Quadrantid meteors on night of January 3-4

The annual Quadrantid meteor shower is nominally active for roughly two weeks, from about December 27 until about January 10 each year. However, peak activity lasts less than a day, and – to see the best display – you need to be on Earth’s night side during the Quadrantids’ short peak. The International Meteor Organization (IMO) predicts the 2020 peak will come on January 4 at 8 hours UTC. If that forecast holds, it places the peak around 3 a.m. Eastern Time in North America (2 a.m. Central Time, 1 a.m. Mountain Time and 12 midnight Pacific Time) on January 4. Translate UTC to your time.

The hope is always that the shower peaks at about the same time that the radiant is high up in your sky. That won’t be true for everyone across the globe, of course, but the prediction looks good for North America this year.

Keep in mind that meteor showers are fickle. Thus this prediction might – or might not – hold. So avid meteor watchers across the globe will be on the watch no matter what. As we’ve said before, meteor showers are like fishing. You wait, you watch … sometimes you catch something.

For all of us, some good news. In 2020, the waxing gibbous moon will set way before dawn’s first light, enabling you to watch this shower in a deliciously dark sky in the wee hours before dawn.

Another note about the Quadrantids. The shower is best seen from northerly latitudes because the radiant point for this shower (shown on the sky chart at top) is so far north on the sky’s dome.

Look at the sky chart above. The higher that you see the Big Dipper and the star Arcturus in your sky, the more likely that you’ll see some Quandrantid meteors. From mid-northern latitudes across the globe, the Big Dipper sits on the horizon at nightfall and climbs upward during the night. In the predawn hours, at mid-northern latitudes across the globe, the Big Dipper swings above Polaris the North Star. If the IMO prediction holds – and the peak comes around 8 UTC on January 4, 2020 – North American skywatchers have a decent chance of catching perhaps 15 to 25 meteors per hour. If we’re exceptionally lucky, we might see several times that number.

To find out when the moon sets in your sky, click on this Custom Sunrise Sunset Calendar and remember to check the Moonrise and Moonset box.

Will you see any meteors? Maybe!

Eliot Herman in Tucson, Arizona caught this early Quadrantid in late December, 2016. The radiant point was below his horizon then, but you can see a piece of the Big Dipper asterism ascending on the right side of the photo. Thanks, Eliot!

You wouldn’t think people would be so determined to watch such an iffy shower. And yet the Quandrantids is one of the year’s most popular showers. Just remember, the Quadrantid shower has a narrow peak, lasting for only a few hours. If you miss the peak – which is easy to do – you won’t see many meteors.

But the pay-off can be good! The Quadrantids can match the meteor rates of the better-known August Perseid and December Geminid showers. The shower has been known to produce up to 50-100 or more meteors per hour in a dark sky.

Also know that this meteor shower favors the Northern Hemisphere because its radiant point – the point in the sky from which the meteors appear to radiate – is far to the north on the sky’s dome. So it’s not a globally watched shower, as many are.

If you’re thinking of watching the Quadrantids, do it. Meteor shower peaks are rarely a certainty. It’s nearly always a gamble that a shower will reward you with a good show.

The Quadrantid shower is named after the defunct 19th century constellation Quadrans Muralis. If you trace the paths of the Quandrantids backward, they appear to radiate from a point where this constellation once reigned in the sky. If you wish, you can locate the Quadrantid radiant in reference to the Big Dipper and the bright star Arcturus. Use the chart at the top of this post.

But you don’t need to find the radiant to enjoy the Quadrantids. You only need a dark, open sky for an hour or so before dawn.

View larger. | EarthSky Facebook friend Susan Jensen caught this beautiful Quadrantid in 2013.

Bottom line: If you’re at a northerly latitude, try the Quadrantid meteor shower from late night January 3 to dawn January 4, 2020. This shower can produce 50-100 meteors per hour, but its peak is short and sweet.

Want more? Try this post. Everything you need to know: Quadrantid meteor shower

Never miss another full moon! EarthSky moon calendar for 2020

EarthSky’s meteor shower guide for 2020

Big and Little Dippers: Noticeable in northern sky

from EarthSky https://ift.tt/2ubiJ4y

The annual Quadrantid meteor shower is nominally active for roughly two weeks, from about December 27 until about January 10 each year. However, peak activity lasts less than a day, and – to see the best display – you need to be on Earth’s night side during the Quadrantids’ short peak. The International Meteor Organization (IMO) predicts the 2020 peak will come on January 4 at 8 hours UTC. If that forecast holds, it places the peak around 3 a.m. Eastern Time in North America (2 a.m. Central Time, 1 a.m. Mountain Time and 12 midnight Pacific Time) on January 4. Translate UTC to your time.

The hope is always that the shower peaks at about the same time that the radiant is high up in your sky. That won’t be true for everyone across the globe, of course, but the prediction looks good for North America this year.

Keep in mind that meteor showers are fickle. Thus this prediction might – or might not – hold. So avid meteor watchers across the globe will be on the watch no matter what. As we’ve said before, meteor showers are like fishing. You wait, you watch … sometimes you catch something.

For all of us, some good news. In 2020, the waxing gibbous moon will set way before dawn’s first light, enabling you to watch this shower in a deliciously dark sky in the wee hours before dawn.

Another note about the Quadrantids. The shower is best seen from northerly latitudes because the radiant point for this shower (shown on the sky chart at top) is so far north on the sky’s dome.

Look at the sky chart above. The higher that you see the Big Dipper and the star Arcturus in your sky, the more likely that you’ll see some Quandrantid meteors. From mid-northern latitudes across the globe, the Big Dipper sits on the horizon at nightfall and climbs upward during the night. In the predawn hours, at mid-northern latitudes across the globe, the Big Dipper swings above Polaris the North Star. If the IMO prediction holds – and the peak comes around 8 UTC on January 4, 2020 – North American skywatchers have a decent chance of catching perhaps 15 to 25 meteors per hour. If we’re exceptionally lucky, we might see several times that number.

To find out when the moon sets in your sky, click on this Custom Sunrise Sunset Calendar and remember to check the Moonrise and Moonset box.

Will you see any meteors? Maybe!

Eliot Herman in Tucson, Arizona caught this early Quadrantid in late December, 2016. The radiant point was below his horizon then, but you can see a piece of the Big Dipper asterism ascending on the right side of the photo. Thanks, Eliot!

You wouldn’t think people would be so determined to watch such an iffy shower. And yet the Quandrantids is one of the year’s most popular showers. Just remember, the Quadrantid shower has a narrow peak, lasting for only a few hours. If you miss the peak – which is easy to do – you won’t see many meteors.

But the pay-off can be good! The Quadrantids can match the meteor rates of the better-known August Perseid and December Geminid showers. The shower has been known to produce up to 50-100 or more meteors per hour in a dark sky.

Also know that this meteor shower favors the Northern Hemisphere because its radiant point – the point in the sky from which the meteors appear to radiate – is far to the north on the sky’s dome. So it’s not a globally watched shower, as many are.

If you’re thinking of watching the Quadrantids, do it. Meteor shower peaks are rarely a certainty. It’s nearly always a gamble that a shower will reward you with a good show.

The Quadrantid shower is named after the defunct 19th century constellation Quadrans Muralis. If you trace the paths of the Quandrantids backward, they appear to radiate from a point where this constellation once reigned in the sky. If you wish, you can locate the Quadrantid radiant in reference to the Big Dipper and the bright star Arcturus. Use the chart at the top of this post.

