FRB being studied – called FRB 121102 – is one of a few so far that have been found to repeat on a regular cycle. FRB 121102 had previously been found to repeat on a 157-day cycle. The new observations also refine that time period a bit more.

The new report on FRB 121102 comes from astronomer Pei Wang of the National Astronomy Observatory of China (NAOC), who used the Five-hundred-meter Aperture Spherical radio Telescope (FAST) – world’s largest dish-type radio telescope – to monitor FRB 121102 on several dates between March and August 2020. Their findings were posted to The Astronomer’s Telegram on August 21, 2020.

As reported in Science Alert on August 24, from mid-March to late July 2020, the FRB had been silent, as expected. Previous observations showed that it would remain in an inactive phase for about 67 days, then “turn on” again for another 90 days, during which time it would repeatedly emit intense radio flares. The 157-day cycle then keeps repeating. On August 17, Wang’s team detected new activity again with FAST, at least 12 bursts, right about when expected.

Artist’s illustration of an FRB being detected by radio telescopes on Earth. Image via Danielle Futselaar/ artsource.nl/ Space.com.

The timing supports previous observations from a team led by Marilyn Cruces of the Max Planck Institute for Radio Astronomy, as well as by University of Manchester astronomer Kaustubh Rajwade and his team. It was Rajwade who first discovered the periodicity of FRB 121102. Then, the cycle was calculated to be every 157 days. Cruce’s team, meanwhile, has calculated a cycle of 161 days, and submitted a new pre-print paper to arXiv on August 8, 2020. They detected 36 bursts from FRB 121102 using the Radio Telescope Effelsberg between September 2017 to June 2020.

According to that new paper, the active period for FRB 121102 should be between July 9 and October 14, 2020.

Wang’s team, however, using data from both Cruces and Rajwade, has calculated a periodicity of 156.1 days. Wang said in a statement:

We combine the bursts collected in Rajwade et al. (2020) and Cruces et al. (2020) with these newly detected by FAST in 2019 and 2020, and obtain a new best-fit period of ~156.1 days.

If Wang is right, then the current active phase of FRB 121102 should end sometime between August 31 and September 9, 2020. But if it doesn’t, that would suggest that either the periodicity isn’t actually real, or that it has changed somehow. The calculations may also need a bit of further refinement. As with other FRBs, this one will continue to be monitored. As noted in The Astronomer’s Telegram:

With this putative period, the projected turn-off date is around August 31th – September 9th, 2020. Alternatively, if the source is continuously on after the projected turning-off time, it suggests that the putative period of the source is not real or has evolution. We encourage more follow-up monitoring efforts from other radio observatories.

Photo from January 11, 2020 showing the Five-hundred-meter Aperture Spherical radio Telescope (FAST) in southwest China’s Guizhou province. Image via Xinhua/ China.org.cn.

Fast radio bursts are one of the weirdest phenomena yet discovered in our universe. They are very brief but very powerful blasts of radio waves, lasting only a few milliseconds (a millisecond is a thousandth of a second) and scientists don’t yet know what causes them. Most seem to just give off a single burst, and then are never seen again. Others repeat however, and fewer still repeat on a regular basis. A typical FRB can generate as much energy in a single millisecond burst as the sun does in 80 years!

Last February, another repeating FRB was announced, FRB 180916.J0158+65, and this one has a cycle of 16 days. It was observed by scientists using the Canadian Hydrogen Intensity Mapping Experiment (CHIME) radio telescope in British Columbia, Canada. CHIME observed one to two bursts per hour, a process that continued for four days. But then, for the next 12 days or so, there was no activity at all. The cycle then repeated.

Some 28 bursts were recorded by CHIME in total for this FRB, from September 16, 2018, to October 26, 2019. It is in a spiral galaxy 500 million light-years away, the closest known FRB found so far. The identification of the specific location was previously published in Nature on January 6, 2020.

Pei Wang of the National Astronomy Observatory of China, whose team detected the re-awakening of FRB 121102. Image via ResearchGate.

The first known FRB, called FRB 010724 or the Lorimer Burst, was found in 2007, in data from the Parkes radio telescope in Australia. Over 100 FRBs have been detected so far, originating in distant galaxies. What causes them is still a mystery, but theories include unusual phenomena associated with rapidly rotating neutron stars or merging black holes, or perhaps something that really is completely new to science. There is also still the popular possibility of extraterrestrial intelligence being involved, but so far there is no direct evidence for that, and FRBs appear to be widely distributed among far-flung galaxies, making a natural explanation more likely.

The re-detection of bursts from FRB 121102, as predicted, is more solid evidence that at least some FRBs repeat on a regular basis. This provides valuable clues as to what is really going on with these mysterious objects.

Bottom line: FRB 121102, one of the few known repeating FRBs, has woken up and started bursting radio waves again, just when scientists expected it to.

Source: FRB121102 is active again as revealed by FAST

Source: Repeating behaviour of FRB 121102: periodicity, waiting times and energy distribution

Via Science Alert

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The location of the host galaxy of FRB 121102. Image via Gemini Observatory/ AURA/ NSF/ NRC/ Phys.org.

A repeating fast radio burst (FRB) has woken up again just when scientists had predicted it would, scientists in China have reported. This news supports earlier observations that the FRB being studied – called FRB 121102 – is one of a few so far that have been found to repeat on a regular cycle. FRB 121102 had previously been found to repeat on a 157-day cycle. The new observations also refine that time period a bit more.

The new report on FRB 121102 comes from astronomer Pei Wang of the National Astronomy Observatory of China (NAOC), who used the Five-hundred-meter Aperture Spherical radio Telescope (FAST) – world’s largest dish-type radio telescope – to monitor FRB 121102 on several dates between March and August 2020. Their findings were posted to The Astronomer’s Telegram on August 21, 2020.

As reported in Science Alert on August 24, from mid-March to late July 2020, the FRB had been silent, as expected. Previous observations showed that it would remain in an inactive phase for about 67 days, then “turn on” again for another 90 days, during which time it would repeatedly emit intense radio flares. The 157-day cycle then keeps repeating. On August 17, Wang’s team detected new activity again with FAST, at least 12 bursts, right about when expected.

Artist’s illustration of an FRB being detected by radio telescopes on Earth. Image via Danielle Futselaar/ artsource.nl/ Space.com.

