M6 and M7: Open star clusters in the Scorpion’s Tail

In a dark sky, you’ll see 2 famous star clusters – M6 and M7 – in the constellation Scorpius the Scorpion. In this photo, Messier 7 – aka Ptolemy’s Cluster – is above the tree on the left. Messier 6, the Butterfly Cluster, is a bit smaller, positioned near the center top of the image. And Shaula and Lesath, the stinger stars in Scorpius, are prominent in the lower right. Image via Tom and Jane Wildoner/ Dark Side Observatory/ Flickr. Used with permission.

• The star clusters M6 (Butterfly Cluster) and M7 (Ptolemy’s Cluster) are near the tail of the Scorpion in the constellation Scorpius. Look for them on dark Northern Hemisphere summer nights!
• Both M6 and M7 are open star clusters, which means they are groups of stars that formed together from the same cloud of gas and dust, making them like star siblings.
• You can spot these clusters with your unaided eye on a dark, moonless night, but they look even more beautiful through binoculars.

M6 and M7: Open star clusters in the Scorpion’s Tail

Two spectacular star clusters glitter near Scorpius the Scorpion’s stinger stars, Shaula and Lesath. Messier 6 and Messier 7 – or M6 and M7 – are open star clusters. Each cluster is a group of stars formed from the same huge cloud of gas.

These two clusters are visible on summer evenings in the Northern Hemisphere, or winter evenings in the Southern Hemisphere. They’re best viewed in a dark sky, and are a stunning sight through binoculars.

The constellation Scorpius with the positions of the star clusters M7 and M6 marked. Chart by EarthSky.

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How to find M6 and M7

These star clusters are easy to spot in a dark sky near the curved tail of the constellation Scorpius the Scorpion. Scorpius is shaped like the letter J. And the two stars, Shaula and Lesath – at the end of the curved part of the J – mark the end of the Scorpion’s Tail. They’re known as the Cat’s Eyes, or the stinger of Scorpius.

Plus, if you draw an imaginary line from Lesath through Shaula, you’ll find M7, which is the brighter and larger of the two star clusters. Then from M7, you find M6 only a short hop away.

And although M6 and M7 are visible to the unaided eye on a dark, moonless night, the brilliance and beauty of these deep sky objects is magnificent through binoculars.

If you’re in the northern U.S., Canada or a similar latitude, you’ll need an unobstructed horizon toward the south to find M6 and M7. They are highest in the sky when due south, and even then never climb very high in the sky. Meanwhile, from latitudes like those in the southern U.S., the clusters are easy to spot at their highest in the south, above the Scorpion’s Tail. Generally, Scorpius is much easier to view from the equator and most of the Southern Hemisphere.

View at EarthSky Community Photos. | Dr Ski captured this image from the Philippines and wrote: “The Scorpion’s stinger is comprised of Shaula and Lesath. These stars point the way to magnificent Ptolemy’s Open Cluster (M7). Just 3 degrees to the northwest is the Butterfly Cluster (M6). Binoculars will show you these clusters, along with all the dark nebulae snaking around this region!” Thank you, Dr Ski!

Best time to view

Consequently, in mid-June, these clusters are visible in the sky around midnight (1 a.m. daylight saving time in the U.S.). And keep in mind that all the stars (and star clusters) return to the same place in the sky some four minutes earlier with each passing day, or two hours earlier with each passing month. Therefore, M6 and M7 appear highest in the sky at about 10 p.m. (11 p.m. daylight saving time) in mid-July, and 8 p.m. (9 p.m. daylight saving time) in mid-August.

M6 and M7 science

Even though M6 (Butterfly Cluster) and M7 (Ptolemy’s Cluster) appear close together on the sky’s dome, they are far apart in space. Indeed, M6 is about 1,600 light-years away and shines at magnitude 4.2. M7 is about 980 light-years and shines at magnitude 3.3. So, the clusters are not related to each other, but only appear near each other along our line of sight.