But you don’t need to find the radiant to enjoy the Quadrantids. You only need a dark, open sky for an hour or so before dawn.

View larger. | EarthSky Facebook friend Susan Jensen caught this beautiful Quadrantid in 2013.

Bottom line: If you’re at a northerly latitude, try the Quadrantid meteor shower from late night January 3 to dawn January 4, 2020. This shower can produce 50-100 meteors per hour, but its peak is short and sweet.

Want more? Try this post. Everything you need to know: Quadrantid meteor shower

Never miss another full moon! EarthSky moon calendar for 2020

EarthSky’s meteor shower guide for 2020

Big and Little Dippers: Noticeable in northern sky

from EarthSky https://ift.tt/2ubiJ4y

Artificial intelligence could help breast screening save more lives

Right now, the NHS breast cancer screening programme saves around 1,300 lives in the UK each year.

But there are severe NHS staff shortages, particularly in the teams that help diagnose cancer,  with some reports suggesting that up to 1 in 10 diagnostic posts are currently vacant. Throw  in rising demand to the mix , and the future of these services could be in trouble. 

But new technology could help ease the situation. We’ve partnered with Google Health on research to develop artificial intelligence that not only has the potential to change the way we detect breast cancer but could also save the NHS time and money.  

Helping to train a computer 

Our scientists have created a database of anonymised breast cancer scans (mammograms) that have come from breast screening appointments at a number of  NHS breast screening centres around the UK, to be used for research.

Containing over 2.5 million images, this database is the largest and most dynamic of its kind in the world. And it’s available for academic and commercial partners to use, if they have a smart and scientifically sound research proposal that will benefit patients. But before they get access, their proposal is scrutinized by a group of experts, including people affected by cancer.  

That’s where Google Health comes in. Five years ago, Google and researchers from Imperial College London approached our team with a belief that a fancy computer programme could be developed and trained to spot cancer on mammograms.

“Basically, they were trying to teach a machine to read images and it takes an awful lot of images for it to learn so it can get really good at picking up cancer,” says Helen, a member of the group Independent Cancer Patients’ Voice, that brings together patient advocates to help with medical research. She reviewed Google Health’s application to access the database.

Computers with AI capabilities are only as good as the data they’ve been trained on, so for her, our mammogram collection and Google’s technology prowess were a winning combination. 

Results from this mighty research collaboration, published in Nature, show that the learning paid off. The AI software was able to correctly identify cancers in screening images with a similar degree of accuracy as the experts. The computer programme also reduced the number of errors, including cases where cancer is flagged incorrectly or those that are missed altogether. 

Currently, 2 experts review breast screening scans. But the system isn’t perfect, as screening can miss some cancers and pick up ones that wouldn’t have gone on to cause problems.

“It now looks from this research that having the combination of a human eye and a machine eye over the images could actually give more accurate results,” says Helen. She is referring to the study’s finding that AI reduced false positive results. These are ‘false alarms’ that can occur when someone gets an abnormal result, but they don’t have cancer. 

“That will reduce loads of anxiety for women,” says Helen, who was diagnosed with breast cancer in 2004 and finished reconstruction surgery in 2014. It will also save the NHS time and money by reducing the number of patients who are called back for further tests. 

Artificial intelligence in a real scenario

Professor Ken Young works for the NHS and manages our mammogram collection. He and his colleagues helped Google Health analyse the data and design the trial to make it the most realistic AI study in breast cancer detection to date. 

“What I think is most interesting about this study is its realism,” says Young. “What’s unusual is that it compares the algorithm to a totally realistic clinical scenario.” 

Past studies have used specially selected mammograms that were analysed in a somewhat artificial setting. For example, some other programmes have been tested on a set of images that have more cancer cases than would be found in the general population. 

But in the latest study, researchers compared real decisions made by radiologists analysing the scans of people attending the NHS breast screening programme. 

“We have a sample that is representative of all the women that might come through breast screening,” says Young. “It includes easy cases, difficult cases and everything in between.” 

And thanks to this collaboration, the data set is even richer than it was before. Around 100,000 more normal cases have been added to the database, which are now available to other researchers using the scan collection.  

Giving the gift of time 

NHS staff could also benefit from the partnership. A recent review suggested that this kind of tech will give radiologists ‘the gift of time’, instead of replacing them.

“All the radiologists I know aren’t worried about AI at all,” says Young. “I think they’d be delighted to have some of the quite monotonous work of reading mammograms done for them, so they’re freed up to do other things.” 

Keeping patient data safe

The other concern when it comes to developing AI software is data protection, something that Young, Helen and the team have carefully thought through.

“One of the concerns that comes through is patient confidentiality,” says Helen, who has taken part in trials herself. “It’s very important that I sit there on the lay side to make certain that everything is anonymised, and the ethics are checked.”

Before images enter the database, they’re immediately de-identified so there is no way that a researcher can find out who the mammograms belong to. The scans don’t include any personal information, which is “stripped out before we add the image to the database and share it with researchers,” says Young.

And research groups who are granted access to the images also have to agree to certain conditions, like keeping the patient data confidential and not using it for any other purpose than the development of AI screening algorithms.

AI still has a lot to learn

This well-trained algorithm is still in its early stages, but now has a firm foundation of knowledge to build on. Next the team need to test on a wider population and to see how radiologists can benefit from using the algorithm in the clinic. 

“I genuinely think the potential here is enormous,” says Young. “Breast cancer screening has a number of problems that could be tackled by the introduction of artificial intelligence.”

“These early studies using AI are the beginning of something quite big that will revolutionise medicine, this is just one of the first examples.” 

Gabi 

from Cancer Research UK – Science blog https://ift.tt/2ZRLRtv

Right now, the NHS breast cancer screening programme saves around 1,300 lives in the UK each year.

But there are severe NHS staff shortages, particularly in the teams that help diagnose cancer,  with some reports suggesting that up to 1 in 10 diagnostic posts are currently vacant. Throw  in rising demand to the mix , and the future of these services could be in trouble. 

But new technology could help ease the situation. We’ve partnered with Google Health on research to develop artificial intelligence that not only has the potential to change the way we detect breast cancer but could also save the NHS time and money.  

Helping to train a computer 

Our scientists have created a database of anonymised breast cancer scans (mammograms) that have come from breast screening appointments at a number of  NHS breast screening centres around the UK, to be used for research.

Containing over 2.5 million images, this database is the largest and most dynamic of its kind in the world. And it’s available for academic and commercial partners to use, if they have a smart and scientifically sound research proposal that will benefit patients. But before they get access, their proposal is scrutinized by a group of experts, including people affected by cancer.  

That’s where Google Health comes in. Five years ago, Google and researchers from Imperial College London approached our team with a belief that a fancy computer programme could be developed and trained to spot cancer on mammograms.

“Basically, they were trying to teach a machine to read images and it takes an awful lot of images for it to learn so it can get really good at picking up cancer,” says Helen, a member of the group Independent Cancer Patients’ Voice, that brings together patient advocates to help with medical research. She reviewed Google Health’s application to access the database.

Computers with AI capabilities are only as good as the data they’ve been trained on, so for her, our mammogram collection and Google’s technology prowess were a winning combination. 