The timing supports previous observations from a team led by Marilyn Cruces of the Max Planck Institute for Radio Astronomy, as well as by University of Manchester astronomer Kaustubh Rajwade and his team. It was Rajwade who first discovered the periodicity of FRB 121102. Then, the cycle was calculated to be every 157 days. Cruce’s team, meanwhile, has calculated a cycle of 161 days, and submitted a new pre-print paper to arXiv on August 8, 2020. They detected 36 bursts from FRB 121102 using the Radio Telescope Effelsberg between September 2017 to June 2020.

According to that new paper, the active period for FRB 121102 should be between July 9 and October 14, 2020.

Wang’s team, however, using data from both Cruces and Rajwade, has calculated a periodicity of 156.1 days. Wang said in a statement:

We combine the bursts collected in Rajwade et al. (2020) and Cruces et al. (2020) with these newly detected by FAST in 2019 and 2020, and obtain a new best-fit period of ~156.1 days.

If Wang is right, then the current active phase of FRB 121102 should end sometime between August 31 and September 9, 2020. But if it doesn’t, that would suggest that either the periodicity isn’t actually real, or that it has changed somehow. The calculations may also need a bit of further refinement. As with other FRBs, this one will continue to be monitored. As noted in The Astronomer’s Telegram:

With this putative period, the projected turn-off date is around August 31th – September 9th, 2020. Alternatively, if the source is continuously on after the projected turning-off time, it suggests that the putative period of the source is not real or has evolution. We encourage more follow-up monitoring efforts from other radio observatories.

Photo from January 11, 2020 showing the Five-hundred-meter Aperture Spherical radio Telescope (FAST) in southwest China’s Guizhou province. Image via Xinhua/ China.org.cn.

Fast radio bursts are one of the weirdest phenomena yet discovered in our universe. They are very brief but very powerful blasts of radio waves, lasting only a few milliseconds (a millisecond is a thousandth of a second) and scientists don’t yet know what causes them. Most seem to just give off a single burst, and then are never seen again. Others repeat however, and fewer still repeat on a regular basis. A typical FRB can generate as much energy in a single millisecond burst as the sun does in 80 years!

Last February, another repeating FRB was announced, FRB 180916.J0158+65, and this one has a cycle of 16 days. It was observed by scientists using the Canadian Hydrogen Intensity Mapping Experiment (CHIME) radio telescope in British Columbia, Canada. CHIME observed one to two bursts per hour, a process that continued for four days. But then, for the next 12 days or so, there was no activity at all. The cycle then repeated.

Some 28 bursts were recorded by CHIME in total for this FRB, from September 16, 2018, to October 26, 2019. It is in a spiral galaxy 500 million light-years away, the closest known FRB found so far. The identification of the specific location was previously published in Nature on January 6, 2020.

Pei Wang of the National Astronomy Observatory of China, whose team detected the re-awakening of FRB 121102. Image via ResearchGate.

The first known FRB, called FRB 010724 or the Lorimer Burst, was found in 2007, in data from the Parkes radio telescope in Australia. Over 100 FRBs have been detected so far, originating in distant galaxies. What causes them is still a mystery, but theories include unusual phenomena associated with rapidly rotating neutron stars or merging black holes, or perhaps something that really is completely new to science. There is also still the popular possibility of extraterrestrial intelligence being involved, but so far there is no direct evidence for that, and FRBs appear to be widely distributed among far-flung galaxies, making a natural explanation more likely.

The re-detection of bursts from FRB 121102, as predicted, is more solid evidence that at least some FRBs repeat on a regular basis. This provides valuable clues as to what is really going on with these mysterious objects.

Bottom line: FRB 121102, one of the few known repeating FRBs, has woken up and started bursting radio waves again, just when scientists expected it to.

Source: FRB121102 is active again as revealed by FAST

Source: Repeating behaviour of FRB 121102: periodicity, waiting times and energy distribution

Via Science Alert

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See the Winter Circle before dawn

Although it’s summer in the Northern Hemisphere, a major sign of winter now looms large in the predawn/dawn sky. The dazzling planet Venus beams in front of the great big lasso of stars known as the Winter Circle. For the next several days, Venus shines at the eastern border of the Winter Circle, midway between the Procyon, the Little Dog Star, and the Gemini stars, Castor and Pollux.

The Winter Circle (sometimes called the Winter Hexagon) is an asterism – a star pattern that is not a recognized constellation. This humongous star formation consists of six 1st-magnitude stars in six different constellations.

Capella of the constellation Auriga the charioteer
Pollux of the constellation Gemini the Twins
Procyon of the constellation Canis Minor the Smaller Dog
Sirius of the constellation Canis Major the Big Dog
Rigel of the constellation Orion the Hunter
Aldebaran in the constellation Taurus the Bull

The star Castor in the constellation Gemini, although not a 1st-magnitude star, counts as the sky’s brightest 2nd-magnitude star.

By the way, are you familiar with the constellation Orion the Hunter? The Winter Circle even dwarfs the Mighty Hunter, which only makes up the southwest (lower right) portion of the Winter Circle. If you’ve never seen the Winter Circle, but are acquainted with Orion, this constellation presents a great jumping off place for circumnavigating this brilliant circle of stars. Best of all, these stars are so bright that the’re even visible in the morning twilight.

Steve Pauken captured the Winter Circle on February 24, 2016, and wrote: “After seeing an illustration in EarthSky, I went out the back door to look for it. It was directly overhead, so I put my camera on the tripod, aimed straight up, and captured the image after a few tweaks for focus.”

The Winter Circle is so named because we in the Northern Hemisphere see this star formation on winter evenings. The Winter Circle is also visible from the Southern Hemisphere, though on their summer evenings.

The green line on the feature sky chart at top depicts the ecliptic, the Earth’s orbital plane projected onto the sky. The ecliptic can also be regarded as the sun’s apparent yearly pathway in front of the constellations of the zodiac. If you could see the stars in the daytime, you’d see the sun directly north of the star Aldebaran around June 1. Thereafter, the sun stays in front of the Winter Circle for about 1 1/2 months. Then the sun passes to the south (below) the Gemini stars, Castor and Pollux, in mid-July (about where you see Venus in late August/early September 2020).

We don’t see the Winter Circle in June and July because it’s lost in the glare of the sun. In late August, the Winter Circle returns to the morning sky. But we still won’t see the Winter Circle in the evening sky for months to come.

Aldebaran is out all night long, from dusk till dawn, around December 1; and the Gemini stars, Castor and Pollux, are out all night long, from dusk till dawn, around mid-January. Hence, we in the Northern Hemisphere associate the Winter Circle with short days and long nights, when these brilliant stars light up the dark months of the year.