But, within each cluster, the stars are related. Each cluster was born from a single interstellar cloud of gas and dust. The hundreds of stars in each cluster are indeed sibling stars, in that they are gravitationally bound to one another and travel in the same direction through space. Therefore, astronomers call such a collection of stars an open star cluster.

Messier 6 through a wide field telescope and camera. Image via Fred Espenak. Used with permission.

Messier 7 through a wide field telescope and camera. Image via Fred Espenak. Used with permission.

The clusters are in the thick of the Milky Way

M6 and M7 reside near the galactic equator, the region on the sky’s dome rich with star clusters, star clouds and nebulae. Once you find M6 and M7, try locating other deep-sky binocular doubles, such as M8 and M20. And also check out M16 and M17. These deep-sky wonders loom farther away. Also, M6 and M7 are open star clusters. But M8 and M20, and M16 and M17, are nebulae where stars are forming.

Bottom line: Messier 6 and Messier 7 are striking star clusters near the tail of Scorpius. M6 and M7 are best in dark sky conditions through binoculars.

The post M6 and M7: Open star clusters in the Scorpion’s Tail first appeared on EarthSky.

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In a dark sky, you’ll see 2 famous star clusters – M6 and M7 – in the constellation Scorpius the Scorpion. In this photo, Messier 7 – aka Ptolemy’s Cluster – is above the tree on the left. Messier 6, the Butterfly Cluster, is a bit smaller, positioned near the center top of the image. And Shaula and Lesath, the stinger stars in Scorpius, are prominent in the lower right. Image via Tom and Jane Wildoner/ Dark Side Observatory/ Flickr. Used with permission.

• The star clusters M6 (Butterfly Cluster) and M7 (Ptolemy’s Cluster) are near the tail of the Scorpion in the constellation Scorpius. Look for them on dark Northern Hemisphere summer nights!
• Both M6 and M7 are open star clusters, which means they are groups of stars that formed together from the same cloud of gas and dust, making them like star siblings.
• You can spot these clusters with your unaided eye on a dark, moonless night, but they look even more beautiful through binoculars.

M6 and M7: Open star clusters in the Scorpion’s Tail

Two spectacular star clusters glitter near Scorpius the Scorpion’s stinger stars, Shaula and Lesath. Messier 6 and Messier 7 – or M6 and M7 – are open star clusters. Each cluster is a group of stars formed from the same huge cloud of gas.

These two clusters are visible on summer evenings in the Northern Hemisphere, or winter evenings in the Southern Hemisphere. They’re best viewed in a dark sky, and are a stunning sight through binoculars.

The constellation Scorpius with the positions of the star clusters M7 and M6 marked. Chart by EarthSky.

We live in uncertain times. But things are always so much more peaceful, looking up. Please help EarthSky keep going!

How to find M6 and M7

These star clusters are easy to spot in a dark sky near the curved tail of the constellation Scorpius the Scorpion. Scorpius is shaped like the letter J. And the two stars, Shaula and Lesath – at the end of the curved part of the J – mark the end of the Scorpion’s Tail. They’re known as the Cat’s Eyes, or the stinger of Scorpius.

Plus, if you draw an imaginary line from Lesath through Shaula, you’ll find M7, which is the brighter and larger of the two star clusters. Then from M7, you find M6 only a short hop away.

And although M6 and M7 are visible to the unaided eye on a dark, moonless night, the brilliance and beauty of these deep sky objects is magnificent through binoculars.

If you’re in the northern U.S., Canada or a similar latitude, you’ll need an unobstructed horizon toward the south to find M6 and M7. They are highest in the sky when due south, and even then never climb very high in the sky. Meanwhile, from latitudes like those in the southern U.S., the clusters are easy to spot at their highest in the south, above the Scorpion’s Tail. Generally, Scorpius is much easier to view from the equator and most of the Southern Hemisphere.

