How did this black hole in a triple star system form?

Artist’s concept of the black hole called V404 Cygni. The black hole is consuming the star at left; another star (upper right) orbits the 1st 2 objects from farther away. This is the 1st black hole in a triple star sytem and the first thought to have formed by direct collapse, rather than in a supernova. Image via Jorge Lugo/ MIT.

• Black holes form when the core of a very massive star collapses in on itself at the end of its life, gravitationally crushing all its huge mass into a tiny point in space.
• It’s logical that black holes would form alongside supernova explosions. As the outer layers of a star blast violently outward, the inner part of the star collapses violently inward.
• Now astronomers have found a black hole that’s part of a triple system. It suggests that a history where no supernova occurred, and where the black hole formed by the more “gentle” method of direct collapse.

Black hole in a triple star system

In theory, all you need to create a black hole is a large mass in a small space. A large-enough mass in a small-enough space will inevitably collapse to become a black hole. It’ll be forced to collapse by its own self-gravity. But typically we think of something as triggering that collapse. The star runs out of fuel and explodes as a supernova, for example, crushing the star inward, sparking the collapse, until gravity can take over and do the rest. In the real space of our Milky Way galaxy, astronomers have seen stellar-mass black holes – objects of, say, 5 to 50 times our sun’s mass – in double systems. They’re possible to see in double systems because the presence of a 2nd star means astronomers can see the hole’s effect on the star, often in the form of an accretion disk swirling around the hole. Now, for the first time, astronomers have confirmed a black hole in a triple star system. They say it’s evidence that no supernova took place in this system and that instead the black hole formed by direct collapse.

So here, these astronomers say, is the first stellar-mass black hole ever found that apparently formed without the aid of a supernova. The system is called – called V404 Cygni, and it’s about 8,000 light-years away.

Researchers the Massachusetts Institute of Technology (MIT) and Caltech announced the find on October 23, 2024. They are (somewhat misleadingly) calling it a “black hole triple.” But it’s not three black holes. It’s one black hole in a triple system, with two stars.

The researchers, led by lead author Kevin Burdge in the MIT Department of Physics, published their peer-reviewed discovery in Nature on October 23, 2024. There is also a preprint version of the paper available on arXiv.

1st known ‘black hole triple’

So this is the first known stellar-mass black hole, in a system with three objects instead of just two. The closer star orbits so near the black hole that its “year” is only 6.5 Earth-days long. The black hole is consuming that star, and there’s evidence for an accretion disk of soon-to-be-eaten star-stuff, swirling around the hole. A 2nd star is orbiting much farther out than the first one. The 2nd star takes the star 70,000 years to complete one orbit!

Black holes, of course, are known for their powerful gravitational pull. And gravity is directly dependent on mass; the greater the mass, the stronger the pull. But gravity inversely dependent on distance; that is, the greater the distance, the weaker the pull. And a star orbiting every 70,000 years would be really far from the black hole. So – so if that black hole were once a massive star, and if that star exploded as a supernova – how did the hole hold on to the 3rd, more distant star? That mystery is making astronomers question how the black hole first originated.

Scientists think that black holes tend to form violently. This happens when a dying star explodes in a supernova. The star erupts in one last massive burst of energy and light, then collapses into a much smaller black hole. It isn’t really a hole, but a small object so dense that even light cannot escape it. This renders it invisible to human eyes, hence the name black hole.

A surprising discovery

V404 Cygni is a well-known and studied black hole, first confirmed in 1992. Yet what Burdge and his colleagues found had never been observed before. The researchers used the Aladin Lite sky atlas, an online repository of astronomical observations from telescopes in space and all around the world, for their study. They were actually looking for new black holes in the Milky Way galaxy.

The researchers decided to review images of V404 Cygni as well. They noticed two blobs of light close to each other. Astronomers already knew about the first blob, which was the material around the black hole and an orbiting star. But astronomers had never studied the second blob before. The research team said it was probably another star, much farther away than the first one. They calculated that the outer star was 3,500 astronomical units (AU) away from the black hole. 1 AU is the distance between the Earth and sun. That’s also about 100 times the distance of Pluto from the sun. Burdge said:

The fact that we can see two separate stars over this much distance actually means that the stars have to be really very far apart.

Astrophysicists from Caltech and MIT report that they have observed for the first time a "black hole triple"—a system of three stars, one of which is a black hole.https://t.co/1U0Cjix9l7

— Caltech (@Caltech) October 23, 2024

2nd star in tandem with the 1st

But was this second star actually gravitationally associated with the other star and black hole? Or was it completely separate? Using the Gaia satellite, the researchers determined that the second star moved exactly in tandem with the first star and black hole. So they were all part of the same system. Gaia’s mission has been to track the motions of all stars in the Milky Way since 2014. With calculated odds of about one in 10 million, that couldn’t be a coincidence, the researchers noted. Burdge said:

It’s almost certainly not a coincidence or accident. We’re seeing two stars that are following each other because they’re attached by this weak string of gravity. So this has to be a triple system.

A more gentle formation?

But there’s a problem with knowing how V404 Cygni formed. If it was the result of a typical supernova, then the second star shouldn’t even be there. The incredible force of the explosion should have “kicked it away” completely from the exploding star. So why is it still orbiting the black hole, albeit at a great distance?

The researchers think that it formed through a gentler process, which they call “direct collapse.” Instead of the star ending its life in a fiery explosion, it simply collapses in on itself. This can also theoretically form a black hole, but without the fireworks. The V404 Cygni system may be the first direct evidence of that formation process. As Burdge said:

We think most black holes form from violent explosions of stars, but this discovery helps call that into question. This system is super exciting for black hole evolution, and it also raises questions of whether there are more triples out there.

Artist’s concept of a black hole binary called GW150914. Many black holes come in such pairs, but V404 Cygni is the 1st confirmed black ole triple. Image via Lensing (SXS)/ Wikimedia Commons (CC BY 4.0).

Like pulling a kite

Burdge likened the process to pulling a kite:

Imagine you’re pulling a kite, and instead of a strong string, you’re pulling with a spider web. If you tugged too hard, the web would break and you’d lose the kite. Gravity is like this barely bound string that’s really weak, and if you do anything dramatic to the inner binary, you’re going to lose the outer star.

The researchers tested thousands of computer simulations, all beginning with three stars (the third star being the one that will become the black hole). For the supernova, the simulations varied the amount of energy the blast would give off, and in what direction. They also compared the supernova versus direct collapse scenarios.

Direct collapse was the clear winner. As Burdge noted:

The vast majority of simulations show that the easiest way to make this triple work is through direct collapse.

Black hole triple is almost as old as our solar system

The simulations not only showed how the V404 Cygni system came to be. They also revealed its age. The outer distant star is in the process of becoming a red giant. That means it is around 4 billion years old. Our own solar system is about 4.5 billion years old. The rest of the V404 Cygni system is also likely to be the same age, since other nearby stars are also thought to have first formed about the same time as the outer star in the system. As Burdge concluded:

We’ve never been able to do this before for an old black hole. Now we know V404 Cygni is part of a triple, it could have formed from direct collapse, and it formed about 4 billion years ago, thanks to this discovery.

In 2021, astronomers also identified eight concentric rings of material around V404 Cygni, only seen in X-rays and not visible light. The astronomers used NASA’s Chandra X-ray Observatory and the Neil Gehrels Swift Observatory (Swift) to detect the rings.

Bottom line: Physicists say they have discovered the 1st-known black hole in a triple system. Two stars orbit with the black hole, 1 very close and the other farther away.

Source: The black hole low-mass X-ray binary V404 Cygni is part of a wide triple

Source (preprint): The black hole low mass X-ray binary V404 Cygni is part of a wide hierarchical triple, and formed without a kick

Via MIT

Read more: Dark matter black holes could make Mars wobble

Read more: Direct black hole images that are 50% clearer?

The post How did this black hole in a triple star system form? first appeared on EarthSky.

