Peak Perseid mornings: August 11, 12, 13

EarthSky’s yearly crowd-funding campaign is in progress. In 2020, we are donating 8.5% to No Kids Hungry. Please donate to help us keep going, and help feed a kid!

The composite image above – from John Ashley at Glacier National Park in Montana, in 2016 – perfectly captures the feeling of standing outside as dawn is approaching, after a peak night of Perseid meteor-watching. As viewed from anywhere in the Northern Hemisphere, the Perseids’ radiant point is highest at dawn, and so the meteors rain down from overhead. In 2020, the moon may somewhat intrude on this shower. View the full image here.

In 2020, the peak morning of the Perseid meteor shower is most likely August 12, under the light of a wide waning crescent moon. The mornings of August 11 and 13 are worth trying, too. The morning of August 13 will present a thinner and less bright moon than on the previous dates … and also more hours of dark sky for meteor watching. So moonrise is a key factor for watching 2020’s Perseid meteor shower. Visit the Sunrise Sunset Calendars to find out when the moon rises in your sky, remembering to check the moonrise and moonset box.

Also, keep in mind that the Perseids tend to be bright. So we expect a number of them to overcome the moonlit glare over the next several mornings. Will you see as many as 40 to 50 meteors per hour in the predawn hours? Maybe!

The thinner waning crescent moon on August 13 will be less obtrusive than the lunar crescent on August 12. The lit side of the waning moon points at the dazzling planet Venus, which beams near the club of Orion the Hunter.

Can you watch the shower in the evening hours before moonrise? Yes, in the Northern Hemisphere, you can, but the meteor numbers are rather modest in the evening hours. However, evening is the best time of night to try to catch an earthgrazer, which is an elongated, long-lasting meteor that travels horizontally across the sky. Earthgrazers are rare but most memorable if you’re lucky enough to spot one.

What if you’re in the Southern Hemisphere? From the Southern Hemisphere, the first meteors – and possible earthgrazers – won’t be flying until after midnight or the wee hours of the morning. In either the Northern or the Southern Hemisphere, the greatest number of meteors streak the sky in the few hours before dawn.

View larger. Annie Lewis told us, “Finally the clouds cleared. Perseid meteor just before dawn (August 13, 2019) in Madrid, Spain.” Thank you Annie!

The Perseids begin in July every year and rise slowly to their August peak. Eliot Herman in Tucson, Arizona, captured this bright Perseid meteor on the morning of August 8, 2019. Thank you, Eliot!

Enjoying EarthSky so far? Sign up for our free daily newsletter today!

The earliest historical account of Perseid activity comes from a Chinese record in 36 A.D., where it was said that:

… more than 100 meteors flew in the morning.

Numerous references to the August Perseids appear in Chinese, Japanese and Korean records throughout the 8th, 9th, 10th and 11th centuries. Meanwhile, according to ancient western skylore, the Perseid shower commemorates the time when the god Zeus visited the mortal maiden Danaë in the form of a shower of gold. Zeus and Danaë became the parents of Perseus the Hero, from whose constellation the Perseid meteors radiate. More about the Perseid’s radiant point below.

The Perseid meteors happen around this time every year, as Earth in its orbit crosses the orbital path of Comet Swift-Tuttle. Dusty debris left behind by this comet smashes into Earth’s upper atmosphere, lighting up the nighttime as fiery Perseid meteors. The meteors start out slowly in the evening hours, begin to pick up steam after midnight and put out the greatest numbers in the dark hours before dawn.

You might catch a meteor in moonlight tonight, or the shower might be a bust for you in 2020. Never fear. The Perseids will come again next year. Their parent comet – Swift-Tuttle – takes about 130 years to orbit the sun once. It last rounded the sun in the early 1990s and is now far away. But we see the Perseids each year, when Earth intersects the comet’s orbit, and debris left behind by Swift-Tuttle enters our atmosphere. Chart via Guy Ottewell.

The paths of the Perseid meteors, when traced backward, appear to originate in the constellation Perseus. Hence, this meteor shower’s name. While out there peering into dark skies, try looking for the Perseid’s radiant point. You don’t need to find it to enjoy the meteors, but it’s fun to find.

Perseus itself isn’t all that easy to find, but a nearby constellation – Cassiopeia the Queen – is. Look northward for Cassiopeia. It has a very distinctive shape of the letter W or the number 3. See it? Good.

The constellation Perseus, radiant for the annual Perseid meteor shower. The easy-to-spot constellation Cassiopeia is nearby.

Want to go deeper? Then look for the Double Cluster in Perseus. This dual cluster of stars almost exactly marks the radiant point of the Perseid meteor shower. You can find it by scanning with your binoculars between Perseus and Cassiopeia.

Although the Double Cluster can be seen with the unaided eye in a dark country sky, the Double Clusters’ stars burst into view through binoculars. The clusters are more formally known as NGC 884 (Chi Persei) and NGC 869 (h Persei). The Double Cluster is thought to be over 7,000 light-years away from us, in the Perseus arm of the Milky Way galaxy.

Double cluster in Perseus via Greg Hogan of Kathleen, Georgia.

Now here’s the good news. You don’t need to know the constellation Perseus to watch the Perseid meteor shower. You don’t need to find the radiant point. The Perseids do radiate from there, but they will appear in all parts of a dark night sky.

Here’s all you do need to know about the radiant point. As viewed from the Northern Hemisphere, the radiant sits low in the northeast sky at evening and climbs upward throughout the night. The higher that the radiant is in your sky, the more Perseid meteors you’re likely to see. For the Perseids, the radiant is highest before dawn.

Some Perseid meteors will be visible in the Southern Hemisphere, although the numbers will not be as high. Photo from northern Chile, via the European Southern Observatory/ S. Guisard.

Looking for a dark area to observe from? Check out EarthSky’s interactive, worldwide Best Places to Stargaze map.

Bottom line: The greatest number of Perseid meteors is most likely to fall during the predawn hours on August 12, yet under the light of a wide waning crescent moon. The mornings of August 11 and 13 are surely worth trying, too. Will you see as many as 40 to 50 meteors per hour at the shower’s peak, in the moonlight? Maybe!

EarthSky’s meteor shower guide for 2020

Top 10 tips for meteor watchers

from EarthSky https://ift.tt/33mnViZ

EarthSky’s yearly crowd-funding campaign is in progress. In 2020, we are donating 8.5% to No Kids Hungry. Please donate to help us keep going, and help feed a kid!

The composite image above – from John Ashley at Glacier National Park in Montana, in 2016 – perfectly captures the feeling of standing outside as dawn is approaching, after a peak night of Perseid meteor-watching. As viewed from anywhere in the Northern Hemisphere, the Perseids’ radiant point is highest at dawn, and so the meteors rain down from overhead. In 2020, the moon may somewhat intrude on this shower. View the full image here.

In 2020, the peak morning of the Perseid meteor shower is most likely August 12, under the light of a wide waning crescent moon. The mornings of August 11 and 13 are worth trying, too. The morning of August 13 will present a thinner and less bright moon than on the previous dates … and also more hours of dark sky for meteor watching. So moonrise is a key factor for watching 2020’s Perseid meteor shower. Visit the Sunrise Sunset Calendars to find out when the moon rises in your sky, remembering to check the moonrise and moonset box.

Also, keep in mind that the Perseids tend to be bright. So we expect a number of them to overcome the moonlit glare over the next several mornings. Will you see as many as 40 to 50 meteors per hour in the predawn hours? Maybe!

The thinner waning crescent moon on August 13 will be less obtrusive than the lunar crescent on August 12. The lit side of the waning moon points at the dazzling planet Venus, which beams near the club of Orion the Hunter.