View at EarthSky Community Photos. | Dr Ski captured this image from the Philippines and wrote: “The Scorpion’s stinger is comprised of Shaula and Lesath. These stars point the way to magnificent Ptolemy’s Open Cluster (M7). Just 3 degrees to the northwest is the Butterfly Cluster (M6). Binoculars will show you these clusters, along with all the dark nebulae snaking around this region!” Thank you, Dr Ski!

Best time to view

Consequently, in mid-June, these clusters are visible in the sky around midnight (1 a.m. daylight saving time in the U.S.). And keep in mind that all the stars (and star clusters) return to the same place in the sky some four minutes earlier with each passing day, or two hours earlier with each passing month. Therefore, M6 and M7 appear highest in the sky at about 10 p.m. (11 p.m. daylight saving time) in mid-July, and 8 p.m. (9 p.m. daylight saving time) in mid-August.

M6 and M7 science

Even though M6 (Butterfly Cluster) and M7 (Ptolemy’s Cluster) appear close together on the sky’s dome, they are far apart in space. Indeed, M6 is about 1,600 light-years away and shines at magnitude 4.2. M7 is about 980 light-years and shines at magnitude 3.3. So, the clusters are not related to each other, but only appear near each other along our line of sight.

But, within each cluster, the stars are related. Each cluster was born from a single interstellar cloud of gas and dust. The hundreds of stars in each cluster are indeed sibling stars, in that they are gravitationally bound to one another and travel in the same direction through space. Therefore, astronomers call such a collection of stars an open star cluster.

Messier 6 through a wide field telescope and camera. Image via Fred Espenak. Used with permission.

Messier 7 through a wide field telescope and camera. Image via Fred Espenak. Used with permission.

The clusters are in the thick of the Milky Way

M6 and M7 reside near the galactic equator, the region on the sky’s dome rich with star clusters, star clouds and nebulae. Once you find M6 and M7, try locating other deep-sky binocular doubles, such as M8 and M20. And also check out M16 and M17. These deep-sky wonders loom farther away. Also, M6 and M7 are open star clusters. But M8 and M20, and M16 and M17, are nebulae where stars are forming.

Bottom line: Messier 6 and Messier 7 are striking star clusters near the tail of Scorpius. M6 and M7 are best in dark sky conditions through binoculars.

The post M6 and M7: Open star clusters in the Scorpion’s Tail first appeared on EarthSky.

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Have we found the first exomoon … around a brown dwarf?

Astronomers have discovered an object orbiting a brown dwarf or “failed star”. Is it the first exomoon, or moon outside our solar system? Astronomers are debating what to call it. Why? Because moons orbit planets … And this exomoon is orbiting a brown dwarf, which is an object that’s too massive to be a planet but not massive enough to shine like a star. Video via ESO.

Did we find an exomoon around a brown dwarf?

Exomoons are moons that exist outside our own solar system. We’ve yet to definitively find a single one! That’s because they are small and dim, circling exoplanets that are also small and dim, hidden in the glare of the stars they orbit. But on July 22, 2026, the European Southern Observatory said astronomers using the Very Large Telescope in Chile believe they have detected an exomoon.

Only, there’s one problem: it doesn’t orbit a planet. Instead, it orbits a brown dwarf. A brown dwarf is an object that’s too massive to be considered a planet, but not massive enough to ignite and shine like a star. And this particular brown dwarf orbits a star, named CD-35 2722. So astronomers are debating what to call the newly discovered object. Is it the first discovered exomoon, or something else?

The researchers published their peer-reviewed paper on July 22, 2026, in the journal Nature.

A ‘super weird’ system

Not all brown dwarfs orbit stars, but this one does. The star in this system is named CD-35 2722, and it’s about half the mass of our sun. But even though the brown dwarf orbits this star, it’s not a planet, because it’s too massive. Brown dwarfs are so massive compared to planets that they’re sometimes called “failed stars”. Though far heavier than the objects we call planets, they aren’t quite massive enough to begin nuclear fusion and shine like a star does.