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Artist’s concept of the black hole called V404 Cygni. The black hole is consuming the star at left; another star (upper right) orbits the 1st 2 objects from farther away. This is the 1st black hole in a triple star sytem and the first thought to have formed by direct collapse, rather than in a supernova. Image via Jorge Lugo/ MIT.

• Black holes form when the core of a very massive star collapses in on itself at the end of its life, gravitationally crushing all its huge mass into a tiny point in space.
• It’s logical that black holes would form alongside supernova explosions. As the outer layers of a star blast violently outward, the inner part of the star collapses violently inward.
• Now astronomers have found a black hole that’s part of a triple system. It suggests that a history where no supernova occurred, and where the black hole formed by the more “gentle” method of direct collapse.

Black hole in a triple star system

In theory, all you need to create a black hole is a large mass in a small space. A large-enough mass in a small-enough space will inevitably collapse to become a black hole. It’ll be forced to collapse by its own self-gravity. But typically we think of something as triggering that collapse. The star runs out of fuel and explodes as a supernova, for example, crushing the star inward, sparking the collapse, until gravity can take over and do the rest. In the real space of our Milky Way galaxy, astronomers have seen stellar-mass black holes – objects of, say, 5 to 50 times our sun’s mass – in double systems. They’re possible to see in double systems because the presence of a 2nd star means astronomers can see the hole’s effect on the star, often in the form of an accretion disk swirling around the hole. Now, for the first time, astronomers have confirmed a black hole in a triple star system. They say it’s evidence that no supernova took place in this system and that instead the black hole formed by direct collapse.

So here, these astronomers say, is the first stellar-mass black hole ever found that apparently formed without the aid of a supernova. The system is called – called V404 Cygni, and it’s about 8,000 light-years away.

Researchers the Massachusetts Institute of Technology (MIT) and Caltech announced the find on October 23, 2024. They are (somewhat misleadingly) calling it a “black hole triple.” But it’s not three black holes. It’s one black hole in a triple system, with two stars.

The researchers, led by lead author Kevin Burdge in the MIT Department of Physics, published their peer-reviewed discovery in Nature on October 23, 2024. There is also a preprint version of the paper available on arXiv.

1st known ‘black hole triple’

So this is the first known stellar-mass black hole, in a system with three objects instead of just two. The closer star orbits so near the black hole that its “year” is only 6.5 Earth-days long. The black hole is consuming that star, and there’s evidence for an accretion disk of soon-to-be-eaten star-stuff, swirling around the hole. A 2nd star is orbiting much farther out than the first one. The 2nd star takes the star 70,000 years to complete one orbit!

Black holes, of course, are known for their powerful gravitational pull. And gravity is directly dependent on mass; the greater the mass, the stronger the pull. But gravity inversely dependent on distance; that is, the greater the distance, the weaker the pull. And a star orbiting every 70,000 years would be really far from the black hole. So – so if that black hole were once a massive star, and if that star exploded as a supernova – how did the hole hold on to the 3rd, more distant star? That mystery is making astronomers question how the black hole first originated.

Scientists think that black holes tend to form violently. This happens when a dying star explodes in a supernova. The star erupts in one last massive burst of energy and light, then collapses into a much smaller black hole. It isn’t really a hole, but a small object so dense that even light cannot escape it. This renders it invisible to human eyes, hence the name black hole.

A surprising discovery

V404 Cygni is a well-known and studied black hole, first confirmed in 1992. Yet what Burdge and his colleagues found had never been observed before. The researchers used the Aladin Lite sky atlas, an online repository of astronomical observations from telescopes in space and all around the world, for their study. They were actually looking for new black holes in the Milky Way galaxy.

The researchers decided to review images of V404 Cygni as well. They noticed two blobs of light close to each other. Astronomers already knew about the first blob, which was the material around the black hole and an orbiting star. But astronomers had never studied the second blob before. The research team said it was probably another star, much farther away than the first one. They calculated that the outer star was 3,500 astronomical units (AU) away from the black hole. 1 AU is the distance between the Earth and sun. That’s also about 100 times the distance of Pluto from the sun. Burdge said:

The fact that we can see two separate stars over this much distance actually means that the stars have to be really very far apart.

Astrophysicists from Caltech and MIT report that they have observed for the first time a "black hole triple"—a system of three stars, one of which is a black hole.https://t.co/1U0Cjix9l7

— Caltech (@Caltech) October 23, 2024

2nd star in tandem with the 1st

But was this second star actually gravitationally associated with the other star and black hole? Or was it completely separate? Using the Gaia satellite, the researchers determined that the second star moved exactly in tandem with the first star and black hole. So they were all part of the same system. Gaia’s mission has been to track the motions of all stars in the Milky Way since 2014. With calculated odds of about one in 10 million, that couldn’t be a coincidence, the researchers noted. Burdge said:

It’s almost certainly not a coincidence or accident. We’re seeing two stars that are following each other because they’re attached by this weak string of gravity. So this has to be a triple system.

A more gentle formation?

But there’s a problem with knowing how V404 Cygni formed. If it was the result of a typical supernova, then the second star shouldn’t even be there. The incredible force of the explosion should have “kicked it away” completely from the exploding star. So why is it still orbiting the black hole, albeit at a great distance?

The researchers think that it formed through a gentler process, which they call “direct collapse.” Instead of the star ending its life in a fiery explosion, it simply collapses in on itself. This can also theoretically form a black hole, but without the fireworks. The V404 Cygni system may be the first direct evidence of that formation process. As Burdge said:

We think most black holes form from violent explosions of stars, but this discovery helps call that into question. This system is super exciting for black hole evolution, and it also raises questions of whether there are more triples out there.

Artist’s concept of a black hole binary called GW150914. Many black holes come in such pairs, but V404 Cygni is the 1st confirmed black ole triple. Image via Lensing (SXS)/ Wikimedia Commons (CC BY 4.0).

Like pulling a kite

Burdge likened the process to pulling a kite:

Imagine you’re pulling a kite, and instead of a strong string, you’re pulling with a spider web. If you tugged too hard, the web would break and you’d lose the kite. Gravity is like this barely bound string that’s really weak, and if you do anything dramatic to the inner binary, you’re going to lose the outer star.

The researchers tested thousands of computer simulations, all beginning with three stars (the third star being the one that will become the black hole). For the supernova, the simulations varied the amount of energy the blast would give off, and in what direction. They also compared the supernova versus direct collapse scenarios.

Direct collapse was the clear winner. As Burdge noted:

The vast majority of simulations show that the easiest way to make this triple work is through direct collapse.

Black hole triple is almost as old as our solar system

The simulations not only showed how the V404 Cygni system came to be. They also revealed its age. The outer distant star is in the process of becoming a red giant. That means it is around 4 billion years old. Our own solar system is about 4.5 billion years old. The rest of the V404 Cygni system is also likely to be the same age, since other nearby stars are also thought to have first formed about the same time as the outer star in the system. As Burdge concluded:

We’ve never been able to do this before for an old black hole. Now we know V404 Cygni is part of a triple, it could have formed from direct collapse, and it formed about 4 billion years ago, thanks to this discovery.

In 2021, astronomers also identified eight concentric rings of material around V404 Cygni, only seen in X-rays and not visible light. The astronomers used NASA’s Chandra X-ray Observatory and the Neil Gehrels Swift Observatory (Swift) to detect the rings.

Bottom line: Physicists say they have discovered the 1st-known black hole in a triple system. Two stars orbit with the black hole, 1 very close and the other farther away.

Source: The black hole low-mass X-ray binary V404 Cygni is part of a wide triple

Source (preprint): The black hole low mass X-ray binary V404 Cygni is part of a wide hierarchical triple, and formed without a kick

Via MIT

Read more: Dark matter black holes could make Mars wobble

Read more: Direct black hole images that are 50% clearer?

The post How did this black hole in a triple star system form? first appeared on EarthSky.

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Why were prehistoric insects such giant bugs?