Can you watch the shower in the evening hours before moonrise? Yes, in the Northern Hemisphere, you can, but the meteor numbers are rather modest in the evening hours. However, evening is the best time of night to try to catch an earthgrazer, which is an elongated, long-lasting meteor that travels horizontally across the sky. Earthgrazers are rare but most memorable if you’re lucky enough to spot one.

What if you’re in the Southern Hemisphere? From the Southern Hemisphere, the first meteors – and possible earthgrazers – won’t be flying until after midnight or the wee hours of the morning. In either the Northern or the Southern Hemisphere, the greatest number of meteors streak the sky in the few hours before dawn.

View larger. Annie Lewis told us, “Finally the clouds cleared. Perseid meteor just before dawn (August 13, 2019) in Madrid, Spain.” Thank you Annie!

The Perseids begin in July every year and rise slowly to their August peak. Eliot Herman in Tucson, Arizona, captured this bright Perseid meteor on the morning of August 8, 2019. Thank you, Eliot!

Enjoying EarthSky so far? Sign up for our free daily newsletter today!

The earliest historical account of Perseid activity comes from a Chinese record in 36 A.D., where it was said that:

… more than 100 meteors flew in the morning.

Numerous references to the August Perseids appear in Chinese, Japanese and Korean records throughout the 8th, 9th, 10th and 11th centuries. Meanwhile, according to ancient western skylore, the Perseid shower commemorates the time when the god Zeus visited the mortal maiden Danaë in the form of a shower of gold. Zeus and Danaë became the parents of Perseus the Hero, from whose constellation the Perseid meteors radiate. More about the Perseid’s radiant point below.

The Perseid meteors happen around this time every year, as Earth in its orbit crosses the orbital path of Comet Swift-Tuttle. Dusty debris left behind by this comet smashes into Earth’s upper atmosphere, lighting up the nighttime as fiery Perseid meteors. The meteors start out slowly in the evening hours, begin to pick up steam after midnight and put out the greatest numbers in the dark hours before dawn.

You might catch a meteor in moonlight tonight, or the shower might be a bust for you in 2020. Never fear. The Perseids will come again next year. Their parent comet – Swift-Tuttle – takes about 130 years to orbit the sun once. It last rounded the sun in the early 1990s and is now far away. But we see the Perseids each year, when Earth intersects the comet’s orbit, and debris left behind by Swift-Tuttle enters our atmosphere. Chart via Guy Ottewell.

The paths of the Perseid meteors, when traced backward, appear to originate in the constellation Perseus. Hence, this meteor shower’s name. While out there peering into dark skies, try looking for the Perseid’s radiant point. You don’t need to find it to enjoy the meteors, but it’s fun to find.

Perseus itself isn’t all that easy to find, but a nearby constellation – Cassiopeia the Queen – is. Look northward for Cassiopeia. It has a very distinctive shape of the letter W or the number 3. See it? Good.

The constellation Perseus, radiant for the annual Perseid meteor shower. The easy-to-spot constellation Cassiopeia is nearby.

Want to go deeper? Then look for the Double Cluster in Perseus. This dual cluster of stars almost exactly marks the radiant point of the Perseid meteor shower. You can find it by scanning with your binoculars between Perseus and Cassiopeia.

Although the Double Cluster can be seen with the unaided eye in a dark country sky, the Double Clusters’ stars burst into view through binoculars. The clusters are more formally known as NGC 884 (Chi Persei) and NGC 869 (h Persei). The Double Cluster is thought to be over 7,000 light-years away from us, in the Perseus arm of the Milky Way galaxy.

Double cluster in Perseus via Greg Hogan of Kathleen, Georgia.

Now here’s the good news. You don’t need to know the constellation Perseus to watch the Perseid meteor shower. You don’t need to find the radiant point. The Perseids do radiate from there, but they will appear in all parts of a dark night sky.

Here’s all you do need to know about the radiant point. As viewed from the Northern Hemisphere, the radiant sits low in the northeast sky at evening and climbs upward throughout the night. The higher that the radiant is in your sky, the more Perseid meteors you’re likely to see. For the Perseids, the radiant is highest before dawn.

Some Perseid meteors will be visible in the Southern Hemisphere, although the numbers will not be as high. Photo from northern Chile, via the European Southern Observatory/ S. Guisard.

Looking for a dark area to observe from? Check out EarthSky’s interactive, worldwide Best Places to Stargaze map.

Bottom line: The greatest number of Perseid meteors is most likely to fall during the predawn hours on August 12, yet under the light of a wide waning crescent moon. The mornings of August 11 and 13 are surely worth trying, too. Will you see as many as 40 to 50 meteors per hour at the shower’s peak, in the moonlight? Maybe!

EarthSky’s meteor shower guide for 2020

Top 10 tips for meteor watchers

from EarthSky https://ift.tt/33mnViZ

These dogs are trained to sniff out the coronavirus

Image via Shutterstock/ The Conversation.

EarthSky’s yearly crowd-funding campaign is in progress. In 2020, we are donating 8.5% to No Kids Hungry. Please donate to help us keep going, and help feed a kid!

Susan Hazel, University of Adelaide and Anne-Lise Chaber, University of Adelaide

What does a pandemic smell like? If dogs could talk, they might be able to tell us.

We’re part of an international research team, led by Dominique Grandjean at France’s National Veterinary School of Alfort, that has been training detector dogs to sniff out traces of the novel coronavirus (SARS-CoV-2) since March.

These detector dogs are trained using sweat samples from people infected with COVID-19. When introduced to a line of sweat samples, most dogs can detect a positive one from a line of negative ones with 100% accuracy.

Across the globe, coronavirus detector dogs are being trained in the United Arab Emirates (UAE), Chile, Argentina, Brazil and Belgium.

In the UAE, detector dogs – stationed at various airports – have already started helping efforts to control Covid-19’s spread. This is something we hope will soon be available in Australia too.

A keen nose

Our international colleagues found detector dogs were able to detect SARS-CoV-2 in infected people when they were still asymptomatic, before later testing positive.

On average, dogs have about 220 million scent receptors. Image via Shutterstock/ The Conversation .

When it comes to SARS-CoV-2 detection, we don’t know for sure what the dogs are smelling.

The volatile organic compounds (VOCs) given off in the sweat samples are a complex mix. So it’s likely the dogs are detecting a particular profile rather than individual compounds.

Sweat is used for tests as it’s not considered infectious for Covid-19. This means it presents less risk when handling samples.

Covid-19 sniffing dogs in Australia

Here in Australia, we’re currently working with professional trainers of detector dogs in South Australia, Victoria and New South Wales. The most common breed used for this work so far has been the German shepherd, with various other breeds also involved.

We are also negotiating with health authorities to collect sweat samples from people who have tested positive to the virus, and from those who are negative. We hope to start collecting these within the next few months.

We will need to collect thousands of negative samples to make sure the dogs aren’t detecting other viral infection, such as the common cold or influenza. In other countries, they’ve passed this test with flying colours.

Once operational, detector dogs in Australia could be hugely valuable in many scenarios, such as screening people at airports and state borders, or monitoring staff working in aged care facilities and hospitals daily (so they don’t need repeat testing).

To properly train a dog to detect SARS-CoV-2, it takes:

– 6-8 weeks for a dog that is already trained to detect other scents, or
– 3-6 months for a dog that has never been trained.

Coronavirus cases recently peaked in Victoria. Having trained sniffer dogs at hand could greatly help manage future waves of COVID-19. Image via Daniel Pockett/ AAP/ The Conversation.

Could the dogs spread the virus further?

Dogs in experimental studies have not been shown to be able to replicate the virus (within their body). Simply, they themselves are not a source of infection.

Currently, there are two case reports in the world of dogs being potentially contaminated with the Covid-19 virus by their owners. Those dogs didn’t become sick.

