Manhattanhenge in 2024: See it tonight and tomorrow night

View at EarthSky Community Photos. | Walter Karling at Gantry Plaza State Park, Long Island City, took this image on July 12, 2022. Walter wrote: “Photographing Manhattanhenge from Queens looking east toward Manhattan.” Thank you, Walter!

The second set of Manhattanhenge will occur on the evenings of July 12 and 13, 2024.

Manhattanhenge, and how to see it

Twice a year – around May 28, 29 or 30, and again around July 11, 12 or 13 – people in New York City look for Manhattanhenge. It’s a phenomenon where the sunset aligns perfectly on east-west oriented streets and avenues of Manhattan. So cool!

In 2024, the first set of Manhattanhenge dates fell on May 28 (half sun) and May 29 (full sun).

According to the American Museum of Natural History:

Four nights a year, the streets of Manhattan’s grid become the site for a stunning sunset phenomenon known as Manhattanhenge. During Manhattanhenge, the sun sets in perfect alignment with Manhattan’s east-west numbered streets, creating cinema-worthy photo opportunities …

The second set of Manhattanhenge dates falls on July 12 (full sun at 8:20 p.m. EDT) and July 13 (half sun at 8:21 p.m. EDT).

Some of the best places to spot it are along 14th, 23rd, 34th (includes the Empire State Building), 42nd, 57th, and 79th Streets.

Another good place is from the Tudor City Bridge in Manhattan (though it can be crowded) or Hunter’s Point South Park in Long Island City, Queens.

Regardless of where you watch the sunset, make sure you’re as far east as possible while keeping New Jersey in the background across the Hudson River to accentuate the effect.

More good locations and tips from the NYC Parks Department

Neil deGrasse Tyson on Manhattanhenge

The name Manhattanhenge was coined by astrophysicist Neil deGrasse Tyson. It’s a nod to the prehistoric monument Stonehenge in England, which was designed to frame the summer solstice sunrise and the winter solstice sunset. Manhattanhenge is accidental. It happens because Manhattan was built with a grid system of streets running north-south and east-west, Tyson explains in the video above.

Aligned sunsets

Each Manhattanhenge is actually two days. On one day the sun’s full disk aligns with the street grid, and then on the other day half the sun’s disk aligns with the street grid.

The two sets of aligned sunsets are centered around the dates of the summer solstice, leading to the effect’s other name, not as commonly used: the Manhattan Solstice.

Six months later, Reverse Manhattanhenge happens around the mornings around January 11, when the rising sun creates the same effect on the other side of the island at shortly after 7 a.m. EST.

Manhattanhenge on July 12, 2016, at 42nd Street. Tourists blocked an entire section of 42nd Street, including its intersection with 6th Avenue, to take pictures of the sunset. Image via Fred Hsu/ Wikimedia Commons (CC BY-SA 3.0).

Solstice and equinox alignments around the world

The phenomenon of Manhattanhenge is fun. And it’s one of many similar alignments that occur around the world on various dates. Think Stonehenge at the equinoxes and solstices.

The point of sunset along the horizon varies throughout the year. At this time of the year – before the June solstice – the sunset point is shifting northward each day on the horizon as seen from around the globe. It’s the northward-shifting path of the sun that gives us summer in the Northern Hemisphere and winter in the Southern Hemisphere. And it’s the shifting path of the sun that gives people various alignments of the sunset with familiar landmarks.

Abhijit Juvekar in Dombivli, India, created this composite image of sunsets over a period of months to show how the sun sets progressively farther north in the months leading up to the June solstice. Abhijit posted this image on EarthSky Facebook. Used with permission.

Watching Manhattanhenge

You can observe Manhattanhenge from lots of different places on the east-west streets of the Manhattan street grid. The best places to watch Manhattanhenge are wide streets with an unobstructed view toward New Jersey across the Hudson River.

Popular spots are 34th Street near the Empire State Building and 42nd Street near the Chrysler Building. Wide cross streets – such as 14th, 34th, 42nd and 57th Streets – that ensure the best views of the west-northwest horizon (toward New Jersey) are generally good spots.

Keep in mind that Manhattanhenge draws large crowds, especially around the city’s landmarks.

Here’s a video of Manhattanhenge on May 30, 2024.

#Manhattanhenge as seen from MSG today pic.twitter.com/c3L90GHe4P

— ChrisSavva (@ilcapitanCristo) May 31, 2024

Why does Manhattanhenge happen?

The June solstice on June 21 will bring the sun’s northernmost point in our sky and northernmost sunset. Afterward, the sun’s path in our sky, and the sunset point, will both start shifting southward again. As for the sun’s alignment with the city of New York, and the streets of Manhattan Island … well, thank the original planners of this city. Scientific American explained:

The phenomenon is based on a design for Manhattan outlined in The Commissioners’ Plan of 1811 for a rectilinear grid or gridiron of straight streets and avenues that intersect one another at right angles. This design runs from north of Houston Street in Lower Manhattan to just south of 155th Street in Upper Manhattan. Most cross streets in between were arranged in a regular right-angled grid that was tilted 29 degrees east of true north to roughly replicate the angle of the island of Manhattan.

And because of this 29-degree tilt in the grid, the magic moment of the setting sun aligning with Manhattan’s cross streets does not coincide with the June solstice but rather with specific dates in late May and early July.

EarthSky Community Photos of Manhattanhenge

Manhattanhenge in 2017. Gowrishankar Lakshminarayanan was in Gantry Plaza State Park, Queens, New York, looking straight through 42nd Street with the Chrysler building to the right. He said he created this 3-image composite to preserve the disk of the sun and also show shadow details of the surroundings. Used with permission.

Did you get a photo of Manhattanhenge? We’d love to see it! Submit it to us at EarthSky Community Photos.

Bottom line: Each year around May 29, and again around July 12, New Yorkers watch for Manhattanhenge. The second set of Manhattanhenge dates is July 12 and 13, 2024.

Read more about Manhattanhenge from ScientificAmerican.com

Read more about Manhattanhenge from American Museum of Natural History

The post Manhattanhenge in 2024: See it tonight and tomorrow night first appeared on EarthSky.

from EarthSky https://ift.tt/1TNBGu4

View at EarthSky Community Photos. | Walter Karling at Gantry Plaza State Park, Long Island City, took this image on July 12, 2022. Walter wrote: “Photographing Manhattanhenge from Queens looking east toward Manhattan.” Thank you, Walter!

The second set of Manhattanhenge will occur on the evenings of July 12 and 13, 2024.

Manhattanhenge, and how to see it

Twice a year – around May 28, 29 or 30, and again around July 11, 12 or 13 – people in New York City look for Manhattanhenge. It’s a phenomenon where the sunset aligns perfectly on east-west oriented streets and avenues of Manhattan. So cool!

In 2024, the first set of Manhattanhenge dates fell on May 28 (half sun) and May 29 (full sun).

According to the American Museum of Natural History:

Four nights a year, the streets of Manhattan’s grid become the site for a stunning sunset phenomenon known as Manhattanhenge. During Manhattanhenge, the sun sets in perfect alignment with Manhattan’s east-west numbered streets, creating cinema-worthy photo opportunities …

The second set of Manhattanhenge dates falls on July 12 (full sun at 8:20 p.m. EDT) and July 13 (half sun at 8:21 p.m. EDT).

Some of the best places to spot it are along 14th, 23rd, 34th (includes the Empire State Building), 42nd, 57th, and 79th Streets.

Another good place is from the Tudor City Bridge in Manhattan (though it can be crowded) or Hunter’s Point South Park in Long Island City, Queens.

Regardless of where you watch the sunset, make sure you’re as far east as possible while keeping New Jersey in the background across the Hudson River to accentuate the effect.

More good locations and tips from the NYC Parks Department

Neil deGrasse Tyson on Manhattanhenge

The name Manhattanhenge was coined by astrophysicist Neil deGrasse Tyson. It’s a nod to the prehistoric monument Stonehenge in England, which was designed to frame the summer solstice sunrise and the winter solstice sunset. Manhattanhenge is accidental. It happens because Manhattan was built with a grid system of streets running north-south and east-west, Tyson explains in the video above.

Aligned sunsets

Each Manhattanhenge is actually two days. On one day the sun’s full disk aligns with the street grid, and then on the other day half the sun’s disk aligns with the street grid.

The two sets of aligned sunsets are centered around the dates of the summer solstice, leading to the effect’s other name, not as commonly used: the Manhattan Solstice.

Six months later, Reverse Manhattanhenge happens around the mornings around January 11, when the rising sun creates the same effect on the other side of the island at shortly after 7 a.m. EST.

Manhattanhenge on July 12, 2016, at 42nd Street. Tourists blocked an entire section of 42nd Street, including its intersection with 6th Avenue, to take pictures of the sunset. Image via Fred Hsu/ Wikimedia Commons (CC BY-SA 3.0).

Solstice and equinox alignments around the world

The phenomenon of Manhattanhenge is fun. And it’s one of many similar alignments that occur around the world on various dates. Think Stonehenge at the equinoxes and solstices.

The point of sunset along the horizon varies throughout the year. At this time of the year – before the June solstice – the sunset point is shifting northward each day on the horizon as seen from around the globe. It’s the northward-shifting path of the sun that gives us summer in the Northern Hemisphere and winter in the Southern Hemisphere. And it’s the shifting path of the sun that gives people various alignments of the sunset with familiar landmarks.

Abhijit Juvekar in Dombivli, India, created this composite image of sunsets over a period of months to show how the sun sets progressively farther north in the months leading up to the June solstice. Abhijit posted this image on EarthSky Facebook. Used with permission.

Watching Manhattanhenge

You can observe Manhattanhenge from lots of different places on the east-west streets of the Manhattan street grid. The best places to watch Manhattanhenge are wide streets with an unobstructed view toward New Jersey across the Hudson River.

Popular spots are 34th Street near the Empire State Building and 42nd Street near the Chrysler Building. Wide cross streets – such as 14th, 34th, 42nd and 57th Streets – that ensure the best views of the west-northwest horizon (toward New Jersey) are generally good spots.