Okay, prehistoric insects weren’t this big … but they were bigger than our insects today. Poster for the film “The Deadly Mantis” (1957) by artist Reynold Brown, via Wikimedia Commons (public domain).

Prehistoric insects were giant bugs

When you complain about dead bugs on your windshield, be thankful that insects today are considerably smaller than their prehistoric ancestors.

Hundreds of millions of years ago, giant insects were common on Earth. Consider Meganeura, a genus of extinct insects from approximately 300 million years ago. They were related to modern-day dragonflies. One member of this group – M. permiana – was first described by researchers in Kansas in 1937 as having a wingspan of over 2 feet (0.6 meters). It’s still considered one of the largest known insects that ever lived.

While over a million insect species live today, truly giant insects no longer exist. Why did they disappear?

Why did prehistoric insects disappear?

There are two main reasons. The most important is that our atmosphere has changed. Millions of years ago, the air surrounding our planet was warmer, moister and contained more oxygen. During the Carboniferous and Permian periods, Earth’s air contained 31-35% oxygen. Today, there is just 21% oxygen in the air.

Oxygen levels are especially important for insects because they don’t have lungs. Instead, they rely on air flowing through a series of openings across their bodies called spiracles, which connect via tiny tubes to the tissues that need oxygen.

Fossil remains of Meganeura monyi, a member of the extinct insect genus Meganeura. Their wingspans could reach 2 feet (0.6 meters). This specimen is housed at the Muséum d’Histoire Naturelle in Toulouse, France. Image via Wikimedia Commons (CC BY-SA 4.0).

Dinosaurs helped clean out the giant bugs

But there’s another reason giant insects disappeared. As ancient dinosaurs evolved the ability to fly, eventually becoming modern birds, they put a cap on insect size through predation and competition.

The earliest known bird – Archaeopteryx – appeared about 150 million years ago. Birds proved to be faster and more agile than the giant insects. In an article in LiveScience, paleobiologist Matthew Clapham of UC Santa Cruz commented:

The change in insect size is gradual. This gradual change fits quite nicely with the gradual evolution in birds at the time.

Read more: Ancient insect graveyards reveal an explosion in bug diversity 237 million years ago

Bottom line: Hundreds of millions of years ago, giant insects were common on Earth. The decline in atmospheric oxygen and the rise of birds contributed to their demise.

The post Why were prehistoric insects such giant bugs? first appeared on EarthSky.

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Okay, prehistoric insects weren’t this big … but they were bigger than our insects today. Poster for the film “The Deadly Mantis” (1957) by artist Reynold Brown, via Wikimedia Commons (public domain).

Prehistoric insects were giant bugs

When you complain about dead bugs on your windshield, be thankful that insects today are considerably smaller than their prehistoric ancestors.

Hundreds of millions of years ago, giant insects were common on Earth. Consider Meganeura, a genus of extinct insects from approximately 300 million years ago. They were related to modern-day dragonflies. One member of this group – M. permiana – was first described by researchers in Kansas in 1937 as having a wingspan of over 2 feet (0.6 meters). It’s still considered one of the largest known insects that ever lived.

While over a million insect species live today, truly giant insects no longer exist. Why did they disappear?

Why did prehistoric insects disappear?

There are two main reasons. The most important is that our atmosphere has changed. Millions of years ago, the air surrounding our planet was warmer, moister and contained more oxygen. During the Carboniferous and Permian periods, Earth’s air contained 31-35% oxygen. Today, there is just 21% oxygen in the air.

Oxygen levels are especially important for insects because they don’t have lungs. Instead, they rely on air flowing through a series of openings across their bodies called spiracles, which connect via tiny tubes to the tissues that need oxygen.

Fossil remains of Meganeura monyi, a member of the extinct insect genus Meganeura. Their wingspans could reach 2 feet (0.6 meters). This specimen is housed at the Muséum d’Histoire Naturelle in Toulouse, France. Image via Wikimedia Commons (CC BY-SA 4.0).

Dinosaurs helped clean out the giant bugs

But there’s another reason giant insects disappeared. As ancient dinosaurs evolved the ability to fly, eventually becoming modern birds, they put a cap on insect size through predation and competition.

The earliest known bird – Archaeopteryx – appeared about 150 million years ago. Birds proved to be faster and more agile than the giant insects. In an article in LiveScience, paleobiologist Matthew Clapham of UC Santa Cruz commented:

The change in insect size is gradual. This gradual change fits quite nicely with the gradual evolution in birds at the time.

Read more: Ancient insect graveyards reveal an explosion in bug diversity 237 million years ago

Bottom line: Hundreds of millions of years ago, giant insects were common on Earth. The decline in atmospheric oxygen and the rise of birds contributed to their demise.

The post Why were prehistoric insects such giant bugs? first appeared on EarthSky.

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Brightest star, Sirius, high on October mornings

No matter when you see it in the sky, Orion’s Belt always points to the sky’s brightest star, Sirius. On October mornings, Sirius and Orion can be found in the south before dawn. Southern Hemisphere? Look north and find Orion’s Belt. Chart via EarthSky.

Watch for the brightest star, Sirius

The planet Jupiter is up at dawn now. And it’s very bright, much brighter than any other planet or star. But – at this time of the year – we always get questions about another bright object in the dawn sky. Andy wrote:

Early this morning, looking south, I saw a beautiful star, bright and multicolored … Can you identify it for me?

And Paula wrote:

This morning two of us got up early. We found a pulsing star straight down the sky below Orion’s Belt. It was pulsing the colors of green, yellow, blue and red like a strobe light. I will search for it every morning as it was so enchanting.

If you’re up before daybreak on these October mornings, take a moment to see this star, which is the sky’s brightest star, Sirius. This star is so brilliant that you can even see it from a light-polluted city. And you can see it if you stay up late, too! It’s rising in the middle of the night now, as seen from around the globe, and is high in the sky – at its best – by dawn.

Want a specific view from your location on the globe? Visit Stellarium and enter your location.

What is that bright twinkling star?

This star is enchanting, so much so that – every year, beginning in Northern Hemisphere autumn – we get many, many questions about a multicolored star twinkling in the southeastern to southern sky after midnight. This star typically turns out to be Sirius, which is in the constellation Canis Major the Greater Dog and is sometimes called the Dog Star.

Why does Sirius twinkle so much?

Sirius appears to flash different colors when it’s low in the sky. Really, all the stars are flashing different colors, because light is composed of all the colors of a rainbow, and the journey through our atmosphere breaks starlight into its component colors via refraction. But you don’t notice the colors of the other stars much, because they’re not as bright as Sirius. Sirius is the brightest star visible from anywhere on Earth.

Since our atmosphere is causing the light to break into its colors, and since Sirius is often seen low in the sky now (where you are peering at it through a thicker layer of atmosphere than when it’s overhead), the flashing colors of Sirius are very obvious. When Sirius is higher in the sky – which it is close to dawn in the month of October – or in the evening sky in January and February – you’ll find that Sirius shines with a steadier, whiter light.

So, on these October mornings, watch as Sirius winks at you in the wee hours before dawn!

View at EarthSky Community Photos. | Sergei Timofeevski shared this image from November 13, 2023. Sergei wrote: “The constellation Orion the Hunter and the star Sirius rising just above the eastern horizon in the Anza-Borrego Desert State Park, California.” Thank you, Sergei! Note bright Sirius is on the bottom, and Orion’s Belt pointing to it.

Bottom line: We get many questions about a bright, colorful, twinkling star on these October mornings. It’s the brightest star, Sirius, in the constellation Canis Major, brightest in the sky. You’ll know it’s Sirius, because Orion’s Belt always points to it.

Read more: Flashing star in autumn? Here are 3 candidates

The post Brightest star, Sirius, high on October mornings first appeared on EarthSky.