To further reduce any potential risk of transmission to both people and dogs, the apparatus used to train the dogs doesn’t allow any direct contact between the dog’s nose and the sweat sample.

The dog’s nose goes into a stainless steel cone, with the sweat sample in a receptacle behind. This allows free access to the volatile olfactory compounds but no physical contact.

Furthermore, all the dogs trained to detect COVID-19 are regularly checked by nasal swab tests, rectal swab tests and blood tests to identify antibodies. So far, none of the detector dogs has been found to be infected.

Dogs are not susceptible to the negative effects of the novel coronavirus. Image via Eyepix/ Sipa USA/ The Conversation.

Hurdles to jump

Now and in the future, it will be important for us to identify any instances where detector dogs may present false positives (signaling a sample is positive when it’s negative) or false negatives (signaling the sample is negative when it’s positive).

We’re also hoping our work can reveal exactly which volatile olfactory compound(s) is/are specific to Covid-19 infection.

This knowledge might help us understand the disease process resulting from COVID-19 infection – and in detecting other diseases using detector dogs.

This pandemic has been a huge challenge for everyone. Being able to find asymptomatic people infected with the coronavirus would be a game-changer – and that’s what we need right now.

A Covid-19 detector dog enrolled in the NOSAIS program led by professor Dominique Grandjean and Clothilde Julien from the Alfort Veterinary School (France). Image via The Conversation.

A friend to us (and science)

Perhaps we shouldn’t be surprised about dogs’ ability to detect Covid-19, as we already know their noses are amazing.

Dogs can help detect hypoglycaemia in diabetics, warn people who are about to have an epileptic seizure and have been used to sniff out some cancers.

Their great potential in dealing with the current pandemic is just one of myriad examples of how dogs enrich our lives.

We acknowledge Professor Riad Sarkis from the Saint Joseph University (Beirut) and Clothilde Lecoq-Julien from the Alfort Veterinary School (France) for first conceiving the idea underpinning this work back in March.

Susan Hazel, Senior Lecturer, School of Animal and Veterinary Science, University of Adelaide and Anne-Lise Chaber, One Health Lecturer, School of Animal and Veterinary Science, University of Adelaide

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

Bottom line: Dogs are being trained to use their sense of smell to detect the novel coronavirus that causes Covid-19.

from EarthSky https://ift.tt/33Ld30D

Image via Shutterstock/ The Conversation.

EarthSky’s yearly crowd-funding campaign is in progress. In 2020, we are donating 8.5% to No Kids Hungry. Please donate to help us keep going, and help feed a kid!

Susan Hazel, University of Adelaide and Anne-Lise Chaber, University of Adelaide

What does a pandemic smell like? If dogs could talk, they might be able to tell us.

We’re part of an international research team, led by Dominique Grandjean at France’s National Veterinary School of Alfort, that has been training detector dogs to sniff out traces of the novel coronavirus (SARS-CoV-2) since March.

These detector dogs are trained using sweat samples from people infected with COVID-19. When introduced to a line of sweat samples, most dogs can detect a positive one from a line of negative ones with 100% accuracy.

Across the globe, coronavirus detector dogs are being trained in the United Arab Emirates (UAE), Chile, Argentina, Brazil and Belgium.

In the UAE, detector dogs – stationed at various airports – have already started helping efforts to control Covid-19’s spread. This is something we hope will soon be available in Australia too.

A keen nose

Our international colleagues found detector dogs were able to detect SARS-CoV-2 in infected people when they were still asymptomatic, before later testing positive.

On average, dogs have about 220 million scent receptors. Image via Shutterstock/ The Conversation .

When it comes to SARS-CoV-2 detection, we don’t know for sure what the dogs are smelling.

The volatile organic compounds (VOCs) given off in the sweat samples are a complex mix. So it’s likely the dogs are detecting a particular profile rather than individual compounds.

Sweat is used for tests as it’s not considered infectious for Covid-19. This means it presents less risk when handling samples.

Covid-19 sniffing dogs in Australia

Here in Australia, we’re currently working with professional trainers of detector dogs in South Australia, Victoria and New South Wales. The most common breed used for this work so far has been the German shepherd, with various other breeds also involved.

We are also negotiating with health authorities to collect sweat samples from people who have tested positive to the virus, and from those who are negative. We hope to start collecting these within the next few months.

We will need to collect thousands of negative samples to make sure the dogs aren’t detecting other viral infection, such as the common cold or influenza. In other countries, they’ve passed this test with flying colours.

Once operational, detector dogs in Australia could be hugely valuable in many scenarios, such as screening people at airports and state borders, or monitoring staff working in aged care facilities and hospitals daily (so they don’t need repeat testing).

To properly train a dog to detect SARS-CoV-2, it takes:

– 6-8 weeks for a dog that is already trained to detect other scents, or
– 3-6 months for a dog that has never been trained.

Coronavirus cases recently peaked in Victoria. Having trained sniffer dogs at hand could greatly help manage future waves of COVID-19. Image via Daniel Pockett/ AAP/ The Conversation.

Could the dogs spread the virus further?

Dogs in experimental studies have not been shown to be able to replicate the virus (within their body). Simply, they themselves are not a source of infection.

Currently, there are two case reports in the world of dogs being potentially contaminated with the Covid-19 virus by their owners. Those dogs didn’t become sick.

To further reduce any potential risk of transmission to both people and dogs, the apparatus used to train the dogs doesn’t allow any direct contact between the dog’s nose and the sweat sample.

The dog’s nose goes into a stainless steel cone, with the sweat sample in a receptacle behind. This allows free access to the volatile olfactory compounds but no physical contact.

Furthermore, all the dogs trained to detect COVID-19 are regularly checked by nasal swab tests, rectal swab tests and blood tests to identify antibodies. So far, none of the detector dogs has been found to be infected.

Dogs are not susceptible to the negative effects of the novel coronavirus. Image via Eyepix/ Sipa USA/ The Conversation.

Hurdles to jump

Now and in the future, it will be important for us to identify any instances where detector dogs may present false positives (signaling a sample is positive when it’s negative) or false negatives (signaling the sample is negative when it’s positive).

We’re also hoping our work can reveal exactly which volatile olfactory compound(s) is/are specific to Covid-19 infection.

This knowledge might help us understand the disease process resulting from COVID-19 infection – and in detecting other diseases using detector dogs.

This pandemic has been a huge challenge for everyone. Being able to find asymptomatic people infected with the coronavirus would be a game-changer – and that’s what we need right now.

A Covid-19 detector dog enrolled in the NOSAIS program led by professor Dominique Grandjean and Clothilde Julien from the Alfort Veterinary School (France). Image via The Conversation.

A friend to us (and science)

Perhaps we shouldn’t be surprised about dogs’ ability to detect Covid-19, as we already know their noses are amazing.

Dogs can help detect hypoglycaemia in diabetics, warn people who are about to have an epileptic seizure and have been used to sniff out some cancers.

Their great potential in dealing with the current pandemic is just one of myriad examples of how dogs enrich our lives.

We acknowledge Professor Riad Sarkis from the Saint Joseph University (Beirut) and Clothilde Lecoq-Julien from the Alfort Veterinary School (France) for first conceiving the idea underpinning this work back in March.

Susan Hazel, Senior Lecturer, School of Animal and Veterinary Science, University of Adelaide and Anne-Lise Chaber, One Health Lecturer, School of Animal and Veterinary Science, University of Adelaide

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

Bottom line: Dogs are being trained to use their sense of smell to detect the novel coronavirus that causes Covid-19.

from EarthSky https://ift.tt/33Ld30D

See it! This weekend’s moon and Mars

View at EarthSky Community Photos. | Peter Lowenstein in Mutare, Zimbabwe caught the waning moon, Mars, and a flock of whistling ducks at dawn on August 9, 2020. He wrote, “… the waning gibbous moon and Mars were close together high in the northern dawn sky. Several pictures of the pair were taken as daylight approached between 6 and 6:30 a.m. Just before it became too light for Mars to remain visible, a flock of whistling ducks passed by in bow and arrow formation!” Thank you, Peter!