Keep in mind that Manhattanhenge draws large crowds, especially around the city’s landmarks.

Here’s a video of Manhattanhenge on May 30, 2024.

#Manhattanhenge as seen from MSG today pic.twitter.com/c3L90GHe4P

— ChrisSavva (@ilcapitanCristo) May 31, 2024

Why does Manhattanhenge happen?

The June solstice on June 21 will bring the sun’s northernmost point in our sky and northernmost sunset. Afterward, the sun’s path in our sky, and the sunset point, will both start shifting southward again. As for the sun’s alignment with the city of New York, and the streets of Manhattan Island … well, thank the original planners of this city. Scientific American explained:

The phenomenon is based on a design for Manhattan outlined in The Commissioners’ Plan of 1811 for a rectilinear grid or gridiron of straight streets and avenues that intersect one another at right angles. This design runs from north of Houston Street in Lower Manhattan to just south of 155th Street in Upper Manhattan. Most cross streets in between were arranged in a regular right-angled grid that was tilted 29 degrees east of true north to roughly replicate the angle of the island of Manhattan.

And because of this 29-degree tilt in the grid, the magic moment of the setting sun aligning with Manhattan’s cross streets does not coincide with the June solstice but rather with specific dates in late May and early July.

EarthSky Community Photos of Manhattanhenge

Manhattanhenge in 2017. Gowrishankar Lakshminarayanan was in Gantry Plaza State Park, Queens, New York, looking straight through 42nd Street with the Chrysler building to the right. He said he created this 3-image composite to preserve the disk of the sun and also show shadow details of the surroundings. Used with permission.

Did you get a photo of Manhattanhenge? We’d love to see it! Submit it to us at EarthSky Community Photos.

Bottom line: Each year around May 29, and again around July 12, New Yorkers watch for Manhattanhenge. The second set of Manhattanhenge dates is July 12 and 13, 2024.

Read more about Manhattanhenge from ScientificAmerican.com

Read more about Manhattanhenge from American Museum of Natural History

The post Manhattanhenge in 2024: See it tonight and tomorrow night first appeared on EarthSky.

from EarthSky https://ift.tt/1TNBGu4

Denisovans coexisted with modern humans on Tibetan plateau

This 2020 video from Ben G. Thomas on YouTube will introduce you to Denisovans, an extinct species of archaic humans that ranged across Asia some 285,000 to 25,000 years ago. The date of a new fossil shows Denisovans coexisted with modern humans on the Tibetan plateau. Curious about this artwork? See how scientists and artists created it, below.

A long-extinct species of humans, known as Denisovans, lived on the Tibetan plateau for over 100,000 years, overlapping with modern humans. The University of Reading said on July 3, 2024, that this finding is based on the study of fossils found in a cave on the Tibetan plateau, called Baishiya Karst Cave. The new work provides insights to the story of how and when Tibet was settled, the researchers said.

Researchers dated a rib bone found in the cave to an individual who lived about 40,000 years ago. That would make it the youngest Denisovan bone found so far and would mean the Denisovans coexisted with modern humans in what is now Tibet. Another site, some 800 miles (1,300 km) away on the Tibetan plateau, contains artifacts that reveal the characteristics of modern human craftsmanship and date to 40,000 to 30,000 years ago. As co-author Dongju Zhang of Lanzhou University in China told Science:

That means Denisovans survived until modern humans appeared in the region, which makes it possible [the two groups] had genetic communication.

The scientists published their peer-reviewed findings in the journal Nature on July 3, 2024.

Links between humans and Denisovans in Asia are not new. A 2018 study showed DNA matches between humans and Denisovans in parts of Asia. In particular, the 2018 study showed Denisovan DNA matches among Han Chinese, Chinese Dai, and Japanese. Prior to the 2018 study, it was known that the genomes of certain populations, such as indigenous peoples of Western New Guinea in Indonesia and Papua New Guinea, contained about 5% Denisovan ancestry.

Scientists studied the remains of extinct humans – known as Denisovans – from the Baishiya Karst Cave, located at the edge of the Ganjia Basin on the Tibetan Plateau. Image via Dongju Zhang/ Lanzhou University/ University of Reading. Used with permission.

Mysterious extinct humans, the Denisovans

Neanderthals were an extinct human species that once co-existed with modern humans (Homo sapiens). Another human species, not as well known, also existed around the same time. Scientists call them the Denisovans. These enigmatic ancient humans lived 285,000 to 25,000 years ago.

Denisovans got their name from the Denisova Cave in the Altai Mountains of Siberia, Russia, where scientists first found their fossils. The first identification of a Denisovan – from a young female finger bone – came in 2010. Then, in 2019, researchers reported a second discovery, this time in China. They had studied a lower jaw found in the Baishiya Karst Cave on the Tibetan Plateau, and it turned out to be Denisovan. That same cave subsequently yielded a second Denisovan fossil, a single rib bone, which researchers announced in 2024. And a 2022 paper revealed a third location: a tooth from a cave in Laos was Denisovan.

We don’t know a lot about Denisovans because their fossil record, which spans northern Russia to Southeast Asia, is sparse. Since there are so few fossils, it’s not possible to reconstruct their appearance based on a fossil skeleton. To identify Denisovan fossils, researchers use DNA or collagen protein analysis to show they were a human species distinct from Neanderthals and modern humans.

Making the portrait of the Denisovan girl

So there’s no way to know what the ancient Denisovan people really looked like. That’s because there isn’t a rich fossil record for Denisovans, as there is for Neanderthals. The Denisovans are known from only a few bone fragments. But, in 2019, scientists and artist Maayan Harel were able to reconstruct this portrait of an extinct Denisovan girl, thanks to DNA from the bone of her little finger.

A common ancestor

Neanderthals, Denisovans, and modern humans descended from a common ancestor known as Homo heidelbergensis. Scientists think a population of H. heidelbergensis left Africa. Subsequently, some of them moved to Western Asia and Europe to become Neanderthals, while others branched eastward to Asia to become Denisovans. (A population of H. heidelbergensis remained in Africa to eventually evolve into modern humans.)

There was interbreeding between these three human species when their populations overlapped. At least one Neanderthal-Denisovan individual has been identified from a fossil found in the Denisova Cave in Russia. Meanwhile, most modern humans around the world today retain very small percentages of Neanderthal or Denisovan DNA.

A rare new fossil of Denisovans

The Baishiya Karst Cave on the Tibetan Plateau in China is about 10,800 feet (3,280 m) above sea level. There, in 2018 and 2019, scientists excavated fossil bones. They then studied over 2,500 of those bones to tease out their secrets.

Among the fossils was a rib bone that belonged to a Denisovan. It’s the second Denisovan bone recovered from that cave, a rare addition to a very sparse fossil record for this extinct human species. It came from an individual that lived between 48,000 and 32,000 years ago. That’s also about the same timeframe that modern humans had started populating Europe and Asia.

It also shows the Denisovans inhabited the Tibetan Plateau from 200,000 to 40,000 years ago, a time period that spans two ice ages.

Scientists found a rib from a Denisovan among the fossil bones at the Baishiya Karst Cave. Image via Dongju Zhang / Lanzhou University/ University of Reading. Used with permission.

What the fossils tell us about these extinct humans

The other fossils belonged to animals the Denisovans had hunted. With a few exceptions, the bones were in such tiny fragments the scientists could not identify what they belonged to. Therefore, they analyzed bone collagen in the fossils using a technique called zooarchaeology by mass spectrometry to identify the animal species. They found most bones came from blue sheep, wild yaks, horse-like animals, the extinct woolly rhino and the spotted hyena. There were also bones from small mammals and birds.

Co-author Geoff Smith of the University of Reading said:

We were able to identify that Denisovans hunted, butchered and ate a range of animal species. Our study reveals new information about the behavior and adaptation of Denisovans both to high altitude conditions and shifting climates. We are only just beginning to understand the behavior of this extraordinary human species.

Co-author Jian Wang of Lanzhou University said:

Current evidence suggests that it was Denisovans, not any other human groups, who occupied the cave and made efficient use of all the animal resources available to them throughout their occupation.

Scientist excavating fossils inside the Baishiya Karst Cave. Image via Dongju Zhang/ Lanzhou University. Used with permission.

Surviving the ice ages

The fossils presented a record of how these humans survived in changing climate conditions 160,000 to 45,000 years ago. That period included two ice ages and a warm period. The condition of the bones, such as cut and chop marks, indicated that Denisovans had removed meat and bone marrow from the animals they hunted, and perhaps harvested hides. They had also used the bones to create tools.

Co-author Frido Welker of the University of Copenhagen commented:

Together, the fossil and molecular evidence indicates that Ganjia Basin, where Baishiya Karst Cave is located, provided a relatively stable environment for Denisovans, despite its high altitude.

The question now arises when and why these Denisovans on the Tibetan Plateau went extinct.

A sweeping view of the Ganjia Basin in the Tibetan Plateau. Image via Dongju Zhang/ Lanzhou University. Used with permission.

Bottom line: Scientists reported that an extinct species of humans, known as Denisovans, coexisted on the Tibetan plateau with modern humans.

Source: Middle and Late Pleistocene Denisovan subsistence at Baishiya Karst Cave

Via University of Reading

Via Science

The post Denisovans coexisted with modern humans on Tibetan plateau first appeared on EarthSky.

from EarthSky https://ift.tt/UrOyRzd

This 2020 video from Ben G. Thomas on YouTube will introduce you to Denisovans, an extinct species of archaic humans that ranged across Asia some 285,000 to 25,000 years ago. The date of a new fossil shows Denisovans coexisted with modern humans on the Tibetan plateau. Curious about this artwork? See how scientists and artists created it, below.

A long-extinct species of humans, known as Denisovans, lived on the Tibetan plateau for over 100,000 years, overlapping with modern humans. The University of Reading said on July 3, 2024, that this finding is based on the study of fossils found in a cave on the Tibetan plateau, called Baishiya Karst Cave. The new work provides insights to the story of how and when Tibet was settled, the researchers said.

