Built not born: Huge black holes form in mergers, study says

This illustration shows 2 black holes spiraling toward a colossal collision. A new study says mergers like this could explain how mysteriously large black holes form. Image via LIGO/ Caltech/ Simulating eXtreme Spacetimes Collaboration.

• Over the past decade, astronomers have detected many black holes that seem too massive to have formed from the collapse of a single star. So how did they form?
• Researchers have just found new evidence that these black holes form from chaotic collisions between multiple smaller black holes.
• The finding comes from studying ripples in the fabric of spacetime that these black holes send out into the universe.

You deserve a daily dose of good news. For the latest in science and the night sky, subscribe to EarthSky’s free daily newsletter.

Huge black holes form from mergers

A new study has provided fresh evidence that some of the largest stellar-mass black holes didn’t form directly from the collapse of massive stars. Instead, the research suggests, they were built from chaotic collisions and repeated mergers between multiple smaller black holes.

Stellar-mass black holes are black holes ranging from a few times the mass of our sun to tens of solar masses. And on May 7, 2026, the researchers said they’ve identified two distinct populations of these black holes.

The first population, those less than 45 times the mass of our sun, formed as we’d typically expect: from stars collapsing at the end of their lives. But the second population – those over 45 solar masses – is more mysterious. Astronomers have long suspected that these are too massive to have formed from the collapse of single stars. And the new research helps explain how they’ve come to exist.

The scientists noticed that these larger black holes are spinning faster and in much more varied directions than the smaller ones. They say this is evidence that the larger black holes are the product of black hole collisions in the maelstrom of dense star clusters.

They performed this study using new data from gravitational waves observations. The research team analyzed data from a catalog of observations, called the LIGO–Virgo–KAGRA Gravitational-Wave Transient Catalog version 4 (GWTC4). In it, they found 153 detections of black hole mergers.

Fabio Antonini is the first author of this study. He said, in a statement:

Gravitational wave astronomy is now doing more than counting black hole mergers. It is starting to reveal how black holes grow, where they grow, and what that tells us about the lives and deaths of massive stars. This is exciting because we can use the information to test our understanding of how stars and [star] clusters evolve in the universe.

The team published its findings in the peer-reviewed journal Nature Astronomy on May 7, 2026.

Detecting ripples in spacetime

A black hole first forms when a massive star runs out of fuel for nuclear fusion. As a result, it collapses under its own gravity. The star’s mass becomes so compact that nothing can escape its powerful gravitational force … not even light.

In dense star clusters, two black holes often get close enough to start orbiting each other. As the two objects rotate, they generate a unique pattern of gravitational waves, or ripples in the fabric of the universe. The wave characteristics depend on the mass of each object, as well as their distance and orbit orientation from Earth.

This computer simulation shows the merger of 2 black holes. As the black holes spiral toward each other, collide and merge, they create gravitational waves. Scientists made this simulation using equations from Albert Einstein’s theory of general relativity and data from the Laser Interferometer Gravitational-wave Observatory (LIGO). Video via the Simulating eXtreme Spacetimes (SXS) project.

Gravitational waves are ripples in the four-dimensional realm where space and time are woven together. They can be detected on Earth by very sensitive instruments called gravitational wave laser interferometers.

The orbiting black hole pair radiates gravitational waves, resulting in some loss of orbital energy. As a result, the black holes get closer. That causes them to orbit each other faster, which radiates even stronger gravitational waves, which makes them get closer, and so on. The final outcome is a violent merger of the two objects.

Gravitational wave laser interferometers are able to detect the final orbits of the black holes just before the merger, which occurs over a timeframe of seconds.

Two populations of black holes

The scientists analyzed 153 black hole mergers in the LIGO–Virgo–KAGRA’s Gravitational-Wave Transient Catalog version 4. This catalog is a compilation of all gravitational wave detections from May 2023 to January 2024.

They noticed two distinct populations of stellar black holes. Isobel Romero-Shaw, also of Cardiff University, said:

What surprised us most was how clearly the high mass black holes [over 45 solar masses] stand out as a separate population.

Unlike the lower mass systems we analyzed, which were generally slowly-spinning, the higher mass systems are consistent with having more rapid spins, oriented in seemingly random directions. This is the exact signature you would expect if black holes were repeatedly merging in dense star clusters.

Messier 80 is a dense globular star cluster, about 28,000 light-years away, in the constellation Scorpius the Scorpion. The new study suggests that huge stellar-mass black holes form via chaotic collisions between multiple smaller black holes in dense star clusters like this. Image via NASA, ESA, G. Piotto, and G. Kober.

The pair-instability mass gap

There’s a theory in stellar evolution called the pair-instability mass gap. It states that stars above a certain mass limit will violently explode, rather than becoming a black hole. In their study, the team established that this limit was 45 solar masses. Therefore, any star over that value would explode at the end of its lifetime.

According to this theory, a collapsing star wouldn’t be able to form a black hole over 45 solar masses. However, gravitational wave detections have shown that stellar-mass black holes over this threshold do indeed exist.

Antonini said:

In our study we find evidence for the long-predicted pair-instability mass gap — a range of masses where stars are not expected to leave behind black holes at all. Gravitational wave detectors have successfully found black holes that appear to sit in or near that gap, which we identify at around 45 solar masses.

So how did these huge black holes form? The answer, Antonini says, lies in their spin:

The biggest black holes in the current sample seem to be telling us about [star] cluster dynamics, not just stellar evolution. Above about 45 solar masses the [black hole] spin distribution changes in a way that is hard to explain with normal stellar binaries alone but is naturally explained if these black holes have already been through earlier mergers in dense [star] clusters.

So the smaller black holes have similar spins, having formed from a population of similar stars. But when the black holes cross this 45-solar-mass line, they start to show a wide range of different spin speeds and orientations. The researchers think this erratic spinning is a sign that the large black holes have been through a series of violent collisions and mergers.

How gravitational wave laser interferometers work

If you threw two stones into a pond, each stone creates concentric ripples. The sections where the ripples intersect are called interference patterns. Gravitational wave laser interferometers look for laser beam interference patterns caused by gravitational waves.

A gravitational wave observatory has two long, perpendicular arms. For instance, at the LIGO observatories in Washington and Louisiana, each arm is 2.5 miles (4 km) long. A laser beam is split to shine along each arm. At the end of the arm, a mirror reflects the beam back and the two beams meet to form an interference pattern.

When gravitational waves pass through, spacetime itself oscillates. As a result, each wave stretches one arm and compresses the other. Therefore, the lasers move through slightly different lengths. The resulting interference patterns reveal information about the objects that generated the gravitational waves. This instrument is so sensitive that it can detect an arm length difference that’s 1/10,000th the width of a proton.

A brief animation showing the basic operation of the LIGO interferometer. Video via LIGO/ Einstein’s Messengers/ NSF.

Besides LIGO, there are two other gravitational wave observatories: the Virgo interferometer in Italy and the Kamioka Gravitational Wave Detector (KAGRA) in Japan. Ideally, all three observatories should detect a gravitational wave event to confirm it.

Bottom line: A new study suggests the largest stellar-mass black holes form not from single stars collapsing, but from collisions and mergers between smaller black holes.

Source: Gravitational-wave constraints on the pair-instability mass gap and nuclear burning in massive stars

Via Cardiff University

Read more: Gravitational waves discoveries surge in new catalog

The post Built not born: Huge black holes form in mergers, study says first appeared on EarthSky.

from EarthSky https://ift.tt/Mub6PLJ

This illustration shows 2 black holes spiraling toward a colossal collision. A new study says mergers like this could explain how mysteriously large black holes form. Image via LIGO/ Caltech/ Simulating eXtreme Spacetimes Collaboration.

• Over the past decade, astronomers have detected many black holes that seem too massive to have formed from the collapse of a single star. So how did they form?
• Researchers have just found new evidence that these black holes form from chaotic collisions between multiple smaller black holes.
• The finding comes from studying ripples in the fabric of spacetime that these black holes send out into the universe.

You deserve a daily dose of good news. For the latest in science and the night sky, subscribe to EarthSky’s free daily newsletter.

Huge black holes form from mergers

A new study has provided fresh evidence that some of the largest stellar-mass black holes didn’t form directly from the collapse of massive stars. Instead, the research suggests, they were built from chaotic collisions and repeated mergers between multiple smaller black holes.

Stellar-mass black holes are black holes ranging from a few times the mass of our sun to tens of solar masses. And on May 7, 2026, the researchers said they’ve identified two distinct populations of these black holes.

The first population, those less than 45 times the mass of our sun, formed as we’d typically expect: from stars collapsing at the end of their lives. But the second population – those over 45 solar masses – is more mysterious. Astronomers have long suspected that these are too massive to have formed from the collapse of single stars. And the new research helps explain how they’ve come to exist.

The scientists noticed that these larger black holes are spinning faster and in much more varied directions than the smaller ones. They say this is evidence that the larger black holes are the product of black hole collisions in the maelstrom of dense star clusters.

They performed this study using new data from gravitational waves observations. The research team analyzed data from a catalog of observations, called the LIGO–Virgo–KAGRA Gravitational-Wave Transient Catalog version 4 (GWTC4). In it, they found 153 detections of black hole mergers.

Fabio Antonini is the first author of this study. He said, in a statement:

Gravitational wave astronomy is now doing more than counting black hole mergers. It is starting to reveal how black holes grow, where they grow, and what that tells us about the lives and deaths of massive stars. This is exciting because we can use the information to test our understanding of how stars and [star] clusters evolve in the universe.

The team published its findings in the peer-reviewed journal Nature Astronomy on May 7, 2026.

Detecting ripples in spacetime

A black hole first forms when a massive star runs out of fuel for nuclear fusion. As a result, it collapses under its own gravity. The star’s mass becomes so compact that nothing can escape its powerful gravitational force … not even light.

In dense star clusters, two black holes often get close enough to start orbiting each other. As the two objects rotate, they generate a unique pattern of gravitational waves, or ripples in the fabric of the universe. The wave characteristics depend on the mass of each object, as well as their distance and orbit orientation from Earth.

This computer simulation shows the merger of 2 black holes. As the black holes spiral toward each other, collide and merge, they create gravitational waves. Scientists made this simulation using equations from Albert Einstein’s theory of general relativity and data from the Laser Interferometer Gravitational-wave Observatory (LIGO). Video via the Simulating eXtreme Spacetimes (SXS) project.

Gravitational waves are ripples in the four-dimensional realm where space and time are woven together. They can be detected on Earth by very sensitive instruments called gravitational wave laser interferometers.

The orbiting black hole pair radiates gravitational waves, resulting in some loss of orbital energy. As a result, the black holes get closer. That causes them to orbit each other faster, which radiates even stronger gravitational waves, which makes them get closer, and so on. The final outcome is a violent merger of the two objects.

Gravitational wave laser interferometers are able to detect the final orbits of the black holes just before the merger, which occurs over a timeframe of seconds.

Two populations of black holes

The scientists analyzed 153 black hole mergers in the LIGO–Virgo–KAGRA’s Gravitational-Wave Transient Catalog version 4. This catalog is a compilation of all gravitational wave detections from May 2023 to January 2024.

They noticed two distinct populations of stellar black holes. Isobel Romero-Shaw, also of Cardiff University, said:

What surprised us most was how clearly the high mass black holes [over 45 solar masses] stand out as a separate population.

Unlike the lower mass systems we analyzed, which were generally slowly-spinning, the higher mass systems are consistent with having more rapid spins, oriented in seemingly random directions. This is the exact signature you would expect if black holes were repeatedly merging in dense star clusters.