View at EarthSky Community Photos. | Helio de Carvalho Vital wrote from Rio de Janeiro, Brazil that he captured the occultation of Mars by the moon – an event in which the moon temporarily covered Mars – on August 9, 2020. He wrote, “A Nikon CoolPix P900 camera on a tripod was the only equipment I used … The photo shows the planet approaching the moon`s lighted limb some seconds before ingress. At that moment, relative to Mars, the moon was 224 times closer and about 7 thousand times brighter.” Thank you, Helio!

April Singer in northern New Mexico caught the moon and Mars Saturday night around midnight, when the pair had just risen and was low in the eastern sky. Thanks, April!

View at EarthSky Community Photos. | Dennis Chabot in Rehoboth, Massachusetts captured this image of Mars early Sunday morning, August 9, 2020. At that time, the moon and red planet were high in the dawn sky, not far from the famous tip of the V in the constellation Pisces the Fish. Dennis wrote: “Fiery Mars above the moon this morning just before the fog rolled in to fill the skies with gray. Thank you, Dennis!

View at EarthSky Community Photos. | Aurelian Neacsu in Visina, Dambovita, Romania captured this telescopic image of Mars on August 5, 2020. The white dot on the planet is its icy pole. Thank you, Aurelian!

Bottom line: Photos from the EarthSky community showing the August 2020 waning gibbous moon near the red planet Mars.

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View at EarthSky Community Photos. | Peter Lowenstein in Mutare, Zimbabwe caught the waning moon, Mars, and a flock of whistling ducks at dawn on August 9, 2020. He wrote, “… the waning gibbous moon and Mars were close together high in the northern dawn sky. Several pictures of the pair were taken as daylight approached between 6 and 6:30 a.m. Just before it became too light for Mars to remain visible, a flock of whistling ducks passed by in bow and arrow formation!” Thank you, Peter!

View at EarthSky Community Photos. | Helio de Carvalho Vital wrote from Rio de Janeiro, Brazil that he captured the occultation of Mars by the moon – an event in which the moon temporarily covered Mars – on August 9, 2020. He wrote, “A Nikon CoolPix P900 camera on a tripod was the only equipment I used … The photo shows the planet approaching the moon`s lighted limb some seconds before ingress. At that moment, relative to Mars, the moon was 224 times closer and about 7 thousand times brighter.” Thank you, Helio!

April Singer in northern New Mexico caught the moon and Mars Saturday night around midnight, when the pair had just risen and was low in the eastern sky. Thanks, April!

View at EarthSky Community Photos. | Dennis Chabot in Rehoboth, Massachusetts captured this image of Mars early Sunday morning, August 9, 2020. At that time, the moon and red planet were high in the dawn sky, not far from the famous tip of the V in the constellation Pisces the Fish. Dennis wrote: “Fiery Mars above the moon this morning just before the fog rolled in to fill the skies with gray. Thank you, Dennis!

View at EarthSky Community Photos. | Aurelian Neacsu in Visina, Dambovita, Romania captured this telescopic image of Mars on August 5, 2020. The white dot on the planet is its icy pole. Thank you, Aurelian!

Bottom line: Photos from the EarthSky community showing the August 2020 waning gibbous moon near the red planet Mars.

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

A surprising spiral around a planet factory

In a surprising discovery, the ALMA telescope in Chile captured this image of a massive spiral of gas surrounding the planet-forming disk of the young star RU Lup. Image via ALMA (ESO/ NAOJ/ NRAO)/ J. Huang/ AUI/ NSF/ S. Dagnello.

EarthSky’s yearly crowd-funding campaign is in progress. In 2020, we are donating 8.5% to No Kids Hungry. Please donate to help us keep going, and help feed a kid!

Planets form in orbit around stars, in great spinning wheels of dust and gas. In recent decades, scientists have acquired images of these protoplanetary disks, and for the most part the disks look quite similar to each other, with discernible gaps in them planets are forming. Now new observations of one such disk, around the young star RU Lup, show that some protoplanetary disks are more complex and chaotic than first thought. Astronomers announced on August 3, 2020, that the disk surrounding RU Lup isn’t only larger than previously known, but also has a distinctly spiral shape, not unlike a spiral galaxy.

And why not? After all, nature loves spirals. More about that below.

The new observations, by scientists at the Center for Astrophysics, Harvard & Smithsonian (CfA), were made using the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, and the peer-reviewed results were published in The Astrophysical Journal on the same day.

RU Lup is located in our sky in the direction of the constellation Lupus. The star is estimated to be about 400 light-years from Earth. ALMA had taken high-resolution images of the RU Lup disk before, but the new ones focused more on the gas in the disk instead of the dust. They revealed not only the originally seen protoplanetary disk with its gaps where planets are forming, but also a much larger, encompassing, more complex structure that looked like a mini-galaxy with spiral arms.

The spiral structure around RU Lup extends to nearly 1,000 astronomical units (AU) from the star – that is, 1,000 Earth-sun units of distance – much farther than the star’s dust disk, which extends to about 60 AU. Jane Huang of CfA, lead author of the new paper, said:

We discovered a complex set of spiral arms in carbon monoxide (CO) emission extending to nearly 1,000 astronomical units from the young star RU Lup, which has previously been found to exhibit signs of ongoing planet formation via concentric dust gaps in its protoplanetary disk. The CO emission reveals complex structures in the planet-formation environment that are invisible in dust observations alone.

ALMA image of the galaxy-like spiral formation of gas around the protoplanetary disk of the young star RU Lup. The inset shows a previous observation of the central dust disk. Image via ALMA (ESO/ NAOJ/ NRAO)/ J. Huang/ S. Andrews/ AUI/ NSF/ S. Dagnello.

Previous observations with ALMA had already shown evidence of planetary formation in this disk. Huang said:

But we also noticed some faint carbon monoxide (CO) gas structures that extended beyond the disk. That’s why we decided to observe the disk around the star again, this time focusing on the gas instead of the dust.

Protoplanetary disks can look very organized, with neat, regular rings of dust surrounding a star. Unusual stellar brightness variations had been seen at RU Lup before, however, and were not yet explained. Huang said:

The planet-forming environment can be much more complex and chaotic than implied by the numerous, well-known images of concentric ringed protoplanetary disks mapped in millimeter continuum emission.

The fact that we observed this spiral structure in the gas after a deep observation suggests that we have likely not seen the full diversity and complexity of planet-forming environments. We may have missed much of the gas structures in other disks.

Protoplanetary disks are known to contain much more gas than dust, but seeing this gas around RU Lup in such a massive spiral formation was surprising.

The star RU Lup is located in the constellation Lupus. Image via IAU/ Sky & Telescope/ NRAO/ AUI/ NSF/ S. Dagnello.

Jane Huang of CfA, lead author of the new paper. Image via S. Gomez/ CfA.

As usually happens, the new observations raise more questions than they provide answers. How did these huge spiral arms form? Huang’s team suggests that the disk may be collapsing under its own gravity due to its significant mass, or it may be accreting interstellar matter through environmental interactions. But neither of those are a simple answer, according to Sean Andrews, CfA astrophysicist and co-author on the paper:

None of these scenarios completely explain what we have observed. There might be unknown processes happening during planet formation that we have not yet accounted for in our models. We will only learn what they are if we find other disks out there that look like RU Lup.