Researchers dated a rib bone found in the cave to an individual who lived about 40,000 years ago. That would make it the youngest Denisovan bone found so far and would mean the Denisovans coexisted with modern humans in what is now Tibet. Another site, some 800 miles (1,300 km) away on the Tibetan plateau, contains artifacts that reveal the characteristics of modern human craftsmanship and date to 40,000 to 30,000 years ago. As co-author Dongju Zhang of Lanzhou University in China told Science:

That means Denisovans survived until modern humans appeared in the region, which makes it possible [the two groups] had genetic communication.

The scientists published their peer-reviewed findings in the journal Nature on July 3, 2024.

Links between humans and Denisovans in Asia are not new. A 2018 study showed DNA matches between humans and Denisovans in parts of Asia. In particular, the 2018 study showed Denisovan DNA matches among Han Chinese, Chinese Dai, and Japanese. Prior to the 2018 study, it was known that the genomes of certain populations, such as indigenous peoples of Western New Guinea in Indonesia and Papua New Guinea, contained about 5% Denisovan ancestry.

Scientists studied the remains of extinct humans – known as Denisovans – from the Baishiya Karst Cave, located at the edge of the Ganjia Basin on the Tibetan Plateau. Image via Dongju Zhang/ Lanzhou University/ University of Reading. Used with permission.

Mysterious extinct humans, the Denisovans

Neanderthals were an extinct human species that once co-existed with modern humans (Homo sapiens). Another human species, not as well known, also existed around the same time. Scientists call them the Denisovans. These enigmatic ancient humans lived 285,000 to 25,000 years ago.

Denisovans got their name from the Denisova Cave in the Altai Mountains of Siberia, Russia, where scientists first found their fossils. The first identification of a Denisovan – from a young female finger bone – came in 2010. Then, in 2019, researchers reported a second discovery, this time in China. They had studied a lower jaw found in the Baishiya Karst Cave on the Tibetan Plateau, and it turned out to be Denisovan. That same cave subsequently yielded a second Denisovan fossil, a single rib bone, which researchers announced in 2024. And a 2022 paper revealed a third location: a tooth from a cave in Laos was Denisovan.

We don’t know a lot about Denisovans because their fossil record, which spans northern Russia to Southeast Asia, is sparse. Since there are so few fossils, it’s not possible to reconstruct their appearance based on a fossil skeleton. To identify Denisovan fossils, researchers use DNA or collagen protein analysis to show they were a human species distinct from Neanderthals and modern humans.

Making the portrait of the Denisovan girl

So there’s no way to know what the ancient Denisovan people really looked like. That’s because there isn’t a rich fossil record for Denisovans, as there is for Neanderthals. The Denisovans are known from only a few bone fragments. But, in 2019, scientists and artist Maayan Harel were able to reconstruct this portrait of an extinct Denisovan girl, thanks to DNA from the bone of her little finger.

A common ancestor

Neanderthals, Denisovans, and modern humans descended from a common ancestor known as Homo heidelbergensis. Scientists think a population of H. heidelbergensis left Africa. Subsequently, some of them moved to Western Asia and Europe to become Neanderthals, while others branched eastward to Asia to become Denisovans. (A population of H. heidelbergensis remained in Africa to eventually evolve into modern humans.)

There was interbreeding between these three human species when their populations overlapped. At least one Neanderthal-Denisovan individual has been identified from a fossil found in the Denisova Cave in Russia. Meanwhile, most modern humans around the world today retain very small percentages of Neanderthal or Denisovan DNA.

A rare new fossil of Denisovans

The Baishiya Karst Cave on the Tibetan Plateau in China is about 10,800 feet (3,280 m) above sea level. There, in 2018 and 2019, scientists excavated fossil bones. They then studied over 2,500 of those bones to tease out their secrets.

Among the fossils was a rib bone that belonged to a Denisovan. It’s the second Denisovan bone recovered from that cave, a rare addition to a very sparse fossil record for this extinct human species. It came from an individual that lived between 48,000 and 32,000 years ago. That’s also about the same timeframe that modern humans had started populating Europe and Asia.

It also shows the Denisovans inhabited the Tibetan Plateau from 200,000 to 40,000 years ago, a time period that spans two ice ages.

Scientists found a rib from a Denisovan among the fossil bones at the Baishiya Karst Cave. Image via Dongju Zhang / Lanzhou University/ University of Reading. Used with permission.

What the fossils tell us about these extinct humans

The other fossils belonged to animals the Denisovans had hunted. With a few exceptions, the bones were in such tiny fragments the scientists could not identify what they belonged to. Therefore, they analyzed bone collagen in the fossils using a technique called zooarchaeology by mass spectrometry to identify the animal species. They found most bones came from blue sheep, wild yaks, horse-like animals, the extinct woolly rhino and the spotted hyena. There were also bones from small mammals and birds.

Co-author Geoff Smith of the University of Reading said:

We were able to identify that Denisovans hunted, butchered and ate a range of animal species. Our study reveals new information about the behavior and adaptation of Denisovans both to high altitude conditions and shifting climates. We are only just beginning to understand the behavior of this extraordinary human species.

Co-author Jian Wang of Lanzhou University said:

Current evidence suggests that it was Denisovans, not any other human groups, who occupied the cave and made efficient use of all the animal resources available to them throughout their occupation.

Scientist excavating fossils inside the Baishiya Karst Cave. Image via Dongju Zhang/ Lanzhou University. Used with permission.

Surviving the ice ages

The fossils presented a record of how these humans survived in changing climate conditions 160,000 to 45,000 years ago. That period included two ice ages and a warm period. The condition of the bones, such as cut and chop marks, indicated that Denisovans had removed meat and bone marrow from the animals they hunted, and perhaps harvested hides. They had also used the bones to create tools.

Co-author Frido Welker of the University of Copenhagen commented:

Together, the fossil and molecular evidence indicates that Ganjia Basin, where Baishiya Karst Cave is located, provided a relatively stable environment for Denisovans, despite its high altitude.

The question now arises when and why these Denisovans on the Tibetan Plateau went extinct.

A sweeping view of the Ganjia Basin in the Tibetan Plateau. Image via Dongju Zhang/ Lanzhou University. Used with permission.

Bottom line: Scientists reported that an extinct species of humans, known as Denisovans, coexisted on the Tibetan plateau with modern humans.

Source: Middle and Late Pleistocene Denisovan subsistence at Baishiya Karst Cave

Via University of Reading

Via Science

The post Denisovans coexisted with modern humans on Tibetan plateau first appeared on EarthSky.

from EarthSky https://ift.tt/UrOyRzd

Summer Triangle star Deneb is distant and luminous

The bright star Deneb is part of the famous Summer Triangle asterism. Its constellation Cygnus the Swan flies across the July evening sky.

Deneb or Alpha Cygni is the northernmost star in the famous Summer Triangle, a prominent asterism visible in the east on July and August evenings. Three bright stars make up the Summer Triangle. They are the brightest stars in three separate constellations. Deneb’s constellation is Cygnus the Swan. In a dark sky, you can imagine the Swan, flying along the starlit trail of the summer Milky Way. The constellation Cygnus also makes an obvious cross shape, and that’s another asterism. That is, it’s another prominent star pattern. It’s called the Northern Cross.

Okay, we’ve given you a lot of names here: Summer Triangle, Cygnus and Northern Cross.

Just remember, the constellation Cygnus the Swan contains the asterism of the Northern Cross. The Cross is just another way to see the Swan. Deneb is at the top of the Cross, but at the tail of the Swan (the star name “deneb” always means “tail”). The little star Albireo is at the head of the Swan, but at the base of the Cross. Whew!

The constellation Cygnus represents a graceful swan. But many also see it as a cross, and so these stars have become known as the Northern Cross. Deneb marks the Tail of Cygnus the Swan … and the head of a cross-like pattern known as the Northern Cross.

Very far away, and very luminous

The star Deneb in the constellation Cygnus the Swan is one of the most distant stars you’ll ever see with your eye alone. That’s because it’s one of our Milky Way galaxy’s most luminous stars.

Deneb is somewhere around 1,500 light-years away. That’s in contrast to most visible stars in our sky, located tens to hundreds of light-years away.

But astronomers still aren’t certain of the exact distance for this very luminous star. There are varying estimates for its distance. Why?

For some decades, ESA’s Earth-orbiting Hipparcos satellite, which operated from 1989 to 1993, provided the most important distance measurement for Deneb. Hipparcos was the predecessor to the Gaia space observatory, which is currently in space and collecting data, with the goal of creating a 3D map of our Milky Way galaxy.

Both Hipparcos and Gaia gather what’s called astrometric data on the stars. That is, they measure stars’ positions, motions and brightnesses not just once, but again and again. Those measurements let earthly astronomers calculate a distance, see how the star is moving, and much more.

Early analyses of Hipparcos data indicated a distance around 2,600 light-years for Deneb. Then, in 2009, a newer study – which used more powerful analysis techniques on Hipparcos data – gave a distance for Deneb that’s about half the widely accepted value, closer to 1,500 light-years.

Today, that value – around 1,500 light-years – is the most widely accepted value for Deneb’s distance.

Astronomers use the parallax method to find distances to nearby stars. But Deneb is too far away for accurate parallax measurements from Earth’s surface. Image via NASA/ ESA/ A. Feild (STScI).

When will we know the distance to Deneb?

Gaia has now released three sets of data. Why haven’t Gaia’s newer measurements let astronomers measure Deneb’s distance more precisely? It’s mainly because Gaia isn’t geared toward observing such a bright star as Deneb. Astronomer Anthony G.A. Brown of Leiden Observatory in the Netherlands – a member of the Gaia team – told EarthSky in July 2021 that Gaia data still haven’t been used to determine a new distance for Deneb. He said:

The Hipparcos distance estimate still stands.

Deneb is so bright that we can only observe it with Gaia through specially programmed observation sequences (the observing instruments on the spacecraft do not automatically pick up the star). We have observations of
Deneb in hand but these will require a dedicated processing which we have not yet started.