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No matter when you see it in the sky, Orion’s Belt always points to the sky’s brightest star, Sirius. On October mornings, Sirius and Orion can be found in the south before dawn. Southern Hemisphere? Look north and find Orion’s Belt. Chart via EarthSky.

Watch for the brightest star, Sirius

The planet Jupiter is up at dawn now. And it’s very bright, much brighter than any other planet or star. But – at this time of the year – we always get questions about another bright object in the dawn sky. Andy wrote:

Early this morning, looking south, I saw a beautiful star, bright and multicolored … Can you identify it for me?

And Paula wrote:

This morning two of us got up early. We found a pulsing star straight down the sky below Orion’s Belt. It was pulsing the colors of green, yellow, blue and red like a strobe light. I will search for it every morning as it was so enchanting.

If you’re up before daybreak on these October mornings, take a moment to see this star, which is the sky’s brightest star, Sirius. This star is so brilliant that you can even see it from a light-polluted city. And you can see it if you stay up late, too! It’s rising in the middle of the night now, as seen from around the globe, and is high in the sky – at its best – by dawn.

Want a specific view from your location on the globe? Visit Stellarium and enter your location.

What is that bright twinkling star?

This star is enchanting, so much so that – every year, beginning in Northern Hemisphere autumn – we get many, many questions about a multicolored star twinkling in the southeastern to southern sky after midnight. This star typically turns out to be Sirius, which is in the constellation Canis Major the Greater Dog and is sometimes called the Dog Star.

Why does Sirius twinkle so much?

Sirius appears to flash different colors when it’s low in the sky. Really, all the stars are flashing different colors, because light is composed of all the colors of a rainbow, and the journey through our atmosphere breaks starlight into its component colors via refraction. But you don’t notice the colors of the other stars much, because they’re not as bright as Sirius. Sirius is the brightest star visible from anywhere on Earth.

Since our atmosphere is causing the light to break into its colors, and since Sirius is often seen low in the sky now (where you are peering at it through a thicker layer of atmosphere than when it’s overhead), the flashing colors of Sirius are very obvious. When Sirius is higher in the sky – which it is close to dawn in the month of October – or in the evening sky in January and February – you’ll find that Sirius shines with a steadier, whiter light.

So, on these October mornings, watch as Sirius winks at you in the wee hours before dawn!

View at EarthSky Community Photos. | Sergei Timofeevski shared this image from November 13, 2023. Sergei wrote: “The constellation Orion the Hunter and the star Sirius rising just above the eastern horizon in the Anza-Borrego Desert State Park, California.” Thank you, Sergei! Note bright Sirius is on the bottom, and Orion’s Belt pointing to it.

Bottom line: We get many questions about a bright, colorful, twinkling star on these October mornings. It’s the brightest star, Sirius, in the constellation Canis Major, brightest in the sky. You’ll know it’s Sirius, because Orion’s Belt always points to it.

Read more: Flashing star in autumn? Here are 3 candidates

The post Brightest star, Sirius, high on October mornings first appeared on EarthSky.

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Halloween is an astronomy holiday. It’s a cross-quarter day

Halloween is a cross-quarter day

Sure, Halloween is the modern-day descendant of Samhain, a sacred festival of the ancient Celts and Druids in the British Isles. And, yes, Halloween is short for All Hallows’ Eve. But, at its heart, Halloween is an astronomy holiday. It’s a day rooted in Earth’s orbit around the sun. It’s a cross-quarter day and a testament to our ancestors’ deep understanding of the sky.

The cross-quarter days fall more or less midway between the equinoxes (when the sun sets due west) and solstices (when the sun sets at its most northern or southern point on the horizon). Halloween – October 31 – is approximately midway between our Northern Hemisphere autumn (September) equinox and winter (December) solstice In the Southern Hemisphere, the September equinox heralds spring and the December solstice, summer.

In other words, in traditional astronomy, there are eight major seasonal subdivisions of every year. They include the March and September equinoxes, the June and December solstices, and the intervening four cross-quarter days.

In modern times, the four cross-quarter days are often called Groundhog Day (February 2), May Day (May 1), Lammas (August 1) and – the most sinister cross-quarter day because it comes at a dark time of year – Halloween (October 31).

Halloween falls at a dark time of year

For us in the Northern Hemisphere, Halloween is the darkest of the cross-quarter days. And it comes at a time of year when the days are growing shorter. Early people once said that the spirits of the dead wander from sunset until midnight around this cross-quarter day. After midnight – on November 1, now called All Saints’ Day – the ghosts supposedly go back to rest.

The October 31 date for Halloween is fixed by tradition. The true cross-quarter day falls on November 7, representing a discrepancy of about a week. According to the ancient Celts, a cross-quarter day marks the beginning – not the middle – of a season.

Equinoxes, solstices and cross-quarter days are all hallmarks of Earth’s orbit around the sun. Halloween is the 4th cross-quarter day of the year. Image via NASA.

The Pleiades connection

Some believe that the early forebear of Halloween – Samhain – happened on the night that the Pleiades star cluster culminated at midnight.

In other words, the Pleiades climbed to its highest point in the sky at midnight on or near the same date as this cross-quarter day. Now, the midnight culmination of the Pleiades cluster now occurs on November 21, but Halloween is fixed on October 31.

Presuming the supposed connection between Samhain and the midnight culmination of the Pleiades, the two events took place on or near the same date in the 11th century (1001-1100) and 12th century (1101-1200). This was several centuries before the introduction of the Gregorian calendar.

At that time, when the Julian calendar was in use, the cross-quarter day and the midnight culmination of the Pleiades fell – amazingly enough – on or near October 31. But, then, the Julian calendar was about one week out of step with the seasons. Had the Gregorian calendar been in use back then, the date of the cross-quarter day celebration would have been November 7.

Calendar converter via Fourmilab

But Halloween falls on October 31 now. Meanwhile, the true cross-quarter day happens on or near November 7. And the midnight culmination of the Pleiades cluster is on or near November 21.

View at EarthSky Community Photos. | Stojan Stojanovski in Debrca, Macedonia, caught this wonderful image on Halloween Night in 2020, when there was a full moon. Thank you, Stojan! By the way, the next time there’ll be a full moon on Halloween is 2039.

Pleiades is associated with Halloween

View at EarthSky Community Photos. | Jeremy Likness in Newport Oregon, captured the Pleiades star cluster on January 16, 2024. Jeremy wrote: “Can’t get enough of these winter sapphires.” Thank you, Jeremy! Reflection nebulae around the hot blue luminous stars of the Pleiades gives them an eerie and spectacular glow.

Bottom line: October 31, the date for Halloween, marks the approximate midway point between the September equinox and the December solstice. So Halloween is an astronomy holiday, and one of the year’s four cross-quarter days.

Read about another cross-quarter day, Groundhog Day

May Day is a cross-quarter day

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The post Halloween is an astronomy holiday. It’s a cross-quarter day first appeared on EarthSky.

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Halloween is a cross-quarter day

Sure, Halloween is the modern-day descendant of Samhain, a sacred festival of the ancient Celts and Druids in the British Isles. And, yes, Halloween is short for All Hallows’ Eve. But, at its heart, Halloween is an astronomy holiday. It’s a day rooted in Earth’s orbit around the sun. It’s a cross-quarter day and a testament to our ancestors’ deep understanding of the sky.

The cross-quarter days fall more or less midway between the equinoxes (when the sun sets due west) and solstices (when the sun sets at its most northern or southern point on the horizon). Halloween – October 31 – is approximately midway between our Northern Hemisphere autumn (September) equinox and winter (December) solstice In the Southern Hemisphere, the September equinox heralds spring and the December solstice, summer.

In other words, in traditional astronomy, there are eight major seasonal subdivisions of every year. They include the March and September equinoxes, the June and December solstices, and the intervening four cross-quarter days.

In modern times, the four cross-quarter days are often called Groundhog Day (February 2), May Day (May 1), Lammas (August 1) and – the most sinister cross-quarter day because it comes at a dark time of year – Halloween (October 31).