Messier 80 is a dense globular star cluster, about 28,000 light-years away, in the constellation Scorpius the Scorpion. The new study suggests that huge stellar-mass black holes form via chaotic collisions between multiple smaller black holes in dense star clusters like this. Image via NASA, ESA, G. Piotto, and G. Kober.

The pair-instability mass gap

There’s a theory in stellar evolution called the pair-instability mass gap. It states that stars above a certain mass limit will violently explode, rather than becoming a black hole. In their study, the team established that this limit was 45 solar masses. Therefore, any star over that value would explode at the end of its lifetime.

According to this theory, a collapsing star wouldn’t be able to form a black hole over 45 solar masses. However, gravitational wave detections have shown that stellar-mass black holes over this threshold do indeed exist.

Antonini said:

In our study we find evidence for the long-predicted pair-instability mass gap — a range of masses where stars are not expected to leave behind black holes at all. Gravitational wave detectors have successfully found black holes that appear to sit in or near that gap, which we identify at around 45 solar masses.

So how did these huge black holes form? The answer, Antonini says, lies in their spin:

The biggest black holes in the current sample seem to be telling us about [star] cluster dynamics, not just stellar evolution. Above about 45 solar masses the [black hole] spin distribution changes in a way that is hard to explain with normal stellar binaries alone but is naturally explained if these black holes have already been through earlier mergers in dense [star] clusters.

So the smaller black holes have similar spins, having formed from a population of similar stars. But when the black holes cross this 45-solar-mass line, they start to show a wide range of different spin speeds and orientations. The researchers think this erratic spinning is a sign that the large black holes have been through a series of violent collisions and mergers.

How gravitational wave laser interferometers work

If you threw two stones into a pond, each stone creates concentric ripples. The sections where the ripples intersect are called interference patterns. Gravitational wave laser interferometers look for laser beam interference patterns caused by gravitational waves.

A gravitational wave observatory has two long, perpendicular arms. For instance, at the LIGO observatories in Washington and Louisiana, each arm is 2.5 miles (4 km) long. A laser beam is split to shine along each arm. At the end of the arm, a mirror reflects the beam back and the two beams meet to form an interference pattern.

When gravitational waves pass through, spacetime itself oscillates. As a result, each wave stretches one arm and compresses the other. Therefore, the lasers move through slightly different lengths. The resulting interference patterns reveal information about the objects that generated the gravitational waves. This instrument is so sensitive that it can detect an arm length difference that’s 1/10,000th the width of a proton.

A brief animation showing the basic operation of the LIGO interferometer. Video via LIGO/ Einstein’s Messengers/ NSF.

Besides LIGO, there are two other gravitational wave observatories: the Virgo interferometer in Italy and the Kamioka Gravitational Wave Detector (KAGRA) in Japan. Ideally, all three observatories should detect a gravitational wave event to confirm it.

Bottom line: A new study suggests the largest stellar-mass black holes form not from single stars collapsing, but from collisions and mergers between smaller black holes.

Source: Gravitational-wave constraints on the pair-instability mass gap and nuclear burning in massive stars

Via Cardiff University

Read more: Gravitational waves discoveries surge in new catalog

The post Built not born: Huge black holes form in mergers, study says first appeared on EarthSky.

from EarthSky https://ift.tt/Mub6PLJ

Polaris is the present-day North Star of Earth

View at EarthSky Community Photos. | Eddie Little of North Carolina captured the stars circling around Polaris, the North Star, on January 2, 2025, and wrote: “I had a mostly cloudless, nearly moonless night on one of the longest nights of the year. Approximately 12 hours of shooting.” Thank you, Eddie!

Polaris is the North Star

The North Star or Pole Star – aka Polaris – is famous for holding nearly still in our sky while the entire northern sky moves around it. That’s because it’s located very close to the north celestial pole: the point around which the entire northern sky turns.

Polaris is not the brightest star in the nighttime sky, despite the common belief. In fact, it’s only the 47th brightest star. But you can find it easily, and, once you do, you’ll see it shining in the northern sky every night from Northern Hemisphere locations.

Polaris marks the spot that is due north. As you face Polaris and stretch your arms sideways, your right hand points due east, and your left hand points due west. Then, an about-face from Polaris steers you due south.

Star trails shown circling around Polaris, the North Star. Image via Good Free Photos/ Unsplash.

A star to steer by

In a dark country sky, even when the full moon obscures a good deal of the starry heavens, the North Star is relatively easy to see. That fact has made this star a boon to travelers throughout the Northern Hemisphere, both over land and sea. So finding Polaris means you know the direction north.

Best of all, you can readily find Polaris by using the prominent group of stars known as the Big Dipper, called the Plough in the United Kingdom, which may be the Northern Hemisphere’s most famous star pattern. To locate Polaris, all you have to do is to find the Big Dipper pointer stars Dubhe and Merak. These two stars outline the outer part of the Big Dipper’s bowl. Simply draw a line from Merak through Dubhe, and go about five times the Merak/Dubhe distance to Polaris.

If you can find the Big Dipper, you can find Polaris. The 2 outer stars in the bowl of the Dipper – Dubhe and Merak – always point to the North Star. Chart via EarthSky.

This clock runs backward

Polaris marks the center of nature’s grandest celestial clock!

The Big Dipper, like a great big hour hand, goes full circle around Polaris in one day. More specifically, the Big Dipper circles Polaris – in a counterclockwise direction – in 23 hours and 56 minutes. You could set your watch by it!

Although the Big Dipper travels around Polaris all night long, the Big Dipper pointer stars always point to Polaris at any time of the night, and on any day of the year.

It’s part of the Little Dipper

Polaris is also famous for marking the end of the Little Dipper‘s handle. The Little Dipper is tougher to spot in the night sky than the Big Dipper. But if you use the Big Dipper’s pointer stars to locate Polaris, you’ll be one step closer to seeing the Little Dipper.

The Big Dipper leads you to the Little Dipper. Polaris marks the end of the handle of the Little Dipper. Chart via EarthSky.

Its height in the sky depends on your location

As you travel northward, Polaris climbs higher in the sky. If you go as far north as the North Pole, you’ll see Polaris directly overhead.

As you travel south, Polaris drops closer to the northern horizon.

If you get as far as the equator, Polaris sinks to the horizon.

South of the equator, Polaris drops below the northern horizon.

Trusting Polaris with their lives

At one time in human history, people literally depended on their lucky stars for their lives and livelihood. Luckily, they could trust the Big Dipper and the North Star to guide them. People could sail the seas and cross the trackless deserts without getting lost. When slavery existed in the United States, people escaping slavery counted on the Big Dipper to show them the North Star, lighting their way to the free states and Canada.

While being honored as the North Star, Polaris enjoys the title of Lodestar and Cynosure as well.

What if you’re in the Southern Hemisphere?

Via Daniel Gaussen, Founder & Guide – Stargaze Mackenzie – New Zealand

Stargazers in the Southern Hemisphere can’t use Polaris to find the direction north. That’s because – as seen from Earth’s equator, and southward – this northernmost, moderately bright star remains permanently below the northern horizon. Instead, to find the south celestial pole, we rely on the distinctive Southern Cross.

By extending an imaginary line through the Southern Cross’ two pointer stars, Alpha and Beta Centauri, and drawing a triangle with the cross, we can locate the South Celestial Pole. This point in the sky acts like a pole star, guiding us in our navigation.

But wait, is there no pole star in the South?

Well, technically yes, there is a southern pole star: Sigma Octantis. Sometimes called Polaris Australis, this star is in the Octans constellation. It lies approximately 1 degree away from the south celestial pole.

Sigma Octantis is around 4.4 times the radius of the sun and radiates roughly 44 times more energy. Yet despite its impressive size and luminosity, its distance of 294 light-years means it appears extremely faint from Earth. It glows at just magnitude 5.5, making it visible only under dark skies and to observers with keen eyesight.

As a result, for many centuries, both European navigators and Polynesian sailors have had to rely on the Southern Cross to guide them across oceans. Like Polaris in the north, the Southern Cross and its pointer stars are circumpolar for much of the southern hemisphere, meaning they never set below the horizon and can be seen year-round.

Today, the Southern Cross proudly adorns the New Zealand and Australian national flag, a testament to its enduring importance as a celestial compass and a beacon for navigation.

History of Polaris

Polaris hasn’t always been the North Star and won’t remain the North Star forever. For example, a famous star called Thuban, in the constellation Draco the Dragon, was the North Star when the Egyptians built the pyramids.

But Polaris is a good North Star because it’s the sky’s 48th brightest star. So it’s noticeable in the sky. It served well as the North Star, for example, when the Europeans first sailed across the Atlantic over five centuries ago.

And Polaris will continue its reign as the North Star for many centuries to come. It will align most closely with the north celestial pole – the point in the sky directly above Earth’s north rotational axis – on March 24, 2100. The computational wizard Jean Meeus figures Polaris will be 27′ 09″ (0.4525 degrees) from the north celestial pole at that time (a little less than the angular diameter of the moon when at its farthest from Earth).

Meanwhile, there is currently no visible star marking the celestial pole in the Southern Hemisphere. What’s more, the Southern Hemisphere won’t see a pole star appreciably close to the south celestial pole for another 2,000 years.

Polaris is a triple star

The single point of light that we see as Polaris is a triple star system, or three stars orbiting a common center of mass. The primary star, Polaris A, is a supergiant with about six times the mass of our sun. A close companion, Polaris Ab, orbits 2 billion miles (3.2 billion km) from Polaris. You are unlikely to ever see this star, because it is very close to Polaris.

Much farther away, near the top of this illustration, is the third companion, Polaris B. Polaris B, with magnitude 8.7, is located approximately 240 billion miles (390 billion km) from Polaris A. This translates to 18.4 arcseconds, and you can discern – split – these two stars in a small telescope. This split is always a hit at public star parties. The two companion stars have the same temperature as Polaris A but are dwarf stars.

Artist’s concept of Polaris and its two known companion stars. Image via NASA/ Wikimedia Commons.

Star bright, star light

Astronomers estimate Polaris’ distance at 434 light-years. Considering the distance, Polaris must be a respectably luminous star. Polaris is a yellow supergiant star shining with the luminosity of 1,260 suns.

And it varies in brightness, too!

Polaris is a variable star. In the past, it had varied between magnitudes 1.86 and 2.13 every four days. In recent decades, this variability decreased from 10% to 2%, then it went back up to 4% variability. Astronomers are not sure why this happened. It’s the type of variable star known as a Cepheid variable star, a class of stars that astronomers use to figure distances to star clusters and galaxies.

Seeing Polaris in a telescope during the day

Since Polaris hardly moves, this makes it easy to see in the daytime. Set your telescope on Polaris in the early morning, before dawn. Focus sharply on it. Turn off your clock drive, if you have one, and keep your telescope stationary. Come back just after sunrise and look for it again. It should still be in your field of view, having moved about 30 arcminutes in the past three hours.

What’s the RA today?

In the year 2000, Polaris’ position was RA: 2h 31m 48.7s, dec: +89° 15′ 51″. Due to precession, since this star is so close to the celestial north pole, its Right Ascension (RA) can change quickly. Presently it is sitting at about 03h 00m. Here is a graph showing how the RA of the star changes over the next century.

The right ascension of Polaris for the next century. Graph by Don Machholz using data from Stub Mandrel.