So, for now, the updated Hipparcos number of approximately 1,500 light-years is still the best estimate of Deneb’s distance.

And that’s impressive. So, for us to see a star shine so brightly in our sky from this great distance away, the star must be very powerful. Deneb is one of the most luminous stars – one of the brightest stars, intrinsically – that we can see with the eye.

Deneb (bottom half of frame) is some 200 times bigger than our sun. Image via AstroBob.

Science of Deneb

Deneb is a blue-white supergiant star with a spectral class of A2Ia. It is the 19th brightest star in the sky shining at +1.25 magnitude. It’s about 196,000 times more luminous than our sun. Deneb contains about 20 solar masses, and as mentioned above its distance is uncertain. Deneb has a diameter about 203 times that of the sun. And that makes Deneb one of the largest type A spectral class stars known.

Deneb is the prototype for the Alpha Cygni variable stars. Its brightness varies due to non-radial fluctuations on the surface of the star. The fluctuations originate from areas on the surface of the star either expanding and contracting at the same time. They can last for days to weeks and their origin is unknown. The change in brightness is minimal, but detectable. For example, Deneb varies in brightness from magnitude 1.21 to 1.29. Another Alpha Cygni variable star is Rigel, in the constellation of Orion the Hunter.

Deneb was once a spectral class O-type main sequence star with a mass about 23 times that of the sun. Now that it’s a supergiant, it’s no longer fusing hydrogen in its core. It will evolve into a very luminous red supergiant or possibly a highly luminous blue variable star or maybe a Wolf-Rayet star. Regardless of which type of star it becomes, it’s expected to explode as a supernova sometime in the next few million years.

Deneb will be the North Pole Star around 9800 AD, but will be seven degrees from the pole. By the way, Deneb is the North Pole Star for Mars.

Deneb in history and mythology

The name Deneb derives from the Arabic Al Dhanab al Dajajah meaning Tail of the Hen. It obviously dates from an earlier incarnation of Cygnus not as a swan but as a chicken. Like many bright stars, Deneb has been called by a number of other names, but the oddest, according to Richard Hinckley Allen, who cites the Arabic name above, was Uropygium, meaning the posterior part of a bird’s body from which feathers grow, and oddly sometimes called the “Pope’s nose.”

In Chinese mythology Deneb is associated with the story of the Celestial Princess or the Weaver Girl. In this story a girl (the star Vega) is separated from her beloved (a cowherd represented by the star Altair) by the Milky Way. Once a year, the girl and the cowherd are allowed to meet briefly when a large flock of magpies forms a bridge across the starry river. Deneb represents the bridge.

The constellation Lacerta the Lizard lies just behind the tail feathers of Cygnus the Swan. The chart also shows Lyra and Vulpecula. This star chart is from Urania’s Mirror, a set of celestial cards by Sidney Hall published in 1825. Image via Wikipedia.

How to see Deneb

You can gaze at this faraway star in the evening starting around May, or late spring in the Northern Hemisphere. From this hemisphere, in July and August, Deneb shines in the east at nightfall and appears high up in the sky around the middle of the night.

Like all stars, Deneb is found about one degree farther west at the same time each day, and climbs to its highest point about four minutes earlier per day, 1/2 hour earlier per week, or two hours earlier per month.

Deneb is circumpolar as seen from locations of about 45 degrees north latitude, roughly the northern tier of U.S. states. In other words, from the northern U.S. and similar latitudes, Deneb never sets but instead circles round and round the pole star.

This star is not visible south of about 45 degrees south latitude. That includes Antarctica, far southern Argentina and Chile, and perhaps the far southern tip of New Zealand’s South Island.

Aside from that, just about anyone should have a chance to see Deneb at one time or another. When you do see it, think of the power of this mighty star shining over such a great distance in space!

Deneb’s position is RA: 20h 41m 26s, dec: +45° 16′ 49″.

Bottom line: Read here about the luminous Summer Triangle star Deneb, and learn how to see it in your sky.

Our Summer Triangle series includes:

Vega is bright and blue-white

Deneb is distant and very luminous

Altair spins fast!

The post Summer Triangle star Deneb is distant and luminous first appeared on EarthSky.

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The bright star Deneb is part of the famous Summer Triangle asterism. Its constellation Cygnus the Swan flies across the July evening sky.

Deneb or Alpha Cygni is the northernmost star in the famous Summer Triangle, a prominent asterism visible in the east on July and August evenings. Three bright stars make up the Summer Triangle. They are the brightest stars in three separate constellations. Deneb’s constellation is Cygnus the Swan. In a dark sky, you can imagine the Swan, flying along the starlit trail of the summer Milky Way. The constellation Cygnus also makes an obvious cross shape, and that’s another asterism. That is, it’s another prominent star pattern. It’s called the Northern Cross.

Okay, we’ve given you a lot of names here: Summer Triangle, Cygnus and Northern Cross.

Just remember, the constellation Cygnus the Swan contains the asterism of the Northern Cross. The Cross is just another way to see the Swan. Deneb is at the top of the Cross, but at the tail of the Swan (the star name “deneb” always means “tail”). The little star Albireo is at the head of the Swan, but at the base of the Cross. Whew!

The constellation Cygnus represents a graceful swan. But many also see it as a cross, and so these stars have become known as the Northern Cross. Deneb marks the Tail of Cygnus the Swan … and the head of a cross-like pattern known as the Northern Cross.

Very far away, and very luminous

The star Deneb in the constellation Cygnus the Swan is one of the most distant stars you’ll ever see with your eye alone. That’s because it’s one of our Milky Way galaxy’s most luminous stars.

Deneb is somewhere around 1,500 light-years away. That’s in contrast to most visible stars in our sky, located tens to hundreds of light-years away.

But astronomers still aren’t certain of the exact distance for this very luminous star. There are varying estimates for its distance. Why?

For some decades, ESA’s Earth-orbiting Hipparcos satellite, which operated from 1989 to 1993, provided the most important distance measurement for Deneb. Hipparcos was the predecessor to the Gaia space observatory, which is currently in space and collecting data, with the goal of creating a 3D map of our Milky Way galaxy.

Both Hipparcos and Gaia gather what’s called astrometric data on the stars. That is, they measure stars’ positions, motions and brightnesses not just once, but again and again. Those measurements let earthly astronomers calculate a distance, see how the star is moving, and much more.

Early analyses of Hipparcos data indicated a distance around 2,600 light-years for Deneb. Then, in 2009, a newer study – which used more powerful analysis techniques on Hipparcos data – gave a distance for Deneb that’s about half the widely accepted value, closer to 1,500 light-years.

Today, that value – around 1,500 light-years – is the most widely accepted value for Deneb’s distance.

Astronomers use the parallax method to find distances to nearby stars. But Deneb is too far away for accurate parallax measurements from Earth’s surface. Image via NASA/ ESA/ A. Feild (STScI).

When will we know the distance to Deneb?

Gaia has now released three sets of data. Why haven’t Gaia’s newer measurements let astronomers measure Deneb’s distance more precisely? It’s mainly because Gaia isn’t geared toward observing such a bright star as Deneb. Astronomer Anthony G.A. Brown of Leiden Observatory in the Netherlands – a member of the Gaia team – told EarthSky in July 2021 that Gaia data still haven’t been used to determine a new distance for Deneb. He said:

The Hipparcos distance estimate still stands.

Deneb is so bright that we can only observe it with Gaia through specially programmed observation sequences (the observing instruments on the spacecraft do not automatically pick up the star). We have observations of
Deneb in hand but these will require a dedicated processing which we have not yet started.

So, for now, the updated Hipparcos number of approximately 1,500 light-years is still the best estimate of Deneb’s distance.

And that’s impressive. So, for us to see a star shine so brightly in our sky from this great distance away, the star must be very powerful. Deneb is one of the most luminous stars – one of the brightest stars, intrinsically – that we can see with the eye.

Deneb (bottom half of frame) is some 200 times bigger than our sun. Image via AstroBob.

Science of Deneb

Deneb is a blue-white supergiant star with a spectral class of A2Ia. It is the 19th brightest star in the sky shining at +1.25 magnitude. It’s about 196,000 times more luminous than our sun. Deneb contains about 20 solar masses, and as mentioned above its distance is uncertain. Deneb has a diameter about 203 times that of the sun. And that makes Deneb one of the largest type A spectral class stars known.

Deneb is the prototype for the Alpha Cygni variable stars. Its brightness varies due to non-radial fluctuations on the surface of the star. The fluctuations originate from areas on the surface of the star either expanding and contracting at the same time. They can last for days to weeks and their origin is unknown. The change in brightness is minimal, but detectable. For example, Deneb varies in brightness from magnitude 1.21 to 1.29. Another Alpha Cygni variable star is Rigel, in the constellation of Orion the Hunter.

Deneb was once a spectral class O-type main sequence star with a mass about 23 times that of the sun. Now that it’s a supergiant, it’s no longer fusing hydrogen in its core. It will evolve into a very luminous red supergiant or possibly a highly luminous blue variable star or maybe a Wolf-Rayet star. Regardless of which type of star it becomes, it’s expected to explode as a supernova sometime in the next few million years.

Deneb will be the North Pole Star around 9800 AD, but will be seven degrees from the pole. By the way, Deneb is the North Pole Star for Mars.

Deneb in history and mythology

The name Deneb derives from the Arabic Al Dhanab al Dajajah meaning Tail of the Hen. It obviously dates from an earlier incarnation of Cygnus not as a swan but as a chicken. Like many bright stars, Deneb has been called by a number of other names, but the oddest, according to Richard Hinckley Allen, who cites the Arabic name above, was Uropygium, meaning the posterior part of a bird’s body from which feathers grow, and oddly sometimes called the “Pope’s nose.”

In Chinese mythology Deneb is associated with the story of the Celestial Princess or the Weaver Girl. In this story a girl (the star Vega) is separated from her beloved (a cowherd represented by the star Altair) by the Milky Way. Once a year, the girl and the cowherd are allowed to meet briefly when a large flock of magpies forms a bridge across the starry river. Deneb represents the bridge.