Bottom line: These next few days, before daybreak, let Venus, the third-brightest celestial body, after the sun and moon, respectively, serve as your guide to the majestic Winter Circle.

from EarthSky https://ift.tt/3lpZXMO

Although it’s summer in the Northern Hemisphere, a major sign of winter now looms large in the predawn/dawn sky. The dazzling planet Venus beams in front of the great big lasso of stars known as the Winter Circle. For the next several days, Venus shines at the eastern border of the Winter Circle, midway between the Procyon, the Little Dog Star, and the Gemini stars, Castor and Pollux.

The Winter Circle (sometimes called the Winter Hexagon) is an asterism – a star pattern that is not a recognized constellation. This humongous star formation consists of six 1st-magnitude stars in six different constellations.

Capella of the constellation Auriga the charioteer
Pollux of the constellation Gemini the Twins
Procyon of the constellation Canis Minor the Smaller Dog
Sirius of the constellation Canis Major the Big Dog
Rigel of the constellation Orion the Hunter
Aldebaran in the constellation Taurus the Bull

The star Castor in the constellation Gemini, although not a 1st-magnitude star, counts as the sky’s brightest 2nd-magnitude star.

By the way, are you familiar with the constellation Orion the Hunter? The Winter Circle even dwarfs the Mighty Hunter, which only makes up the southwest (lower right) portion of the Winter Circle. If you’ve never seen the Winter Circle, but are acquainted with Orion, this constellation presents a great jumping off place for circumnavigating this brilliant circle of stars. Best of all, these stars are so bright that the’re even visible in the morning twilight.

Steve Pauken captured the Winter Circle on February 24, 2016, and wrote: “After seeing an illustration in EarthSky, I went out the back door to look for it. It was directly overhead, so I put my camera on the tripod, aimed straight up, and captured the image after a few tweaks for focus.”

The Winter Circle is so named because we in the Northern Hemisphere see this star formation on winter evenings. The Winter Circle is also visible from the Southern Hemisphere, though on their summer evenings.

The green line on the feature sky chart at top depicts the ecliptic, the Earth’s orbital plane projected onto the sky. The ecliptic can also be regarded as the sun’s apparent yearly pathway in front of the constellations of the zodiac. If you could see the stars in the daytime, you’d see the sun directly north of the star Aldebaran around June 1. Thereafter, the sun stays in front of the Winter Circle for about 1 1/2 months. Then the sun passes to the south (below) the Gemini stars, Castor and Pollux, in mid-July (about where you see Venus in late August/early September 2020).

We don’t see the Winter Circle in June and July because it’s lost in the glare of the sun. In late August, the Winter Circle returns to the morning sky. But we still won’t see the Winter Circle in the evening sky for months to come.

Aldebaran is out all night long, from dusk till dawn, around December 1; and the Gemini stars, Castor and Pollux, are out all night long, from dusk till dawn, around mid-January. Hence, we in the Northern Hemisphere associate the Winter Circle with short days and long nights, when these brilliant stars light up the dark months of the year.

Bottom line: These next few days, before daybreak, let Venus, the third-brightest celestial body, after the sun and moon, respectively, serve as your guide to the majestic Winter Circle.

from EarthSky https://ift.tt/3lpZXMO

What is a fogbow?

See the full-sized panorama here. | April Singer wrote on July 28: “This morning we had a little fog here in the high desert of New Mexico, USA. We had rain the last few afternoons and the ground is pretty saturated, and now this morning the sun was out. Perfect recipe for fog – and apparently for a fogbow! First time I’ve captured one. This is a pano with my iPhone. I didn’t realize the bow was there until I saw the picture. Since it’s been cloudy all through the comet viewing period, and I didn’t get any pictures, I’m happy to have something a little interesting to share now.” Lovely, April! Thank you.

Fogbows – sometimes called white rainbows, cloudbows or ghost rainbows – are made much as rainbows are, from the same configuration of sunlight and moisture. Rainbows happen when the air is filled with raindrops, and you always see a rainbow in the direction opposite the sun. Fogbows are much the same, always opposite the sun, but fogbows are caused by the small droplets inside a fog or cloud rather than larger raindrops.

Look for fogbows in a thin fog when the sun is bright. You might see one when the sun breaks through a fog. Or watch for fogbows over the ocean.

Because the water droplets in fog are so small, fogbows have only weak colors or are colorless.

View larger at EarthSky Community Photos. | Peter Lowenstein caught this fogbow in Mutare, Zimbabwe, on April 29, 2020. He wrote: “Half-an-hour after the Sun rose behind my house on Wednesday, a beautiful fogbow developed in the middle of a misty morning view from my front veranda. All the conditions were right – bright sunshine from the rear with the Sun less than twenty degrees above the horizon and clearing clouds of mist at the antisolar point. The scene was framed by a beautiful flowering Poinsettia to the left, a lush banana grove to the right, and clear blue sky beginning to appear on top!”

View at EarthSky Community Photos. | Alan Nicolle in New South Wales, Australia, captured this image on July 16, 2019. He wrote: “I was out geocaching in the outskirts of Broken Hill, when I turned back to see this fogbow developing. I took quite a few photos with the iPhone, and rode back to the car on my bike, but by the time I got back to the car to use my SLR, it had faded.” Thank you, Alan!

Edith Smith in Aberdeenshire, Scotland, captured this fogbow on November 1, 2018. She wrote: “The camera spotted it before I did with eye, as I was too engrossed in foggy conditions.”

Tommy Johnson captured this early morning fogbow near Jonesport, Maine, in August 2016. He wrote: “Early in the morning and blueberry rakers are starting to fill their buckets with the fruit. I called out to them to look at the fogbow, it was the first time any of us had seen one.”

Wonderful fogbow caught by Robyn Smith in New Zealand on the morning of September 19, 2017 “… opposite the foggy sunrise.”

GregDiesel Landscape Photography wrote in October 2015: “Saw my first fogbow / white rainbow. Photo taken with cell phone. Moyock, North Carolina.”

Katherine Keyes Millet captured this fogbow in July 2014 at Winter Island Park in Salem, Massachusetts.

Venus and Jupiter above a fogbow in Blacklough, Dungannon, Ireland. Mars is up there, too, but tough to see. John Fagan captured them all in October 2015.

Eileen Claffey in Brookline, Massachusetts, captured this fogbow over a field in September 2014.

Les Cowley of the great website Atmospheric Optics says:

Look away from the sun and at an angle of 35-40 degrees from your shadow which marks the direction of the antisolar point. Some fogbows have very low contrast so look for small brightenings in the misty background. Once caught, they are unmistakable.