The view of Polaris you will never see: the Integrated Flux Nebula

Just when you think you have seen it all … maybe you have. Because this next bit will blow your mind, and you will never visually see it. Below we see an image of Polaris, which is several images stacked to bring out the contrast. Those are not clouds in our atmosphere. They are not clouds between us and Polaris. They are clouds well beyond Polaris, illuminated by the light of our galaxy. These clouds are called the Integrated Flux Nebula.

An example of the faint integrated flux nebula around the star Polaris. Image via Kush Chandaria/ Wikipedia (CC BY-SA 4.0).

Bottom line: Polaris is the North Star, and the entire northern sky wheels around it. But it’s not the brightest star in the sky. In fact, Polaris ranks only 48th in brightness.

Read more: Does Mars have a North Star?

Read more: Does the North Star ever move?

The post Polaris is the present-day North Star of Earth first appeared on EarthSky.

from EarthSky https://ift.tt/wPuTiSd

View at EarthSky Community Photos. | Eddie Little of North Carolina captured the stars circling around Polaris, the North Star, on January 2, 2025, and wrote: “I had a mostly cloudless, nearly moonless night on one of the longest nights of the year. Approximately 12 hours of shooting.” Thank you, Eddie!

Polaris is the North Star

The North Star or Pole Star – aka Polaris – is famous for holding nearly still in our sky while the entire northern sky moves around it. That’s because it’s located very close to the north celestial pole: the point around which the entire northern sky turns.

Polaris is not the brightest star in the nighttime sky, despite the common belief. In fact, it’s only the 47th brightest star. But you can find it easily, and, once you do, you’ll see it shining in the northern sky every night from Northern Hemisphere locations.

Polaris marks the spot that is due north. As you face Polaris and stretch your arms sideways, your right hand points due east, and your left hand points due west. Then, an about-face from Polaris steers you due south.

Star trails shown circling around Polaris, the North Star. Image via Good Free Photos/ Unsplash.

A star to steer by

In a dark country sky, even when the full moon obscures a good deal of the starry heavens, the North Star is relatively easy to see. That fact has made this star a boon to travelers throughout the Northern Hemisphere, both over land and sea. So finding Polaris means you know the direction north.

Best of all, you can readily find Polaris by using the prominent group of stars known as the Big Dipper, called the Plough in the United Kingdom, which may be the Northern Hemisphere’s most famous star pattern. To locate Polaris, all you have to do is to find the Big Dipper pointer stars Dubhe and Merak. These two stars outline the outer part of the Big Dipper’s bowl. Simply draw a line from Merak through Dubhe, and go about five times the Merak/Dubhe distance to Polaris.

If you can find the Big Dipper, you can find Polaris. The 2 outer stars in the bowl of the Dipper – Dubhe and Merak – always point to the North Star. Chart via EarthSky.

This clock runs backward

Polaris marks the center of nature’s grandest celestial clock!

The Big Dipper, like a great big hour hand, goes full circle around Polaris in one day. More specifically, the Big Dipper circles Polaris – in a counterclockwise direction – in 23 hours and 56 minutes. You could set your watch by it!

Although the Big Dipper travels around Polaris all night long, the Big Dipper pointer stars always point to Polaris at any time of the night, and on any day of the year.

It’s part of the Little Dipper

Polaris is also famous for marking the end of the Little Dipper‘s handle. The Little Dipper is tougher to spot in the night sky than the Big Dipper. But if you use the Big Dipper’s pointer stars to locate Polaris, you’ll be one step closer to seeing the Little Dipper.

The Big Dipper leads you to the Little Dipper. Polaris marks the end of the handle of the Little Dipper. Chart via EarthSky.

Its height in the sky depends on your location

As you travel northward, Polaris climbs higher in the sky. If you go as far north as the North Pole, you’ll see Polaris directly overhead.

As you travel south, Polaris drops closer to the northern horizon.

If you get as far as the equator, Polaris sinks to the horizon.

South of the equator, Polaris drops below the northern horizon.

Trusting Polaris with their lives

At one time in human history, people literally depended on their lucky stars for their lives and livelihood. Luckily, they could trust the Big Dipper and the North Star to guide them. People could sail the seas and cross the trackless deserts without getting lost. When slavery existed in the United States, people escaping slavery counted on the Big Dipper to show them the North Star, lighting their way to the free states and Canada.

While being honored as the North Star, Polaris enjoys the title of Lodestar and Cynosure as well.

What if you’re in the Southern Hemisphere?

Via Daniel Gaussen, Founder & Guide – Stargaze Mackenzie – New Zealand

Stargazers in the Southern Hemisphere can’t use Polaris to find the direction north. That’s because – as seen from Earth’s equator, and southward – this northernmost, moderately bright star remains permanently below the northern horizon. Instead, to find the south celestial pole, we rely on the distinctive Southern Cross.

By extending an imaginary line through the Southern Cross’ two pointer stars, Alpha and Beta Centauri, and drawing a triangle with the cross, we can locate the South Celestial Pole. This point in the sky acts like a pole star, guiding us in our navigation.

But wait, is there no pole star in the South?

Well, technically yes, there is a southern pole star: Sigma Octantis. Sometimes called Polaris Australis, this star is in the Octans constellation. It lies approximately 1 degree away from the south celestial pole.

Sigma Octantis is around 4.4 times the radius of the sun and radiates roughly 44 times more energy. Yet despite its impressive size and luminosity, its distance of 294 light-years means it appears extremely faint from Earth. It glows at just magnitude 5.5, making it visible only under dark skies and to observers with keen eyesight.

As a result, for many centuries, both European navigators and Polynesian sailors have had to rely on the Southern Cross to guide them across oceans. Like Polaris in the north, the Southern Cross and its pointer stars are circumpolar for much of the southern hemisphere, meaning they never set below the horizon and can be seen year-round.

Today, the Southern Cross proudly adorns the New Zealand and Australian national flag, a testament to its enduring importance as a celestial compass and a beacon for navigation.

History of Polaris

Polaris hasn’t always been the North Star and won’t remain the North Star forever. For example, a famous star called Thuban, in the constellation Draco the Dragon, was the North Star when the Egyptians built the pyramids.

But Polaris is a good North Star because it’s the sky’s 48th brightest star. So it’s noticeable in the sky. It served well as the North Star, for example, when the Europeans first sailed across the Atlantic over five centuries ago.

And Polaris will continue its reign as the North Star for many centuries to come. It will align most closely with the north celestial pole – the point in the sky directly above Earth’s north rotational axis – on March 24, 2100. The computational wizard Jean Meeus figures Polaris will be 27′ 09″ (0.4525 degrees) from the north celestial pole at that time (a little less than the angular diameter of the moon when at its farthest from Earth).

Meanwhile, there is currently no visible star marking the celestial pole in the Southern Hemisphere. What’s more, the Southern Hemisphere won’t see a pole star appreciably close to the south celestial pole for another 2,000 years.

Polaris is a triple star

The single point of light that we see as Polaris is a triple star system, or three stars orbiting a common center of mass. The primary star, Polaris A, is a supergiant with about six times the mass of our sun. A close companion, Polaris Ab, orbits 2 billion miles (3.2 billion km) from Polaris. You are unlikely to ever see this star, because it is very close to Polaris.

Much farther away, near the top of this illustration, is the third companion, Polaris B. Polaris B, with magnitude 8.7, is located approximately 240 billion miles (390 billion km) from Polaris A. This translates to 18.4 arcseconds, and you can discern – split – these two stars in a small telescope. This split is always a hit at public star parties. The two companion stars have the same temperature as Polaris A but are dwarf stars.

Artist’s concept of Polaris and its two known companion stars. Image via NASA/ Wikimedia Commons.

Star bright, star light

Astronomers estimate Polaris’ distance at 434 light-years. Considering the distance, Polaris must be a respectably luminous star. Polaris is a yellow supergiant star shining with the luminosity of 1,260 suns.

And it varies in brightness, too!

Polaris is a variable star. In the past, it had varied between magnitudes 1.86 and 2.13 every four days. In recent decades, this variability decreased from 10% to 2%, then it went back up to 4% variability. Astronomers are not sure why this happened. It’s the type of variable star known as a Cepheid variable star, a class of stars that astronomers use to figure distances to star clusters and galaxies.

Seeing Polaris in a telescope during the day

Since Polaris hardly moves, this makes it easy to see in the daytime. Set your telescope on Polaris in the early morning, before dawn. Focus sharply on it. Turn off your clock drive, if you have one, and keep your telescope stationary. Come back just after sunrise and look for it again. It should still be in your field of view, having moved about 30 arcminutes in the past three hours.

What’s the RA today?

In the year 2000, Polaris’ position was RA: 2h 31m 48.7s, dec: +89° 15′ 51″. Due to precession, since this star is so close to the celestial north pole, its Right Ascension (RA) can change quickly. Presently it is sitting at about 03h 00m. Here is a graph showing how the RA of the star changes over the next century.

The right ascension of Polaris for the next century. Graph by Don Machholz using data from Stub Mandrel.

The view of Polaris you will never see: the Integrated Flux Nebula

Just when you think you have seen it all … maybe you have. Because this next bit will blow your mind, and you will never visually see it. Below we see an image of Polaris, which is several images stacked to bring out the contrast. Those are not clouds in our atmosphere. They are not clouds between us and Polaris. They are clouds well beyond Polaris, illuminated by the light of our galaxy. These clouds are called the Integrated Flux Nebula.

An example of the faint integrated flux nebula around the star Polaris. Image via Kush Chandaria/ Wikipedia (CC BY-SA 4.0).

Bottom line: Polaris is the North Star, and the entire northern sky wheels around it. But it’s not the brightest star in the sky. In fact, Polaris ranks only 48th in brightness.

Read more: Does Mars have a North Star?

Read more: Does the North Star ever move?

The post Polaris is the present-day North Star of Earth first appeared on EarthSky.

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Vega is a bright bluish star on May evenings

The 3 brightest stars in this image make up the asterism of the Summer Triangle, a giant triangle in the sky composed of the bright stars Vega (top left), Altair (lower middle) and Deneb (far left). Also in this image, under a dark sky and on a moonless night, is the Great Rift that passes right through the Summer Triangle. Image via NASA/ A. Fujii/ ESA.

Vega shines brightly on May evenings

Look for Vega tonight. It’s the 5th brightest star in our sky. If you’re in the Northern Hemisphere, you’ll find beautiful, bluish Vega easily, simply by looking northeastward at mid-evening in May. Vega is so bright that you can see it on a moonlit night.

From far south in the Southern Hemisphere, you’ll see Vega late at night in May. That’s because Vega is located so far north on the sky’s dome. Vega will reach its high point for the night around three to four hours after midnight, at which time people in the Southern Hemisphere can see Vega in their northern sky. As seen from mid-northern latitudes, Vega shines high overhead at this early morning hour.

Because it’s the brightest star in the constellation Lyra the Harp, Vega is sometimes called the Harp Star. Like all stars, Vega rises some four minutes earlier each day as Earth moves around the sun. So, Vega will adorn our evening sky throughout the summer and fall.

And it’s also part of the Summer Triangle. That’s an asterism made of the three bright stars Vega, Altair and Deneb.

Vega is visible most nights from mid-northern latitudes

Although Vega is considered a late spring or summer star, it’s so far north on the sky’s dome that – from mid-latitudes in the Northern Hemisphere – you can find it at some time during the night, nearly every night of the year.

Observers in the Northern Hemisphere typically begin noticing Vega in the evening around May, when this star comes into view in the northeast in mid-evening. Throughout northern summer, Vega shines brightly in the east in the evening. It’s high overhead on northern autumn evenings, and in the northwest by December evenings.