The constellation Lacerta the Lizard lies just behind the tail feathers of Cygnus the Swan. The chart also shows Lyra and Vulpecula. This star chart is from Urania’s Mirror, a set of celestial cards by Sidney Hall published in 1825. Image via Wikipedia.

How to see Deneb

You can gaze at this faraway star in the evening starting around May, or late spring in the Northern Hemisphere. From this hemisphere, in July and August, Deneb shines in the east at nightfall and appears high up in the sky around the middle of the night.

Like all stars, Deneb is found about one degree farther west at the same time each day, and climbs to its highest point about four minutes earlier per day, 1/2 hour earlier per week, or two hours earlier per month.

Deneb is circumpolar as seen from locations of about 45 degrees north latitude, roughly the northern tier of U.S. states. In other words, from the northern U.S. and similar latitudes, Deneb never sets but instead circles round and round the pole star.

This star is not visible south of about 45 degrees south latitude. That includes Antarctica, far southern Argentina and Chile, and perhaps the far southern tip of New Zealand’s South Island.

Aside from that, just about anyone should have a chance to see Deneb at one time or another. When you do see it, think of the power of this mighty star shining over such a great distance in space!

Deneb’s position is RA: 20h 41m 26s, dec: +45° 16′ 49″.

Bottom line: Read here about the luminous Summer Triangle star Deneb, and learn how to see it in your sky.

Our Summer Triangle series includes:

Vega is bright and blue-white

Deneb is distant and very luminous

Altair spins fast!

The post Summer Triangle star Deneb is distant and luminous first appeared on EarthSky.

from EarthSky https://ift.tt/srocpqJ

World Population Day 2024 is today, July 11

View this map as interactive. | Relative populations of the nations on Earth at the time of World Population Day, July 11, 2024. Map via the UN’s World Population Dashboard.

World Population Day is July 11

Today is World Population Day, observed on July 11 every year since 1990. The United Nations Population Fund organizes it, with the goal of raising awareness of global population issues. And the 2024 event comes less than two years after November 2022, when, according to various estimates, the world population reached 8 billion. The U.N. describes World Population Day as:

… a moment for all of us to commit to doing more to ensure that our data systems capture the full range of human diversity so that everyone is seen, can exercise their human rights and can reach their full potential.

According to Worldometer, the current population of Earth is 8.1 billion. Previously, China had long held the title of most populous nation, but sometime in 2023, India overtook China. Now, India currently has a population around 1.44 billion, with China’s population around 1.42 billion.

The 2024 theme of World Population Day is: “To leave no one behind, count everyone.”

?? This #WorldPopulationDay, let's embrace the power of data! Reliable data is key to understanding population dynamics and shaping policies that promote health, equality, and sustainable development. Together, we can build a brighter future for all. #DataForDevelopment #UNFPA pic.twitter.com/qBk3gG9AZP

— UNFPALesotho (@UNFPA_LSO) July 4, 2024

Using data to count everyone

The U.N. explained:

Over the past three decades, societies around the world have made remarkable progress in improving population data gathering, analysis and use. New population figures, disaggregated by age, ethnicity, gender and other factors, now reflect the diversity of our societies more accurately.

World Population Day 2024 is a moment to ask who is still going uncounted – and why – and what this costs individuals, societies and our global efforts to leave no one behind.

From the 2024 State of the World Population Report:

The future of population data

A safe digital future

Women play a critical role

In recent decades, multiple studies have suggested that women play a key role in stabilizing population growth. Indeed, the education of women, and falling growth rates, appear to go hand in hand. But, in much of the world, women still do not have the right of equal education to men, and do not have the right of control over their own bodies. The UN offers these statistics:

– More than 40% of women around the world cannot make decisions on sexual and reproductive health and reproductive rights.

– As few as one in four women across low- and middle income countries are realizing their desired fertility.

– A woman dies every two minutes due to pregnancy or childbirth (and in conflict settings, the number of deaths is twice as high).

– Nearly 1/3 of women have experienced intimate partner violence, non-partner sexual violence or both.

– Just six countries have 50% or more women in parliament.

– More than 2/3 of the 800 million people globally who cannot read are women.

With this in mind, the U.N. pointed to studies suggesting that, when women and girls are empowered by societies to exert autonomy over their lives and bodies, they and their families thrive. For illustrations of this idea, check out the UNFPA 2024 State of World Population report and the studies that follow.

From the World Bank: Female education and childbearing: A closer look at the data

From the European Union: Educating all girls is key for global population size

And from Frontiers in Public Health: Is educating girls the best investment for South Asia? Association between female education and fertility choices in South Asia: A systematic review of the literature

How World Population Day began

The Indian scholar K.C. Zachariah proposed a World Population Day. Zachariah was a senior demographer for the World Bank. He died in early 2023 at age 98.

Initially, World Population Day stemmed from public interest in 5 Billion Day, the approximate date on which global population reached 5 billion people, on July 11, 1987. Later, the first official World Population Day was July 11, 1990. More than 90 countries observed the day, overall. From then on, in partnership with governments and civil societies, a number of United Nations Population Fund country offices and other organizations and institutions commemorate World Population Day.

Bottom line: World Population Day is an annual event, organized by the United Nations and observed on July 11 every year.

The post World Population Day 2024 is today, July 11 first appeared on EarthSky.

from EarthSky https://ift.tt/PUIb2oj

View this map as interactive. | Relative populations of the nations on Earth at the time of World Population Day, July 11, 2024. Map via the UN’s World Population Dashboard.

World Population Day is July 11

Today is World Population Day, observed on July 11 every year since 1990. The United Nations Population Fund organizes it, with the goal of raising awareness of global population issues. And the 2024 event comes less than two years after November 2022, when, according to various estimates, the world population reached 8 billion. The U.N. describes World Population Day as:

… a moment for all of us to commit to doing more to ensure that our data systems capture the full range of human diversity so that everyone is seen, can exercise their human rights and can reach their full potential.

According to Worldometer, the current population of Earth is 8.1 billion. Previously, China had long held the title of most populous nation, but sometime in 2023, India overtook China. Now, India currently has a population around 1.44 billion, with China’s population around 1.42 billion.

The 2024 theme of World Population Day is: “To leave no one behind, count everyone.”

?? This #WorldPopulationDay, let's embrace the power of data! Reliable data is key to understanding population dynamics and shaping policies that promote health, equality, and sustainable development. Together, we can build a brighter future for all. #DataForDevelopment #UNFPA pic.twitter.com/qBk3gG9AZP

— UNFPALesotho (@UNFPA_LSO) July 4, 2024

Using data to count everyone

The U.N. explained:

Over the past three decades, societies around the world have made remarkable progress in improving population data gathering, analysis and use. New population figures, disaggregated by age, ethnicity, gender and other factors, now reflect the diversity of our societies more accurately.

World Population Day 2024 is a moment to ask who is still going uncounted – and why – and what this costs individuals, societies and our global efforts to leave no one behind.

From the 2024 State of the World Population Report:

The future of population data

A safe digital future

Women play a critical role

In recent decades, multiple studies have suggested that women play a key role in stabilizing population growth. Indeed, the education of women, and falling growth rates, appear to go hand in hand. But, in much of the world, women still do not have the right of equal education to men, and do not have the right of control over their own bodies. The UN offers these statistics:

– More than 40% of women around the world cannot make decisions on sexual and reproductive health and reproductive rights.

– As few as one in four women across low- and middle income countries are realizing their desired fertility.

– A woman dies every two minutes due to pregnancy or childbirth (and in conflict settings, the number of deaths is twice as high).

– Nearly 1/3 of women have experienced intimate partner violence, non-partner sexual violence or both.

– Just six countries have 50% or more women in parliament.

– More than 2/3 of the 800 million people globally who cannot read are women.

With this in mind, the U.N. pointed to studies suggesting that, when women and girls are empowered by societies to exert autonomy over their lives and bodies, they and their families thrive. For illustrations of this idea, check out the UNFPA 2024 State of World Population report and the studies that follow.

From the World Bank: Female education and childbearing: A closer look at the data

From the European Union: Educating all girls is key for global population size

And from Frontiers in Public Health: Is educating girls the best investment for South Asia? Association between female education and fertility choices in South Asia: A systematic review of the literature

How World Population Day began

The Indian scholar K.C. Zachariah proposed a World Population Day. Zachariah was a senior demographer for the World Bank. He died in early 2023 at age 98.

Initially, World Population Day stemmed from public interest in 5 Billion Day, the approximate date on which global population reached 5 billion people, on July 11, 1987. Later, the first official World Population Day was July 11, 1990. More than 90 countries observed the day, overall. From then on, in partnership with governments and civil societies, a number of United Nations Population Fund country offices and other organizations and institutions commemorate World Population Day.

Bottom line: World Population Day is an annual event, organized by the United Nations and observed on July 11 every year.

The post World Population Day 2024 is today, July 11 first appeared on EarthSky.

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Death Valley to break all-time Earth heat record?

Will Death Valley National Park, which straddles the U.S. states of California and Nevada, break Earth high heat records this week? Image via NOAA/ NWS.

Death Valley on the brink of a new high temperature record?

As of Tuesday night (July 9, 2024), the National Weather Service (NWS) was forecasting a high of 131 degrees Fahrenheit (55 C) for Death Valley National Park on Thursday, July 11. Death Valley in the U.S. West is the hottest, driest and lowest of all the U.S. national parks. If the mercury does climb that high there this week, it’ll be the hottest temperature ever reliably measured on planet Earth. The NWS has issued an Excessive Heat Warning through July 12 for the area, which includes the city of Las Vegas, Nevada (population 650,000). The advisory states:

Hot temperatures overnight will mean little relief from the daytime heat, especially in Las Vegas and Death Valley, where low temperatures may not fall below 90 degrees (32 C) for several days.

ABC News reported yesterday that – despite the predictions for extreme heat this week – hundreds of Europeans touring the American West and adventurers from around the U.S. are still flocking to Death Valley National Park this week. The NWS advisory includes precautions for those intending to travel to this area.