The sun must be less than 30-40 degrees high unless you are on a hill or high up on a ship where the mist and fogbow can be viewed from above.

Fogbows are huge, almost as large as a rainbow and much, much broader.

Look here for Les Cowley’s explanation of how fogbows form.

Thomas Kast in Finland captured this fogbow in 2013. He wrote: “In this rather cold August night (+8C [46F]) there was patchy fog, especially in open fields. This lake remained clear for a long time. At one point I saw this white bow with moon in waning gibbous phase behind me.”

Jim Grant caught this fogbow over Sunset Cliffs in San Diego. He wrote: “The skies were sunny and clear, and then the fog rolled in, and with it this beautiful fogbow.”

Lynton Brown of Australia captured this fogbow over a barren field in the autumn of 2012.

Bottom line: Fogbows are made by much the same process as rainbows, but with the small water droplets inside a fog instead of larger raindrops. Because the water droplets in fog are so small, fogbows have only weak colors or are colorless.

from EarthSky https://ift.tt/2RuWZ9W

See the full-sized panorama here. | April Singer wrote on July 28: “This morning we had a little fog here in the high desert of New Mexico, USA. We had rain the last few afternoons and the ground is pretty saturated, and now this morning the sun was out. Perfect recipe for fog – and apparently for a fogbow! First time I’ve captured one. This is a pano with my iPhone. I didn’t realize the bow was there until I saw the picture. Since it’s been cloudy all through the comet viewing period, and I didn’t get any pictures, I’m happy to have something a little interesting to share now.” Lovely, April! Thank you.

Fogbows – sometimes called white rainbows, cloudbows or ghost rainbows – are made much as rainbows are, from the same configuration of sunlight and moisture. Rainbows happen when the air is filled with raindrops, and you always see a rainbow in the direction opposite the sun. Fogbows are much the same, always opposite the sun, but fogbows are caused by the small droplets inside a fog or cloud rather than larger raindrops.

Look for fogbows in a thin fog when the sun is bright. You might see one when the sun breaks through a fog. Or watch for fogbows over the ocean.

Because the water droplets in fog are so small, fogbows have only weak colors or are colorless.

View larger at EarthSky Community Photos. | Peter Lowenstein caught this fogbow in Mutare, Zimbabwe, on April 29, 2020. He wrote: “Half-an-hour after the Sun rose behind my house on Wednesday, a beautiful fogbow developed in the middle of a misty morning view from my front veranda. All the conditions were right – bright sunshine from the rear with the Sun less than twenty degrees above the horizon and clearing clouds of mist at the antisolar point. The scene was framed by a beautiful flowering Poinsettia to the left, a lush banana grove to the right, and clear blue sky beginning to appear on top!”

View at EarthSky Community Photos. | Alan Nicolle in New South Wales, Australia, captured this image on July 16, 2019. He wrote: “I was out geocaching in the outskirts of Broken Hill, when I turned back to see this fogbow developing. I took quite a few photos with the iPhone, and rode back to the car on my bike, but by the time I got back to the car to use my SLR, it had faded.” Thank you, Alan!

Edith Smith in Aberdeenshire, Scotland, captured this fogbow on November 1, 2018. She wrote: “The camera spotted it before I did with eye, as I was too engrossed in foggy conditions.”

Tommy Johnson captured this early morning fogbow near Jonesport, Maine, in August 2016. He wrote: “Early in the morning and blueberry rakers are starting to fill their buckets with the fruit. I called out to them to look at the fogbow, it was the first time any of us had seen one.”

Wonderful fogbow caught by Robyn Smith in New Zealand on the morning of September 19, 2017 “… opposite the foggy sunrise.”

GregDiesel Landscape Photography wrote in October 2015: “Saw my first fogbow / white rainbow. Photo taken with cell phone. Moyock, North Carolina.”

Katherine Keyes Millet captured this fogbow in July 2014 at Winter Island Park in Salem, Massachusetts.

Venus and Jupiter above a fogbow in Blacklough, Dungannon, Ireland. Mars is up there, too, but tough to see. John Fagan captured them all in October 2015.

Eileen Claffey in Brookline, Massachusetts, captured this fogbow over a field in September 2014.

Les Cowley of the great website Atmospheric Optics says:

Look away from the sun and at an angle of 35-40 degrees from your shadow which marks the direction of the antisolar point. Some fogbows have very low contrast so look for small brightenings in the misty background. Once caught, they are unmistakable.

The sun must be less than 30-40 degrees high unless you are on a hill or high up on a ship where the mist and fogbow can be viewed from above.

Fogbows are huge, almost as large as a rainbow and much, much broader.

Look here for Les Cowley’s explanation of how fogbows form.

Thomas Kast in Finland captured this fogbow in 2013. He wrote: “In this rather cold August night (+8C [46F]) there was patchy fog, especially in open fields. This lake remained clear for a long time. At one point I saw this white bow with moon in waning gibbous phase behind me.”

Jim Grant caught this fogbow over Sunset Cliffs in San Diego. He wrote: “The skies were sunny and clear, and then the fog rolled in, and with it this beautiful fogbow.”

Lynton Brown of Australia captured this fogbow over a barren field in the autumn of 2012.

Bottom line: Fogbows are made by much the same process as rainbows, but with the small water droplets inside a fog instead of larger raindrops. Because the water droplets in fog are so small, fogbows have only weak colors or are colorless.

from EarthSky https://ift.tt/2RuWZ9W

Astronomers issue report on the effect of ‘satellite constellations’ on astronomy

In May 2019 SpaceX launched its first batch of 60 Starlink communication satellites, which surprised astronomers and laypeople with their appearance in the night sky. Astronomers have only now, a little over a year later, accumulated enough observations of constellation satellites like those being launched by SpaceX and OneWeb to run computer simulations of their likely impact. These simulations will help researchers thoroughly understand the magnitude and complexity of the problem. This research informed the discussion at the Satellite Constellations 1 (SATCON1) workshop and led to recommendations for observatories and constellation operators. The SATCON1 report concludes that the effects on astronomical research and on the human experience of the night sky range from “negligible” to “extreme.” Image via AAS/ NOIRLab/ NSF/ AURA/ P. Marenfeld.

Originally published by the American Astronomical Society on August 25, 2020

A report by experts representing the global astronomical community concludes that large constellations of bright satellites in low Earth orbit will fundamentally change ground-based optical and infrared astronomy and could impact the appearance of the night sky for stargazers worldwide. The report is the outcome of the recent SATCON1 virtual workshop, which brought together more than 250 scientists, engineers, satellite operators, and other stakeholders.