Here’s Vega (and Lyra) as seen around 3 a.m. from Valencia, Philippines, in early May, from our friend Dr Ski. See Vega’s beautiful blue color? Notice the star near Vega, marked with the Greek letter Epsilon. This star is Epsilon Lyrae, a famous double-double star.

A northern beacon from southern skies

Via Daniel Gaussen, Founder & Guide – Stargaze Mackenzie – New Zealand

From the Southern Hemisphere, Vega remains a low northern star. It never climbs high above the horizon, reaching a maximum altitude of only about 15° as seen from New Zealand. From these latitudes, Vega’s entire passage across the sky – from rising to setting – takes only about four hours!

In May evenings it is not yet a prominent evening star. Instead, it appears in the early morning hours and gradually climbs toward its best altitude before dawn. As the months progress through winter, Vega shifts into more convenient evening viewing, and by August through September it reaches its highest point in the evening, becoming a clear bluish presence above the northern horizon.

Because Vega stays low in southern skies, it is more strongly affected by atmospheric dimming and color distortion than it is for northern observers, often appearing less sharp in a telescope and more noticeably twinkling to the naked eye.

Yet even from far southern latitudes, Vega’s brilliance makes it easy to identify. It remains one of the brightest northern stars visible from the south, with its blue-white light providing a useful and easily recognisable reference point for orienting the northern sky.

Bottom line: If you’re in the Northern Hemisphere, Vega is easy to identify in its constellation Lyra at this time of year. Just look northeast in the evening hours for a bright, bluish star above the northeastern horizon.

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

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The 3 brightest stars in this image make up the asterism of the Summer Triangle, a giant triangle in the sky composed of the bright stars Vega (top left), Altair (lower middle) and Deneb (far left). Also in this image, under a dark sky and on a moonless night, is the Great Rift that passes right through the Summer Triangle. Image via NASA/ A. Fujii/ ESA.

Vega shines brightly on May evenings

Look for Vega tonight. It’s the 5th brightest star in our sky. If you’re in the Northern Hemisphere, you’ll find beautiful, bluish Vega easily, simply by looking northeastward at mid-evening in May. Vega is so bright that you can see it on a moonlit night.

From far south in the Southern Hemisphere, you’ll see Vega late at night in May. That’s because Vega is located so far north on the sky’s dome. Vega will reach its high point for the night around three to four hours after midnight, at which time people in the Southern Hemisphere can see Vega in their northern sky. As seen from mid-northern latitudes, Vega shines high overhead at this early morning hour.

Because it’s the brightest star in the constellation Lyra the Harp, Vega is sometimes called the Harp Star. Like all stars, Vega rises some four minutes earlier each day as Earth moves around the sun. So, Vega will adorn our evening sky throughout the summer and fall.

And it’s also part of the Summer Triangle. That’s an asterism made of the three bright stars Vega, Altair and Deneb.

Vega is visible most nights from mid-northern latitudes

Although Vega is considered a late spring or summer star, it’s so far north on the sky’s dome that – from mid-latitudes in the Northern Hemisphere – you can find it at some time during the night, nearly every night of the year.

Observers in the Northern Hemisphere typically begin noticing Vega in the evening around May, when this star comes into view in the northeast in mid-evening. Throughout northern summer, Vega shines brightly in the east in the evening. It’s high overhead on northern autumn evenings, and in the northwest by December evenings.

Here’s Vega (and Lyra) as seen around 3 a.m. from Valencia, Philippines, in early May, from our friend Dr Ski. See Vega’s beautiful blue color? Notice the star near Vega, marked with the Greek letter Epsilon. This star is Epsilon Lyrae, a famous double-double star.

A northern beacon from southern skies

Via Daniel Gaussen, Founder & Guide – Stargaze Mackenzie – New Zealand

From the Southern Hemisphere, Vega remains a low northern star. It never climbs high above the horizon, reaching a maximum altitude of only about 15° as seen from New Zealand. From these latitudes, Vega’s entire passage across the sky – from rising to setting – takes only about four hours!

In May evenings it is not yet a prominent evening star. Instead, it appears in the early morning hours and gradually climbs toward its best altitude before dawn. As the months progress through winter, Vega shifts into more convenient evening viewing, and by August through September it reaches its highest point in the evening, becoming a clear bluish presence above the northern horizon.

Because Vega stays low in southern skies, it is more strongly affected by atmospheric dimming and color distortion than it is for northern observers, often appearing less sharp in a telescope and more noticeably twinkling to the naked eye.

Yet even from far southern latitudes, Vega’s brilliance makes it easy to identify. It remains one of the brightest northern stars visible from the south, with its blue-white light providing a useful and easily recognisable reference point for orienting the northern sky.

Bottom line: If you’re in the Northern Hemisphere, Vega is easy to identify in its constellation Lyra at this time of year. Just look northeast in the evening hours for a bright, bluish star above the northeastern horizon.

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

The post Vega is a bright bluish star on May evenings first appeared on EarthSky.

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Pentagon UFO files released: Views from the moon and more

View larger. | A UAP – Unidentified Anomalous Phenomenon – from the 1969 Apollo 12 mission to the moon. The triangle of faint bluish “lights” is on the far right, highlighted in the larger square. It’s interesting. But other random colorful dots in images, even at the edges of the film, suggest it might just be an anomaly or blemish in the film used for the photos. This is just one of the 162 Pentagon UFO files released on May 8, 2026. Image via NASA/ US government.

• The U.S. Pentagon released its 1st batch of UAP files to the public. UAP stands for Unidentified Anomalous (formerly Aerial) Phenomena.
• There are 162 files in total, including 12 from NASA. The NASA ones are from Apollo 12, Apollo 17 and Gemini 7. They were already in the public domain.
• The file release is expected to be the first of several rollouts in the coming weeks.

You deserve a daily dose of good news. For the latest in science and the night sky, click here to subscribe to our free daily newsletter.

1st batch of Pentagon UFO files released

For the past few months, there were rumors and hints on social media that the U.S. government was about to start releasing information on UAP (still known by many as UFOs). On May 8, 2026, the first public records were released. The Pentagon unveiled its new website called PURSUE (Presidential Unsealing and Reporting System for UAP Encounters). This batch of info is said to be the first batch of more to come in rolling releases over the next weeks. So what does it show?

In this first batch, there are 162 records in total. They consists of 120 PDF documents, 28 videos and 14 images. Eighty-two of the total came from the Pentagon, 56 from the FBI, 12 from NASA, eight from the State Department and four with the agency not identified.

You can find all the documents, videos and images at War.gov/UFO.

You can also keep track of these files and future ones, which are better organized, at UFO Release Tracker and Pentagon UAP Files.

New Pentagon UFO files include reports from moon landings trib.al/DJBprKC

— Task & Purpose (@taskandpurpose.com) 2026-05-08T18:45:07.649633Z

Details on Pentagon UFO files

This first batch of records contains a wide range of documents, videos and images. They are split between older historical records and modern-day reports. The historical files, largely from the 1940s to 1960s, are FBI files, NASA transcripts and photos, State Department cables and Cold War-era UFO reports. The modern reports come from AARO (military reports), still imagery from U.S. military systems, 302 FBI interviews and a 2023 Western U.S. event summary.

But much of the material has already been in the public realm for years, even decades. So those items are not actually newly declassified.

The documents include the famous “Twining Memo” from 1947, in which General Nathan Twining stated:

The phenomenon reported is something real and not visionary or fictitious. There are objects probably approximating the shape of a disc, of such appreciable size as to appear to be as large as man-made.

The full memo can also be seen here (three images).

And, as seems to be typical for the Trump administration, some of the documents are still largely redacted even though they are “released.” For example, one document contains the rather cryptic sentence “2X round white white hot UAPS dynamic south” after six pages that have been completely blacked out.

View larger. | Another image from Apollo 12, showing multiple bright and fainter spots in the black sky. Image via NASA/ US government.

Apollo 11, 12 and 17

The files contain some of the old NASA UAP reports. Apollo 11, 12 and 17, as well as Gemini 7, are in there. The public has known about these cases for decades. But it is interesting to see them included. And there are other NASA cases as well, but not included in this file dump. Perhaps in a subsequent one?

For example, from the included files, the Technical Crew Briefing for Apollo 11 records an object on the way out to the moon, flashes of light inside the astronauts’ cabin and a sighting on the return trip of a bright light tentatively assumed by the crew to be a laser.

And images taken from the lunar surface during Apollo 12 show several faint but colorful dots or lights in the black sky. These include a tight formation of three lights in a triangle (shown at top). It is still not known what the origin of these were, although most analysts think they were likely anomalies/blemishes in the film used at the time.

The Apollo 17 sighting took place out in space. All crew members, including Commander Eugene Cernan, saw a “flashing object” estimated to be several miles from their capsule, as well as closer “particles.” As Cernan told Mission Control at the time:

It’s way out in the distance, as I say, because there are particles that are close by and it’s obviously not one of those. It’s apparently rotating in a very rhythmic fashion because the flashes come round almost … almost on time.

Gemini 7

In addition, the original audio of the Gemini 7 sighting in in the files. too. That’s the one where astronaut Frank Borman said:

We have a bogey at 10 o’clock high … This is an actual sighting … very many A … it looks like hundreds of little particles.

Both Borman and astronaut Jim Lovell thought they were looking at debris from the mission itself, which is common. But whether that included the “bogey” is debated to this today. Sadly, both astronauts have now passed away.

Skylab

There is also the Technical Crew Debriefing from Skylab in 1973. It mentions crew observations of flashing lights outside of the Skylab space station.

Pentagon releases swath of UFO files

— Politico (@politico.com) 2026-05-08T14:06:11Z

COMETA

Also in the files is the French COMETA report “UFOs and Defense: What Should We Prepare For?” It was originally published in July 1999. It details a lengthy study of UAP by the French Institute of Higher Studies for National Defence.

COMETA consisted of former military and defense officials and experts in France. The report concluded that there was an “almost certain physical reality” of completely unknown flying objects displaying extraordinary capabilities that current science could not explain. And it even went as far to say that the extraterrestrial hypothesis for UAP was a “probable or credible explanation.” This was based on the roughly 5% of cases that were documented with radar data, etc., but still difficult to explain. In fact, that number is similar to other studies, including from AARO.

It was not widely circulated at the time due to copyright restrictions. But it was finally made public in 2007 by GEIPAN. GEIPAN is a unit of the National Space Centre (CNES) in France.

View larger. | Composite sketch from the FBI of a report from 2023. Image via US goverment.

Other videos in Pentagon UFO files

There are 28 videos together, mostly from various U.S. military stations or surveillance missions. One of the most interesting is this one from the Indo-Pacific Command in 2024. It shows a small, bright object quickly moving around numerous wind turbines, flying close to the water. The video was taken by an infrared sensor. Download the higher-resolution version here:

Video of a UAP from the Indo-Pacific Command

Bottom line: On May 8, 2026, the U.S. Pentagon released its first batch of Pentagon UFO files. They include some from Apollo moon missions 11, 12 and 17.

Via U.S. Pentagon

Via Task & Purpose

Read more: UAP and science: Testing new methods of scientific analysis

Read more: New UAP study: This one is from NASA

The post Pentagon UFO files released: Views from the moon and more first appeared on EarthSky.

from EarthSky https://ift.tt/By3HPnM

View larger. | A UAP – Unidentified Anomalous Phenomenon – from the 1969 Apollo 12 mission to the moon. The triangle of faint bluish “lights” is on the far right, highlighted in the larger square. It’s interesting. But other random colorful dots in images, even at the edges of the film, suggest it might just be an anomaly or blemish in the film used for the photos. This is just one of the 162 Pentagon UFO files released on May 8, 2026. Image via NASA/ US government.