Results from this mighty research collaboration, published in Nature, show that the learning paid off. The AI software was able to correctly identify cancers in screening images with a similar degree of accuracy as the experts. The computer programme also reduced the number of errors, including cases where cancer is flagged incorrectly or those that are missed altogether. 

Currently, 2 experts review breast screening scans. But the system isn’t perfect, as screening can miss some cancers and pick up ones that wouldn’t have gone on to cause problems.

“It now looks from this research that having the combination of a human eye and a machine eye over the images could actually give more accurate results,” says Helen. She is referring to the study’s finding that AI reduced false positive results. These are ‘false alarms’ that can occur when someone gets an abnormal result, but they don’t have cancer. 

“That will reduce loads of anxiety for women,” says Helen, who was diagnosed with breast cancer in 2004 and finished reconstruction surgery in 2014. It will also save the NHS time and money by reducing the number of patients who are called back for further tests. 

Artificial intelligence in a real scenario

Professor Ken Young works for the NHS and manages our mammogram collection. He and his colleagues helped Google Health analyse the data and design the trial to make it the most realistic AI study in breast cancer detection to date. 

“What I think is most interesting about this study is its realism,” says Young. “What’s unusual is that it compares the algorithm to a totally realistic clinical scenario.” 

Past studies have used specially selected mammograms that were analysed in a somewhat artificial setting. For example, some other programmes have been tested on a set of images that have more cancer cases than would be found in the general population. 

But in the latest study, researchers compared real decisions made by radiologists analysing the scans of people attending the NHS breast screening programme. 

“We have a sample that is representative of all the women that might come through breast screening,” says Young. “It includes easy cases, difficult cases and everything in between.” 

And thanks to this collaboration, the data set is even richer than it was before. Around 100,000 more normal cases have been added to the database, which are now available to other researchers using the scan collection.  

Giving the gift of time 

NHS staff could also benefit from the partnership. A recent review suggested that this kind of tech will give radiologists ‘the gift of time’, instead of replacing them.

“All the radiologists I know aren’t worried about AI at all,” says Young. “I think they’d be delighted to have some of the quite monotonous work of reading mammograms done for them, so they’re freed up to do other things.” 

Keeping patient data safe

The other concern when it comes to developing AI software is data protection, something that Young, Helen and the team have carefully thought through.

“One of the concerns that comes through is patient confidentiality,” says Helen, who has taken part in trials herself. “It’s very important that I sit there on the lay side to make certain that everything is anonymised, and the ethics are checked.”

Before images enter the database, they’re immediately de-identified so there is no way that a researcher can find out who the mammograms belong to. The scans don’t include any personal information, which is “stripped out before we add the image to the database and share it with researchers,” says Young.

And research groups who are granted access to the images also have to agree to certain conditions, like keeping the patient data confidential and not using it for any other purpose than the development of AI screening algorithms.

AI still has a lot to learn

This well-trained algorithm is still in its early stages, but now has a firm foundation of knowledge to build on. Next the team need to test on a wider population and to see how radiologists can benefit from using the algorithm in the clinic. 

“I genuinely think the potential here is enormous,” says Young. “Breast cancer screening has a number of problems that could be tackled by the introduction of artificial intelligence.”

“These early studies using AI are the beginning of something quite big that will revolutionise medicine, this is just one of the first examples.” 

Gabi 

from Cancer Research UK – Science blog https://ift.tt/2ZRLRtv

An ancient star burst in the Milky Way’s center

Detailed images of our Milky Way galaxy’s central region, obtained by astronomers using the Very Large Telescope (VLT) in Chile’s Atacama Desert, reveal that the galactic center underwent an intense period of star formation about a billion years ago. As the most massive stars in this burst of star formation came of age, the result was over a hundred thousand stars exploding as supernovae. The new findings were published in December 2019 in the peer-reviewed journal Nature Astronomy (published article here, and preprint here).

An earlier related article was published in the journal Astronomy & Astrophysics in October 2019 (published article here and preprint here).

The VLT is operated by the European Southern Observatory (ESO). A statement from ESO quoted Rainer Schödel of the Institute of Astrophysics of Andalusia in Granada, Spain, who led the observations. He said:

Our unprecedented survey of a large part of the galactic center has given us detailed insights into the formation process of stars in this region of the Milky Way.

Francisco Nogueras-Lara, who led the two new studies of the Milky Way central region while at the same institute in Granada, added:

Contrary to what had been accepted up to now, we found that the formation of stars has not been continuous.

In these new studies, according to their statement, the astronomers found that:

… about 80% of the stars in the Milky Way’s central region formed in the earliest years of our galaxy, between eight and 13.5 billion years ago. This initial period of star formation was followed by about six billion years during which very few stars were born. This was brought to an end by an intense burst of star formation around one billion years ago when, over a period of less than 100 million years, stars with a combined mass possibly as high as a few tens of million suns formed in this central region.

This chart shows the location of the Milky Way central region in the night sky. It lies in the direction of the constellation of Sagittarius the Archer, and is marked with a red circle in the image. Via ESO/ IAU/ Sky & Telescope.

Nogueras-Lara, now based at the Max Planck Institute for Astronomy in Heidelberg, Germany, added:

The conditions in the studied region during this burst of activity must have resembled those in ‘starburst’ galaxies, which form stars at rates of more than 100 solar masses per year.

This burst of activity, which must have resulted in the explosion of more than a hundred thousand supernovae, was probably one of the most energetic events in the whole history of the Milky Way.

At present, the whole Milky Way is forming stars at a rate of about one or two solar masses per year.

During a starburst, many massive stars are created; since they have shorter lifespans than lower-mass stars, they reach the end of their lives much faster, dying in violent supernova explosions.

Read more via ESO

Taken with the HAWK-I instrument on ESO’s Very Large Telescope in the Chilean Atacama Desert, this stunning image shows the Milky Way’s central region with an angular resolution of 0.2 arcseconds. This means the level of detail picked up by HAWK-I is roughly equivalent to seeing a soccer ball (football) in Zurich, Switzerland, from Munich, Germany, where ESO’s headquarters are located. Read more about this image. Image via ESO/ Nogueras-Lara et al.

Bottom line: Recent observations of the Milky Way’s center reveal new information about our galaxy’s star formation history. About 80% of the stars formed between eight and 13.5 billion years ago, followed by a six billion year hiatus. Then, about one billion years ago, there was a period of intense star formation in the galactic center that resulted in over a hundred thousand supernovae.

Source: The nuclear disc of the Milky Way: Early formation, long quiescence, and starburst activity one billion years ago

Source: GALACTICNUCLEUS. A high angular resolution JHKs imaging survey of the galactic center

Via ESO

from EarthSky https://ift.tt/2QGtxz0

Detailed images of our Milky Way galaxy’s central region, obtained by astronomers using the Very Large Telescope (VLT) in Chile’s Atacama Desert, reveal that the galactic center underwent an intense period of star formation about a billion years ago. As the most massive stars in this burst of star formation came of age, the result was over a hundred thousand stars exploding as supernovae. The new findings were published in December 2019 in the peer-reviewed journal Nature Astronomy (published article here, and preprint here).

An earlier related article was published in the journal Astronomy & Astrophysics in October 2019 (published article here and preprint here).