Huang commented that a broader approach to studying “planet factories” – that is, stars with protoplanetary disks – might be needed:

The RU Lup results show that some important information about the disk structure can only be identified through mapping the molecular emission. These results indicate that it will be important going forward to invest as much time in surveying molecular emission as has been invested in surveying dust emission.

The process of planet formation seemed fairly straightforward when images of protoplanetary disks showed nice orderly disks of concentric rings around the stars, with the planets forming in the gaps. But the new observations of RU Lup indicate that view is too simplistic.

A spiral galaxy, NGC 1232, as seen on September 21, 1998, by ESO. Interestingly, in the early 20th century, some astronomers believed that the spiral-shaped objects seen through their telescopes – called spiral nebulae at the time – were indeed forming solar systems.

Nature loves spirals. Spirals are common in nature. A good example is the Fibonacci sequence found in sunflowers.

There are many other spiraling forms in nature as well, including snail shells, flower petals, pine cones, snakes, storms, DNA and curly hair. Here’s a great collection of photos on Pinterest of spirals in nature, for you to browse.

Spirals are common in nature. The spiraling Fibonacci sequence can be easily seen at the hearts of sunflowers. Image via michalschein.com/ Pinterest.

A Fibonacci-sequence spiral in a shell. Image via imgfave.com/ Pinterest.

Bottom line: A new image of the planet-forming disk around the star RU Lup reveals an unexpected massive spiral of gas surrounding the main disk.

Source: Large-scale CO spiral arms and complex kinematics associated with the T Tauri star RU Lup

Via Center for Astrophysics

Via NRAO

from EarthSky https://ift.tt/3agFMf9

In a surprising discovery, the ALMA telescope in Chile captured this image of a massive spiral of gas surrounding the planet-forming disk of the young star RU Lup. Image via ALMA (ESO/ NAOJ/ NRAO)/ J. Huang/ AUI/ NSF/ S. Dagnello.

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Planets form in orbit around stars, in great spinning wheels of dust and gas. In recent decades, scientists have acquired images of these protoplanetary disks, and for the most part the disks look quite similar to each other, with discernible gaps in them planets are forming. Now new observations of one such disk, around the young star RU Lup, show that some protoplanetary disks are more complex and chaotic than first thought. Astronomers announced on August 3, 2020, that the disk surrounding RU Lup isn’t only larger than previously known, but also has a distinctly spiral shape, not unlike a spiral galaxy.

And why not? After all, nature loves spirals. More about that below.

The new observations, by scientists at the Center for Astrophysics, Harvard & Smithsonian (CfA), were made using the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, and the peer-reviewed results were published in The Astrophysical Journal on the same day.

RU Lup is located in our sky in the direction of the constellation Lupus. The star is estimated to be about 400 light-years from Earth. ALMA had taken high-resolution images of the RU Lup disk before, but the new ones focused more on the gas in the disk instead of the dust. They revealed not only the originally seen protoplanetary disk with its gaps where planets are forming, but also a much larger, encompassing, more complex structure that looked like a mini-galaxy with spiral arms.

The spiral structure around RU Lup extends to nearly 1,000 astronomical units (AU) from the star – that is, 1,000 Earth-sun units of distance – much farther than the star’s dust disk, which extends to about 60 AU. Jane Huang of CfA, lead author of the new paper, said:

We discovered a complex set of spiral arms in carbon monoxide (CO) emission extending to nearly 1,000 astronomical units from the young star RU Lup, which has previously been found to exhibit signs of ongoing planet formation via concentric dust gaps in its protoplanetary disk. The CO emission reveals complex structures in the planet-formation environment that are invisible in dust observations alone.

ALMA image of the galaxy-like spiral formation of gas around the protoplanetary disk of the young star RU Lup. The inset shows a previous observation of the central dust disk. Image via ALMA (ESO/ NAOJ/ NRAO)/ J. Huang/ S. Andrews/ AUI/ NSF/ S. Dagnello.

Previous observations with ALMA had already shown evidence of planetary formation in this disk. Huang said:

But we also noticed some faint carbon monoxide (CO) gas structures that extended beyond the disk. That’s why we decided to observe the disk around the star again, this time focusing on the gas instead of the dust.

Protoplanetary disks can look very organized, with neat, regular rings of dust surrounding a star. Unusual stellar brightness variations had been seen at RU Lup before, however, and were not yet explained. Huang said:

The planet-forming environment can be much more complex and chaotic than implied by the numerous, well-known images of concentric ringed protoplanetary disks mapped in millimeter continuum emission.

The fact that we observed this spiral structure in the gas after a deep observation suggests that we have likely not seen the full diversity and complexity of planet-forming environments. We may have missed much of the gas structures in other disks.

Protoplanetary disks are known to contain much more gas than dust, but seeing this gas around RU Lup in such a massive spiral formation was surprising.

The star RU Lup is located in the constellation Lupus. Image via IAU/ Sky & Telescope/ NRAO/ AUI/ NSF/ S. Dagnello.

Jane Huang of CfA, lead author of the new paper. Image via S. Gomez/ CfA.

As usually happens, the new observations raise more questions than they provide answers. How did these huge spiral arms form? Huang’s team suggests that the disk may be collapsing under its own gravity due to its significant mass, or it may be accreting interstellar matter through environmental interactions. But neither of those are a simple answer, according to Sean Andrews, CfA astrophysicist and co-author on the paper:

None of these scenarios completely explain what we have observed. There might be unknown processes happening during planet formation that we have not yet accounted for in our models. We will only learn what they are if we find other disks out there that look like RU Lup.

Huang commented that a broader approach to studying “planet factories” – that is, stars with protoplanetary disks – might be needed:

The RU Lup results show that some important information about the disk structure can only be identified through mapping the molecular emission. These results indicate that it will be important going forward to invest as much time in surveying molecular emission as has been invested in surveying dust emission.

The process of planet formation seemed fairly straightforward when images of protoplanetary disks showed nice orderly disks of concentric rings around the stars, with the planets forming in the gaps. But the new observations of RU Lup indicate that view is too simplistic.

A spiral galaxy, NGC 1232, as seen on September 21, 1998, by ESO. Interestingly, in the early 20th century, some astronomers believed that the spiral-shaped objects seen through their telescopes – called spiral nebulae at the time – were indeed forming solar systems.

Nature loves spirals. Spirals are common in nature. A good example is the Fibonacci sequence found in sunflowers.

There are many other spiraling forms in nature as well, including snail shells, flower petals, pine cones, snakes, storms, DNA and curly hair. Here’s a great collection of photos on Pinterest of spirals in nature, for you to browse.

Spirals are common in nature. The spiraling Fibonacci sequence can be easily seen at the hearts of sunflowers. Image via michalschein.com/ Pinterest.

A Fibonacci-sequence spiral in a shell. Image via imgfave.com/ Pinterest.

Bottom line: A new image of the planet-forming disk around the star RU Lup reveals an unexpected massive spiral of gas surrounding the main disk.

Source: Large-scale CO spiral arms and complex kinematics associated with the T Tauri star RU Lup

Via Center for Astrophysics

Via NRAO

from EarthSky https://ift.tt/3agFMf9

What is a globular cluster?

The globular cluster M5, as seen by the Hubble Space Telescope. This photo was an Astronomy Picture of the Day in June 2015. Via HST/ NASA/ ESA/ APOD.

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Globular clusters are tightly packed, symmetrical collections of stars, orbiting mostly in the extended star halos surrounding most spiral galaxies. Globular clusters contain some of the oldest stars in a galaxy and are thought to have formed early in its history. Could it be that – when it was first forming – a spiral galaxy like our Milky Way was once an amorphous cloud of gas and dust? Could its first stars have collected into globular clusters? Could these clusters have stayed put in the halo around a galaxy’s center, as the rest of the spinning galaxy flattened out and formed spiral arms? That scenario would explain why globular clusters orbit in a galaxy’s halo and contain its oldest stars.