The report from the Satellite Constellations 1 (SATCON1) workshop, organized jointly by NSF’s NOIRLab and the American Astronomical Society (AAS), has been delivered to the National Science Foundation (NSF). Held virtually from 29 June to 2 July 2020, SATCON1 focused on technical aspects of the impact of existing and planned large satellite constellations on optical and infrared astronomy. NSF, which funded the workshop, also finances most of the large ground-based telescopes widely available to researchers in the United States. More than 250 astronomers, engineers, commercial satellite operators, and other stakeholders attended SATCON1. Their goals were to better quantify the scientific impacts of huge ensembles of low-Earth-orbiting satellites (LEOsats) contaminating astronomical observations and to explore possible ways to minimize those impacts.

Read the SATCON1 report

SATCON1 co-chair Connie Walker from NSF’s NOIRLab explained:

Recent technology developments for astronomical research — especially cameras with wide fields of view on large optical-infrared telescopes — are happening at the same time as the rapid deployment of many thousands of LEOsats by companies rolling out new space-based communication technologies.

The report concludes that the effects of large satellite constellations on astronomical research and on the human experience of the night sky range from “negligible” to “extreme.” This new hazard was not on astronomers’ radar in 2010, when New Worlds, New Horizons — the report of the National Academies’ Astro2010 decadal survey of astronomy and astrophysics — was issued. Astro2010’s top recommendation for ground-based optical astronomy, Vera C. Rubin Observatory, will soon begin conducting exactly the type of observations to which Walker refers. When SpaceX launched its first batch of 60 Starlink communication satellites in May 2019 and people all over the world saw them in the sky, astronomers reacted with alarm. Not only were the Starlink satellites brighter than anyone expected, but there could be tens of thousands more like them. As they pass through Rubin’s camera field, they will affect the 8.4-meter (27.6-foot) telescope’s view of the faint celestial objects astronomers hope to study with it.

SATCON1 co-chair Jeff Hall from Lowell Observatory is chair of the AAS Committee on Light Pollution, Radio Interference, and Space Debris. Hall said:

Rubin Observatory and the giant 30-meter telescopes coming online in the next decade will substantially enhance humankind’s understanding of the cosmos. For reasons of expense, maintenance, and instrumentation, such facilities cannot be operated from space. Ground-based astronomy is, and will remain, vital and relevant.

Constellations of LEOsats are designed in part to provide communication services to underserved and remote areas, a goal everyone can support. Recognizing this, astronomers have engaged satellite operators in cooperative discussions about how to achieve that goal without unduly harming ground-based astronomical observations. The SATCON1 workshop is just the latest, and most significant, step in this ongoing dialog.

The report offers two main findings. The first is that LEOsats disproportionately affect science programs that require twilight observations, such as searches for Earth-threatening asteroids and comets, outer solar system objects, and visible-light counterparts of fleeting gravitational-wave sources. During twilight the Sun is below the horizon for observers on the ground, but not for satellites hundreds of kilometers overhead, which are still illuminated. As long as satellites remain below 600 kilometers (not quite 400 miles), their interference with astronomical observations is somewhat limited during the night’s darkest hours. But satellites at higher altitudes, such as the constellation planned by OneWeb that will orbit at 1,200 kilometers (about 750 miles), may be visible all night long during summer and for much of the night in other seasons. These constellations could have serious negative consequences for many research programs at the world’s premier optical observatories. Depending on their altitude and brightness, constellation satellites could also spoil starry nights for amateur astronomers, astrophotographers, and other nature enthusiasts.

The report’s second finding is that there are at least six ways to mitigate harm to astronomy from large satellite constellations:

1. Launch fewer or no LEOsats. However impractical or unlikely, this is the only option identified that can achieve zero astronomical impact.

2. Deploy satellites at orbital altitudes no higher than ~600 km.

3. Darken satellites or use sunshades to shadow their reflective surfaces.

4. Control each satellite’s orientation in space to reflect less sunlight to Earth.

5. Minimize or eventually be able to eliminate the effect of satellite trails during the processing of astronomical images.

6. Make more accurate orbital information available for satellites so that observers can avoid pointing telescopes at them.

Astronomers have only now, a little over a year after the first SpaceX Starlink launch, accumulated enough observations of constellation satellites and run computer simulations of their likely impact when fully deployed to thoroughly understand the magnitude and complexity of the problem. This research informed the discussion at SATCON1 and led to ten recommendations for observatories, constellation operators, and those two groups in collaboration. Some involve actions that can be taken immediately, while others urge further study to develop effective strategies to address problems anticipated as new large telescopes come online and as satellite constellations proliferate.

The SATCON1 workshop was an important step towards managing a challenging future. NOIRLab director Patrick McCarthy said:

I hope that the collegiality and spirit of partnership between astronomers and commercial satellite operators will expand to include more members of both communities and that it will continue to prove useful and productive. I also hope that the findings and recommendations in the SATCON1 report will serve as guidelines for observatories and satellite operators alike as we work towards a more detailed understanding of the impacts and mitigations and we learn to share the sky, one of nature’s priceless treasures.

AAS President Paula Szkody of the University of Washington participated in the workshop. She said:

Our team at the AAS was enthusiastic to partner with NOIRLab and bring representatives of the astronomical and satellite communities together for a very fruitful exchange of ideas. Even though we’re still at an early stage of understanding and addressing the threats posed to astronomy by large satellite constellations, we have made good progress and have plenty of reasons to hope for a positive outcome.

The next workshop, SATCON2, which will tackle the significant issues of policy and regulation, is tentatively planned for early to mid-2021.

Bottom line: A new report by experts concludes that large constellations of bright satellites in low-Earth orbit will fundamentally change ground-based astronomy and impact the appearance of the night sky for stargazers worldwide.

from EarthSky https://ift.tt/3lmY2bV

In May 2019 SpaceX launched its first batch of 60 Starlink communication satellites, which surprised astronomers and laypeople with their appearance in the night sky. Astronomers have only now, a little over a year later, accumulated enough observations of constellation satellites like those being launched by SpaceX and OneWeb to run computer simulations of their likely impact. These simulations will help researchers thoroughly understand the magnitude and complexity of the problem. This research informed the discussion at the Satellite Constellations 1 (SATCON1) workshop and led to recommendations for observatories and constellation operators. The SATCON1 report concludes that the effects on astronomical research and on the human experience of the night sky range from “negligible” to “extreme.” Image via AAS/ NOIRLab/ NSF/ AURA/ P. Marenfeld.