The VLT is operated by the European Southern Observatory (ESO). A statement from ESO quoted Rainer Schödel of the Institute of Astrophysics of Andalusia in Granada, Spain, who led the observations. He said:

Our unprecedented survey of a large part of the galactic center has given us detailed insights into the formation process of stars in this region of the Milky Way.

Francisco Nogueras-Lara, who led the two new studies of the Milky Way central region while at the same institute in Granada, added:

Contrary to what had been accepted up to now, we found that the formation of stars has not been continuous.

In these new studies, according to their statement, the astronomers found that:

… about 80% of the stars in the Milky Way’s central region formed in the earliest years of our galaxy, between eight and 13.5 billion years ago. This initial period of star formation was followed by about six billion years during which very few stars were born. This was brought to an end by an intense burst of star formation around one billion years ago when, over a period of less than 100 million years, stars with a combined mass possibly as high as a few tens of million suns formed in this central region.

This chart shows the location of the Milky Way central region in the night sky. It lies in the direction of the constellation of Sagittarius the Archer, and is marked with a red circle in the image. Via ESO/ IAU/ Sky & Telescope.

Nogueras-Lara, now based at the Max Planck Institute for Astronomy in Heidelberg, Germany, added:

The conditions in the studied region during this burst of activity must have resembled those in ‘starburst’ galaxies, which form stars at rates of more than 100 solar masses per year.

This burst of activity, which must have resulted in the explosion of more than a hundred thousand supernovae, was probably one of the most energetic events in the whole history of the Milky Way.

At present, the whole Milky Way is forming stars at a rate of about one or two solar masses per year.

During a starburst, many massive stars are created; since they have shorter lifespans than lower-mass stars, they reach the end of their lives much faster, dying in violent supernova explosions.

Read more via ESO

Taken with the HAWK-I instrument on ESO’s Very Large Telescope in the Chilean Atacama Desert, this stunning image shows the Milky Way’s central region with an angular resolution of 0.2 arcseconds. This means the level of detail picked up by HAWK-I is roughly equivalent to seeing a soccer ball (football) in Zurich, Switzerland, from Munich, Germany, where ESO’s headquarters are located. Read more about this image. Image via ESO/ Nogueras-Lara et al.

Bottom line: Recent observations of the Milky Way’s center reveal new information about our galaxy’s star formation history. About 80% of the stars formed between eight and 13.5 billion years ago, followed by a six billion year hiatus. Then, about one billion years ago, there was a period of intense star formation in the galactic center that resulted in over a hundred thousand supernovae.

Source: The nuclear disc of the Milky Way: Early formation, long quiescence, and starburst activity one billion years ago

Source: GALACTICNUCLEUS. A high angular resolution JHKs imaging survey of the galactic center

Via ESO

from EarthSky https://ift.tt/2QGtxz0

Clouds that look like ocean waves

View at EarthSky Community Photos. | Suzanne Kelley of Littleton, Colorado caught these Kelvin-Helmholtz clouds – clouds that look like ocean waves – at sunset over the Rocky Mountains on New Year’s Eve, December 31, 2019. Thank you, Suzanne!

Here’s a collection of beautiful images of a special kind of cloud known to scientists as Kelvin-Helmholtz clouds. These clouds look like breaking ocean waves, with the rolling eddies seen at the top of the cloud layers. The eddies are usually evenly spaced, making the clouds easily identifiable.

Kelvin-Helmholtz clouds are named for Lord Kelvin and Hermann von Helmholtz, who studied the physics of the instability that leads to this type of cloud formation. A Kelvin-Helmholtz instability forms where there’s a velocity difference across the interface between two fluids: for example, wind blowing over water. You’ll often see the characteristic wave structure in this type of cloud when two different layers of air in our atmosphere are moving at different speeds. The upper layers of air are moving at higher speeds and will often scoop the top of the cloud layer into these wave-like rolling structures.

The clouds often form on windy days, when there’s a difference in densities of the air, for example, during a temperature inversion. They’re often good indicators of atmospheric instability and the presence of turbulence for aircraft.

It’s widely believed that these waves in the sky inspired the swirls in van Gogh’s masterpiece Starry Night.

Enjoy the photos!

Surf in the sky via Yoav Naccache

Kelvin-Helmholtz clouds seen in Tupper Lake, New York, in the Adirondack Mountains. Photo via Paul Chartier.

View larger. | EarthSky Facebook friend Risa Bender caught these Kelvin-Helmholtz clouds from Dallas, Texas.

Cindy Gurmann caught these Kelvin-Helmholzt clouds near New York, New York.

Helio de Carvalho Vital caught these Kelvin-Helmholtz clouds over Rio de Janeiro, Brazil.

View larger. | Helio de Carvalho Vital also submitted this photo to EarthSky. It’s a Kelvin-Helmholtz effect in virga, or rain that falls but doesn’t reach the ground. He caught it in Rio de Janeiro, Brazil, on May 15, 2015.

Kelvin-Helmholtz clouds seen over San Francisco. These clouds, sometimes called “billow clouds,” are produced by instability, when horizontal layers of air brush by one another at different velocities. Photo via Wikimedia Commons.

Earth isn’t the only planet with Kelvin-Helmholtz clouds. Here they are on Saturn; Jupiter has them, too. Image via Wikimedia Commons.

Bottom line: Kelvin-Helmholtz clouds – also called billow clouds – form when two different layers of air in our atmosphere are moving at different speeds.

from EarthSky https://ift.tt/2F7liXA

View at EarthSky Community Photos. | Suzanne Kelley of Littleton, Colorado caught these Kelvin-Helmholtz clouds – clouds that look like ocean waves – at sunset over the Rocky Mountains on New Year’s Eve, December 31, 2019. Thank you, Suzanne!

Here’s a collection of beautiful images of a special kind of cloud known to scientists as Kelvin-Helmholtz clouds. These clouds look like breaking ocean waves, with the rolling eddies seen at the top of the cloud layers. The eddies are usually evenly spaced, making the clouds easily identifiable.

Kelvin-Helmholtz clouds are named for Lord Kelvin and Hermann von Helmholtz, who studied the physics of the instability that leads to this type of cloud formation. A Kelvin-Helmholtz instability forms where there’s a velocity difference across the interface between two fluids: for example, wind blowing over water. You’ll often see the characteristic wave structure in this type of cloud when two different layers of air in our atmosphere are moving at different speeds. The upper layers of air are moving at higher speeds and will often scoop the top of the cloud layer into these wave-like rolling structures.

The clouds often form on windy days, when there’s a difference in densities of the air, for example, during a temperature inversion. They’re often good indicators of atmospheric instability and the presence of turbulence for aircraft.

It’s widely believed that these waves in the sky inspired the swirls in van Gogh’s masterpiece Starry Night.

Enjoy the photos!

Surf in the sky via Yoav Naccache

Kelvin-Helmholtz clouds seen in Tupper Lake, New York, in the Adirondack Mountains. Photo via Paul Chartier.

View larger. | EarthSky Facebook friend Risa Bender caught these Kelvin-Helmholtz clouds from Dallas, Texas.

Cindy Gurmann caught these Kelvin-Helmholzt clouds near New York, New York.

Helio de Carvalho Vital caught these Kelvin-Helmholtz clouds over Rio de Janeiro, Brazil.

View larger. | Helio de Carvalho Vital also submitted this photo to EarthSky. It’s a Kelvin-Helmholtz effect in virga, or rain that falls but doesn’t reach the ground. He caught it in Rio de Janeiro, Brazil, on May 15, 2015.