Halloween falls at a dark time of year

For us in the Northern Hemisphere, Halloween is the darkest of the cross-quarter days. And it comes at a time of year when the days are growing shorter. Early people once said that the spirits of the dead wander from sunset until midnight around this cross-quarter day. After midnight – on November 1, now called All Saints’ Day – the ghosts supposedly go back to rest.

The October 31 date for Halloween is fixed by tradition. The true cross-quarter day falls on November 7, representing a discrepancy of about a week. According to the ancient Celts, a cross-quarter day marks the beginning – not the middle – of a season.

Equinoxes, solstices and cross-quarter days are all hallmarks of Earth’s orbit around the sun. Halloween is the 4th cross-quarter day of the year. Image via NASA.

The Pleiades connection

Some believe that the early forebear of Halloween – Samhain – happened on the night that the Pleiades star cluster culminated at midnight.

In other words, the Pleiades climbed to its highest point in the sky at midnight on or near the same date as this cross-quarter day. Now, the midnight culmination of the Pleiades cluster now occurs on November 21, but Halloween is fixed on October 31.

Presuming the supposed connection between Samhain and the midnight culmination of the Pleiades, the two events took place on or near the same date in the 11th century (1001-1100) and 12th century (1101-1200). This was several centuries before the introduction of the Gregorian calendar.

At that time, when the Julian calendar was in use, the cross-quarter day and the midnight culmination of the Pleiades fell – amazingly enough – on or near October 31. But, then, the Julian calendar was about one week out of step with the seasons. Had the Gregorian calendar been in use back then, the date of the cross-quarter day celebration would have been November 7.

Calendar converter via Fourmilab

But Halloween falls on October 31 now. Meanwhile, the true cross-quarter day happens on or near November 7. And the midnight culmination of the Pleiades cluster is on or near November 21.

View at EarthSky Community Photos. | Stojan Stojanovski in Debrca, Macedonia, caught this wonderful image on Halloween Night in 2020, when there was a full moon. Thank you, Stojan! By the way, the next time there’ll be a full moon on Halloween is 2039.

Pleiades is associated with Halloween

View at EarthSky Community Photos. | Jeremy Likness in Newport Oregon, captured the Pleiades star cluster on January 16, 2024. Jeremy wrote: “Can’t get enough of these winter sapphires.” Thank you, Jeremy! Reflection nebulae around the hot blue luminous stars of the Pleiades gives them an eerie and spectacular glow.

Bottom line: October 31, the date for Halloween, marks the approximate midway point between the September equinox and the December solstice. So Halloween is an astronomy holiday, and one of the year’s four cross-quarter days.

Read about another cross-quarter day, Groundhog Day

May Day is a cross-quarter day

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

The post Halloween is an astronomy holiday. It’s a cross-quarter day first appeared on EarthSky.

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Boeing satellite breakup adds to space junk around Earth

On October 19-20, 2024, the satellite breakup of Intelsat 33e added at least 20 more pieces of space junk to the growing collection in orbit around Earth. Image via NASA ODPO.

• The satellite Intelsat 33e broke up at 04:30 UTC on October 19, 2024, while in geostationary orbit. Boeing designed and manufactured the satellite, which launched to space in August 2016.
• The breakup resulted in at least 20 pieces of newly made space junk, which the U.S. Space Force is now tracking.
• This space junk adds to the growing debris pile currently in Earth-orbit. This debris poses an increasingly dire threat to other spacecraft and spaceflights, experts say.

By Sara Webb, Swinburne University of Technology; Christopher Fluke, Swinburne University of Technology and Tallulah Waterson, Swinburne University of Technology

Satellite breakup on October 19-20

A large communications satellite broke up in orbit, affecting users in Europe, Central Africa, the Middle East, Asia and Australia. And it adds to the growing swarm of space junk clouding our planet’s neighborhood.

The Intelsat 33e satellite provided broadband communication from a point some 35,000 kilometers (22,000 miles) above the Indian Ocean, in a geostationary orbit around the equator.

Initial reports on October 20 said Intelsat 33e experienced a sudden power loss. Hours later, US Space Forces-Space confirmed the satellite broke up into at least 20 pieces.

So what happened? And is this a sign of things to come as more and more satellites head into orbit?

A space whodunnit

There are no confirmed reports about what caused the breakup of Intelsat 33e. However, it is not the first event of its kind.

In the past we’ve seen deliberate satellite destructions, accidental collisions and loss of satellites due to increased solar activity.

What we do know is that Intelsat 33e has a history of issues while in orbit. Boeing designed and manufactured the satellite, which launched to space in August 2016.

In 2017, the satellite reached its desired orbit three months later than anticipated. That was due to a reported issue with its primary thruster, which controls its altitude and acceleration.

More propulsion troubles emerged when the satellite performed something called a station keeping activity, which keeps it at the right altitude. It was burning more fuel than expected, which meant its mission would end around 3.5 years early, in 2027. Intelsat lodged a US$78 million insurance claim as a result of these problems.

However, at the time of its breakup, the satellite was reportedly not insured.

Intelsat is investigating what went wrong, but we may never know exactly what caused the satellite’s breakup. We do know another Intelsat satellite of the same model, a Boeing-built EpicNG 702 MP, failed in 2019.

More importantly, we can learn from the aftermath of the breakup: space junk.

EarthSky’s Dave Adalian interviewed Jonathan McDowell of the Harvard Center for Astrophysics – a world expert on space debris – in September 2024. Watch in the player above, or on YouTube.

Satellite breakup adds to 30 blue whales of space junk

The amount of debris in orbit around Earth is increasing rapidly. The European Space Agency (ESA) estimates there are more than 40,000 pieces larger than 10 centimeters (4 inches) in orbit. And it says there are more than 130,000,000 smaller than 1 centimeter (0.4 inch).

The total mass of human-made space objects in Earth orbit is some 13,000 tonnes (28.6 million pounds). That’s about the same mass as 90 adult male blue whales. About one third of this mass (30 blue whales’ worth) is debris (4,300 tonnes or 9.5 million pounds), mostly in the form of leftover rocket bodies.

Tracking and identifying space debris is a challenging task. At higher altitudes, such as Intelsat 33e’s orbit around 35,000 kilometers (22,000 miles) up, we can only see objects above a certain size.

One of the most concerning things about the loss of Intelsat 33e is that the breakup likely produced debris that is too small for us to see from ground level with current facilities.

The past few months have seen a string of uncontrolled breakups of decommissioned and abandoned objects in orbit.

In June, the RESURS-P1 satellite fractured in low Earth orbit (an altitude of around 470 km or 300 miles), creating more than 100 trackable pieces of debris. This event also likely created many more pieces of debris too small to track.

In July, another decommissioned satellite – the Defense Meteorological Satellite Program (DMSP) 5D-2 F8 spacecraft – broke up. In August, the upper stage of a Long March 6A (CZ-6A) rocket fragmented, creating at least 283 pieces of trackable debris, and potentially hundreds of thousands of untrackable fragments.

We don’t yet know whether this most recent event will affect other objects in orbit. This is where continuous monitoring of the sky becomes vital, to understand these complex space debris environments.

Who is responsible?

When satellites and so forth become space debris, who is responsible for cleaning it up or monitoring it?

In principle, the country that launched the object into space has the burden of responsibility where fault can be proved. The Convention of International Liability for Damage Caused by Space Objects explored this in 1972.

In practice, there is often little accountability. The US Federal Communications Commission issued the first fine over space debris in 2023.

It’s not clear whether Intelsat 33e resulted in a similar fine.

Looking ahead

As the human use of space accelerates, Earth orbit gets increasingly crowded. To manage the hazards of orbital debris, we will need continuous monitoring and improved tracking technology alongside deliberate efforts to minimize the amount of debris in order to manage the hazards of orbital debris.

Most satellites are much closer to Earth than Intelsat 33e. Often, companies and governments can safely bring down these low-Earth-orbit satellites from orbit at the end of their missions without creating space debris, especially with a bit of forward planning.