But the fact is that no one knows precisely how globular clusters formed, and what role, if any, they played in the development of galaxies. We do know that globular clusters are the oldest, largest and most massive type of star cluster and that they contain the oldest stars. Their age can be demonstrated by their almost complete lack of what astronomers call metals, that is, elements heavier than the hydrogen and helium present in the early universe before the first stars and galaxies were born. The heavier elements were forged in star interiors.

Omega Centauri — containing as many as 10 million stars — is by far the largest globular cluster associated with our Milky Way galaxy. The image shows only the central part of the cluster, an area about the size of the full moon on the sky’s dome. Image via La Silla Observatory/ ESO.

Globular clusters are big. They can reach 300 light-years in diameter and contain 10 million stars. Unlike the open star clusters – containing sibling stars, scattered through the disk of our galaxy and presumably other galaxies – globular clusters are big, symmetric and old, like an earthly city’s oldest and most staid citizens.

Here are some ways that globular star clusters and open star clusters are different:

Globular star cluster are very symmetrical in shape, and are densest toward their centers. Open star clusters are more irregular in shape.

Globular clusters orbit in the halo of our galaxy, centered on the galaxy’s center and expanding above and below the galactic disk. Open star clusters tend to orbit within the disk.

Globular star clusters contain hundreds of thousands of stars, and some – like Omega Centauri, shown above – contain millions of stars. Open star clusters tend to contain only hundreds of stars.

View larger. | The famous globular cluster Messier 13 or M13 – largest and brightest globular cluster easily visible from the Northern Hemisphere – seen against its star field. At 25,000 light-years away and about 145 light-years in diameter, M13 is a popular target for amateur astronomers using small telescopes. Image via Fred Espenak.

Here is M13 again. Notice its very symmetrical structure, which is typical of globular star clusters. Photo via Bareket Observatory in Israel.

Our own Milky Way has around 150 globular clusters, with perhaps more awaiting discovery, hidden by galactic dust. Our neighboring spiral galaxy in the direction of the constellation Andromeda – M31 or the Andromeda galaxy – appears to have around 300 globular clusters. Some football-shaped, elliptical galaxies do have globular clusters, too, like M87 in the direction of the constellation Virgo, home to the supermassive black hole that was famously imaged by the Event Horizon Telescope in 2019. This giant elliptical galaxy, M87, has been estimated to possess around 15,000 globular clusters, with more than 1,000 having been directly observed telescopically so far.

About 150 globular star clusters are known to surround our galaxy’s center.

Globular clusters orbit galaxies in orbits which are highly eccentric and highly inclined to the galactic plane. Orbiting in the “outskirts” of a galaxy, they take perhaps a few hundred million years to complete a single orbit. In a telescope, a globular cluster looks like a fuzzy ball, with individual stars at the periphery merging into a solid ball of light towards the center. However, this is simply because the stars are so close together that they can’t be resolved individually telescopically. At the center of a globular cluster, stars may reach a density of between 100 and 1,000 stars per cubic parsec. That’s in contrast to the density of stars near our sun, estimated at about 0.14 star per cubic parsec. If you were standing on a planet orbiting a star in a globular cluster, your night sky would be extremely crowded with nearby stars!

This Hubble Space Telescope image shows the core of the great globular cluster Messier 13, in the constellation Hercules. Read more about this image from SpaceTelescope.org.

The stars in globular clusters are the galaxy’s most ancient inhabitants, comprising a population of what astronomers call Population II stars. Those whose age have been measured are between 11 and 13 billion years old, making them almost as old as the galaxy itself. Not surprisingly, many of these ancient stars have evolved into huge, bloated red giant stars, as our sun will do in a few billion years. The stars are extremely metal-poor, which is to say – in the peculiar language of astronomy – they have tiny amounts of materials heavier than helium compared to the surrounding interstellar medium (astronomers refer to all elements heavier than helium as “metals”). Because the heavier elements are made inside stars – and then spread throughout the interstellar medium via supernova explosions – this paucity of metals is exactly what would normally be expected from such old stars. In other worlds, Population II stars consist almost exclusively of hydrogen and helium, the materials that were present in the early universe.

However, there is a mystery: globular clusters also have “abundance anomalies” of heavier metals, meaning there are elements present which are found elsewhere, in stars that formed more recently. In particular, there appears to be excesses of sodium, carbon, oxygen and aluminum, with heavier metals such as strontium, yttrium, barium and europium also being present in some clusters. These anomalies have not been satisfactorily explained, although there have been several explanations put forward, such as the early presence of supermassive stars .

The most famous globular cluster in the northern hemisphere is M13 in the constellation of Hercules, sometimes referred to as the Great Globular Cluster, which was discovered by Edmond Halley in 1714. Charles Messier later added it into his famous catalog in 1764. In amateur telescopes, it is a small fuzzy patch of light, some 22,000 light-years from Earth. At the center of this cluster, stars orbit so closely that occasionally they collide, their deaths leading to the creation of new stars known as “blue stragglers.” This stellar population is the only type of newer stars in globular clusters.

Other globular clusters of note are M22 in Sagittarius – one of the brightest in the sky – M5 in Serpens and M12 in Ophiuchus. Many of the night sky’s biggest and brightest globular clusters are best viewed on spring nights and often feature in so-called “Messier Marathons.”

Globular clusters are a wonderful sight in even the smallest telescopes, although a large instrument is needed to resolve individual stars toward their centers.

When you look at them, you are seeing populations of stars born in our galaxy’s infancy!

Amateur astronomers enjoy peering at globular clusters through their small telescopes. Here is Omega Centauri, captured by Greg Hogan in Kathleen, Georgia. Thanks, Greg!

Bottom line: Globular clusters are spherical collections of stars, orbiting mostly in the star halo of spiral galaxies. Our Milky Way galaxy has about 150 globulars, which contain some of our galaxy’s oldest stars.

from EarthSky https://ift.tt/2wy0J5m

The globular cluster M5, as seen by the Hubble Space Telescope. This photo was an Astronomy Picture of the Day in June 2015. Via HST/ NASA/ ESA/ APOD.

EarthSky’s yearly crowd-funding campaign is in progress. In 2020, we are donating 8.5% of all incoming revenues to No Kids Hungry. Click to learn more and donate.

Globular clusters are tightly packed, symmetrical collections of stars, orbiting mostly in the extended star halos surrounding most spiral galaxies. Globular clusters contain some of the oldest stars in a galaxy and are thought to have formed early in its history. Could it be that – when it was first forming – a spiral galaxy like our Milky Way was once an amorphous cloud of gas and dust? Could its first stars have collected into globular clusters? Could these clusters have stayed put in the halo around a galaxy’s center, as the rest of the spinning galaxy flattened out and formed spiral arms? That scenario would explain why globular clusters orbit in a galaxy’s halo and contain its oldest stars.

But the fact is that no one knows precisely how globular clusters formed, and what role, if any, they played in the development of galaxies. We do know that globular clusters are the oldest, largest and most massive type of star cluster and that they contain the oldest stars. Their age can be demonstrated by their almost complete lack of what astronomers call metals, that is, elements heavier than the hydrogen and helium present in the early universe before the first stars and galaxies were born. The heavier elements were forged in star interiors.

Omega Centauri — containing as many as 10 million stars — is by far the largest globular cluster associated with our Milky Way galaxy. The image shows only the central part of the cluster, an area about the size of the full moon on the sky’s dome. Image via La Silla Observatory/ ESO.

Globular clusters are big. They can reach 300 light-years in diameter and contain 10 million stars. Unlike the open star clusters – containing sibling stars, scattered through the disk of our galaxy and presumably other galaxies – globular clusters are big, symmetric and old, like an earthly city’s oldest and most staid citizens.