Death Valley and its 1913 high temperature record

Death Valley already holds the official world record for highest temperature, at 134 degrees Fahrenheit (56.7 C) on July 10, 1913. However, that measurement is said not to be reliable. In fact, Christopher C. Burt, author of Extreme Weather: A Guide and Record Book calls the 134 degree record bogus. Burt gives an in-depth explanation for why the world record was actually an observer error at Wunderground.

But the current reliably recorded high temperature on Earth also belongs to Death Valley. In fact, the national park took the title two years in a row. On August 16, 2020, the park hit 129.9 F (54.38 C). Then, the following year, on July 9, 2021, it hit 130 F (54.44 C).

Clearly, Death Valley is no stranger to brutal heat.

Death comes to hikers in the Grand Canyon

Death Valley is far from being the only place feeling the heat this summer. Grand Canyon National Park in northern Arizona has reported three hikers succumbing to high temperatures within the past month, most recently on July 7. KTNV Las Vegas reported on July 8, 2024:

For the third time in three weeks, a hiker has died at Grand Canyon National Park.

On Sunday, rangers received a call about an unresponsive hiker on the Bright Angel Trail, about 100 feet (30 m) below the Bright Angel Trailhead.

Bystanders started CPR as medical personnel responded from the rim. All attempts to resuscitate the man were unsuccessful and he died.

Park rangers told KTNV that, at the Grand Canyon, in summer, temperatures on exposed parts of the trail can reach over 120 degrees F (48.88 C) in the shade. An alert at the park’s website today (July 10) says:

Excessive Heat Warning! Hiking into the canyon is not advised. Limit outdoor activities between 10 a.m.-5 p.m. to reduce heat risk.

All-time highs across U.S. West in 2024 so far

Other places across the American West have seen all-time high records.

Some of the more notable all-time records over the past couple of days! Lots more records will fall in the week ahead. pic.twitter.com/pidt3nnxLq

— Jeff Berardelli (@WeatherProf) July 9, 2024

Almost any way you slice it, June 2024 was the hottest ever in Las Vegas.

Avg High Temp: 106.2°F (1st)
Avg Low Temp: 83.0°F (1st)
Avg Temp: 94.6°F (1st)

Number of 100°+ highs: 28 (1st)
Number of 80°+ lows: 23 (1st) #nvwx #vegasweather #climate

— NWS Las Vegas (@NWSVegas) July 1, 2024

How to stay safe in the heat

The National Weather Service provides the following precautions:

Drink plenty of fluids, stay in an air-conditioned room, stay out of the sun, and check up on relatives and neighbors.

Do not leave young children and pets in unattended vehicles. Car interiors will reach lethal temperatures in a matter of minutes.

Take extra precautions when outside. Wear lightweight and loose-fitting clothing. Try to limit strenuous activities to early morning or evening. Take action when you see symptoms of heat exhaustion and heat stroke.

To reduce risk during outdoor work, the Occupational Safety and Health Administration (OSHA) recommends scheduling frequent rest breaks in shaded or air-conditioned environments. Anyone overcome by heat should be moved to a cool and shaded location. Heat stroke is an emergency! Call 911.

Bottom line: The National Weather Service is forecasting a high of 131 F (55 C) for Death Valley National Park in California on Thursday. If it reaches that mark, it will be the hottest reliably recorded temperature on Earth.

Read more: Heat dome kills people and animals in Mexico

The post Death Valley to break all-time Earth heat record? first appeared on EarthSky.

from EarthSky https://ift.tt/atbxZHj

Will Death Valley National Park, which straddles the U.S. states of California and Nevada, break Earth high heat records this week? Image via NOAA/ NWS.

Death Valley on the brink of a new high temperature record?

As of Tuesday night (July 9, 2024), the National Weather Service (NWS) was forecasting a high of 131 degrees Fahrenheit (55 C) for Death Valley National Park on Thursday, July 11. Death Valley in the U.S. West is the hottest, driest and lowest of all the U.S. national parks. If the mercury does climb that high there this week, it’ll be the hottest temperature ever reliably measured on planet Earth. The NWS has issued an Excessive Heat Warning through July 12 for the area, which includes the city of Las Vegas, Nevada (population 650,000). The advisory states:

Hot temperatures overnight will mean little relief from the daytime heat, especially in Las Vegas and Death Valley, where low temperatures may not fall below 90 degrees (32 C) for several days.

ABC News reported yesterday that – despite the predictions for extreme heat this week – hundreds of Europeans touring the American West and adventurers from around the U.S. are still flocking to Death Valley National Park this week. The NWS advisory includes precautions for those intending to travel to this area.

Death Valley and its 1913 high temperature record

Death Valley already holds the official world record for highest temperature, at 134 degrees Fahrenheit (56.7 C) on July 10, 1913. However, that measurement is said not to be reliable. In fact, Christopher C. Burt, author of Extreme Weather: A Guide and Record Book calls the 134 degree record bogus. Burt gives an in-depth explanation for why the world record was actually an observer error at Wunderground.

But the current reliably recorded high temperature on Earth also belongs to Death Valley. In fact, the national park took the title two years in a row. On August 16, 2020, the park hit 129.9 F (54.38 C). Then, the following year, on July 9, 2021, it hit 130 F (54.44 C).

Clearly, Death Valley is no stranger to brutal heat.

Death comes to hikers in the Grand Canyon

Death Valley is far from being the only place feeling the heat this summer. Grand Canyon National Park in northern Arizona has reported three hikers succumbing to high temperatures within the past month, most recently on July 7. KTNV Las Vegas reported on July 8, 2024:

For the third time in three weeks, a hiker has died at Grand Canyon National Park.

On Sunday, rangers received a call about an unresponsive hiker on the Bright Angel Trail, about 100 feet (30 m) below the Bright Angel Trailhead.

Bystanders started CPR as medical personnel responded from the rim. All attempts to resuscitate the man were unsuccessful and he died.

Park rangers told KTNV that, at the Grand Canyon, in summer, temperatures on exposed parts of the trail can reach over 120 degrees F (48.88 C) in the shade. An alert at the park’s website today (July 10) says:

Excessive Heat Warning! Hiking into the canyon is not advised. Limit outdoor activities between 10 a.m.-5 p.m. to reduce heat risk.

All-time highs across U.S. West in 2024 so far

Other places across the American West have seen all-time high records.

Some of the more notable all-time records over the past couple of days! Lots more records will fall in the week ahead. pic.twitter.com/pidt3nnxLq

— Jeff Berardelli (@WeatherProf) July 9, 2024

Almost any way you slice it, June 2024 was the hottest ever in Las Vegas.

Avg High Temp: 106.2°F (1st)
Avg Low Temp: 83.0°F (1st)
Avg Temp: 94.6°F (1st)

Number of 100°+ highs: 28 (1st)
Number of 80°+ lows: 23 (1st) #nvwx #vegasweather #climate

— NWS Las Vegas (@NWSVegas) July 1, 2024

How to stay safe in the heat

The National Weather Service provides the following precautions:

Drink plenty of fluids, stay in an air-conditioned room, stay out of the sun, and check up on relatives and neighbors.

Do not leave young children and pets in unattended vehicles. Car interiors will reach lethal temperatures in a matter of minutes.

Take extra precautions when outside. Wear lightweight and loose-fitting clothing. Try to limit strenuous activities to early morning or evening. Take action when you see symptoms of heat exhaustion and heat stroke.

To reduce risk during outdoor work, the Occupational Safety and Health Administration (OSHA) recommends scheduling frequent rest breaks in shaded or air-conditioned environments. Anyone overcome by heat should be moved to a cool and shaded location. Heat stroke is an emergency! Call 911.

Bottom line: The National Weather Service is forecasting a high of 131 F (55 C) for Death Valley National Park in California on Thursday. If it reaches that mark, it will be the hottest reliably recorded temperature on Earth.

Read more: Heat dome kills people and animals in Mexico

The post Death Valley to break all-time Earth heat record? first appeared on EarthSky.

from EarthSky https://ift.tt/atbxZHj

Do dark matter collisions on Jupiter glow in the infrared?

This image of Jupiter’s atmosphere from the Webb telescope – and its NIRCam camera – shows details in infrared light. A pair of researchers at Princeton University said they’ve discovered evidence of dark matter collisions glowing in the infrared on Jupiter’s dark side. Image via NASA/ ESA/ CSA/ STScI/ Ricardo Hueso (UPV)/ Imke de Pater (UC Berkeley)/ Thierry Fouchet (Observatory of Paris)/ Leigh Fletcher (University of Leicester)/ Michael H. Wong (UC Berkeley)/ Joseph DePasquale (STScI).

Dark matter collisions may show up in the infrared on Jupiter

The dark side of Jupiter at midnight might be aglow with the fallout of dark matter collisions. That’s what a pair of researchers claimed in a paper published June 27, 2024, in the peer-reviewed Physical Review Letters. Dark matter, combined with dark energy, makes up 95% of our universe. But, so far, we haven’t been able to detect dark matter (or dark energy) directly. We can only see its effects. Now comes another dark matter effect, in this case taking the form of an unexplained glow in the atmosphere of Jupiter.

Carlos Blanco of Princeton University in New Jersey and Rebecca Leane of the SLAC National Accelerator Laboratory in California said dark matter particles may be colliding in Jupiter’s atmosphere. If so, the collisions would produce infrared light. Plus, these scientists said, we should see an excess of ions containing three hydrogen nuclei and only two electrons, or trihydrogen cations (H3+). The researchers said:

We apply this search strategy to the night side of Jupiter near the equator. The night side has zero solar irradiation, and low latitudes are sufficiently far from ionizing auroras, leading to a low-background search.

H3+ is the most abundant cation (positive charge) in the universe. Discovered in 1911, it is produced when hydrogen comes under intense pressure. And it’s stable in interstellar space, but breaks down under gravity. Finding it in excess on Jupiter might be a telltale sign of dark matter colliding in the planet’s outer atmosphere.