And then we have the newly discovered object, which orbits the brown dwarf. Normally we think of a moon as something that orbits a planet, which orbits a star. So what orbits a brown dwarf? Is it an exomoon? That’s what astronomers are having to decide: the semantics of the system. In any case, the lead author of the new study, Kevin Hoy, an ESO student in Chile, calls it:

super weird.

Right now, the team is calling the object an exosatellite. The object is at least as massive as Jupiter. Meanwhile, the brown dwarf it orbits is about 30 times as massive as Jupiter. Hoy said:

This system is somewhat hard to define using solar-system-based words like ‘planet’ and ‘moon’. The exosatellite is clearly massive enough to be a planet, but it does not orbit a star, though it orbits an object that orbits a star. Being the third wheel in this system makes us want to call it a moon, even if it is nothing like the small, rocky moons we have in our system.

This is an artist’s concept of the star system CD-35 2722. The star, about half the mass of our sun, is on the left. The large object on the right is the brown dwarf that orbits the star. And at center is the newly discovered object orbiting the brown dwarf. Should it be called an exomoon, even though it doesn’t orbit a planet? It’s massive enough to be a planet, but planets orbit stars, not brown dwarfs. Image via ESO/M. Kornmesser.

The name game

Humans have a need to neatly categorize the things they encounter in the world. But nature is not so rigid. Pluto itself did not change when its classification changed from planet to dwarf planet. And asteroids, comets and meteors are all leftover material from the formation of our solar system under different names.

But naming things – or nomenclature – is part of the scientific process. It’s just not always easy to do. Co-author Alice Zurlo of Universidad Diego Portales said:

We have a clear delineation between the planets and the sun in the solar system, so defining things like moons is simple. In the CD-35 2722 system, where we are blurring the lines between stars, planets and moons, the whole thing becomes more complicated to describe.

Exomoons around exoplanets

Astronomers didn’t confirm the first exoplanet – or planet around a star other than the sun – until 1992. Because they are so small and dim compared to their parent star, they are particularly hard to find. But astronomers long thought they were there. And now we’ve confirmed some 6,000 exoplanets.

So far, it’s been a similar story with exomoons. Astronomers assume there are many exomoons in other stellar systems, just as there are many moons in our solar system. It’s simply a challenge to find them. Astronomers have found exomoon candidates around distant exoplanets, but no confirmation yet.

This candidate exomoon – if it ends up with that label – has strong evidence. It’s causing the brown dwarf that it orbits to wobble. And those wobbles show up in the brown dwarf’s spectra. Zurlo said:

As exotic as it is, this system is truly unique and represents a breakthrough: the first plausible detection of an exosatellite.

Bottom line: Have astronomers found the first exomoon? We think of moons as objects that orbit planets. So what do we call this object, which orbits a brown dwarf?

Source: Planetary-Mass Exosatellite Detected Around a Star’s Substellar Companion

Via ESO

The post Have we found the first exomoon … around a brown dwarf? first appeared on EarthSky.

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Astronomers have discovered an object orbiting a brown dwarf or “failed star”. Is it the first exomoon, or moon outside our solar system? Astronomers are debating what to call it. Why? Because moons orbit planets … And this exomoon is orbiting a brown dwarf, which is an object that’s too massive to be a planet but not massive enough to shine like a star. Video via ESO.

Did we find an exomoon around a brown dwarf?

Exomoons are moons that exist outside our own solar system. We’ve yet to definitively find a single one! That’s because they are small and dim, circling exoplanets that are also small and dim, hidden in the glare of the stars they orbit. But on July 22, 2026, the European Southern Observatory said astronomers using the Very Large Telescope in Chile believe they have detected an exomoon.

Only, there’s one problem: it doesn’t orbit a planet. Instead, it orbits a brown dwarf. A brown dwarf is an object that’s too massive to be considered a planet, but not massive enough to ignite and shine like a star. And this particular brown dwarf orbits a star, named CD-35 2722. So astronomers are debating what to call the newly discovered object. Is it the first discovered exomoon, or something else?