Here are some ways that globular star clusters and open star clusters are different:

Globular star cluster are very symmetrical in shape, and are densest toward their centers. Open star clusters are more irregular in shape.

Globular clusters orbit in the halo of our galaxy, centered on the galaxy’s center and expanding above and below the galactic disk. Open star clusters tend to orbit within the disk.

Globular star clusters contain hundreds of thousands of stars, and some – like Omega Centauri, shown above – contain millions of stars. Open star clusters tend to contain only hundreds of stars.

View larger. | The famous globular cluster Messier 13 or M13 – largest and brightest globular cluster easily visible from the Northern Hemisphere – seen against its star field. At 25,000 light-years away and about 145 light-years in diameter, M13 is a popular target for amateur astronomers using small telescopes. Image via Fred Espenak.

Here is M13 again. Notice its very symmetrical structure, which is typical of globular star clusters. Photo via Bareket Observatory in Israel.

Our own Milky Way has around 150 globular clusters, with perhaps more awaiting discovery, hidden by galactic dust. Our neighboring spiral galaxy in the direction of the constellation Andromeda – M31 or the Andromeda galaxy – appears to have around 300 globular clusters. Some football-shaped, elliptical galaxies do have globular clusters, too, like M87 in the direction of the constellation Virgo, home to the supermassive black hole that was famously imaged by the Event Horizon Telescope in 2019. This giant elliptical galaxy, M87, has been estimated to possess around 15,000 globular clusters, with more than 1,000 having been directly observed telescopically so far.

About 150 globular star clusters are known to surround our galaxy’s center.

Globular clusters orbit galaxies in orbits which are highly eccentric and highly inclined to the galactic plane. Orbiting in the “outskirts” of a galaxy, they take perhaps a few hundred million years to complete a single orbit. In a telescope, a globular cluster looks like a fuzzy ball, with individual stars at the periphery merging into a solid ball of light towards the center. However, this is simply because the stars are so close together that they can’t be resolved individually telescopically. At the center of a globular cluster, stars may reach a density of between 100 and 1,000 stars per cubic parsec. That’s in contrast to the density of stars near our sun, estimated at about 0.14 star per cubic parsec. If you were standing on a planet orbiting a star in a globular cluster, your night sky would be extremely crowded with nearby stars!

This Hubble Space Telescope image shows the core of the great globular cluster Messier 13, in the constellation Hercules. Read more about this image from SpaceTelescope.org.

The stars in globular clusters are the galaxy’s most ancient inhabitants, comprising a population of what astronomers call Population II stars. Those whose age have been measured are between 11 and 13 billion years old, making them almost as old as the galaxy itself. Not surprisingly, many of these ancient stars have evolved into huge, bloated red giant stars, as our sun will do in a few billion years. The stars are extremely metal-poor, which is to say – in the peculiar language of astronomy – they have tiny amounts of materials heavier than helium compared to the surrounding interstellar medium (astronomers refer to all elements heavier than helium as “metals”). Because the heavier elements are made inside stars – and then spread throughout the interstellar medium via supernova explosions – this paucity of metals is exactly what would normally be expected from such old stars. In other worlds, Population II stars consist almost exclusively of hydrogen and helium, the materials that were present in the early universe.

However, there is a mystery: globular clusters also have “abundance anomalies” of heavier metals, meaning there are elements present which are found elsewhere, in stars that formed more recently. In particular, there appears to be excesses of sodium, carbon, oxygen and aluminum, with heavier metals such as strontium, yttrium, barium and europium also being present in some clusters. These anomalies have not been satisfactorily explained, although there have been several explanations put forward, such as the early presence of supermassive stars .

The most famous globular cluster in the northern hemisphere is M13 in the constellation of Hercules, sometimes referred to as the Great Globular Cluster, which was discovered by Edmond Halley in 1714. Charles Messier later added it into his famous catalog in 1764. In amateur telescopes, it is a small fuzzy patch of light, some 22,000 light-years from Earth. At the center of this cluster, stars orbit so closely that occasionally they collide, their deaths leading to the creation of new stars known as “blue stragglers.” This stellar population is the only type of newer stars in globular clusters.

Other globular clusters of note are M22 in Sagittarius – one of the brightest in the sky – M5 in Serpens and M12 in Ophiuchus. Many of the night sky’s biggest and brightest globular clusters are best viewed on spring nights and often feature in so-called “Messier Marathons.”

Globular clusters are a wonderful sight in even the smallest telescopes, although a large instrument is needed to resolve individual stars toward their centers.

When you look at them, you are seeing populations of stars born in our galaxy’s infancy!

Amateur astronomers enjoy peering at globular clusters through their small telescopes. Here is Omega Centauri, captured by Greg Hogan in Kathleen, Georgia. Thanks, Greg!

Bottom line: Globular clusters are spherical collections of stars, orbiting mostly in the star halo of spiral galaxies. Our Milky Way galaxy has about 150 globulars, which contain some of our galaxy’s oldest stars.

from EarthSky https://ift.tt/2wy0J5m

Comet NEOWISE and globular star cluster M53

Comet C/2020 F3 NEOWISE and globular cluster Messier 53, August 6, 2020, via Virtual Telescope.

Originally published August 7, 2020 by the Virtual Telescope Project. Re-printed here with permission.

While slowly leaving the inner solar system, Comet C/2020 F3 NEOWISE is surfing our skies, having very interesting encounters on our sky’s dome with stars and deep-sky objects. On August 6, 2020, the Virtual Telescope Project caught it with globular star cluster Messier 53.

The image above comes from the average of five, 60-seconds exposures, unfiltered, remotely taken with the Elena (PlaneWave 17?+Paramount ME+SBIG STL-6303E) robotic unit available as part of the Virtual Telescope Project. The sky was bright because of twilight.

Of course, this is just a matter of perspective: comet C/2020 F3 was at about 140 million kilometers (about 90 million miles) from us, while the Messier 53 globular cluster is placed at 58,000 light-years. To put these distances on the same scale, traveling at the speed of light, you would reach the comet in almost 8 minutes. Then you would need 58,000 years to reach the cluster!

We at the Virtual Telescope Project covered comet NEOWISE extensively: the images we already released are available for you to enjoy.

How to see Comet NEOWISE on August 9, 2020. Writing in Forbes, Jamie Carter wrote on August 6, 2020: “The comet can be found above the western horizon as soon as it gets dark, around 90 minutes after sunset. Do remember that you need binoculars because it’s now almost impossible to find the comet with your unaided naked eyes even in dark skies. 10×50 binoculars are a good option, though anything you already have, or can borrow, is probably good enough.” Image via Jamie Carter/ Cartes du Ciel/ Forbes.

Bottom line: A photo from the Virtual Telescope Project in Rome of Comet C/2020 F3 NEOWISE and the globular star cluster M52.

Via Virtual Telescope

from EarthSky https://ift.tt/2F76hZ3

Comet C/2020 F3 NEOWISE and globular cluster Messier 53, August 6, 2020, via Virtual Telescope.

Originally published August 7, 2020 by the Virtual Telescope Project. Re-printed here with permission.

While slowly leaving the inner solar system, Comet C/2020 F3 NEOWISE is surfing our skies, having very interesting encounters on our sky’s dome with stars and deep-sky objects. On August 6, 2020, the Virtual Telescope Project caught it with globular star cluster Messier 53.

The image above comes from the average of five, 60-seconds exposures, unfiltered, remotely taken with the Elena (PlaneWave 17?+Paramount ME+SBIG STL-6303E) robotic unit available as part of the Virtual Telescope Project. The sky was bright because of twilight.