Using a mission to Saturn to study Jupiter

Blanco and Leane used data gathered during the Cassini-Huygens mission’s flyby of the immense gas giant Jupiter on its way to the ringed world Saturn. During the mission, the Saturn-bound probe used Jupiter’s gravity to accelerate as it flew deeper into the solar system.

The study looked at data from Cassini-Huygens taken three hours on either side of the Jovian dark side’s midnight. The data are from 2000, but Blanco and Leane only recently analyzed them. They were searching for a glow in infrared light. That light could be coming from dark matter colliding with itself after being sucked into Jupiter’s gravity well. The paper stated:

This will be produced if dark matter scatters and is captured by planets, and consequently annihilates, producing ionizing radiation. To produce detectable H3+, the dark matter must produce ionization in the planet’s ionosphere.

The charged particles are then funneled to Jupiter’s poles by its intense magnetic field. The researchers found the signal of dark matter collisions they expected, perhaps giving us another way to detect the elusive substance. And they said the same technique could be used to discover dark matter on Jupiter-like exoplanets.

This schematic shows trihydrogen cation (H3+) production on Jupiter. The paper said: “Auroral H3+ emission near the magnetic poles is sourced by precipitating electrons, and solar extreme UV irradiates the day side and dominates H3+ production near the equator. No significant H3+ is expected at low latitudes on the night side, making it an ideal dark matter signal region.” Image via Physical Review Letters (2024).

More studies needed to confirm dark matter collisions

In their paper, Blanco and Leane lay out how H3+ is usually produced and how astronomers detect it using spectroscopy. Some of the interactions that can produce H3+ include cosmic rays, EUV stellar irradiation, planetary lightning or electrons accelerated in planetary magnetic fields. But looking at the Cassini-Huygens data, they found a clear excess of H3+ on Jupiter’s dark side than those sources can produce.

So, is dark matter responsible? The scientists said they’ll need more studies to be entirely certain. The excess could be from an undiscovered source, but Blanco and Leane don’t think so. They said:

We have pointed out and shown for the first time that dark matter can produce ionizing radiation in planetary atmospheres, which is detectable through a smoking-gun excess of atmospheric trihydrogen cations.

Expanding the search beyond Jupiter

If they’re right, then their techniques could lead to detecting dark matter in more exotic locals than the solar system. The paper said:

We also showed that exoplanets in denser dark matter environments such as the inner galaxy could provide even stronger sensitivities to dark matter atmospheric ionization. While an inner-galaxy search would not benefit from low-latitude searches, as auroras would not be able to be distinguished with the resolution of current telescopes, the dark matter ionization rate still can be significantly larger than auroral backgrounds.

And when it comes to exoplanets, the bigger the better. So-called super-Jupiters, with their enormous gravity, would gather and annihilate far more dark matter than puny Jupiter. Such research will require better astronomical instruments. We’ll have to wait for future missions like the Nancy Grace Roman Space Telescope to find out.

Bottom line: Researchers think dark matter collisions make Jupiter’s atmosphere glow in infrared light. If true, it would provide another way to detect the mysterious substance.

Source: Search for Dark Matter Ionization on the Night Side of Jupiter with Cassini

Via Phys.org

Read more: Did colliding dark matter shape the El Gordo galaxy cluster?

Read more: Can we detect dark matter using light from pulsars?

The post Do dark matter collisions on Jupiter glow in the infrared? first appeared on EarthSky.

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This image of Jupiter’s atmosphere from the Webb telescope – and its NIRCam camera – shows details in infrared light. A pair of researchers at Princeton University said they’ve discovered evidence of dark matter collisions glowing in the infrared on Jupiter’s dark side. Image via NASA/ ESA/ CSA/ STScI/ Ricardo Hueso (UPV)/ Imke de Pater (UC Berkeley)/ Thierry Fouchet (Observatory of Paris)/ Leigh Fletcher (University of Leicester)/ Michael H. Wong (UC Berkeley)/ Joseph DePasquale (STScI).

Dark matter collisions may show up in the infrared on Jupiter

The dark side of Jupiter at midnight might be aglow with the fallout of dark matter collisions. That’s what a pair of researchers claimed in a paper published June 27, 2024, in the peer-reviewed Physical Review Letters. Dark matter, combined with dark energy, makes up 95% of our universe. But, so far, we haven’t been able to detect dark matter (or dark energy) directly. We can only see its effects. Now comes another dark matter effect, in this case taking the form of an unexplained glow in the atmosphere of Jupiter.

Carlos Blanco of Princeton University in New Jersey and Rebecca Leane of the SLAC National Accelerator Laboratory in California said dark matter particles may be colliding in Jupiter’s atmosphere. If so, the collisions would produce infrared light. Plus, these scientists said, we should see an excess of ions containing three hydrogen nuclei and only two electrons, or trihydrogen cations (H3+). The researchers said:

We apply this search strategy to the night side of Jupiter near the equator. The night side has zero solar irradiation, and low latitudes are sufficiently far from ionizing auroras, leading to a low-background search.

H3+ is the most abundant cation (positive charge) in the universe. Discovered in 1911, it is produced when hydrogen comes under intense pressure. And it’s stable in interstellar space, but breaks down under gravity. Finding it in excess on Jupiter might be a telltale sign of dark matter colliding in the planet’s outer atmosphere.

Using a mission to Saturn to study Jupiter

Blanco and Leane used data gathered during the Cassini-Huygens mission’s flyby of the immense gas giant Jupiter on its way to the ringed world Saturn. During the mission, the Saturn-bound probe used Jupiter’s gravity to accelerate as it flew deeper into the solar system.

The study looked at data from Cassini-Huygens taken three hours on either side of the Jovian dark side’s midnight. The data are from 2000, but Blanco and Leane only recently analyzed them. They were searching for a glow in infrared light. That light could be coming from dark matter colliding with itself after being sucked into Jupiter’s gravity well. The paper stated:

This will be produced if dark matter scatters and is captured by planets, and consequently annihilates, producing ionizing radiation. To produce detectable H3+, the dark matter must produce ionization in the planet’s ionosphere.

The charged particles are then funneled to Jupiter’s poles by its intense magnetic field. The researchers found the signal of dark matter collisions they expected, perhaps giving us another way to detect the elusive substance. And they said the same technique could be used to discover dark matter on Jupiter-like exoplanets.

This schematic shows trihydrogen cation (H3+) production on Jupiter. The paper said: “Auroral H3+ emission near the magnetic poles is sourced by precipitating electrons, and solar extreme UV irradiates the day side and dominates H3+ production near the equator. No significant H3+ is expected at low latitudes on the night side, making it an ideal dark matter signal region.” Image via Physical Review Letters (2024).

More studies needed to confirm dark matter collisions

In their paper, Blanco and Leane lay out how H3+ is usually produced and how astronomers detect it using spectroscopy. Some of the interactions that can produce H3+ include cosmic rays, EUV stellar irradiation, planetary lightning or electrons accelerated in planetary magnetic fields. But looking at the Cassini-Huygens data, they found a clear excess of H3+ on Jupiter’s dark side than those sources can produce.

So, is dark matter responsible? The scientists said they’ll need more studies to be entirely certain. The excess could be from an undiscovered source, but Blanco and Leane don’t think so. They said:

We have pointed out and shown for the first time that dark matter can produce ionizing radiation in planetary atmospheres, which is detectable through a smoking-gun excess of atmospheric trihydrogen cations.

Expanding the search beyond Jupiter

If they’re right, then their techniques could lead to detecting dark matter in more exotic locals than the solar system. The paper said:

We also showed that exoplanets in denser dark matter environments such as the inner galaxy could provide even stronger sensitivities to dark matter atmospheric ionization. While an inner-galaxy search would not benefit from low-latitude searches, as auroras would not be able to be distinguished with the resolution of current telescopes, the dark matter ionization rate still can be significantly larger than auroral backgrounds.

And when it comes to exoplanets, the bigger the better. So-called super-Jupiters, with their enormous gravity, would gather and annihilate far more dark matter than puny Jupiter. Such research will require better astronomical instruments. We’ll have to wait for future missions like the Nancy Grace Roman Space Telescope to find out.

Bottom line: Researchers think dark matter collisions make Jupiter’s atmosphere glow in infrared light. If true, it would provide another way to detect the mysterious substance.

Source: Search for Dark Matter Ionization on the Night Side of Jupiter with Cassini

Via Phys.org

Read more: Did colliding dark matter shape the El Gordo galaxy cluster?

Read more: Can we detect dark matter using light from pulsars?

The post Do dark matter collisions on Jupiter glow in the infrared? first appeared on EarthSky.

from EarthSky https://ift.tt/aow94jU

Summer Triangle star: Altair is variable and spins fast!

Altair, in the constellation Aquila the Eagle, makes up the Summer Triangle along with Deneb and Vega. You’ll find this large triangle in the east in the evening in July. As the months pass, the Triangle will shift westward. It’ll grace our skies until around the year’s end. Chart via EarthSky.

The bright star Altair, aka Alpha Aquilae, shines as the brightest star in the constellation Aquila the Eagle. Mostly known for being one of the three Summer Triangle stars, this star is distinctive in its own right. It shines at magnitude +0.76. It’s only 16.8 light-years away from Earth, making it one of our nearest stellar neighbors. Plus, it has two more noteworthy features.

First, Altair rotates rapidly

This star requires only about 10 hours to spin once on its axis. That’s in contrast to 24 hours for our Earth to spin once, and about 27 days for our sun. In other words, this mighty star spins on its axis more rapidly than Earth! So this speedy spin tends to flatten the star a bit, much as a pizza crust flattens as it spins. Rough estimates are that Altair’s flattening is about 14%. Also, our sun is an oblate spheroid, although its flattening is difficult to measure due to the low rotation rate.

In 2007, University of Michigan astronomers combined light from four widely separated telescopes to produce the first picture (below) showing surface details on Altair. The researchers, led by John Monnier, used optical interferometry to get this image. Read more about the study at SpaceDaily.com.