Kelvin-Helmholtz clouds seen over San Francisco. These clouds, sometimes called “billow clouds,” are produced by instability, when horizontal layers of air brush by one another at different velocities. Photo via Wikimedia Commons.

Earth isn’t the only planet with Kelvin-Helmholtz clouds. Here they are on Saturn; Jupiter has them, too. Image via Wikimedia Commons.

Bottom line: Kelvin-Helmholtz clouds – also called billow clouds – form when two different layers of air in our atmosphere are moving at different speeds.

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January 2020 guide to the bright planets

Click the name of a planet to learn more about its visibility in January 2020:

Evening planets: Venus (all month) and Mercury (late January)
Morning planets: Mars (all month) and Jupiter (late January)

Try Stellarium for a precise view from your location.

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

The young waxing crescent moon joins up with the dazzling planet Venus by the month’s end. Use Venus and the lit side of the waxing lunar crescent to help guide you to Mercury’s location near the horizon. Read more.

Venus – the brightest planet – blazes mightily in the western sky after sunset. In fact, it’s the only bright planet to light up these January evenings all month long, although Mercury might fleetingly appear at dusk by the month’s end. Given clear skies, it’ll be hard to miss Venus, the 3rd-brightest celestial body to light up the heavens, after the sun and moon, respectively. Some sharp-sighted people can even see Venus in a daytime sky.

Watch for the young waxing crescent moon to join up with Venus on January 27 and 28. You can also use Venus and the lit side of the waxing crescent moon to help you find Mercury at the month’s end. (See sky chart above.)

Venus is in good view from around the world, though it stays out longer after dark at more northerly latitudes.

At mid-northern latitudes, Venus sets about 2 3/4 hours after sunset at the beginning of the month, and about 3 1/3 hours after sundown by the month’s end.

At temperate latitudes in the Southern Hemisphere, Venus sets roughly 2 hours after sunset all month long.

Mercury might become visible after sunset, either to the eye alone or binoculars, near the month’s end. Starting around January 26 or 27, use the lit side of the waxing crescent moon to find Mercury near the sunset point on the horizon at evening dusk. (See sky chart above.) The more northerly latitudes have the advantage for catching Mercury in late January.

Near the end of the month, at mid-northern latitudes, Mercury sets about 1 hour after sunset..

Near the end of the month, at temperate latitudes in the Southern Hemisphere, Mercury sets about 3/4 hour after sunset.

Mercury will stay out longer after sunset during the first few weeks of February 2020. Point out Mercury to your valentine on February 14, 2020, as this world reaches its greatest elongation (18 degrees west from the sun) in the February evening sky. This evening apparition of Mercury favors the Northern Hemisphere.

However, the Southern Hemisphere will enjoy the advantage when Mercury becomes a morning object in March and April 2020.

EarthSky lunar calendars make great gifts for astronomy-minded friends and family. Order now. Going fast!

Use the old waning crescent moon to find the red planet planet Mars before sunrise on January 19, 20 and 21, 2020. Read more.

Mars is the only bright planet to adorn the predawn sky throughout January 2020.

At mid-northern latitudes, Mars rises about 3 hours before the sun throughout January.

At temperate latitudes in the Southern Hemisphere, Mars comes up about 2 1/2 hours before sunrise in early January, and nearly 4 hours before the sun by the month’s end.

Mars is now in that part of its cycle with respect to Earth in which it’ll hover – modesty-bright and perhaps not at all prominent – in our predawn sky for some months. Mars was in conjunction with the sun, or most behind the sun as seen from Earth – on September 2, 2019. And now it remains far across the solar system from us, with Earth speeding around in its orbit, trying to catch Mars again. But it’ll be some months before we catch it.

And thus Mars alternates years in being bright in our sky, or faint. 2019 was a dull year, but 2020 will be an exciting one, for Mars! It’ll start slowly, though, with Mars sitting low in the east as the year begins. January, February, March, April 2020 … you’ll still find Mars doing nothing much, low in the east before sunup. Earth will still be far across the solar system from Mars, but rushing along in our smaller, faster orbit, trying to catch up. As northern summer 2020 approaches, Mars will begin to change. It’ll begin to brighten more dramatically as, finally, Earth begins to catch up to Mars. The Red Planet will appear brightest in our sky – very bright indeed and fiery red – around the time of its opposition on October 13, 2020.

Let the old moon help guide your eye to Mars for several mornings, centered on or near January 20, as shown on the sky chart above.

By the way, the red planet Mars is easily visible before dawn right now, but this modesty-bright world may fade from view by the time that Jupiter rises into your sky. Read more.

Jupiter – the second-brightest planet – is nominally a morning planet all month long. Despite its brightness, Jupiter sits too close to the glare of sunrise to be visible in early January. By mid-month or so, look for Jupiter to appear above the sunrise point on the horizon as the predawn darkness gives way to dawn. Before sunrise on January 20, 21 and 22, let the slender waning crescent moon help guide you to Jupiter, as shown on the sky chart above.

At mid-northern latitudes, Jupiter rises about 50 minutes before the sun in mid-January, and nearly 1 1/2 hours before the sun by the month’s end.

At temperate latitudes in the Southern hemisphere, Jupiter rises about 1 hour before the sun in mid-January, and 2 hours before the sun by the month’s end.

Watch for Jupiter to become quite prominent in the morning sky throughout February 2020. On March 20, 2020, Jupiter will catch up with Mars to display a dazzling planetary conjunction in the predawn sky. (See sky chart below.)

This year, in 2020, the planets Mars and Jupiter are in conjunction on the March 20th equinox.

Saturn sits in the glare of the sun all month long. Saturn passes directly behind the sun on January 13, 2020, to transition from the evening to morning sky. Your first glimpse of Saturn in the morning sky will probably have to wait until February 2020.

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 January 2020, dazzling Venus lights up dusk and early evening sky whereas moderately-bright Mars comes up before dawn. Late in the month, you might catch Mercury low in the west at dusk and Jupiter above the eastern horizon at dawn. Saturn, in the meanwhile, hides in the glare of the sun.

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 January 2020:

Evening planets: Venus (all month) and Mercury (late January)
Morning planets: Mars (all month) and Jupiter (late January)

Try Stellarium for a precise view from your location.

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

The young waxing crescent moon joins up with the dazzling planet Venus by the month’s end. Use Venus and the lit side of the waxing lunar crescent to help guide you to Mercury’s location near the horizon. Read more.

Venus – the brightest planet – blazes mightily in the western sky after sunset. In fact, it’s the only bright planet to light up these January evenings all month long, although Mercury might fleetingly appear at dusk by the month’s end. Given clear skies, it’ll be hard to miss Venus, the 3rd-brightest celestial body to light up the heavens, after the sun and moon, respectively. Some sharp-sighted people can even see Venus in a daytime sky.

Watch for the young waxing crescent moon to join up with Venus on January 27 and 28. You can also use Venus and the lit side of the waxing crescent moon to help you find Mercury at the month’s end. (See sky chart above.)

Venus is in good view from around the world, though it stays out longer after dark at more northerly latitudes.

At mid-northern latitudes, Venus sets about 2 3/4 hours after sunset at the beginning of the month, and about 3 1/3 hours after sundown by the month’s end.