Of course, this is just a matter of perspective: comet C/2020 F3 was at about 140 million kilometers (about 90 million miles) from us, while the Messier 53 globular cluster is placed at 58,000 light-years. To put these distances on the same scale, traveling at the speed of light, you would reach the comet in almost 8 minutes. Then you would need 58,000 years to reach the cluster!

We at the Virtual Telescope Project covered comet NEOWISE extensively: the images we already released are available for you to enjoy.

How to see Comet NEOWISE on August 9, 2020. Writing in Forbes, Jamie Carter wrote on August 6, 2020: “The comet can be found above the western horizon as soon as it gets dark, around 90 minutes after sunset. Do remember that you need binoculars because it’s now almost impossible to find the comet with your unaided naked eyes even in dark skies. 10×50 binoculars are a good option, though anything you already have, or can borrow, is probably good enough.” Image via Jamie Carter/ Cartes du Ciel/ Forbes.

Bottom line: A photo from the Virtual Telescope Project in Rome of Comet C/2020 F3 NEOWISE and the globular star cluster M52.

Via Virtual Telescope

from EarthSky https://ift.tt/2F76hZ3

Last quarter moon is August 11

View at EarthSky Community Photos. | Dr Ski in Valencia, Philippines, caught the last quarter moon shortly after it rose around midnight on the morning of September 22, 2019. This moon phase is perfect for helping you envision the location of the sun … below your feet. Thanks, Dr Ski!

August’s last quarter moon falls on Tuesday, August 11, at 04:44 UTC (Monday, August 10, at 11:44 p.m. CDT).

A last quarter moon appears half-lit by sunshine and half-immersed in its own shadow. It rises in the middle of the night, appears at its highest in the sky around dawn, and sets around midday.

A last quarter moon provides a great opportunity to think of yourself on a three-dimensional world in space. Watch for this moon just after moonrise, shortly after midnight. Then the lighted portion points downward, to the sun below your feet. Think of the last quarter moon as a mirror to the world you’re standing on. Think of yourself standing in the midst of Earth’s nightside, on the midnight portion of Earth.

Click here to see animation. As seen from the north side of the moon’s orbital plane, the Earth rotates counterclockwise on its rotational axis, and the moon revolves counterclockwise around Earth. The terminators of the Earth and moon align at first and last quarter moons, and only the near half of the moon’s day side is visible from Earth.

On a last quarter moon, the lunar terminator – the shadow line dividing day and night – shows you where it’s sunset on the moon.

View at EarthSky Community Photos. | September 22, 2019, photo by Dr Ski. He wrote: “The moon’s southern limb at last quarter. The Straight Wall is either black or white depending on the angle of the sun’s rays. At lunar sunset (now), it’s white. Around full moon, Tycho is one of the easiest craters to find due to the impact rays emanating from it. It’s like the hub of a spoked wheel! At last quarter, Tycho becomes unremarkable. Clavius, on the other hand, becomes remarkable at high magnification.”

View at EarthSky Community Photos. | September 22, 2019, photo by Dr Ski. He wrote: “The Sea of Rains at last quarter. The lunar Alps and Apennines are bisected by the moon’s meridian. You can get an idea of the height of these mountains by how far they extend into the dark side of the terminator. At an elevation of over 5,000 meters [16,000 feet], the Apennines are twice as tall as the Alps.”

Also, a last quarter moon can be used as a guidepost to Earth’s direction of motion in orbit around the sun.

In other words, when you look toward a last quarter moon high in the predawn sky, for example, you’re gazing out approximately along the path of Earth’s orbit, in a forward direction. The moon is moving in orbit around the sun with the Earth and never holds still. But, if we could somehow anchor the moon in space … tie it down, keep it still … Earth’s orbital speed of 18 miles per second would carry us across the space between us and the moon in only a few hours.

Want to read more about the last quarter moon as a guidepost for Earth’s motion? Astronomer Guy Ottewell talks about it here.

A great thing about using the moon as a guidepost to Earth’s motion is that you can do it anywhere … as, for example, in the photo below, from large cities.

Ben Orlove wrote from New York City: “I was sitting in the roof garden of my building, and there was the moon, right in front of me. You were right, this is a perfect time to visualize … the Earth’s motion.”

As the moon orbits Earth, it changes phase in an orderly way. Read more: 4 keys to understanding moon phases

Bottom line: The moon reaches its last quarter phase on August 11, 2020, at 04:44 UTC. In the coming week, watch for the moon to rise in the east in the hours after midnight, waning thinner each morning.

from EarthSky https://ift.tt/2ze0n1D

View at EarthSky Community Photos. | Dr Ski in Valencia, Philippines, caught the last quarter moon shortly after it rose around midnight on the morning of September 22, 2019. This moon phase is perfect for helping you envision the location of the sun … below your feet. Thanks, Dr Ski!

August’s last quarter moon falls on Tuesday, August 11, at 04:44 UTC (Monday, August 10, at 11:44 p.m. CDT).

A last quarter moon appears half-lit by sunshine and half-immersed in its own shadow. It rises in the middle of the night, appears at its highest in the sky around dawn, and sets around midday.

A last quarter moon provides a great opportunity to think of yourself on a three-dimensional world in space. Watch for this moon just after moonrise, shortly after midnight. Then the lighted portion points downward, to the sun below your feet. Think of the last quarter moon as a mirror to the world you’re standing on. Think of yourself standing in the midst of Earth’s nightside, on the midnight portion of Earth.

Click here to see animation. As seen from the north side of the moon’s orbital plane, the Earth rotates counterclockwise on its rotational axis, and the moon revolves counterclockwise around Earth. The terminators of the Earth and moon align at first and last quarter moons, and only the near half of the moon’s day side is visible from Earth.

On a last quarter moon, the lunar terminator – the shadow line dividing day and night – shows you where it’s sunset on the moon.

View at EarthSky Community Photos. | September 22, 2019, photo by Dr Ski. He wrote: “The moon’s southern limb at last quarter. The Straight Wall is either black or white depending on the angle of the sun’s rays. At lunar sunset (now), it’s white. Around full moon, Tycho is one of the easiest craters to find due to the impact rays emanating from it. It’s like the hub of a spoked wheel! At last quarter, Tycho becomes unremarkable. Clavius, on the other hand, becomes remarkable at high magnification.”

View at EarthSky Community Photos. | September 22, 2019, photo by Dr Ski. He wrote: “The Sea of Rains at last quarter. The lunar Alps and Apennines are bisected by the moon’s meridian. You can get an idea of the height of these mountains by how far they extend into the dark side of the terminator. At an elevation of over 5,000 meters [16,000 feet], the Apennines are twice as tall as the Alps.”

Also, a last quarter moon can be used as a guidepost to Earth’s direction of motion in orbit around the sun.

In other words, when you look toward a last quarter moon high in the predawn sky, for example, you’re gazing out approximately along the path of Earth’s orbit, in a forward direction. The moon is moving in orbit around the sun with the Earth and never holds still. But, if we could somehow anchor the moon in space … tie it down, keep it still … Earth’s orbital speed of 18 miles per second would carry us across the space between us and the moon in only a few hours.

Want to read more about the last quarter moon as a guidepost for Earth’s motion? Astronomer Guy Ottewell talks about it here.

A great thing about using the moon as a guidepost to Earth’s motion is that you can do it anywhere … as, for example, in the photo below, from large cities.

Ben Orlove wrote from New York City: “I was sitting in the roof garden of my building, and there was the moon, right in front of me. You were right, this is a perfect time to visualize … the Earth’s motion.”

As the moon orbits Earth, it changes phase in an orderly way. Read more: 4 keys to understanding moon phases

Bottom line: The moon reaches its last quarter phase on August 11, 2020, at 04:44 UTC. In the coming week, watch for the moon to rise in the east in the hours after midnight, waning thinner each morning.

from EarthSky https://ift.tt/2ze0n1D