• The U.S. Pentagon released its 1st batch of UAP files to the public. UAP stands for Unidentified Anomalous (formerly Aerial) Phenomena.
• There are 162 files in total, including 12 from NASA. The NASA ones are from Apollo 12, Apollo 17 and Gemini 7. They were already in the public domain.
• The file release is expected to be the first of several rollouts in the coming weeks.

You deserve a daily dose of good news. For the latest in science and the night sky, click here to subscribe to our free daily newsletter.

1st batch of Pentagon UFO files released

For the past few months, there were rumors and hints on social media that the U.S. government was about to start releasing information on UAP (still known by many as UFOs). On May 8, 2026, the first public records were released. The Pentagon unveiled its new website called PURSUE (Presidential Unsealing and Reporting System for UAP Encounters). This batch of info is said to be the first batch of more to come in rolling releases over the next weeks. So what does it show?

In this first batch, there are 162 records in total. They consists of 120 PDF documents, 28 videos and 14 images. Eighty-two of the total came from the Pentagon, 56 from the FBI, 12 from NASA, eight from the State Department and four with the agency not identified.

You can find all the documents, videos and images at War.gov/UFO.

You can also keep track of these files and future ones, which are better organized, at UFO Release Tracker and Pentagon UAP Files.

New Pentagon UFO files include reports from moon landings trib.al/DJBprKC

— Task & Purpose (@taskandpurpose.com) 2026-05-08T18:45:07.649633Z

Details on Pentagon UFO files

This first batch of records contains a wide range of documents, videos and images. They are split between older historical records and modern-day reports. The historical files, largely from the 1940s to 1960s, are FBI files, NASA transcripts and photos, State Department cables and Cold War-era UFO reports. The modern reports come from AARO (military reports), still imagery from U.S. military systems, 302 FBI interviews and a 2023 Western U.S. event summary.

But much of the material has already been in the public realm for years, even decades. So those items are not actually newly declassified.

The documents include the famous “Twining Memo” from 1947, in which General Nathan Twining stated:

The phenomenon reported is something real and not visionary or fictitious. There are objects probably approximating the shape of a disc, of such appreciable size as to appear to be as large as man-made.

The full memo can also be seen here (three images).

And, as seems to be typical for the Trump administration, some of the documents are still largely redacted even though they are “released.” For example, one document contains the rather cryptic sentence “2X round white white hot UAPS dynamic south” after six pages that have been completely blacked out.

View larger. | Another image from Apollo 12, showing multiple bright and fainter spots in the black sky. Image via NASA/ US government.

Apollo 11, 12 and 17

The files contain some of the old NASA UAP reports. Apollo 11, 12 and 17, as well as Gemini 7, are in there. The public has known about these cases for decades. But it is interesting to see them included. And there are other NASA cases as well, but not included in this file dump. Perhaps in a subsequent one?

For example, from the included files, the Technical Crew Briefing for Apollo 11 records an object on the way out to the moon, flashes of light inside the astronauts’ cabin and a sighting on the return trip of a bright light tentatively assumed by the crew to be a laser.

And images taken from the lunar surface during Apollo 12 show several faint but colorful dots or lights in the black sky. These include a tight formation of three lights in a triangle (shown at top). It is still not known what the origin of these were, although most analysts think they were likely anomalies/blemishes in the film used at the time.

The Apollo 17 sighting took place out in space. All crew members, including Commander Eugene Cernan, saw a “flashing object” estimated to be several miles from their capsule, as well as closer “particles.” As Cernan told Mission Control at the time:

It’s way out in the distance, as I say, because there are particles that are close by and it’s obviously not one of those. It’s apparently rotating in a very rhythmic fashion because the flashes come round almost … almost on time.

Gemini 7

In addition, the original audio of the Gemini 7 sighting in in the files. too. That’s the one where astronaut Frank Borman said:

We have a bogey at 10 o’clock high … This is an actual sighting … very many A … it looks like hundreds of little particles.

Both Borman and astronaut Jim Lovell thought they were looking at debris from the mission itself, which is common. But whether that included the “bogey” is debated to this today. Sadly, both astronauts have now passed away.

Skylab

There is also the Technical Crew Debriefing from Skylab in 1973. It mentions crew observations of flashing lights outside of the Skylab space station.

Pentagon releases swath of UFO files

— Politico (@politico.com) 2026-05-08T14:06:11Z

COMETA

Also in the files is the French COMETA report “UFOs and Defense: What Should We Prepare For?” It was originally published in July 1999. It details a lengthy study of UAP by the French Institute of Higher Studies for National Defence.

COMETA consisted of former military and defense officials and experts in France. The report concluded that there was an “almost certain physical reality” of completely unknown flying objects displaying extraordinary capabilities that current science could not explain. And it even went as far to say that the extraterrestrial hypothesis for UAP was a “probable or credible explanation.” This was based on the roughly 5% of cases that were documented with radar data, etc., but still difficult to explain. In fact, that number is similar to other studies, including from AARO.

It was not widely circulated at the time due to copyright restrictions. But it was finally made public in 2007 by GEIPAN. GEIPAN is a unit of the National Space Centre (CNES) in France.

View larger. | Composite sketch from the FBI of a report from 2023. Image via US goverment.

Other videos in Pentagon UFO files

There are 28 videos together, mostly from various U.S. military stations or surveillance missions. One of the most interesting is this one from the Indo-Pacific Command in 2024. It shows a small, bright object quickly moving around numerous wind turbines, flying close to the water. The video was taken by an infrared sensor. Download the higher-resolution version here:

Video of a UAP from the Indo-Pacific Command

Bottom line: On May 8, 2026, the U.S. Pentagon released its first batch of Pentagon UFO files. They include some from Apollo moon missions 11, 12 and 17.

Via U.S. Pentagon

Via Task & Purpose

Read more: UAP and science: Testing new methods of scientific analysis

Read more: New UAP study: This one is from NASA

The post Pentagon UFO files released: Views from the moon and more first appeared on EarthSky.

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Will the Blaze Star explode in 2026? How to see it

Want to see the Blaze Star go nova in 2026? We do, too! And X marks the spot. Astronomers said an impending nova will give the constellation of the Northern Crown – Corona Borealis – a “new star” that rivals the constellation’s brightest star. But when? When?? Image via Chris Harvey/ Stellarium. Used with permission.

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Come on, Blaze Star! Go nova!

Have you ever heard of the Blaze Star? It’s a star in the constellation Corona Borealis the Northern Crown, called T Corona Borealis (T CrB) or “T Cor Bor.” It was supposed to go nova last year. And we’re still waiting. But when it finally does erupt, it’ll be a once-in-a-lifetime show in our night sky.

The eagerly awaited Blaze Star nova is a real opportunity for keen night sky observers to witness a “new star” in the sky … but only for a few days before it fades away again. The trick will be to locate the right place in the sky now. You’ll be looking for the distinctive, C-shaped constellation Corona Borealis. After you find it, go back outside and find that constellation every so often, so you don’t lose track of it. Then, when you hear the Blaze Star has erupted, you’ll be poised to see something fun!

So keep reading to learn why we’re still waiting on the Blaze Star, and about how you can see when the nova finally does erupt. Once its brightness peaks, the nova should be visible to the unaided eye for several days and just over a week with binoculars before it dims again, possibly for decades.

View at EarthSky Community Photos. | Paul Henkiel of Flagstaff, Arizona, captured this image on April 30, 2024. It’s the easy-to-spot C-shaped constellation Corona Borealis the Northern Crown. The brightest star here is Alphecca, sometimes called the Jewel of the Crown. When the Blaze Star erupts, it’ll be approximately as bright as Alphecca. The Northern Crown will have 2 jewels! Thank you, Paul!

Find Corona Borealis from the Northern Hemisphere

Corona Borealis is almost, but not quite, circumpolar from mid-northern latitudes. So it’s not visible all year round for most northern observers.

Instead, northern spring is the best time to start looking for this easy-to-find constellation. No matter where you are on the globe, the constellation looks like a letter C. It’s ascending in the east on May evenings. No matter where you are, you’ll find Corona Borealis approximately on a line between the bright stars Arcturus and Vega. And Corona Borealis is next to another famous star pattern for those with dark skies. It’s the squarish 4-star pattern of the Keystone in Hercules.

Did you hear those words dark sky? You can see the bright stars Arcturus and Vega from inside cities. But you need a dark sky to pick out the Keystone in Hercules and Corona Borealis. Visit EarthSky’s Best Places to Stargaze.

Ready? Now look east on a May evening to find Corona Borealis rising.

By Northern Hemisphere summer, all of these stars and constellations will be high in your sky. You’ll be looking up, not east, to see them.

Do you need binoculars? No. You don’t need them. But binoculars are always a good idea.

Want an exact view from an exact time or your exact location on the globe? Try Stellarium.

Late at night in the spring, and high overhead during summer months, find the bright stars Vega and Arcturus. The famous squarish pattern of the Keystone in the constellation Hercules is between them. And so is an easy-to-see semicircle of stars, the constellation Corona Borealis. The Blaze Star will erupt within Corona Borealis. It’ll be about as bright as Corona Borealis’ brightest star, Alphecca. Image via NASA.

Find Corona Borealis from the Southern Hemisphere

Via Daniel Gaussen, Founder & Guide – Stargaze Mackenzie – New Zealand

We all live under the same sky. But Earth’s Northern and Southern Hemispheres see the sky from different perspectives.

And remember how we said that Corona Borealis was almost – but not quite – circumpolar? That means it’s far to the north on the sky’s dome. From deep in the Southern Hemisphere – for example, the latitude of New Zealand and southern Australia – Corona Borealis rises to only around 20 to 25 degrees above the northern horizon at its highest. So, in addition to a dark sky, you’ll also want a clear view to the north.

Look north to northeast for a delicate semicircle or backward C shape of stars between the bright orange star Arcturus and the bright blue-white star Vega. The famous Keystone pattern in Hercules is also between these two, right next to Corona Borealis.

Want an exact view from an exact time or your exact location on the globe? Try Stellarium.

Star chart of Corona Borealis with red circle indicating location of star T CrB. Image via IAU/ Wikipedia.

What is the Blaze Star?

T Coronae Borealis – called “T Cor Bor” by many – is located about 3,000 light-years from Earth. It’s a double star system, consisting of a large cool star and a smaller hot star, which orbit each other every 228 days.

This system is what’s called a recurring nova. It’s not a supernova or star that blows itself to bits. Novas operate differently from supernovas. They survive to brighten again. T Cor Bor has outbursts about every 80 years.

Its last outburst was in 1946. That’s why astronomers believe another outburst will occur soon. Will we see it in 2026?

What makes the nova erupt? The cool star in the T Corona Borealis system is a swollen red giant. It continually transfers material to its companion in the system, the hot star. The hot star is a white dwarf, surrounded by an accretion disk made of material transferred over from the other star.

All of this is hidden inside a dense cloud of material from the red giant. When the system is quiescent, the red giant dominates the visible light output of the entire system. So the system appears as an M3 giant.

But during outbursts, the transfer of material from the red giant to the hot white dwarf increases greatly. The hot star then expands. And the luminosity of the system increases. Voila. We have a nova.