At temperate latitudes in the Southern Hemisphere, Venus sets roughly 2 hours after sunset all month long.

Mercury might become visible after sunset, either to the eye alone or binoculars, near the month’s end. Starting around January 26 or 27, use the lit side of the waxing crescent moon to find Mercury near the sunset point on the horizon at evening dusk. (See sky chart above.) The more northerly latitudes have the advantage for catching Mercury in late January.

Near the end of the month, at mid-northern latitudes, Mercury sets about 1 hour after sunset..

Near the end of the month, at temperate latitudes in the Southern Hemisphere, Mercury sets about 3/4 hour after sunset.

Mercury will stay out longer after sunset during the first few weeks of February 2020. Point out Mercury to your valentine on February 14, 2020, as this world reaches its greatest elongation (18 degrees west from the sun) in the February evening sky. This evening apparition of Mercury favors the Northern Hemisphere.

However, the Southern Hemisphere will enjoy the advantage when Mercury becomes a morning object in March and April 2020.

EarthSky lunar calendars make great gifts for astronomy-minded friends and family. Order now. Going fast!

Use the old waning crescent moon to find the red planet planet Mars before sunrise on January 19, 20 and 21, 2020. Read more.

Mars is the only bright planet to adorn the predawn sky throughout January 2020.

At mid-northern latitudes, Mars rises about 3 hours before the sun throughout January.

At temperate latitudes in the Southern Hemisphere, Mars comes up about 2 1/2 hours before sunrise in early January, and nearly 4 hours before the sun by the month’s end.

Mars is now in that part of its cycle with respect to Earth in which it’ll hover – modesty-bright and perhaps not at all prominent – in our predawn sky for some months. Mars was in conjunction with the sun, or most behind the sun as seen from Earth – on September 2, 2019. And now it remains far across the solar system from us, with Earth speeding around in its orbit, trying to catch Mars again. But it’ll be some months before we catch it.

And thus Mars alternates years in being bright in our sky, or faint. 2019 was a dull year, but 2020 will be an exciting one, for Mars! It’ll start slowly, though, with Mars sitting low in the east as the year begins. January, February, March, April 2020 … you’ll still find Mars doing nothing much, low in the east before sunup. Earth will still be far across the solar system from Mars, but rushing along in our smaller, faster orbit, trying to catch up. As northern summer 2020 approaches, Mars will begin to change. It’ll begin to brighten more dramatically as, finally, Earth begins to catch up to Mars. The Red Planet will appear brightest in our sky – very bright indeed and fiery red – around the time of its opposition on October 13, 2020.

Let the old moon help guide your eye to Mars for several mornings, centered on or near January 20, as shown on the sky chart above.

By the way, the red planet Mars is easily visible before dawn right now, but this modesty-bright world may fade from view by the time that Jupiter rises into your sky. Read more.

Jupiter – the second-brightest planet – is nominally a morning planet all month long. Despite its brightness, Jupiter sits too close to the glare of sunrise to be visible in early January. By mid-month or so, look for Jupiter to appear above the sunrise point on the horizon as the predawn darkness gives way to dawn. Before sunrise on January 20, 21 and 22, let the slender waning crescent moon help guide you to Jupiter, as shown on the sky chart above.

At mid-northern latitudes, Jupiter rises about 50 minutes before the sun in mid-January, and nearly 1 1/2 hours before the sun by the month’s end.

At temperate latitudes in the Southern hemisphere, Jupiter rises about 1 hour before the sun in mid-January, and 2 hours before the sun by the month’s end.

Watch for Jupiter to become quite prominent in the morning sky throughout February 2020. On March 20, 2020, Jupiter will catch up with Mars to display a dazzling planetary conjunction in the predawn sky. (See sky chart below.)

This year, in 2020, the planets Mars and Jupiter are in conjunction on the March 20th equinox.

Saturn sits in the glare of the sun all month long. Saturn passes directly behind the sun on January 13, 2020, to transition from the evening to morning sky. Your first glimpse of Saturn in the morning sky will probably have to wait until February 2020.

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 January 2020, dazzling Venus lights up dusk and early evening sky whereas moderately-bright Mars comes up before dawn. Late in the month, you might catch Mercury low in the west at dusk and Jupiter above the eastern horizon at dawn. Saturn, in the meanwhile, hides in the glare of the sun.

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

Latest sunrises (north) and sunsets (south) in early January

Photo at top: Peter Bowers

So you like to sleep late, but don’t want to miss the sunrise? If you’re in the Northern Hemisphere, this time of year is for you. Sleep on! The latest sunrises of 2020 are happening this week for mid-latitudes in the Northern Hemisphere. For example, sunrises in the central U.S. – say, around Wichita, Kansas – for the next several days will be around 7:45 a.m.

Meanwhile, if you live in the Southern Hemisphere, your latest sunsets are happening around now, assuming you’re at mid-southern latitudes.

Many sky watchers notice this phenomenon, which is part of an unvarying sequence each year. For us at mid-northern latitudes in the Northern Hemisphere, the sequence is: earliest sunset in early December, shortest day at the solstice around December 21, latest sunrise in early January.

At middle latitudes in the Southern Hemisphere, the sequence is: earliest sunrise in early December, longest day at the December solstice, latest sunset in early January.

This natural order what we can expect every year, on our tilted Earth, pursuing our elliptical orbit around the sun.

The discrepancy between the clock and sun gives us the latest sunrises after the winter solstice for mid-latitudes in the Northern Hemisphere. Photo of the Larkin sundial via Anika Malone.

The December solstice always brings the shortest day to the Northern Hemisphere and the longest day to the Southern Hemisphere. But, clearly, the latest sunrise doesn’t coincide with the day of least daylight, and the latest sunset doesn’t happen on the day of greatest daylight. Why not?

The main reason is that the Earth’s rotational axis is tilted 23.5 degrees out of vertical to the plane of our orbit around the sun. A secondary reason is that the Earth’s orbit isn’t a perfect circle. Due to our eccentric orbit (that’s an orbit shaped like a squashed circle, with the sun slightly off center), Earth travels fastest in January and slowest in July.

Clock time gets a bit out of sync with sun time – by about 1/2 minute per day for several weeks around the December solstice.

Because solar noon (midday) comes later by the clock today than on the solstice, so do the times of sunrise and sunset. The table below helps to explain:

For Philadelphia, Pennsylvania

Date	Sunrise	Solar Noon (Midday)	Sunset	Daylight Hours
December 7	7:08 a.m.	11:52 a.m.	4:35 p.m.	9 hours 27 minutes
December 21	7:18 a.m.	11:58 a.m.	4:38 p.m.	9 hours 20 minutes
January 5	7:23 a.m.	12:06 p.m.	4:40 p.m.	9 hours 26 minutes

The exact date for the latest sunrise or latest sunset varies by latitude. This week, mid-temperate latitudes in the Northern Hemisphere are waking up to their latest sunrises, while the Southern Hemisphere’s mid-temperate latitudes are watching their latest sunsets. At latitudes closer to the equator, the latest sunrise or latest sunset has yet to come. Closer to the Arctic or Antarctic Circles, the latest sunrise or latest sunset has already come and gone.

But in either the Northern or Southern Hemisphere, the sequence is always the same:

1) earliest sunset, winter solstice, latest sunrise
2) earliest sunrise, summer solstice, latest sunset

Sunrise on a cloudy day at Grant Park Beach in South Milwaukee, Wisconsin. Photo by Heather Kamine.