Originally published by the American Astronomical Society on August 25, 2020

A report by experts representing the global astronomical community concludes that large constellations of bright satellites in low Earth orbit will fundamentally change ground-based optical and infrared astronomy and could impact the appearance of the night sky for stargazers worldwide. The report is the outcome of the recent SATCON1 virtual workshop, which brought together more than 250 scientists, engineers, satellite operators, and other stakeholders.

The report from the Satellite Constellations 1 (SATCON1) workshop, organized jointly by NSF’s NOIRLab and the American Astronomical Society (AAS), has been delivered to the National Science Foundation (NSF). Held virtually from 29 June to 2 July 2020, SATCON1 focused on technical aspects of the impact of existing and planned large satellite constellations on optical and infrared astronomy. NSF, which funded the workshop, also finances most of the large ground-based telescopes widely available to researchers in the United States. More than 250 astronomers, engineers, commercial satellite operators, and other stakeholders attended SATCON1. Their goals were to better quantify the scientific impacts of huge ensembles of low-Earth-orbiting satellites (LEOsats) contaminating astronomical observations and to explore possible ways to minimize those impacts.

Read the SATCON1 report

SATCON1 co-chair Connie Walker from NSF’s NOIRLab explained:

Recent technology developments for astronomical research — especially cameras with wide fields of view on large optical-infrared telescopes — are happening at the same time as the rapid deployment of many thousands of LEOsats by companies rolling out new space-based communication technologies.

The report concludes that the effects of large satellite constellations on astronomical research and on the human experience of the night sky range from “negligible” to “extreme.” This new hazard was not on astronomers’ radar in 2010, when New Worlds, New Horizons — the report of the National Academies’ Astro2010 decadal survey of astronomy and astrophysics — was issued. Astro2010’s top recommendation for ground-based optical astronomy, Vera C. Rubin Observatory, will soon begin conducting exactly the type of observations to which Walker refers. When SpaceX launched its first batch of 60 Starlink communication satellites in May 2019 and people all over the world saw them in the sky, astronomers reacted with alarm. Not only were the Starlink satellites brighter than anyone expected, but there could be tens of thousands more like them. As they pass through Rubin’s camera field, they will affect the 8.4-meter (27.6-foot) telescope’s view of the faint celestial objects astronomers hope to study with it.

SATCON1 co-chair Jeff Hall from Lowell Observatory is chair of the AAS Committee on Light Pollution, Radio Interference, and Space Debris. Hall said:

Rubin Observatory and the giant 30-meter telescopes coming online in the next decade will substantially enhance humankind’s understanding of the cosmos. For reasons of expense, maintenance, and instrumentation, such facilities cannot be operated from space. Ground-based astronomy is, and will remain, vital and relevant.

Constellations of LEOsats are designed in part to provide communication services to underserved and remote areas, a goal everyone can support. Recognizing this, astronomers have engaged satellite operators in cooperative discussions about how to achieve that goal without unduly harming ground-based astronomical observations. The SATCON1 workshop is just the latest, and most significant, step in this ongoing dialog.

The report offers two main findings. The first is that LEOsats disproportionately affect science programs that require twilight observations, such as searches for Earth-threatening asteroids and comets, outer solar system objects, and visible-light counterparts of fleeting gravitational-wave sources. During twilight the Sun is below the horizon for observers on the ground, but not for satellites hundreds of kilometers overhead, which are still illuminated. As long as satellites remain below 600 kilometers (not quite 400 miles), their interference with astronomical observations is somewhat limited during the night’s darkest hours. But satellites at higher altitudes, such as the constellation planned by OneWeb that will orbit at 1,200 kilometers (about 750 miles), may be visible all night long during summer and for much of the night in other seasons. These constellations could have serious negative consequences for many research programs at the world’s premier optical observatories. Depending on their altitude and brightness, constellation satellites could also spoil starry nights for amateur astronomers, astrophotographers, and other nature enthusiasts.

The report’s second finding is that there are at least six ways to mitigate harm to astronomy from large satellite constellations:

1. Launch fewer or no LEOsats. However impractical or unlikely, this is the only option identified that can achieve zero astronomical impact.

2. Deploy satellites at orbital altitudes no higher than ~600 km.

3. Darken satellites or use sunshades to shadow their reflective surfaces.

4. Control each satellite’s orientation in space to reflect less sunlight to Earth.

5. Minimize or eventually be able to eliminate the effect of satellite trails during the processing of astronomical images.

6. Make more accurate orbital information available for satellites so that observers can avoid pointing telescopes at them.

Astronomers have only now, a little over a year after the first SpaceX Starlink launch, accumulated enough observations of constellation satellites and run computer simulations of their likely impact when fully deployed to thoroughly understand the magnitude and complexity of the problem. This research informed the discussion at SATCON1 and led to ten recommendations for observatories, constellation operators, and those two groups in collaboration. Some involve actions that can be taken immediately, while others urge further study to develop effective strategies to address problems anticipated as new large telescopes come online and as satellite constellations proliferate.

The SATCON1 workshop was an important step towards managing a challenging future. NOIRLab director Patrick McCarthy said:

I hope that the collegiality and spirit of partnership between astronomers and commercial satellite operators will expand to include more members of both communities and that it will continue to prove useful and productive. I also hope that the findings and recommendations in the SATCON1 report will serve as guidelines for observatories and satellite operators alike as we work towards a more detailed understanding of the impacts and mitigations and we learn to share the sky, one of nature’s priceless treasures.

AAS President Paula Szkody of the University of Washington participated in the workshop. She said:

Our team at the AAS was enthusiastic to partner with NOIRLab and bring representatives of the astronomical and satellite communities together for a very fruitful exchange of ideas. Even though we’re still at an early stage of understanding and addressing the threats posed to astronomy by large satellite constellations, we have made good progress and have plenty of reasons to hope for a positive outcome.

The next workshop, SATCON2, which will tackle the significant issues of policy and regulation, is tentatively planned for early to mid-2021.

Bottom line: A new report by experts concludes that large constellations of bright satellites in low-Earth orbit will fundamentally change ground-based astronomy and impact the appearance of the night sky for stargazers worldwide.

from EarthSky https://ift.tt/3lmY2bV

Moon, Jupiter, Saturn August 27-29

These next several evenings – August 27, 28 and 29, 2020 – watch for the waxing gibbous moon to pass by the 2 biggest planets in our solar system, Jupiter and Saturn. Both worlds are gas giants. Jupiter is by far the brighter planet, shining some 8 times more brilliantly than Saturn. Yet the famous planet of the rings shines as brightly as the brightest stars. Just look up on these nights! You can’t miss these bright worlds near the moon.