In September, ESA de-orbited its Cluster 2 “Salsa” satellite with a targeted re-entry into Earth’s atmosphere, where it burned up safely.

Of course, the bigger the space object, the more debris it can produce. NASA’s Orbital Debris Program Office calculated the International Space Station would produce more than 220 million debris fragments if it broke up in orbit, for example.

Accordingly, planning for de-orbiting of the space station at the end of its operational life in 2030 is now well underway, with SpaceX receiving the contract.

Sara Webb, Swinburne University of Technology; Christopher Fluke, Swinburne University of Technology and Tallulah Waterson, Swinburne University of Technology

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

Space junk with Jonathan McDowell

Intelsat's IS-33e communications sat has undergone a breakup event in geostationary orbit, with US Space Force reporting 20 tracked (but not yet cataloged) debris objects. The sat was launched 2016 Aug 24 and is over the Indian Ocean at 60.1E; breakup was 0430 UTC Oct 19.

— Jonathan McDowell (@planet4589) October 20, 2024

We don't know yet. Two possibilities: 1) satellite was impacted by a piece of space debris. 2) internal energetic event like a propulsion system exploding

— Jonathan McDowell (@planet4589) October 20, 2024

Bottom line: On October 19-20, 2024, the satellite breakup of Intelsat 33e added at least 20 pieces of space junk to the growing debris pile in orbit around Earth.

The post Boeing satellite breakup adds to space junk around Earth first appeared on EarthSky.

from EarthSky https://ift.tt/9SEiK2s

On October 19-20, 2024, the satellite breakup of Intelsat 33e added at least 20 more pieces of space junk to the growing collection in orbit around Earth. Image via NASA ODPO.

• The satellite Intelsat 33e broke up at 04:30 UTC on October 19, 2024, while in geostationary orbit. Boeing designed and manufactured the satellite, which launched to space in August 2016.
• The breakup resulted in at least 20 pieces of newly made space junk, which the U.S. Space Force is now tracking.
• This space junk adds to the growing debris pile currently in Earth-orbit. This debris poses an increasingly dire threat to other spacecraft and spaceflights, experts say.

By Sara Webb, Swinburne University of Technology; Christopher Fluke, Swinburne University of Technology and Tallulah Waterson, Swinburne University of Technology

Satellite breakup on October 19-20

A large communications satellite broke up in orbit, affecting users in Europe, Central Africa, the Middle East, Asia and Australia. And it adds to the growing swarm of space junk clouding our planet’s neighborhood.

The Intelsat 33e satellite provided broadband communication from a point some 35,000 kilometers (22,000 miles) above the Indian Ocean, in a geostationary orbit around the equator.

Initial reports on October 20 said Intelsat 33e experienced a sudden power loss. Hours later, US Space Forces-Space confirmed the satellite broke up into at least 20 pieces.

So what happened? And is this a sign of things to come as more and more satellites head into orbit?

A space whodunnit

There are no confirmed reports about what caused the breakup of Intelsat 33e. However, it is not the first event of its kind.

In the past we’ve seen deliberate satellite destructions, accidental collisions and loss of satellites due to increased solar activity.

What we do know is that Intelsat 33e has a history of issues while in orbit. Boeing designed and manufactured the satellite, which launched to space in August 2016.

In 2017, the satellite reached its desired orbit three months later than anticipated. That was due to a reported issue with its primary thruster, which controls its altitude and acceleration.

More propulsion troubles emerged when the satellite performed something called a station keeping activity, which keeps it at the right altitude. It was burning more fuel than expected, which meant its mission would end around 3.5 years early, in 2027. Intelsat lodged a US$78 million insurance claim as a result of these problems.

However, at the time of its breakup, the satellite was reportedly not insured.

Intelsat is investigating what went wrong, but we may never know exactly what caused the satellite’s breakup. We do know another Intelsat satellite of the same model, a Boeing-built EpicNG 702 MP, failed in 2019.

More importantly, we can learn from the aftermath of the breakup: space junk.

EarthSky’s Dave Adalian interviewed Jonathan McDowell of the Harvard Center for Astrophysics – a world expert on space debris – in September 2024. Watch in the player above, or on YouTube.

Satellite breakup adds to 30 blue whales of space junk

The amount of debris in orbit around Earth is increasing rapidly. The European Space Agency (ESA) estimates there are more than 40,000 pieces larger than 10 centimeters (4 inches) in orbit. And it says there are more than 130,000,000 smaller than 1 centimeter (0.4 inch).

The total mass of human-made space objects in Earth orbit is some 13,000 tonnes (28.6 million pounds). That’s about the same mass as 90 adult male blue whales. About one third of this mass (30 blue whales’ worth) is debris (4,300 tonnes or 9.5 million pounds), mostly in the form of leftover rocket bodies.

Tracking and identifying space debris is a challenging task. At higher altitudes, such as Intelsat 33e’s orbit around 35,000 kilometers (22,000 miles) up, we can only see objects above a certain size.

One of the most concerning things about the loss of Intelsat 33e is that the breakup likely produced debris that is too small for us to see from ground level with current facilities.

The past few months have seen a string of uncontrolled breakups of decommissioned and abandoned objects in orbit.

In June, the RESURS-P1 satellite fractured in low Earth orbit (an altitude of around 470 km or 300 miles), creating more than 100 trackable pieces of debris. This event also likely created many more pieces of debris too small to track.

In July, another decommissioned satellite – the Defense Meteorological Satellite Program (DMSP) 5D-2 F8 spacecraft – broke up. In August, the upper stage of a Long March 6A (CZ-6A) rocket fragmented, creating at least 283 pieces of trackable debris, and potentially hundreds of thousands of untrackable fragments.

We don’t yet know whether this most recent event will affect other objects in orbit. This is where continuous monitoring of the sky becomes vital, to understand these complex space debris environments.

Who is responsible?

When satellites and so forth become space debris, who is responsible for cleaning it up or monitoring it?

In principle, the country that launched the object into space has the burden of responsibility where fault can be proved. The Convention of International Liability for Damage Caused by Space Objects explored this in 1972.

In practice, there is often little accountability. The US Federal Communications Commission issued the first fine over space debris in 2023.

It’s not clear whether Intelsat 33e resulted in a similar fine.

Looking ahead

As the human use of space accelerates, Earth orbit gets increasingly crowded. To manage the hazards of orbital debris, we will need continuous monitoring and improved tracking technology alongside deliberate efforts to minimize the amount of debris in order to manage the hazards of orbital debris.

Most satellites are much closer to Earth than Intelsat 33e. Often, companies and governments can safely bring down these low-Earth-orbit satellites from orbit at the end of their missions without creating space debris, especially with a bit of forward planning.

In September, ESA de-orbited its Cluster 2 “Salsa” satellite with a targeted re-entry into Earth’s atmosphere, where it burned up safely.

Of course, the bigger the space object, the more debris it can produce. NASA’s Orbital Debris Program Office calculated the International Space Station would produce more than 220 million debris fragments if it broke up in orbit, for example.

Accordingly, planning for de-orbiting of the space station at the end of its operational life in 2030 is now well underway, with SpaceX receiving the contract.

Sara Webb, Swinburne University of Technology; Christopher Fluke, Swinburne University of Technology and Tallulah Waterson, Swinburne University of Technology

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

Space junk with Jonathan McDowell

Intelsat's IS-33e communications sat has undergone a breakup event in geostationary orbit, with US Space Force reporting 20 tracked (but not yet cataloged) debris objects. The sat was launched 2016 Aug 24 and is over the Indian Ocean at 60.1E; breakup was 0430 UTC Oct 19.

— Jonathan McDowell (@planet4589) October 20, 2024

We don't know yet. Two possibilities: 1) satellite was impacted by a piece of space debris. 2) internal energetic event like a propulsion system exploding

— Jonathan McDowell (@planet4589) October 20, 2024

Bottom line: On October 19-20, 2024, the satellite breakup of Intelsat 33e added at least 20 pieces of space junk to the growing debris pile in orbit around Earth.