The Blaze Star isn’t 1 star but 2. It’s a binary system with a white dwarf and a red giant. The Blaze Star’s white dwarf has built up material on its surface, siphoned off from the red giant star. Periodically, it “can’t take no more” and explodes, about every 80 years. Despite the powerful explosion, the dwarf itself remains intact. And once things settle down, the Blaze Star (T Corona Borealis) will begin the decades-long preparation for future cosmic fireworks. Image via NASA Goddard Scientific Visualization Studio.

Why hasn’t the Blaze Star blazed?

Astronomers have been waiting several years for the Blaze Star to erupt. One recent prediction came from Jean Schneider of the Paris Observatory, publishing in the Research Notes of the American Astronomical Society in October 2024.

He pinpointed possible dates of March 27, 2025, and November 10, 2025. Those dates have come and gone with no big kablooey.

Schneider came to his possible dates using a combination of the previous eruption dates and the orbital ephemeris of the binary system. But Schneider admits in his paper that no one can exactly predict the eruption.

And, clearly, predicting eruptions of stars isn’t an exact science. The Blaze Star (T Coronae Borealis) underwent two known eruptions recorded by astronomers. Those events were on May 12, 1866, and on February 9, 1946. Those eruptions were 80 years apart. So scientists thought that, in another 80 years, the star would erupt again. Eighty years from 1946 would be 2026.

And so we wait …

Artist’s concept of a red giant star and white dwarf star. A stream of material flows from the red giant to the white dwarf, eventually causing a runaway thermonuclear reaction on the white dwarf that will appear as a new star, or nova, in earthly skies. The constellation Corona Borealis the Northern Crown should have a nova appear from the Blaze Star approximately every 80 years. Image via NASA/ Goddard Space Flight Center.

How bright will the Blaze Star be?

How bright will it get in our sky? Astronomers expect it to reach an apparent magnitude of 2. That’s a respectable brightness for a star. It’s conveniently comparable to the brightest star in the Northern Crown, the Jewel of the Crown, Alphecca. So, for a few days, the Northern Crown will have two jewels!

T Corona Borealis – the Blaze Star – is also one of the most distant stars you’ll ever see. Alphecca is around 75 light-years away, while the Blaze Star is closer to 3,000 light-years away.

So that gives you some perspective on the absolute magnitude (brightness) of this enormous blast. The actual explosion of the Blaze Star nova will likely dwarf any explosion you’ll ever see. But the star is far away. This explosion has travelled 3,000 years to get here. So, in relative terms the nova will have happened during the Bronze Age.

Remember that, when viewing Alphecca and T Corona Borealis side-by-side with approximately the same brightness. The nova is 40 times farther away than Alphecca. Also, we are not seeing the two stars at the same moment in time. One we see as it was 75 years ago. And the other we see as it was 3,000 years ago. It can be hard to get your head around that!

The nova will brighten the star by thousands of times, typically over just a few hours, and then take some days to fade away again. When it’s done, it will go back to its normal appearance … which means we won’t be able to see it anymore, with the eye alone.

So erupt already!

Want more? Here’s a highly regarded lecture by one of the world’s experts on the Blaze Star, LSU astronomer Bradley Schaefer. He discusses T CrB’s history, research into its unusual behavior, and the expected details of its imminent eruption. He also detailed specific ways for amateur astronomers to contribute to the study of this historic event, before answering a wide assortment of audience questions. Watch in the player above or on YouTube.

Bottom line: We’re still waiting for the Blaze Star to go nova! Will it happen in 2026? Here’s how to find Corona Borealis so you’re ready when this star goes kablooey.

Source: When will the Next T CrB Eruption Occur?

Read more: Want more details on the Northern Crown? Click here

The post Will the Blaze Star explode in 2026? How to see it first appeared on EarthSky.

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Want to see the Blaze Star go nova in 2026? We do, too! And X marks the spot. Astronomers said an impending nova will give the constellation of the Northern Crown – Corona Borealis – a “new star” that rivals the constellation’s brightest star. But when? When?? Image via Chris Harvey/ Stellarium. Used with permission.

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Come on, Blaze Star! Go nova!

Have you ever heard of the Blaze Star? It’s a star in the constellation Corona Borealis the Northern Crown, called T Corona Borealis (T CrB) or “T Cor Bor.” It was supposed to go nova last year. And we’re still waiting. But when it finally does erupt, it’ll be a once-in-a-lifetime show in our night sky.

The eagerly awaited Blaze Star nova is a real opportunity for keen night sky observers to witness a “new star” in the sky … but only for a few days before it fades away again. The trick will be to locate the right place in the sky now. You’ll be looking for the distinctive, C-shaped constellation Corona Borealis. After you find it, go back outside and find that constellation every so often, so you don’t lose track of it. Then, when you hear the Blaze Star has erupted, you’ll be poised to see something fun!

So keep reading to learn why we’re still waiting on the Blaze Star, and about how you can see when the nova finally does erupt. Once its brightness peaks, the nova should be visible to the unaided eye for several days and just over a week with binoculars before it dims again, possibly for decades.

View at EarthSky Community Photos. | Paul Henkiel of Flagstaff, Arizona, captured this image on April 30, 2024. It’s the easy-to-spot C-shaped constellation Corona Borealis the Northern Crown. The brightest star here is Alphecca, sometimes called the Jewel of the Crown. When the Blaze Star erupts, it’ll be approximately as bright as Alphecca. The Northern Crown will have 2 jewels! Thank you, Paul!

Find Corona Borealis from the Northern Hemisphere

Corona Borealis is almost, but not quite, circumpolar from mid-northern latitudes. So it’s not visible all year round for most northern observers.

Instead, northern spring is the best time to start looking for this easy-to-find constellation. No matter where you are on the globe, the constellation looks like a letter C. It’s ascending in the east on May evenings. No matter where you are, you’ll find Corona Borealis approximately on a line between the bright stars Arcturus and Vega. And Corona Borealis is next to another famous star pattern for those with dark skies. It’s the squarish 4-star pattern of the Keystone in Hercules.

Did you hear those words dark sky? You can see the bright stars Arcturus and Vega from inside cities. But you need a dark sky to pick out the Keystone in Hercules and Corona Borealis. Visit EarthSky’s Best Places to Stargaze.

Ready? Now look east on a May evening to find Corona Borealis rising.

By Northern Hemisphere summer, all of these stars and constellations will be high in your sky. You’ll be looking up, not east, to see them.

Do you need binoculars? No. You don’t need them. But binoculars are always a good idea.

Want an exact view from an exact time or your exact location on the globe? Try Stellarium.

Late at night in the spring, and high overhead during summer months, find the bright stars Vega and Arcturus. The famous squarish pattern of the Keystone in the constellation Hercules is between them. And so is an easy-to-see semicircle of stars, the constellation Corona Borealis. The Blaze Star will erupt within Corona Borealis. It’ll be about as bright as Corona Borealis’ brightest star, Alphecca. Image via NASA.

Find Corona Borealis from the Southern Hemisphere

Via Daniel Gaussen, Founder & Guide – Stargaze Mackenzie – New Zealand

We all live under the same sky. But Earth’s Northern and Southern Hemispheres see the sky from different perspectives.

And remember how we said that Corona Borealis was almost – but not quite – circumpolar? That means it’s far to the north on the sky’s dome. From deep in the Southern Hemisphere – for example, the latitude of New Zealand and southern Australia – Corona Borealis rises to only around 20 to 25 degrees above the northern horizon at its highest. So, in addition to a dark sky, you’ll also want a clear view to the north.

Look north to northeast for a delicate semicircle or backward C shape of stars between the bright orange star Arcturus and the bright blue-white star Vega. The famous Keystone pattern in Hercules is also between these two, right next to Corona Borealis.

Want an exact view from an exact time or your exact location on the globe? Try Stellarium.

Star chart of Corona Borealis with red circle indicating location of star T CrB. Image via IAU/ Wikipedia.

What is the Blaze Star?

T Coronae Borealis – called “T Cor Bor” by many – is located about 3,000 light-years from Earth. It’s a double star system, consisting of a large cool star and a smaller hot star, which orbit each other every 228 days.

This system is what’s called a recurring nova. It’s not a supernova or star that blows itself to bits. Novas operate differently from supernovas. They survive to brighten again. T Cor Bor has outbursts about every 80 years.

Its last outburst was in 1946. That’s why astronomers believe another outburst will occur soon. Will we see it in 2026?

What makes the nova erupt? The cool star in the T Corona Borealis system is a swollen red giant. It continually transfers material to its companion in the system, the hot star. The hot star is a white dwarf, surrounded by an accretion disk made of material transferred over from the other star.

All of this is hidden inside a dense cloud of material from the red giant. When the system is quiescent, the red giant dominates the visible light output of the entire system. So the system appears as an M3 giant.

But during outbursts, the transfer of material from the red giant to the hot white dwarf increases greatly. The hot star then expands. And the luminosity of the system increases. Voila. We have a nova.

The Blaze Star isn’t 1 star but 2. It’s a binary system with a white dwarf and a red giant. The Blaze Star’s white dwarf has built up material on its surface, siphoned off from the red giant star. Periodically, it “can’t take no more” and explodes, about every 80 years. Despite the powerful explosion, the dwarf itself remains intact. And once things settle down, the Blaze Star (T Corona Borealis) will begin the decades-long preparation for future cosmic fireworks. Image via NASA Goddard Scientific Visualization Studio.

Why hasn’t the Blaze Star blazed?

Astronomers have been waiting several years for the Blaze Star to erupt. One recent prediction came from Jean Schneider of the Paris Observatory, publishing in the Research Notes of the American Astronomical Society in October 2024.

He pinpointed possible dates of March 27, 2025, and November 10, 2025. Those dates have come and gone with no big kablooey.

Schneider came to his possible dates using a combination of the previous eruption dates and the orbital ephemeris of the binary system. But Schneider admits in his paper that no one can exactly predict the eruption.

And, clearly, predicting eruptions of stars isn’t an exact science. The Blaze Star (T Coronae Borealis) underwent two known eruptions recorded by astronomers. Those events were on May 12, 1866, and on February 9, 1946. Those eruptions were 80 years apart. So scientists thought that, in another 80 years, the star would erupt again. Eighty years from 1946 would be 2026.

And so we wait …

Artist’s concept of a red giant star and white dwarf star. A stream of material flows from the red giant to the white dwarf, eventually causing a runaway thermonuclear reaction on the white dwarf that will appear as a new star, or nova, in earthly skies. The constellation Corona Borealis the Northern Crown should have a nova appear from the Blaze Star approximately every 80 years. Image via NASA/ Goddard Space Flight Center.

How bright will the Blaze Star be?

How bright will it get in our sky? Astronomers expect it to reach an apparent magnitude of 2. That’s a respectable brightness for a star. It’s conveniently comparable to the brightest star in the Northern Crown, the Jewel of the Crown, Alphecca. So, for a few days, the Northern Crown will have two jewels!

T Corona Borealis – the Blaze Star – is also one of the most distant stars you’ll ever see. Alphecca is around 75 light-years away, while the Blaze Star is closer to 3,000 light-years away.

So that gives you some perspective on the absolute magnitude (brightness) of this enormous blast. The actual explosion of the Blaze Star nova will likely dwarf any explosion you’ll ever see. But the star is far away. This explosion has travelled 3,000 years to get here. So, in relative terms the nova will have happened during the Bronze Age.

Remember that, when viewing Alphecca and T Corona Borealis side-by-side with approximately the same brightness. The nova is 40 times farther away than Alphecca. Also, we are not seeing the two stars at the same moment in time. One we see as it was 75 years ago. And the other we see as it was 3,000 years ago. It can be hard to get your head around that!