The bright star Altair in the constellation Aquila is spinning on its axis so fast that it's flattened almost like an M&M. While our Sun rotates at a stately pace of once every 25 days, Altair flies around its axis once every 10 hours – close to its breakup speed.#Psalm19 pic.twitter.com/9YboZV7eq1

— Sarah Salviander (@sarahsalviander) September 25, 2019

Second, it’s variable … but not in a usual way

Variable stars brighten and dim, many on a (more or less) regular schedule. But Altair has as many as nine different rates of brightenings and dimmings. You won’t see these brightness variations with your eye. They’re too small to measure without sensitive instruments. But they’re there, and they’re likely related to Altair’s fast rotation.

By the way, if Altair took the place of our sun, at the distance the sun is now, life on Earth would be doomed. That’s because Altair is over 10 times more luminous that our sun. As you might have guessed, Altair is a more massive star than our sun, with about 1.8 times the sun’s mass. Its diameter is estimated to be between 1.6 to 2 times that of the sun. And its surface temperature is between 11,960 degrees F (6,626 C) to 14,840 F (8,226 C).

Altair is a white main sequence star – with a spectral type A7 – and is the 12th brightest star in the sky. It shares that spot with the star Acrux in the constellation Crux.

The star is classified as a Delta Scuti variable star since it shows slight changes in luminosity. It has three dim companion stars visible through telescopes. And not only it is a fast spinner, it moves quickly in front of its background stars. In fact, it’ll move about a full degree over the next 5,000 years.

How to see Altair

Altair has an apparent magnitude of +0.76. So you can see Altair easily with the eye.

But how will you recognize it? If you’re outside on a July or August evening, watch for the large Summer Triangle asterism in the east (as shown on the chart at the top). Look near the horizon for Altair, the last of the three Summer Triangle stars to ascend over your horizon.

You will recognize Altair by the two fainter stars on either side of it.

Also, the Great Rift of the summer Milky Way passes through the Summer Triangle. In fact, it goes right between the stars Vega and Altair. In dark skies in June, July and August, you can see rich star fields with your binoculars on both sides of the Great Rift.

‘Forbidden Planet’

In modern western culture, Altair is probably best known for being the home star system of the aliens in the 1956 science fiction film Forbidden Planet.

Altair in history and myth

The name Altair is Arabic in origin and has the same meaning as the name of the constellation Aquila in Latin; that is, they both mean simply “eagle.”

In classical mythology Aquila, and by extension Altair as well, was an eagle favored by Zeus. He played a part in numerous myths, including the abduction of Ganymede in which Aquila carries off a young boy (Ganymede) to Mount Olympus on Zeus’ command to become the cupbearer to the gods. In another myth Aquila is the eagle that torments Prometheus, until Hercules shoots it with poisoned arrows.

In India, Altair with its two flanking stars, Beta and Gamma (Tarazed and Alshain), in tradition represent the celestial footprints of the god Vishnu.

Altair is separated from the similar looking (but brighter) star Vega in the constellation Lyra the Harp by the great starlit band of the Milky Way. In Asia, this hazy band across our sky is known as the Celestial River. One story common in China, Japan and Korea is of a young herdsman (Altair) who falls in love with a celestial princess (Vega), who weaves the fabric of heaven.

The princess became so enamored of the herdsman that she neglects her weaving duties. This act enrages the princess’s father, the Celestial Emperor, who decrees that the herdsman must stay away from his daughter, on the opposite side of the River. The Emperor finally listened to the princess’s pleas, however, and allowed the herdsman to cross the Celestial River once per year, on the seventh day of the seventh month.

In Japan, Altair is Hikoboshi, and Vega is Orihime (or Tanabata). If it rains on the day of the festival of Tanabata, the rain represents Orihime’s tears shed because Hikoboshi could not navigate the treacherous waters of the Celestial River.

Altair’s position

The position of Altair is RA: 19h 50m 47.0s, dec: +08° 52′ 06″

Altair of Aquila the Eagle, with 2 smaller constellations nearby. Image via Wikipedia.

Bottom line: Altair is the brightest star in the constellation Aquila the Eagle, and one of the closest stars to our solar system. Although 1.8 times our sun’s mass, it spins on its axis in only about 10 hours.

Our Summer Triangle series includes:

Vega is bright and blue-white

Deneb is distant and very luminous

Altair spins fast!

The post Summer Triangle star: Altair is variable and spins fast! first appeared on EarthSky.

from EarthSky https://ift.tt/7kOVE0a

Altair, in the constellation Aquila the Eagle, makes up the Summer Triangle along with Deneb and Vega. You’ll find this large triangle in the east in the evening in July. As the months pass, the Triangle will shift westward. It’ll grace our skies until around the year’s end. Chart via EarthSky.

The bright star Altair, aka Alpha Aquilae, shines as the brightest star in the constellation Aquila the Eagle. Mostly known for being one of the three Summer Triangle stars, this star is distinctive in its own right. It shines at magnitude +0.76. It’s only 16.8 light-years away from Earth, making it one of our nearest stellar neighbors. Plus, it has two more noteworthy features.

First, Altair rotates rapidly

This star requires only about 10 hours to spin once on its axis. That’s in contrast to 24 hours for our Earth to spin once, and about 27 days for our sun. In other words, this mighty star spins on its axis more rapidly than Earth! So this speedy spin tends to flatten the star a bit, much as a pizza crust flattens as it spins. Rough estimates are that Altair’s flattening is about 14%. Also, our sun is an oblate spheroid, although its flattening is difficult to measure due to the low rotation rate.

In 2007, University of Michigan astronomers combined light from four widely separated telescopes to produce the first picture (below) showing surface details on Altair. The researchers, led by John Monnier, used optical interferometry to get this image. Read more about the study at SpaceDaily.com.

The bright star Altair in the constellation Aquila is spinning on its axis so fast that it's flattened almost like an M&M. While our Sun rotates at a stately pace of once every 25 days, Altair flies around its axis once every 10 hours – close to its breakup speed.#Psalm19 pic.twitter.com/9YboZV7eq1

— Sarah Salviander (@sarahsalviander) September 25, 2019

Second, it’s variable … but not in a usual way

Variable stars brighten and dim, many on a (more or less) regular schedule. But Altair has as many as nine different rates of brightenings and dimmings. You won’t see these brightness variations with your eye. They’re too small to measure without sensitive instruments. But they’re there, and they’re likely related to Altair’s fast rotation.

By the way, if Altair took the place of our sun, at the distance the sun is now, life on Earth would be doomed. That’s because Altair is over 10 times more luminous that our sun. As you might have guessed, Altair is a more massive star than our sun, with about 1.8 times the sun’s mass. Its diameter is estimated to be between 1.6 to 2 times that of the sun. And its surface temperature is between 11,960 degrees F (6,626 C) to 14,840 F (8,226 C).

Altair is a white main sequence star – with a spectral type A7 – and is the 12th brightest star in the sky. It shares that spot with the star Acrux in the constellation Crux.

The star is classified as a Delta Scuti variable star since it shows slight changes in luminosity. It has three dim companion stars visible through telescopes. And not only it is a fast spinner, it moves quickly in front of its background stars. In fact, it’ll move about a full degree over the next 5,000 years.

How to see Altair

Altair has an apparent magnitude of +0.76. So you can see Altair easily with the eye.

But how will you recognize it? If you’re outside on a July or August evening, watch for the large Summer Triangle asterism in the east (as shown on the chart at the top). Look near the horizon for Altair, the last of the three Summer Triangle stars to ascend over your horizon.

You will recognize Altair by the two fainter stars on either side of it.

Also, the Great Rift of the summer Milky Way passes through the Summer Triangle. In fact, it goes right between the stars Vega and Altair. In dark skies in June, July and August, you can see rich star fields with your binoculars on both sides of the Great Rift.

‘Forbidden Planet’

In modern western culture, Altair is probably best known for being the home star system of the aliens in the 1956 science fiction film Forbidden Planet.

Altair in history and myth

The name Altair is Arabic in origin and has the same meaning as the name of the constellation Aquila in Latin; that is, they both mean simply “eagle.”

In classical mythology Aquila, and by extension Altair as well, was an eagle favored by Zeus. He played a part in numerous myths, including the abduction of Ganymede in which Aquila carries off a young boy (Ganymede) to Mount Olympus on Zeus’ command to become the cupbearer to the gods. In another myth Aquila is the eagle that torments Prometheus, until Hercules shoots it with poisoned arrows.

In India, Altair with its two flanking stars, Beta and Gamma (Tarazed and Alshain), in tradition represent the celestial footprints of the god Vishnu.

Altair is separated from the similar looking (but brighter) star Vega in the constellation Lyra the Harp by the great starlit band of the Milky Way. In Asia, this hazy band across our sky is known as the Celestial River. One story common in China, Japan and Korea is of a young herdsman (Altair) who falls in love with a celestial princess (Vega), who weaves the fabric of heaven.

The princess became so enamored of the herdsman that she neglects her weaving duties. This act enrages the princess’s father, the Celestial Emperor, who decrees that the herdsman must stay away from his daughter, on the opposite side of the River. The Emperor finally listened to the princess’s pleas, however, and allowed the herdsman to cross the Celestial River once per year, on the seventh day of the seventh month.

In Japan, Altair is Hikoboshi, and Vega is Orihime (or Tanabata). If it rains on the day of the festival of Tanabata, the rain represents Orihime’s tears shed because Hikoboshi could not navigate the treacherous waters of the Celestial River.

Altair’s position

The position of Altair is RA: 19h 50m 47.0s, dec: +08° 52′ 06″

Altair of Aquila the Eagle, with 2 smaller constellations nearby. Image via Wikipedia.

Bottom line: Altair is the brightest star in the constellation Aquila the Eagle, and one of the closest stars to our solar system. Although 1.8 times our sun’s mass, it spins on its axis in only about 10 hours.

Our Summer Triangle series includes:

Vega is bright and blue-white

Deneb is distant and very luminous

Altair spins fast!

The post Summer Triangle star: Altair is variable and spins fast! first appeared on EarthSky.

from EarthSky https://ift.tt/7kOVE0a