The post Boeing satellite breakup adds to space junk around Earth first appeared on EarthSky.

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1st photo of Earth from space, 78 years ago today

The 1st photo of Earth from space shows a look at the clouds from above. The image is from October 24, 1946. Image via White Sands Missile Range/ Applied Physics Laboratory/ Wikimedia Commons.

1st photo of Earth from space

Were you alive before we saw Earth from space? If so, you were born on or before October 24, 1946. That was when a group of soldiers and scientists in the New Mexico desert launched a V-2 rocket – carrying a 35-mm motion picture camera – to a height 65 miles (105 km) above Earth’s surface. NASA defines the edge of space as 50 miles (80 km) above the surface. After a few minutes, the camera dropped back to Earth and was destroyed on impact. But the film survived.

Reliving the momentous day

Air & Space Magazine tells the story of this major event in space history:

Snapping a new frame every second and a half, the rocket-borne camera climbed straight up, then fell back to Earth minutes later, slamming into the ground at 500 feet per second. The camera itself was smashed, but the film, protected in a steel cassette, was unharmed.

Fred Rulli was a 19-year-old enlisted man assigned to the recovery team that drove into the desert to retrieve film from those early V-2 shots. When the scientists found the cassette in good shape, he recalls, “They were ecstatic, they were jumping up and down like kids.” Later, back at the launch site, “when they first projected [the photos] onto the screen, the scientists just went nuts.”

Before 1946, the highest pictures ever taken of the Earth’s surface were from the Explorer II balloon, which had ascended 13.7 miles in 1935, high enough to discern the curvature of the Earth. The V-2 cameras reached more than five times that altitude, where they clearly showed the planet set against the blackness of space. When the movie frames were stitched together, Clyde Holliday, the engineer who developed the camera, wrote in National Geographic in 1950, the V-2 photos showed for the first time “how our Earth would look to visitors from another planet coming in on a space ship.”

Another early image from space

Scientists quickly got better at taking Earth’s picture. Here’s a still frame from about 6 months later, taken from V-2 #21, launched on March 7, 1947. This picture is from 101 miles (163 km) up. The dark area on Earth at upper left is the Gulf of California. Image via White Sands Missile Range/ Naval Research Laboratory/ Wikimedia Commons.

See a panorama of Earth from 1948 here

See videos and read the rest of the story from Air & Space.

Bottom line: On October 24, 1946, a movie camera on board a V-2 rocket captured the first photo of Earth from outer space. We’ve come a long way since then!

Read more: Earth images from space: 10 incredible photos of our planet

Read more: GOES-19 first light images show stunning view of Earth

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

The post 1st photo of Earth from space, 78 years ago today first appeared on EarthSky.

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The 1st photo of Earth from space shows a look at the clouds from above. The image is from October 24, 1946. Image via White Sands Missile Range/ Applied Physics Laboratory/ Wikimedia Commons.

1st photo of Earth from space

Were you alive before we saw Earth from space? If so, you were born on or before October 24, 1946. That was when a group of soldiers and scientists in the New Mexico desert launched a V-2 rocket – carrying a 35-mm motion picture camera – to a height 65 miles (105 km) above Earth’s surface. NASA defines the edge of space as 50 miles (80 km) above the surface. After a few minutes, the camera dropped back to Earth and was destroyed on impact. But the film survived.

Reliving the momentous day

Air & Space Magazine tells the story of this major event in space history:

Snapping a new frame every second and a half, the rocket-borne camera climbed straight up, then fell back to Earth minutes later, slamming into the ground at 500 feet per second. The camera itself was smashed, but the film, protected in a steel cassette, was unharmed.

Fred Rulli was a 19-year-old enlisted man assigned to the recovery team that drove into the desert to retrieve film from those early V-2 shots. When the scientists found the cassette in good shape, he recalls, “They were ecstatic, they were jumping up and down like kids.” Later, back at the launch site, “when they first projected [the photos] onto the screen, the scientists just went nuts.”

Before 1946, the highest pictures ever taken of the Earth’s surface were from the Explorer II balloon, which had ascended 13.7 miles in 1935, high enough to discern the curvature of the Earth. The V-2 cameras reached more than five times that altitude, where they clearly showed the planet set against the blackness of space. When the movie frames were stitched together, Clyde Holliday, the engineer who developed the camera, wrote in National Geographic in 1950, the V-2 photos showed for the first time “how our Earth would look to visitors from another planet coming in on a space ship.”

Another early image from space

Scientists quickly got better at taking Earth’s picture. Here’s a still frame from about 6 months later, taken from V-2 #21, launched on March 7, 1947. This picture is from 101 miles (163 km) up. The dark area on Earth at upper left is the Gulf of California. Image via White Sands Missile Range/ Naval Research Laboratory/ Wikimedia Commons.

See a panorama of Earth from 1948 here

See videos and read the rest of the story from Air & Space.

Bottom line: On October 24, 1946, a movie camera on board a V-2 rocket captured the first photo of Earth from outer space. We’ve come a long way since then!

Read more: Earth images from space: 10 incredible photos of our planet

Read more: GOES-19 first light images show stunning view of Earth

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

The post 1st photo of Earth from space, 78 years ago today first appeared on EarthSky.

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Are mysterious flows on airless worlds made by salty water?

View larger. | NASA’s Dawn spacecraft captured this enhanced color view of the dwarf planet Ceres. The bright spots are salt-rich material in Occator crater; meteoroid impacts excavated this material from the crust. A new study said mysterious flows on airless worlds like Ceres can be the result of temporary flows of briny (salty) water from meteoroid impacts. Image via NASA/ JPL-CalTech/ UCLA/ MPS/ DLR/ IDA.

• Unusual flow-like features appear on some airless bodies in the solar system, such as Vesta, Ceres and Europa. How did they form in the absence of an atmosphere?
• Temporary flows of briny water may be the answer. A new study showed meteoroid impacts could melt salty ice, allowing it to flow briefly on the surface.
• The flows would last long enough to cause significant erosion such as gullies and landslides, even with no atmosphere.

Does salty water create mysterious flows on airless worlds?

Flowing water produces distinct landscape features such as riverbeds, valleys, mudslides and more. We’ve seen their effects on Earth as well as Mars, where liquid water flowed billions of years ago. A new joint study between the Southwest Research Institute (SwRI) and NASA’s Jet Propulsion Laboratory (JPL) suggests water may also explain mysterious flow-like features on airless dwarf planets, small moons and asteroids. On October 21, 2024, the researchers said the water would have been in the form of temporary salty brines resulting from meteoroid impacts.

The researchers, led by Michael J. Poston at SwRI, published their peer-reviewed findings in The Planetary Science Journal on October 21, 2024.

Mysterious flows on airless worlds

The study focused on bodies in the solar system with known ice in their crusts but very little atmosphere. This included asteroids like Vesta, the dwarf planet Ceres and Jupiter’s moon Europa. They all display features on their surfaces that look like those created by flowing water. But how could that happen on bodies with no atmosphere?

The research team found that water could still be the explanation. But it wouldn’t be pure water. Instead, it would be temporary flows of briny (salty) water. Meteoroid impacts could melt ice in the crust, allowing it to flow briefly on the surface. Project Principal Investigator Jennifer Scully at JPL said:

We wanted to investigate our previously proposed idea that ice underneath the surface of an airless world could be excavated and melted by an impact and then flow along the walls of the impact crater to form distinct surface features.

As the paper stated:

The role played by transient impact-induced endogenous brines in the formation of geomorphic features has been proposed on airless worlds such as Europa, Vesta and Ceres, as well as on worlds with thin atmospheres such as Mars. After liquefaction, the hypothesized brines flow in a debris-flow-like process, incising curvilinear gullies and constructing lobate deposits within newly formed craters.