The nova will brighten the star by thousands of times, typically over just a few hours, and then take some days to fade away again. When it’s done, it will go back to its normal appearance … which means we won’t be able to see it anymore, with the eye alone.

So erupt already!

Want more? Here’s a highly regarded lecture by one of the world’s experts on the Blaze Star, LSU astronomer Bradley Schaefer. He discusses T CrB’s history, research into its unusual behavior, and the expected details of its imminent eruption. He also detailed specific ways for amateur astronomers to contribute to the study of this historic event, before answering a wide assortment of audience questions. Watch in the player above or on YouTube.

Bottom line: We’re still waiting for the Blaze Star to go nova! Will it happen in 2026? Here’s how to find Corona Borealis so you’re ready when this star goes kablooey.

Source: When will the Next T CrB Eruption Occur?

Read more: Want more details on the Northern Crown? Click here

The post Will the Blaze Star explode in 2026? How to see it first appeared on EarthSky.

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Von Kármán vortices are mesmerizing, swirling clouds

The Landsat 8 satellite captured these mesmerizing, swirling clouds with their hurricane-like eyes. Meteorologists call these clouds von Kármán vortices. On February 11, 2026, von Kármán vortices appeared on the downwind side of Peter I Island in the Southern Ocean surrounding Antarctica. Image via NASA Earth Observatory/ Michala Garrison.

What are von Kármán vortices?

The cloudy chain of spiraling eddies – like you see above – are known as von Kármán vortices. They’re named for Theodore von Kármán (1881-1963), a Hungarian-American physicist. He was the first to describe the physical processes that create them. The patterns can form nearly anywhere an object disturbs the flow of a fluid. That means oceans … or air.

In the case of the von Kármán vortices above, they formed in Earth’s atmosphere, downwind from Peter I Island. This ice-covered volcanic island sits in the Southern Ocean between Antarctica and South America. Winds were blowing between 11 to 34 miles per hour (18 to 54 kph) on February 11, 2026, when they encountered the volcanic barrier. The wind parted on either side of the island and spun into the shapes you see here. Note that this doesn’t always happen. Stronger winds wouldn’t have allowed the eddies to retain their shape.

More on how von Kármán vortices form

Our atmosphere is composed of gases, but it flows like a fluid. And tall peaks on islands can disrupt the flow of wind, to create the swirling clouds we know as von Kármán vortices. As the winds divert around these high areas, the disturbance in the flow propagates downstream in the form of vortices that alternate their direction of rotation.

Satellites have spotted von Kármán vortices around the globe. We’ve seen these vortices off of Guadalupe Island near the coast of Chile, in the Greenland Sea, in the Arctic and even next to a tropical storm. In the satellite image below, the vortices formed in the eastern Pacific Ocean on April 30, 2024.

These are von Karman vortices, swirling clouds that appeared over the eastern Pacific Ocean on April 30, 2024. Image via CIRA.

Animation of von Kármán vortices

Von Kármán vortices can form nearly anywhere that fluid flow is disturbed by an object. In the images below, that “object” is an island or group of islands. Watch the animation below courtesy of Cesareo de la Rosa Siqueira at the University of São Paulo, Brazil. You’ll see how a von Kármán vortex “street” develops behind a cylinder moving through a fluid.

More images of the cloudy, swirling eddies

These cloud vortices swirled off the Canary Islands on March 19, 2023. Image via NASA Earth Observatory.

These von Kármán vortices formed downwind from the volcanic island Tristan da Cunha in the South Atlantic on June 25, 2017. Image via NASA Earth Observatory.

Swirling clouds over Norwegian island

In the image below, an isolated Norwegian territory in the North Atlantic Ocean, called Jan Mayen Island, is responsible for the spiraling cloud pattern. The unique flow occurs when winds rushing from the north encounter Beerenberg Volcano. This snow-covered peak on the eastern end of the island rises 1.4 miles (2.2 km) above the sea surface. As winds pass around the volcano, the disturbance in the flow propagates downstream in the form of a double row of vortices that alternate their direction of rotation.

Von Kármán vortices in the Greenland Sea around Jan Mayen Island on April 5, 2012. Image via NASA.

Bottom line: See von Kármán vortices – mesmerizing, swirling pattern of clouds – in these satellite images. These clouds form when the wind hits a barrier like a mountain.

Read more from NASA’s Earth Obervatory

Read more: Cloud streets: What are they? How do they form?

The post Von Kármán vortices are mesmerizing, swirling clouds first appeared on EarthSky.

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The Landsat 8 satellite captured these mesmerizing, swirling clouds with their hurricane-like eyes. Meteorologists call these clouds von Kármán vortices. On February 11, 2026, von Kármán vortices appeared on the downwind side of Peter I Island in the Southern Ocean surrounding Antarctica. Image via NASA Earth Observatory/ Michala Garrison.

What are von Kármán vortices?

The cloudy chain of spiraling eddies – like you see above – are known as von Kármán vortices. They’re named for Theodore von Kármán (1881-1963), a Hungarian-American physicist. He was the first to describe the physical processes that create them. The patterns can form nearly anywhere an object disturbs the flow of a fluid. That means oceans … or air.

In the case of the von Kármán vortices above, they formed in Earth’s atmosphere, downwind from Peter I Island. This ice-covered volcanic island sits in the Southern Ocean between Antarctica and South America. Winds were blowing between 11 to 34 miles per hour (18 to 54 kph) on February 11, 2026, when they encountered the volcanic barrier. The wind parted on either side of the island and spun into the shapes you see here. Note that this doesn’t always happen. Stronger winds wouldn’t have allowed the eddies to retain their shape.

More on how von Kármán vortices form

Our atmosphere is composed of gases, but it flows like a fluid. And tall peaks on islands can disrupt the flow of wind, to create the swirling clouds we know as von Kármán vortices. As the winds divert around these high areas, the disturbance in the flow propagates downstream in the form of vortices that alternate their direction of rotation.

Satellites have spotted von Kármán vortices around the globe. We’ve seen these vortices off of Guadalupe Island near the coast of Chile, in the Greenland Sea, in the Arctic and even next to a tropical storm. In the satellite image below, the vortices formed in the eastern Pacific Ocean on April 30, 2024.

These are von Karman vortices, swirling clouds that appeared over the eastern Pacific Ocean on April 30, 2024. Image via CIRA.

Animation of von Kármán vortices

Von Kármán vortices can form nearly anywhere that fluid flow is disturbed by an object. In the images below, that “object” is an island or group of islands. Watch the animation below courtesy of Cesareo de la Rosa Siqueira at the University of São Paulo, Brazil. You’ll see how a von Kármán vortex “street” develops behind a cylinder moving through a fluid.

More images of the cloudy, swirling eddies

These cloud vortices swirled off the Canary Islands on March 19, 2023. Image via NASA Earth Observatory.

These von Kármán vortices formed downwind from the volcanic island Tristan da Cunha in the South Atlantic on June 25, 2017. Image via NASA Earth Observatory.

Swirling clouds over Norwegian island

In the image below, an isolated Norwegian territory in the North Atlantic Ocean, called Jan Mayen Island, is responsible for the spiraling cloud pattern. The unique flow occurs when winds rushing from the north encounter Beerenberg Volcano. This snow-covered peak on the eastern end of the island rises 1.4 miles (2.2 km) above the sea surface. As winds pass around the volcano, the disturbance in the flow propagates downstream in the form of a double row of vortices that alternate their direction of rotation.

Von Kármán vortices in the Greenland Sea around Jan Mayen Island on April 5, 2012. Image via NASA.

Bottom line: See von Kármán vortices – mesmerizing, swirling pattern of clouds – in these satellite images. These clouds form when the wind hits a barrier like a mountain.

Read more from NASA’s Earth Obervatory

Read more: Cloud streets: What are they? How do they form?

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2025 Alaska megatsunami shows need for warning system

An animation showing the Alaska megatsunami – a large wave of about 100 meters (328 ft) or more – as it reached up the fjord walls after the landslide, as well as the large cresting wave as it heads down Tracy Arm. Credit: Shugar et al., 2026.

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• A megatsunami is an incredibly large wave of about 100 meters (328 ft) or more. These huge waves are often triggered by events such as landslides.
• In August 2025, a megatsunami in Alaska happened when a landslide entered a fjord next to South Sawyer Glacier. The event generated a wave 1,580 feet (481 meters) high.
• Scientists believe a warning system could help alert any people in the area. It would be based on seismic activity in the area.

By Michael E. West, University of Alaska Fairbanks and Ezgi Karasözen, University of Alaska Fairbanks

2025 Alaska megatsunami shows need for warning system

On the evening of August 9, 2025, passengers on the Hanse Explorer yacht finished taking selfies and videos of Alaska’s South Sawyer Glacier, and the ship headed back down the fjord. Twelve hours later, a landslide from the adjacent mountain unexpectedly collapsed into the fjord, initiating the second-highest tsunami in recorded history.

We conduct research on earthquakes and tsunamis at the Alaska Earthquake Center. And one of us serves as Alaska state seismologist. In a new study with colleagues, we detail how that landslide sent water and debris 1,580 feet (481 meters) up the other side of the fjord. That’s higher than the top floor of the Taipei 101 skyscraper. And then the tsunami continued down Tracy Arm. The force of the water stripped the fjord’s walls down to bare rock.

The Tracy Arm landslide generated a tsunami that sent a wave so high up the opposite fjord wall that it would have overtopped some of the world’s tallest buildings. Here’s how it compares to other large tsunamis around the world. Image via Steve Hicks/ University College London/ The Conversation.

The landslide at Tracy Arm Fjord, Alaska in August last year sent a tsunami wave far up the opposite side of the fjord near South Sawyer Glacier. This 2025 Alaska megatsunami could have led to tragedy. The event shows the need for a warning system to alert cruise ships and others who might be in the area. Image via John Lyons/ U.S. Geological Survey/ The Conversation.

The 2025 Alaska megatsunami

It was just after 5 o’clock in the morning on a dreary day. And fortunately, no ships were nearby. In the months after, some cruise lines started avoiding Tracy Arm. However, the conditions that led to this event are not at all unique to this fjord.

Landslides are common in the coastal mountains of Alaska. In these areas, rapid uplift – caused by tectonic forces and long-term ice loss – converges with the erosive forces of precipitation and moving glaciers. But a curious pattern has emerged in recent years: Multiple major landslides have occurred precisely at the terminus (end point) of a retreating glacier.

Though the mechanics are still poorly understood, these mountains appear to become unstable when the ice disappears. When the landslide hits the water, the momentum of millions of tons of rock is transferred into tsunami waves.

Maps show how the glacier has retreated over the years, moving past the section of mountain that collapsed (outlined in white on the right) in the days prior to the slide. The map on the right shows the height the tsunami reached on the fjord walls. Image via Planet Labs/ The Conversation.

This same phenomenon is playing out from Alaska to Greenland and Norway, sometimes with deadly consequences. Across the Arctic, countries are trying to come to terms with this growing hazard. The options are not attractive: avoid vast swaths of coastline, or live with a poorly understood risk. We believe there is an obvious role for alert systems. But only if scientists have a better understanding of where and when landslides are likely to occur.

Signs that a landslide might be coming

The Tracy Arm landslide is a powerful example.

The landslide occurred in August, when warm ocean waters and heavier precipitation favor both glacier retreat and slope failure. The glacier below the landslide area had experienced rapid calving: large chunks of ice breaking off and falling into the water. And it had retreated more than a third of a mile in the two months prior. Heavy rain had been falling. Rain enters fractures in the mountain and pushes them closer to failure by increasing the water pressure in cracks.