Bottom line: Notice the time of sunrise and sunset at this time of year. If you’re in the Northern Hemisphere, your latest sunrises are happening this week at mid-northern latitudes. If you’re in the Southern Hemisphere, mid-latitudes are watching the year’s latest sunsets. Enjoy!

A planisphere is virtually indispensable for beginning stargazers. Order your EarthSky Planisphere today!

Earth comes closest to the sun in early January

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Photo at top: Peter Bowers

So you like to sleep late, but don’t want to miss the sunrise? If you’re in the Northern Hemisphere, this time of year is for you. Sleep on! The latest sunrises of 2020 are happening this week for mid-latitudes in the Northern Hemisphere. For example, sunrises in the central U.S. – say, around Wichita, Kansas – for the next several days will be around 7:45 a.m.

Meanwhile, if you live in the Southern Hemisphere, your latest sunsets are happening around now, assuming you’re at mid-southern latitudes.

Many sky watchers notice this phenomenon, which is part of an unvarying sequence each year. For us at mid-northern latitudes in the Northern Hemisphere, the sequence is: earliest sunset in early December, shortest day at the solstice around December 21, latest sunrise in early January.

At middle latitudes in the Southern Hemisphere, the sequence is: earliest sunrise in early December, longest day at the December solstice, latest sunset in early January.

This natural order what we can expect every year, on our tilted Earth, pursuing our elliptical orbit around the sun.

The discrepancy between the clock and sun gives us the latest sunrises after the winter solstice for mid-latitudes in the Northern Hemisphere. Photo of the Larkin sundial via Anika Malone.

The December solstice always brings the shortest day to the Northern Hemisphere and the longest day to the Southern Hemisphere. But, clearly, the latest sunrise doesn’t coincide with the day of least daylight, and the latest sunset doesn’t happen on the day of greatest daylight. Why not?

The main reason is that the Earth’s rotational axis is tilted 23.5 degrees out of vertical to the plane of our orbit around the sun. A secondary reason is that the Earth’s orbit isn’t a perfect circle. Due to our eccentric orbit (that’s an orbit shaped like a squashed circle, with the sun slightly off center), Earth travels fastest in January and slowest in July.

Clock time gets a bit out of sync with sun time – by about 1/2 minute per day for several weeks around the December solstice.

Because solar noon (midday) comes later by the clock today than on the solstice, so do the times of sunrise and sunset. The table below helps to explain:

For Philadelphia, Pennsylvania

Date	Sunrise	Solar Noon (Midday)	Sunset	Daylight Hours
December 7	7:08 a.m.	11:52 a.m.	4:35 p.m.	9 hours 27 minutes
December 21	7:18 a.m.	11:58 a.m.	4:38 p.m.	9 hours 20 minutes
January 5	7:23 a.m.	12:06 p.m.	4:40 p.m.	9 hours 26 minutes

The exact date for the latest sunrise or latest sunset varies by latitude. This week, mid-temperate latitudes in the Northern Hemisphere are waking up to their latest sunrises, while the Southern Hemisphere’s mid-temperate latitudes are watching their latest sunsets. At latitudes closer to the equator, the latest sunrise or latest sunset has yet to come. Closer to the Arctic or Antarctic Circles, the latest sunrise or latest sunset has already come and gone.

But in either the Northern or Southern Hemisphere, the sequence is always the same:

1) earliest sunset, winter solstice, latest sunrise
2) earliest sunrise, summer solstice, latest sunset

Sunrise on a cloudy day at Grant Park Beach in South Milwaukee, Wisconsin. Photo by Heather Kamine.

Bottom line: Notice the time of sunrise and sunset at this time of year. If you’re in the Northern Hemisphere, your latest sunrises are happening this week at mid-northern latitudes. If you’re in the Southern Hemisphere, mid-latitudes are watching the year’s latest sunsets. Enjoy!

A planisphere is virtually indispensable for beginning stargazers. Order your EarthSky Planisphere today!

Earth comes closest to the sun in early January

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Dark skies for 2020’s Quadrantid meteors

View larger. | In 2014, as the Quadrantids were flying, people at far northern latitudes were seeing auroras. Photo by Tommy Eliassen.

The Quadrantid meteor shower is 2020’s first major meteor shower. We’ll have moon-free skies during the predawn hours on January 4 for this year’s peak, expected late night January 3 until dawn January 4. Although the Quadrantids have been known to produce some 50-100 meteors in a dark sky, their peak is extremely narrow, time-wise. Peaks of the Perseid or Geminid meteor showers persist for a day or more, allowing all time zones around the world to enjoy a good display of Perseids or Geminids. But the Quadrantids’ peak lasts only a few hours. So you have to be on the right part of Earth – preferably with the radiant high in your sky – in order to experience the peak of the Quadrantids. What’s more, the shower favors the Northern Hemisphere because its radiant point is so far north on the sky’s dome.

So you need some luck to see the Quadrantids, and being in the Northern Hemisphere does help. Who will see the 2020 shower? Keep in mind the prediction of the Quadrantid peak represents an educated guess, not an ironclad guarantee.

That said, in 2020 the International Meteor Organization gives the peak as January 4 at 08:00 UTC. If that prediction of the peak holds true, North America has a good shot at viewing the shower at its best during the predawn hours on January 4.

Just know that meteor showers are notorious for defying the best-laid forecasts. Thus for the Quadrantids – as for any meteor shower – your best plan is simply to look for yourself.

Barry Simmons in Lake Martin, Alabama, captured this Quadrantid meteor during the 2014 shower.

Any place at mid-northern and far-northern latitudes might be in a decent position to watch the Quadrantids in 2020, especially as there is no moonlight in the predawn hours to ruin this year’s show.

All other things being equal, for any meteor shower, you are likely to see the most meteors when the radiant is high in the sky.

In the case of the Quadrantid shower, the radiant point is seen highest in the sky in the dark hours before dawn.

From mid-northern latitudes, the radiant point for the Quadrantid shower doesn’t climb over the horizon until after midnight.

Where is the Quadrantids’ radiant point?

The radiant point of the Quadrantid shower makes an approximate right angle with the Big Dipper and the bright star Arcturus. If you trace the paths of the Quadrantid meteors backward, they appear to radiate from this point on the starry sky.

Now for our usual caveat. You don’t need to find the meteor shower radiant to see the Quadrantid meteors.

You just have to be at mid-northern or far-northern latitudes, up in the wee hours of the morning and hope the peak comes at just the right time to your part of the world.

The meteors will radiate from the northern sky, but appear in all parts of the sky.

The now-defunct constellation Quadrans Muralis, for which the Quadrantids are named. Image via Atlas Coelestis.

The Quadrantids are named for a constellation that no longer exists. Most meteor showers are named for the constellations from which they appear to radiate. So it is with the Quadrantids. But the Quadrantids’ constellation no longer exists, except in memory. The name Quadrantids comes from the constellation Quadrans Muralis (Mural Quadrant), created by the French astronomer Jerome Lalande in 1795. This now-obsolete constellation was located between the constellations of Bootes the Herdsman and Draco the Dragon. Where did it go?

To understand the history of the Quadrantids’ name, we have to go back to the earliest observations of this shower. In early January 1825, Antonio Brucalassi in Italy reported that:

… the atmosphere was traversed by a multitude of the luminous bodies known by the name of falling stars.