The researchers published their peer-reviewed paper on July 22, 2026, in the journal Nature.

A ‘super weird’ system

Not all brown dwarfs orbit stars, but this one does. The star in this system is named CD-35 2722, and it’s about half the mass of our sun. But even though the brown dwarf orbits this star, it’s not a planet, because it’s too massive. Brown dwarfs are so massive compared to planets that they’re sometimes called “failed stars”. Though far heavier than the objects we call planets, they aren’t quite massive enough to begin nuclear fusion and shine like a star does.

And then we have the newly discovered object, which orbits the brown dwarf. Normally we think of a moon as something that orbits a planet, which orbits a star. So what orbits a brown dwarf? Is it an exomoon? That’s what astronomers are having to decide: the semantics of the system. In any case, the lead author of the new study, Kevin Hoy, an ESO student in Chile, calls it:

super weird.

Right now, the team is calling the object an exosatellite. The object is at least as massive as Jupiter. Meanwhile, the brown dwarf it orbits is about 30 times as massive as Jupiter. Hoy said:

This system is somewhat hard to define using solar-system-based words like ‘planet’ and ‘moon’. The exosatellite is clearly massive enough to be a planet, but it does not orbit a star, though it orbits an object that orbits a star. Being the third wheel in this system makes us want to call it a moon, even if it is nothing like the small, rocky moons we have in our system.

This is an artist’s concept of the star system CD-35 2722. The star, about half the mass of our sun, is on the left. The large object on the right is the brown dwarf that orbits the star. And at center is the newly discovered object orbiting the brown dwarf. Should it be called an exomoon, even though it doesn’t orbit a planet? It’s massive enough to be a planet, but planets orbit stars, not brown dwarfs. Image via ESO/M. Kornmesser.

The name game

Humans have a need to neatly categorize the things they encounter in the world. But nature is not so rigid. Pluto itself did not change when its classification changed from planet to dwarf planet. And asteroids, comets and meteors are all leftover material from the formation of our solar system under different names.

But naming things – or nomenclature – is part of the scientific process. It’s just not always easy to do. Co-author Alice Zurlo of Universidad Diego Portales said:

We have a clear delineation between the planets and the sun in the solar system, so defining things like moons is simple. In the CD-35 2722 system, where we are blurring the lines between stars, planets and moons, the whole thing becomes more complicated to describe.

Exomoons around exoplanets

Astronomers didn’t confirm the first exoplanet – or planet around a star other than the sun – until 1992. Because they are so small and dim compared to their parent star, they are particularly hard to find. But astronomers long thought they were there. And now we’ve confirmed some 6,000 exoplanets.

So far, it’s been a similar story with exomoons. Astronomers assume there are many exomoons in other stellar systems, just as there are many moons in our solar system. It’s simply a challenge to find them. Astronomers have found exomoon candidates around distant exoplanets, but no confirmation yet.

This candidate exomoon – if it ends up with that label – has strong evidence. It’s causing the brown dwarf that it orbits to wobble. And those wobbles show up in the brown dwarf’s spectra. Zurlo said:

As exotic as it is, this system is truly unique and represents a breakthrough: the first plausible detection of an exosatellite.

Bottom line: Have astronomers found the first exomoon? We think of moons as objects that orbit planets. So what do we call this object, which orbits a brown dwarf?

Source: Planetary-Mass Exosatellite Detected Around a Star’s Substellar Companion

Via ESO

The post Have we found the first exomoon … around a brown dwarf? first appeared on EarthSky.

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Our galaxy flipped after a collision, say astronomers

Watch this simulation of a galaxy flipped from edge-on to face-on after a collision with a massive dwarf galaxy. Astronomers said on July 21, 2026, that this scenario likely happened to our own Milky Way galaxy some 10 billion years ago. Video via Auriga Project and Thomas Tomlinson.