Most provocative are the thousands of small seismic tremors that emanated from the area of the slide in the days prior to the mountainside collapsing.

We believe that this combination of signs would have been sufficient to issue progressive alerts to any ships in the vicinity and homes and businesses that could have been harmed by a tsunami at least a day prior to the failure … had a monitoring program existed.

Escalating alerts are used for everything from terrorism and nuclear plant safety to avalanches and volcanic unrest. They don’t remove the risk. But they do make it easier for people to safely coexist with hazards.

For example, though people are still killed in avalanches, alert systems have played an essential role in making winter backcountry travel safer for more people. The collapse at Tracy Arm demonstrates what could be possible for landslides.

What an alert system could look like

We believe that the combination of weather and rapid glacier retreat in early August 2025 was likely sufficient to issue an alert notifying people that the hazard may be temporarily elevated in a general area. On a yellow-orange-red scale, this would be a yellow alert.

In the hours prior to the landslide, the exponential increase in seismic events and telltale transition to what is known as seismic tremor – a continuous “hum” of seismic energy – were sufficient to communicate a time-sensitive warning for a specific region.

Seismic data from the closest monitoring station to the landslide, about 60 miles (100 kilometers) away, shows the “hum” of seismic energy increasing just ahead of the landslide, indicated by the tall yellow spike shortly after 5 a.m. Source: Alaska Earthquake Center.

These observations, recorded as a byproduct of regional earthquake monitoring, warranted an “orange” alert noting immediate concern. The signs were arguably sufficient to recommend keeping boats and ships out of the fjord.

Alerts are possible

Our research over the past few years has demonstrated that once a large landslide has started, it is possible to detect and measure the event within a couple of minutes. In this amount of time, seismic waves in the surrounding area can indicate the rough size of the landslide and whether it occurred near open water.

A monitoring program that could quickly communicate this would be able to issue a red alert, signaling an event in progress.

The National Oceanic and Atmospheric Administration’s tsunami warning program has spent decades fine-tuning rapid message dissemination. A warning system would have offered little help for ships in the immediate vicinity, but it could have provided perhaps 10 minutes of warning for those who rode out the harrowing tsunami farther away.

There is no landslide monitoring system operating yet at this scale in the U.S. Building one will require cooperation across state and federal agencies, and strengthened monitoring and communication networks. Even then, it will not be fail-proof.

Understanding risk, not removing it

Alert systems do not remove the risk entirely, but they are a better option than no warning at all. Over time, they also build awareness as communities and visitors get used to thinking about these hazards.

Many of the most alluring places on Earth come with significant hazards. Arctic fjords are among them. The same processes that create this hazard – glacier retreat, steep terrain, dynamic geology – are also what make these landscapes so compelling. The mix of glaciers, ice-choked waters and steep mountains is exactly what draws people to these places. People will continue to visit and experience them.

The last view of Tracy Arm, taken from the Hanse Explorer motoring away from the South Sawyer glacier, before a landslide from a mountain just out of view on the left crashed into the fjord. The landslide generated a tsunami that sent a wave nearly 1,600 feet (about 490 meters) up the mountain on the right.

The question is not whether these places should be avoided altogether, but how to help people make more informed decisions. We believe that stronger geophysical and meteorological monitoring, coupled with new research and communication channels, is the first step.

On August 9, visitors unknowingly passed through a landscape on the cusp of failure. An alert system might have given tour companies and people in the area the information they needed to make more informed choices and avoid being caught by surprise.

Michael E. West, Director of the Alaska Earthquake Center and State Seismologist, University of Alaska Fairbanks and Ezgi Karasözen, Research Seismologist, Alaska Earthquake Center, University of Alaska Fairbanks

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

Bottom line: A 2025 Alaska megatsunami sent a 1,580-foot wave of water up the Tracy Arm fjord. It revealed the need for a landslide-triggered tsunami warning system.

Read more: Landslide-triggered tsunamis becoming more common

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An animation showing the Alaska megatsunami – a large wave of about 100 meters (328 ft) or more – as it reached up the fjord walls after the landslide, as well as the large cresting wave as it heads down Tracy Arm. Credit: Shugar et al., 2026.

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• A megatsunami is an incredibly large wave of about 100 meters (328 ft) or more. These huge waves are often triggered by events such as landslides.
• In August 2025, a megatsunami in Alaska happened when a landslide entered a fjord next to South Sawyer Glacier. The event generated a wave 1,580 feet (481 meters) high.
• Scientists believe a warning system could help alert any people in the area. It would be based on seismic activity in the area.

By Michael E. West, University of Alaska Fairbanks and Ezgi Karasözen, University of Alaska Fairbanks

2025 Alaska megatsunami shows need for warning system

On the evening of August 9, 2025, passengers on the Hanse Explorer yacht finished taking selfies and videos of Alaska’s South Sawyer Glacier, and the ship headed back down the fjord. Twelve hours later, a landslide from the adjacent mountain unexpectedly collapsed into the fjord, initiating the second-highest tsunami in recorded history.

We conduct research on earthquakes and tsunamis at the Alaska Earthquake Center. And one of us serves as Alaska state seismologist. In a new study with colleagues, we detail how that landslide sent water and debris 1,580 feet (481 meters) up the other side of the fjord. That’s higher than the top floor of the Taipei 101 skyscraper. And then the tsunami continued down Tracy Arm. The force of the water stripped the fjord’s walls down to bare rock.

The Tracy Arm landslide generated a tsunami that sent a wave so high up the opposite fjord wall that it would have overtopped some of the world’s tallest buildings. Here’s how it compares to other large tsunamis around the world. Image via Steve Hicks/ University College London/ The Conversation.

The landslide at Tracy Arm Fjord, Alaska in August last year sent a tsunami wave far up the opposite side of the fjord near South Sawyer Glacier. This 2025 Alaska megatsunami could have led to tragedy. The event shows the need for a warning system to alert cruise ships and others who might be in the area. Image via John Lyons/ U.S. Geological Survey/ The Conversation.

The 2025 Alaska megatsunami

It was just after 5 o’clock in the morning on a dreary day. And fortunately, no ships were nearby. In the months after, some cruise lines started avoiding Tracy Arm. However, the conditions that led to this event are not at all unique to this fjord.

Landslides are common in the coastal mountains of Alaska. In these areas, rapid uplift – caused by tectonic forces and long-term ice loss – converges with the erosive forces of precipitation and moving glaciers. But a curious pattern has emerged in recent years: Multiple major landslides have occurred precisely at the terminus (end point) of a retreating glacier.

Though the mechanics are still poorly understood, these mountains appear to become unstable when the ice disappears. When the landslide hits the water, the momentum of millions of tons of rock is transferred into tsunami waves.

Maps show how the glacier has retreated over the years, moving past the section of mountain that collapsed (outlined in white on the right) in the days prior to the slide. The map on the right shows the height the tsunami reached on the fjord walls. Image via Planet Labs/ The Conversation.

This same phenomenon is playing out from Alaska to Greenland and Norway, sometimes with deadly consequences. Across the Arctic, countries are trying to come to terms with this growing hazard. The options are not attractive: avoid vast swaths of coastline, or live with a poorly understood risk. We believe there is an obvious role for alert systems. But only if scientists have a better understanding of where and when landslides are likely to occur.

Signs that a landslide might be coming

The Tracy Arm landslide is a powerful example.

The landslide occurred in August, when warm ocean waters and heavier precipitation favor both glacier retreat and slope failure. The glacier below the landslide area had experienced rapid calving: large chunks of ice breaking off and falling into the water. And it had retreated more than a third of a mile in the two months prior. Heavy rain had been falling. Rain enters fractures in the mountain and pushes them closer to failure by increasing the water pressure in cracks.

Most provocative are the thousands of small seismic tremors that emanated from the area of the slide in the days prior to the mountainside collapsing.

We believe that this combination of signs would have been sufficient to issue progressive alerts to any ships in the vicinity and homes and businesses that could have been harmed by a tsunami at least a day prior to the failure … had a monitoring program existed.

Escalating alerts are used for everything from terrorism and nuclear plant safety to avalanches and volcanic unrest. They don’t remove the risk. But they do make it easier for people to safely coexist with hazards.

For example, though people are still killed in avalanches, alert systems have played an essential role in making winter backcountry travel safer for more people. The collapse at Tracy Arm demonstrates what could be possible for landslides.

What an alert system could look like

We believe that the combination of weather and rapid glacier retreat in early August 2025 was likely sufficient to issue an alert notifying people that the hazard may be temporarily elevated in a general area. On a yellow-orange-red scale, this would be a yellow alert.

In the hours prior to the landslide, the exponential increase in seismic events and telltale transition to what is known as seismic tremor – a continuous “hum” of seismic energy – were sufficient to communicate a time-sensitive warning for a specific region.

Seismic data from the closest monitoring station to the landslide, about 60 miles (100 kilometers) away, shows the “hum” of seismic energy increasing just ahead of the landslide, indicated by the tall yellow spike shortly after 5 a.m. Source: Alaska Earthquake Center.

These observations, recorded as a byproduct of regional earthquake monitoring, warranted an “orange” alert noting immediate concern. The signs were arguably sufficient to recommend keeping boats and ships out of the fjord.

Alerts are possible

Our research over the past few years has demonstrated that once a large landslide has started, it is possible to detect and measure the event within a couple of minutes. In this amount of time, seismic waves in the surrounding area can indicate the rough size of the landslide and whether it occurred near open water.

A monitoring program that could quickly communicate this would be able to issue a red alert, signaling an event in progress.

The National Oceanic and Atmospheric Administration’s tsunami warning program has spent decades fine-tuning rapid message dissemination. A warning system would have offered little help for ships in the immediate vicinity, but it could have provided perhaps 10 minutes of warning for those who rode out the harrowing tsunami farther away.

There is no landslide monitoring system operating yet at this scale in the U.S. Building one will require cooperation across state and federal agencies, and strengthened monitoring and communication networks. Even then, it will not be fail-proof.

Understanding risk, not removing it

Alert systems do not remove the risk entirely, but they are a better option than no warning at all. Over time, they also build awareness as communities and visitors get used to thinking about these hazards.

Many of the most alluring places on Earth come with significant hazards. Arctic fjords are among them. The same processes that create this hazard – glacier retreat, steep terrain, dynamic geology – are also what make these landscapes so compelling. The mix of glaciers, ice-choked waters and steep mountains is exactly what draws people to these places. People will continue to visit and experience them.

The last view of Tracy Arm, taken from the Hanse Explorer motoring away from the South Sawyer glacier, before a landslide from a mountain just out of view on the left crashed into the fjord. The landslide generated a tsunami that sent a wave nearly 1,600 feet (about 490 meters) up the mountain on the right.

The question is not whether these places should be avoided altogether, but how to help people make more informed decisions. We believe that stronger geophysical and meteorological monitoring, coupled with new research and communication channels, is the first step.

On August 9, visitors unknowingly passed through a landscape on the cusp of failure. An alert system might have given tour companies and people in the area the information they needed to make more informed choices and avoid being caught by surprise.

Michael E. West, Director of the Alaska Earthquake Center and State Seismologist, University of Alaska Fairbanks and Ezgi Karasözen, Research Seismologist, Alaska Earthquake Center, University of Alaska Fairbanks

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

Bottom line: A 2025 Alaska megatsunami sent a 1,580-foot wave of water up the Tracy Arm fjord. It revealed the need for a landslide-triggered tsunami warning system.

Read more: Landslide-triggered tsunamis becoming more common

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