They appeared to radiate from Quadrans Muralis. In 1839, Adolphe Quetelet of Brussels Observatory in Belgium and Edward C. Herrick in Connecticut independently made the suggestion that the Quadrantids are an annual shower.

But in 1922 the International Astronomical Union devised a list 88 modern constellations. The list was agreed upon by the International Astronomical Union at its inaugural General Assembly held in Rome in May 1922. It did not include a constellation Quadrans Muralis.

Today, this meteor shower retains the name Quadrantids, for the original and now obsolete constellation Quadrans Muralis.

The radiant point for the Quadrantids is now considered to be at the northern tip of Bootes, near the Big Dipper asterism in our sky, not far from Bootes’ brightest star Arcturus. It is very far north on the sky’s dome, which is why Southern Hemisphere observers probably won’t see many (if any) Quadrantid meteors. Most of the meteors simply won’t make it above the horizon for Southern Hemisphere skywatchers. But some might!

In 2003, Peter Jenniskens proposed that this object, 2003 EH1, is the parent body of the Quadrantid meteor shower.

Quadrantid meteors have a mysterious parent object. In 2003, astronomer Peter Jenniskens tentatively identified the parent body of the Quadrantids as the asteroid 2003 EH1. If indeed this body is the Quadrantids’ parent, then the Quadrantids, like the Geminid meteors, come from a rocky body – not an icy comet. Strange.

In turn, though, 2003 EH1 might be the same object as the comet C/1490 Y1, which was observed by Chinese, Japanese and Korean astronomers 500 years ago.

So the exact story behind the Quadrantids’ parent object remains somewhat mysterious.

Bottom line: The first major meteor shower of 2020, and every year, the Quadrantid meteor shower will probably be at its best in the hours between 2 a.m. and dawn January 4. Fortunately, in 2020, the absence of moonlight in the predawn sky means dark skies during the peak hours of this year’s annual Quadrantid meteor shower.

Best New Year’s gift ever! EarthSky moon calendar for 2019

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View larger. | In 2014, as the Quadrantids were flying, people at far northern latitudes were seeing auroras. Photo by Tommy Eliassen.

The Quadrantid meteor shower is 2020’s first major meteor shower. We’ll have moon-free skies during the predawn hours on January 4 for this year’s peak, expected late night January 3 until dawn January 4. Although the Quadrantids have been known to produce some 50-100 meteors in a dark sky, their peak is extremely narrow, time-wise. Peaks of the Perseid or Geminid meteor showers persist for a day or more, allowing all time zones around the world to enjoy a good display of Perseids or Geminids. But the Quadrantids’ peak lasts only a few hours. So you have to be on the right part of Earth – preferably with the radiant high in your sky – in order to experience the peak of the Quadrantids. What’s more, the shower favors the Northern Hemisphere because its radiant point is so far north on the sky’s dome.

So you need some luck to see the Quadrantids, and being in the Northern Hemisphere does help. Who will see the 2020 shower? Keep in mind the prediction of the Quadrantid peak represents an educated guess, not an ironclad guarantee.

That said, in 2020 the International Meteor Organization gives the peak as January 4 at 08:00 UTC. If that prediction of the peak holds true, North America has a good shot at viewing the shower at its best during the predawn hours on January 4.

Just know that meteor showers are notorious for defying the best-laid forecasts. Thus for the Quadrantids – as for any meteor shower – your best plan is simply to look for yourself.

Barry Simmons in Lake Martin, Alabama, captured this Quadrantid meteor during the 2014 shower.

Any place at mid-northern and far-northern latitudes might be in a decent position to watch the Quadrantids in 2020, especially as there is no moonlight in the predawn hours to ruin this year’s show.

All other things being equal, for any meteor shower, you are likely to see the most meteors when the radiant is high in the sky.

In the case of the Quadrantid shower, the radiant point is seen highest in the sky in the dark hours before dawn.

From mid-northern latitudes, the radiant point for the Quadrantid shower doesn’t climb over the horizon until after midnight.

Where is the Quadrantids’ radiant point?

The radiant point of the Quadrantid shower makes an approximate right angle with the Big Dipper and the bright star Arcturus. If you trace the paths of the Quadrantid meteors backward, they appear to radiate from this point on the starry sky.

Now for our usual caveat. You don’t need to find the meteor shower radiant to see the Quadrantid meteors.

You just have to be at mid-northern or far-northern latitudes, up in the wee hours of the morning and hope the peak comes at just the right time to your part of the world.

The meteors will radiate from the northern sky, but appear in all parts of the sky.

The now-defunct constellation Quadrans Muralis, for which the Quadrantids are named. Image via Atlas Coelestis.

The Quadrantids are named for a constellation that no longer exists. Most meteor showers are named for the constellations from which they appear to radiate. So it is with the Quadrantids. But the Quadrantids’ constellation no longer exists, except in memory. The name Quadrantids comes from the constellation Quadrans Muralis (Mural Quadrant), created by the French astronomer Jerome Lalande in 1795. This now-obsolete constellation was located between the constellations of Bootes the Herdsman and Draco the Dragon. Where did it go?

To understand the history of the Quadrantids’ name, we have to go back to the earliest observations of this shower. In early January 1825, Antonio Brucalassi in Italy reported that:

… the atmosphere was traversed by a multitude of the luminous bodies known by the name of falling stars.

They appeared to radiate from Quadrans Muralis. In 1839, Adolphe Quetelet of Brussels Observatory in Belgium and Edward C. Herrick in Connecticut independently made the suggestion that the Quadrantids are an annual shower.

But in 1922 the International Astronomical Union devised a list 88 modern constellations. The list was agreed upon by the International Astronomical Union at its inaugural General Assembly held in Rome in May 1922. It did not include a constellation Quadrans Muralis.

Today, this meteor shower retains the name Quadrantids, for the original and now obsolete constellation Quadrans Muralis.

The radiant point for the Quadrantids is now considered to be at the northern tip of Bootes, near the Big Dipper asterism in our sky, not far from Bootes’ brightest star Arcturus. It is very far north on the sky’s dome, which is why Southern Hemisphere observers probably won’t see many (if any) Quadrantid meteors. Most of the meteors simply won’t make it above the horizon for Southern Hemisphere skywatchers. But some might!

In 2003, Peter Jenniskens proposed that this object, 2003 EH1, is the parent body of the Quadrantid meteor shower.

Quadrantid meteors have a mysterious parent object. In 2003, astronomer Peter Jenniskens tentatively identified the parent body of the Quadrantids as the asteroid 2003 EH1. If indeed this body is the Quadrantids’ parent, then the Quadrantids, like the Geminid meteors, come from a rocky body – not an icy comet. Strange.

In turn, though, 2003 EH1 might be the same object as the comet C/1490 Y1, which was observed by Chinese, Japanese and Korean astronomers 500 years ago.

So the exact story behind the Quadrantids’ parent object remains somewhat mysterious.

Bottom line: The first major meteor shower of 2020, and every year, the Quadrantid meteor shower will probably be at its best in the hours between 2 a.m. and dawn January 4. Fortunately, in 2020, the absence of moonlight in the predawn sky means dark skies during the peak hours of this year’s annual Quadrantid meteor shower.

Best New Year’s gift ever! EarthSky moon calendar for 2019

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