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Our galaxy flipped after a collision, say astronomers

Astronomers think that some 10 billion years ago, our Milky Way galaxy collided with another galaxy, which they’ve dubbed the Gaia Sausage. And on July 21, 2026, a team of astronomers at the Royal Astronomical Society’s National Astronomy Meeting said that this collision flipped the disk of our galaxy.

The team of astronomers, from Durham University in the U.K., used supercomputer simulations to study how 25 galaxies like our own would have evolved over billions of years. The simulations helped explain how the collision and aftermath resulted in our galaxy’s disk flipping by more than 90 degrees. And, they said, this scenario helps explain why stars in the halo around our galaxy behave the way they do.

The Milky Way galaxy and its clones

Our Milky Way is a spiral galaxy with a central bar. Most of the galaxy’s stars are in the bulge and disk, but there are other stars orbiting in a diffuse halo – a vast, much sparser sphere of stars – around the galaxy’s core and spiral arms.

These stars in the halo come from mergers, over time, with other smaller galaxies. The Gaia mission, which tracked the motions and distances of billions of stars, showed that the Milky Way’s halo is very slowly rotating. But scientists didn’t know why.

This is where the simulations came in. The researchers found that other galaxies with slowly rotating halos had a couple of things in common. First, these simulated galaxies experienced a major head-on merger with another galaxy during their evolution. And second, they experienced a disk flip. These two ingredients appeared to be the keys to creating the slowly rotating halo.

Lead researcher Kirill Batrakov at Durham University said:

We already know that the Milky Way had a massive head-on collision in the past with a galaxy known as Gaia-Sausage-Enceladus (often simply called the Gaia Sausage). So, we think that the Milky Way disk likely flipped in the past.

The Gaia Sausage hit us

This galaxy that hit us was a dwarf galaxy. It was particularly massive for a dwarf galaxy, but it was still smaller than the Milky Way.

Why do scientists call it the Gaia Sausage? Well, after the collision some 10 to 11 billion years ago, our galaxy absorbed the stars of the Gaia Sausage. The leftover stars from this galaxy now take long, elliptical paths – sausage-shaped, if you will – about the Milky Way’s center.

Artist’s concept of the merger between the Milky Way and Gaia Sausage. The yellow arrows show the positions and motions of the stars from the Gaia Sausage in this early phase of the merger, as predicted by a computer simulation. Image via ESA (artist’s impression and composition)/ Koppelman, Villalobos and Helmi (simulation)/ NASA/ESA/Hubble (galaxy image)/ RAS.

Artist’s concept showing remnants of the Gaia Sausage. Yellow arrows again show the positions and motions of the Gaia Sausage stars in the halo of our Milky Way. Image via ESA (artist’s impression and composition)/ Koppelman, Villalobos and Helmi (simulation)/ RAS.

Simulated galaxies with and without a flip

In the images below, we see two simulated galaxies. The first set of simulations are of a galaxy researchers call Halo 18. This galaxy underwent a disk flip. The one below it – simulated galaxy Halo 6 – did not have a collision or disk flip.

Views of a simulated galaxy the team calls Halo 18. After a head-on collision, the galaxy experiences a disk flip. You can see this by comparing the disk’s orientation at z=1.4 and z=0. The z and number at the bottom correspond to a redshift, which measures time. So z=0 is now, with larger numbers denoting events farther back in time. Each period of time illustrated in the simulation has a face-on and edge-on view. Image via Auriga Project/ RAS.

Views of simulated galaxy Halo 6. It undergoes neither a head-on collision or disk flip. Image via Auriga Project/ RAS.

Insight into galactic evolution and dark matter

A collision and disk flip gives astronomers more insight into the history of our own galaxy. And it also provides insight into other galaxies similar to ours. Batrakov said:

Because we live inside the Milky Way, we can study it in more detail than any other galaxy, which makes it a key testbed for understanding galaxies more broadly.