Jupiter ranks as the 4th-brightest celestial body to light up the heavens, after the sun, moon and the planet Venus. But there’s no way to mistake Venus for Jupiter, or vice versa, because – at present – Jupiter rules the evening sky while Venus is up at dawn. Around the world, in the wee hours of the morning, Jupiter sets in southwest at roughly the same time that Venus rises in the northeast.

Meanwhile, Saturn – the most distant word that you can see easily with the unaided eye – is twice as bright as the 1st-magnitude star Antares, Heart of the Scorpion. You might have seen the moon in the vicinity of Antares a few days ago.

Live in the US or Canada? Find out when Jupiter sets and Venus rises via Old Farmer’s Almanac.

For virtually anywhere worldwide, find out when Jupiter sets and Venus rises via TimeandDate.

Click on Heaven-Above Moon for the moon’s present position on the zodiac

Here’s a constellation to look for near the moon, Jupiter and Saturn in the next few days. Scorpius is one of the few constellations that looks like its namesake. The bright red star Antares marks the Scorpion’s Heart. On the night of August 27, an imaginary line drawn from Jupiter and past the moon points to Antares. Also, notice the 2 stars at the tip of the Scorpion’s Tail. These 2 stars – Shaula and Lesath – are known as The Stinger.

There are two reasons for Jupiter and Saturn’s brilliance. First of all, these planets are huge; and, secondly, they have a high albedo (reflectivity). Jupiter has 1,331 times the volume of Earth, whereas Saturn has 764 times the Earth’s volume. Jupiter reflects about 52 percent of the incoming sunlight, while Saturn reflects about 47 percent. In contrast, our moon only reflects about 12 percent of the incoming sunlight.

Unlike the stars, which shine by their own light, Jupiter and Saturn shine by reflecting the light of the sun. Despite Jupiter residing 4.4 astronomical units (AU) from Earth and Saturn at 9.2 AU from Earth right now, these planets still stand out in Earth’s sky. By the way, one AU = one sun/Earth distance.

Find out planetary distances from Earth and the sun via Heavens-Above.

Saturn’s brilliance also depends the tilt of its majestic rings. You need a telescope to view the rings, but their inclination affects the planet’s brightness as seen from Earth, when looking with the eye alone. Saturn appears brightest when the rings are inclined at a maximum of 27 degrees toward Earth, and dimmest when the rings appear edge-on (0 degrees).

Presently, the rings are inclined at little more than 21 degrees, adding to Saturn’s overall brilliance.

Image via Wikimedia Commons. The tilt of Saturn’s rings has a great impact on its overall brightness. In years when Saturn’s rings are edge-on as seen from Earth (2009 and 2025), Saturn appears considerably dimmer than in years when Saturn’s rings a maximally titled toward Earth (2017 and 2032). This year, in 2020, Saturn’s rings are still quite inclined.

Bottom line: On August 25, 26 and 27, 2020, use the moon locate the two largest planets of the solar system, Jupiter and Saturn.

from EarthSky https://ift.tt/2G5rMKp

These next several evenings – August 27, 28 and 29, 2020 – watch for the waxing gibbous moon to pass by the 2 biggest planets in our solar system, Jupiter and Saturn. Both worlds are gas giants. Jupiter is by far the brighter planet, shining some 8 times more brilliantly than Saturn. Yet the famous planet of the rings shines as brightly as the brightest stars. Just look up on these nights! You can’t miss these bright worlds near the moon.

Jupiter ranks as the 4th-brightest celestial body to light up the heavens, after the sun, moon and the planet Venus. But there’s no way to mistake Venus for Jupiter, or vice versa, because – at present – Jupiter rules the evening sky while Venus is up at dawn. Around the world, in the wee hours of the morning, Jupiter sets in southwest at roughly the same time that Venus rises in the northeast.

Meanwhile, Saturn – the most distant word that you can see easily with the unaided eye – is twice as bright as the 1st-magnitude star Antares, Heart of the Scorpion. You might have seen the moon in the vicinity of Antares a few days ago.

Live in the US or Canada? Find out when Jupiter sets and Venus rises via Old Farmer’s Almanac.

For virtually anywhere worldwide, find out when Jupiter sets and Venus rises via TimeandDate.

Click on Heaven-Above Moon for the moon’s present position on the zodiac

Here’s a constellation to look for near the moon, Jupiter and Saturn in the next few days. Scorpius is one of the few constellations that looks like its namesake. The bright red star Antares marks the Scorpion’s Heart. On the night of August 27, an imaginary line drawn from Jupiter and past the moon points to Antares. Also, notice the 2 stars at the tip of the Scorpion’s Tail. These 2 stars – Shaula and Lesath – are known as The Stinger.

There are two reasons for Jupiter and Saturn’s brilliance. First of all, these planets are huge; and, secondly, they have a high albedo (reflectivity). Jupiter has 1,331 times the volume of Earth, whereas Saturn has 764 times the Earth’s volume. Jupiter reflects about 52 percent of the incoming sunlight, while Saturn reflects about 47 percent. In contrast, our moon only reflects about 12 percent of the incoming sunlight.

Unlike the stars, which shine by their own light, Jupiter and Saturn shine by reflecting the light of the sun. Despite Jupiter residing 4.4 astronomical units (AU) from Earth and Saturn at 9.2 AU from Earth right now, these planets still stand out in Earth’s sky. By the way, one AU = one sun/Earth distance.

Find out planetary distances from Earth and the sun via Heavens-Above.

Saturn’s brilliance also depends the tilt of its majestic rings. You need a telescope to view the rings, but their inclination affects the planet’s brightness as seen from Earth, when looking with the eye alone. Saturn appears brightest when the rings are inclined at a maximum of 27 degrees toward Earth, and dimmest when the rings appear edge-on (0 degrees).

Presently, the rings are inclined at little more than 21 degrees, adding to Saturn’s overall brilliance.

Image via Wikimedia Commons. The tilt of Saturn’s rings has a great impact on its overall brightness. In years when Saturn’s rings are edge-on as seen from Earth (2009 and 2025), Saturn appears considerably dimmer than in years when Saturn’s rings a maximally titled toward Earth (2017 and 2032). This year, in 2020, Saturn’s rings are still quite inclined.