View larger. | Lobate deposits and curvilinear gullies in Cornelia crater on the asteroid Vesta. The new study said temporary flows of briny (salty) water from a meteoroid impact likely produced them. Image via NASA/ JPL/ SwRI.

Flowing water in an airless vacuum

So how long could briny water flow on an airless body? To find out, the researchers simulated the surface conditions of the asteroid Vesta. They wanted to know how much pressure the surface ice experiences when a meteoroid impacts it. And, subsequently, how long could the water remain liquid before re-freezing again.

Poston and his colleagues used a modified test chamber at JPL to rapidly decrease the pressure on a sample of water. A meteoroid impact on Vesta would create a temporary localized atmosphere. The test simulated the sudden drop in pressure as the atmosphere then dissipated. In the experiment, the water immediately expanded as a result and ejected material from the sample chamber.

SwRI and JPL co-led study offers insights into mysterious features on airless worldshttps://t.co/S4qTsiRZoH

— Southwest Research Institute (@SwRI) October 21, 2024

Salty brines needed

Overall, pure water re-froze too quickly to have much of an effect, but briny water lasted longer. As Poston explained:

Through our simulated impacts, we found that the pure water froze too quickly in a vacuum to effect meaningful change, but salt and water mixtures, or brines, stayed liquid and flowing for a minimum of one hour. This is sufficient for the brine to destabilize slopes on crater walls on rocky bodies, cause erosion and landslides and potentially form other unique geological features found on icy moons.

If the findings are consistent across these dry and airless or thin-atmosphere bodies, it demonstrates that water existed on these worlds in the recent past, indicating water might still be expelled from impacts. There may still be water out there to be found.

Water on other small worlds in the solar system

Scully also led another study, announced back in 2015, of evidence for briny water flows on Vesta. The new work now expands on those previous findings and extends them to other airless bodies like Ceres and Europa.

And just earlier this month, scientist said there is evidence that Ceres might have been a muddy ocean world. Europa, as we now know, is still an ocean world, under its outer icy crust. And it’s just one of several known ocean moons in our solar system. Saturn’s ocean moon Enceladus literally shoots out jets of salty water vapor into space through cracks in its icy surface. So it’s quite possible other small icy and watery bodies in the solar system can still have water on their surfaces, even if only very briefly.

Bottom line: A new study from researchers at SwRI and JPL suggested that briny water could explain unusual flows on airless worlds like Vesta, Ceres and Europa.

Source: Experimental Examination of Brine and Water Lifetimes after Impact on Airless Worlds

Via SwRI

Read more: Flowing water on Vesta?

Read more: Dwarf planet Ceres might have been a muddy ocean world

The post Are mysterious flows on airless worlds made by salty water? first appeared on EarthSky.

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View larger. | NASA’s Dawn spacecraft captured this enhanced color view of the dwarf planet Ceres. The bright spots are salt-rich material in Occator crater; meteoroid impacts excavated this material from the crust. A new study said mysterious flows on airless worlds like Ceres can be the result of temporary flows of briny (salty) water from meteoroid impacts. Image via NASA/ JPL-CalTech/ UCLA/ MPS/ DLR/ IDA.

• Unusual flow-like features appear on some airless bodies in the solar system, such as Vesta, Ceres and Europa. How did they form in the absence of an atmosphere?
• Temporary flows of briny water may be the answer. A new study showed meteoroid impacts could melt salty ice, allowing it to flow briefly on the surface.
• The flows would last long enough to cause significant erosion such as gullies and landslides, even with no atmosphere.

Does salty water create mysterious flows on airless worlds?

Flowing water produces distinct landscape features such as riverbeds, valleys, mudslides and more. We’ve seen their effects on Earth as well as Mars, where liquid water flowed billions of years ago. A new joint study between the Southwest Research Institute (SwRI) and NASA’s Jet Propulsion Laboratory (JPL) suggests water may also explain mysterious flow-like features on airless dwarf planets, small moons and asteroids. On October 21, 2024, the researchers said the water would have been in the form of temporary salty brines resulting from meteoroid impacts.

The researchers, led by Michael J. Poston at SwRI, published their peer-reviewed findings in The Planetary Science Journal on October 21, 2024.

Mysterious flows on airless worlds

The study focused on bodies in the solar system with known ice in their crusts but very little atmosphere. This included asteroids like Vesta, the dwarf planet Ceres and Jupiter’s moon Europa. They all display features on their surfaces that look like those created by flowing water. But how could that happen on bodies with no atmosphere?

The research team found that water could still be the explanation. But it wouldn’t be pure water. Instead, it would be temporary flows of briny (salty) water. Meteoroid impacts could melt ice in the crust, allowing it to flow briefly on the surface. Project Principal Investigator Jennifer Scully at JPL said:

We wanted to investigate our previously proposed idea that ice underneath the surface of an airless world could be excavated and melted by an impact and then flow along the walls of the impact crater to form distinct surface features.

As the paper stated:

The role played by transient impact-induced endogenous brines in the formation of geomorphic features has been proposed on airless worlds such as Europa, Vesta and Ceres, as well as on worlds with thin atmospheres such as Mars. After liquefaction, the hypothesized brines flow in a debris-flow-like process, incising curvilinear gullies and constructing lobate deposits within newly formed craters.

View larger. | Lobate deposits and curvilinear gullies in Cornelia crater on the asteroid Vesta. The new study said temporary flows of briny (salty) water from a meteoroid impact likely produced them. Image via NASA/ JPL/ SwRI.

Flowing water in an airless vacuum

So how long could briny water flow on an airless body? To find out, the researchers simulated the surface conditions of the asteroid Vesta. They wanted to know how much pressure the surface ice experiences when a meteoroid impacts it. And, subsequently, how long could the water remain liquid before re-freezing again.

Poston and his colleagues used a modified test chamber at JPL to rapidly decrease the pressure on a sample of water. A meteoroid impact on Vesta would create a temporary localized atmosphere. The test simulated the sudden drop in pressure as the atmosphere then dissipated. In the experiment, the water immediately expanded as a result and ejected material from the sample chamber.

SwRI and JPL co-led study offers insights into mysterious features on airless worldshttps://t.co/S4qTsiRZoH

— Southwest Research Institute (@SwRI) October 21, 2024

Salty brines needed

Overall, pure water re-froze too quickly to have much of an effect, but briny water lasted longer. As Poston explained:

Through our simulated impacts, we found that the pure water froze too quickly in a vacuum to effect meaningful change, but salt and water mixtures, or brines, stayed liquid and flowing for a minimum of one hour. This is sufficient for the brine to destabilize slopes on crater walls on rocky bodies, cause erosion and landslides and potentially form other unique geological features found on icy moons.

If the findings are consistent across these dry and airless or thin-atmosphere bodies, it demonstrates that water existed on these worlds in the recent past, indicating water might still be expelled from impacts. There may still be water out there to be found.

Water on other small worlds in the solar system

Scully also led another study, announced back in 2015, of evidence for briny water flows on Vesta. The new work now expands on those previous findings and extends them to other airless bodies like Ceres and Europa.

And just earlier this month, scientist said there is evidence that Ceres might have been a muddy ocean world. Europa, as we now know, is still an ocean world, under its outer icy crust. And it’s just one of several known ocean moons in our solar system. Saturn’s ocean moon Enceladus literally shoots out jets of salty water vapor into space through cracks in its icy surface. So it’s quite possible other small icy and watery bodies in the solar system can still have water on their surfaces, even if only very briefly.

Bottom line: A new study from researchers at SwRI and JPL suggested that briny water could explain unusual flows on airless worlds like Vesta, Ceres and Europa.

Source: Experimental Examination of Brine and Water Lifetimes after Impact on Airless Worlds

Via SwRI

Read more: Flowing water on Vesta?

Read more: Dwarf planet Ceres might have been a muddy ocean world

The post Are mysterious flows on airless worlds made by salty water? first appeared on EarthSky.

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