Bottom line: On August 25, 26 and 27, 2020, use the moon locate the two largest planets of the solar system, Jupiter and Saturn.

from EarthSky https://ift.tt/2G5rMKp

What are cloud streets?

View at EarthSky Community Photos. | Michael Padbury in Wellington Point, Australia captured this image with his iPhone on August 22, 2020. He wrote: “My daughter Hannah pointed out how unusual and beautiful these clouds were last Saturday morning … Not sure what you would call them.” Cloud arrays of this type are called cloud streets. They’re most often captured by satellites, because they tend to form over the ocean. But sometimes – as this photo shows – people see them from the ground, too. Awesome catch, Michael. Thank you, Hannah, too.

Cloud streets are long rows of cumulus clouds that are oriented parallel to the direction of the wind. Over the past decades, they’ve been seen most often in satellite photos; we only rarely see them in photos taken from the ground, as in the photo above. You can recognize cloud streets as rows of puffy cumulus or cumulus-type clouds. They most often straight, but might form patterns when the wind driving the clouds hits an obstacle.

Cloud streets are formed by what are called convection rolls of rising warm air and sinking cool air. Rising warm air cools gradually as it ascends into the atmosphere. When moisture in the warm air mass cools and condenses, it forms clouds.

Meanwhile, sinking cool air on either side of the cloud formation zone creates a cloud-free area. When several of these alternating rising and sinking air masses align with the wind, cloud streets develop.

Cloud streets are technically called horizontal convective rolls.

Convection rolls and the formation of cloud streets. Image via NOAA.

The MODIS instrument on NASA’s Aqua satellite captured this image of cloud streets over the Black Sea on January 8, 2015. NASA Earth Observatory image courtesy Jeff Schmaltz LANCE/EOSDIS MODIS Rapid Response Team, GSFC. Read more about this image

The U.S. National Aeronautics and Space Administration (NASA) has taken some amazing photographs of cloud streets over the past few years with the MODIS (Moderate Resolution Imaging Spectroradiometer) instruments on board the Terra and Aqua satellites. The satellite images on this page are from these instruments.

Cloud streets typically form fairly straight lines over large flat areas such as the ocean. When geological features like islands disrupt the flow of the wind, this disruption can create spiral patterns in the cloud streets similar to the way in which large boulders create downstream eddies in rivers. The spiral patterns in clouds are called von Karman vortex streets, were named after Theodore von Kármán, a co-founder of NASA’s Jet Propulsion Laboratory. He was one of the first scientists to describe this type of atmospheric phenomenon.

Meteorological phenomena such as cloud streets and von Karman vortices are a manifestation of Earth’s atmosphere in motion.

The MODIS instrument on NASA’s Terra satellite captured these cloud streets over the Bering Sea on January 20, 2006. Image via Jesse Allen/NASA. Read more about this image.

The MODIS instrument on NASA’s Aqua satellite acquired this image of a von Karman vortex that formed off the coast of Greenland on February 24, 2009. Image via Jeff Schmaltz, MODIS Rapid Response Team. Read more about this image.

Morning cloud streets over Vancouver Island. Image via CTV News Vancouver Island.

Clouds streets are most readily seen in satellite photography, but this aerial image comes from Rosimar Rios Berrios, via NOAA’s Hurricane Research Division.

Bottom line: Cloud streets are long rows of cumulus clouds oriented parallel to the direction of the wind.

from EarthSky https://ift.tt/32t4rcP

View at EarthSky Community Photos. | Michael Padbury in Wellington Point, Australia captured this image with his iPhone on August 22, 2020. He wrote: “My daughter Hannah pointed out how unusual and beautiful these clouds were last Saturday morning … Not sure what you would call them.” Cloud arrays of this type are called cloud streets. They’re most often captured by satellites, because they tend to form over the ocean. But sometimes – as this photo shows – people see them from the ground, too. Awesome catch, Michael. Thank you, Hannah, too.

Cloud streets are long rows of cumulus clouds that are oriented parallel to the direction of the wind. Over the past decades, they’ve been seen most often in satellite photos; we only rarely see them in photos taken from the ground, as in the photo above. You can recognize cloud streets as rows of puffy cumulus or cumulus-type clouds. They most often straight, but might form patterns when the wind driving the clouds hits an obstacle.

Cloud streets are formed by what are called convection rolls of rising warm air and sinking cool air. Rising warm air cools gradually as it ascends into the atmosphere. When moisture in the warm air mass cools and condenses, it forms clouds.

Meanwhile, sinking cool air on either side of the cloud formation zone creates a cloud-free area. When several of these alternating rising and sinking air masses align with the wind, cloud streets develop.

Cloud streets are technically called horizontal convective rolls.

Convection rolls and the formation of cloud streets. Image via NOAA.

The MODIS instrument on NASA’s Aqua satellite captured this image of cloud streets over the Black Sea on January 8, 2015. NASA Earth Observatory image courtesy Jeff Schmaltz LANCE/EOSDIS MODIS Rapid Response Team, GSFC. Read more about this image

The U.S. National Aeronautics and Space Administration (NASA) has taken some amazing photographs of cloud streets over the past few years with the MODIS (Moderate Resolution Imaging Spectroradiometer) instruments on board the Terra and Aqua satellites. The satellite images on this page are from these instruments.

Cloud streets typically form fairly straight lines over large flat areas such as the ocean. When geological features like islands disrupt the flow of the wind, this disruption can create spiral patterns in the cloud streets similar to the way in which large boulders create downstream eddies in rivers. The spiral patterns in clouds are called von Karman vortex streets, were named after Theodore von Kármán, a co-founder of NASA’s Jet Propulsion Laboratory. He was one of the first scientists to describe this type of atmospheric phenomenon.

Meteorological phenomena such as cloud streets and von Karman vortices are a manifestation of Earth’s atmosphere in motion.

The MODIS instrument on NASA’s Terra satellite captured these cloud streets over the Bering Sea on January 20, 2006. Image via Jesse Allen/NASA. Read more about this image.

The MODIS instrument on NASA’s Aqua satellite acquired this image of a von Karman vortex that formed off the coast of Greenland on February 24, 2009. Image via Jeff Schmaltz, MODIS Rapid Response Team. Read more about this image.

Morning cloud streets over Vancouver Island. Image via CTV News Vancouver Island.

Clouds streets are most readily seen in satellite photography, but this aerial image comes from Rosimar Rios Berrios, via NOAA’s Hurricane Research Division.

Bottom line: Cloud streets are long rows of cumulus clouds oriented parallel to the direction of the wind.

from EarthSky https://ift.tt/32t4rcP