Not every galaxy experiences a disk flip. But now it seems the Milky Way experienced at least one in the past. Batrakov said:

Finding that its disk flipped adds a new chapter to that story, one we must account for when placing the Milky Way in a broader context of other galaxies. What excites me the most is that this complex history can be reconstructed just from present-day observations.

And the insight could extend to the elusive substance astronomers call dark matter. Astronomers have already known from earlier measurements of the movements of our galaxy that an invisible dark matter halo surrounds the Milky Way. In fact, dark matter makes up 90% of the mass of our galaxy.

The new study found that the starry halo rotating around the Milky Way is closely linked to the rotation of its dark matter halo. So this suggests that the Gaia Sausage remnants, along with other smaller galaxies that collided with us, may have evolved in step with the dark matter halo.

Bottom line: Our galaxy flipped after a collision with a dwarf galaxy 10 billion years ago, changing the Milky Way’s evolution, new simulations suggest.

Via Royal Astronomical Society

Read more: Did galaxy-killing wind shape the early universe?

Read more: The black hole or galaxy: Which came 1st?

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Watch this simulation of a galaxy flipped from edge-on to face-on after a collision with a massive dwarf galaxy. Astronomers said on July 21, 2026, that this scenario likely happened to our own Milky Way galaxy some 10 billion years ago. Video via Auriga Project and Thomas Tomlinson.

Science matters. Wonder matters. You matter. Join our 2026 Donation Campaign today.

Our galaxy flipped after a collision, say astronomers

Astronomers think that some 10 billion years ago, our Milky Way galaxy collided with another galaxy, which they’ve dubbed the Gaia Sausage. And on July 21, 2026, a team of astronomers at the Royal Astronomical Society’s National Astronomy Meeting said that this collision flipped the disk of our galaxy.

The team of astronomers, from Durham University in the U.K., used supercomputer simulations to study how 25 galaxies like our own would have evolved over billions of years. The simulations helped explain how the collision and aftermath resulted in our galaxy’s disk flipping by more than 90 degrees. And, they said, this scenario helps explain why stars in the halo around our galaxy behave the way they do.

The Milky Way galaxy and its clones

Our Milky Way is a spiral galaxy with a central bar. Most of the galaxy’s stars are in the bulge and disk, but there are other stars orbiting in a diffuse halo – a vast, much sparser sphere of stars – around the galaxy’s core and spiral arms.

These stars in the halo come from mergers, over time, with other smaller galaxies. The Gaia mission, which tracked the motions and distances of billions of stars, showed that the Milky Way’s halo is very slowly rotating. But scientists didn’t know why.

This is where the simulations came in. The researchers found that other galaxies with slowly rotating halos had a couple of things in common. First, these simulated galaxies experienced a major head-on merger with another galaxy during their evolution. And second, they experienced a disk flip. These two ingredients appeared to be the keys to creating the slowly rotating halo.

Lead researcher Kirill Batrakov at Durham University said:

We already know that the Milky Way had a massive head-on collision in the past with a galaxy known as Gaia-Sausage-Enceladus (often simply called the Gaia Sausage). So, we think that the Milky Way disk likely flipped in the past.

The Gaia Sausage hit us

This galaxy that hit us was a dwarf galaxy. It was particularly massive for a dwarf galaxy, but it was still smaller than the Milky Way.

Why do scientists call it the Gaia Sausage? Well, after the collision some 10 to 11 billion years ago, our galaxy absorbed the stars of the Gaia Sausage. The leftover stars from this galaxy now take long, elliptical paths – sausage-shaped, if you will – about the Milky Way’s center.

Artist’s concept of the merger between the Milky Way and Gaia Sausage. The yellow arrows show the positions and motions of the stars from the Gaia Sausage in this early phase of the merger, as predicted by a computer simulation. Image via ESA (artist’s impression and composition)/ Koppelman, Villalobos and Helmi (simulation)/ NASA/ESA/Hubble (galaxy image)/ RAS.

Artist’s concept showing remnants of the Gaia Sausage. Yellow arrows again show the positions and motions of the Gaia Sausage stars in the halo of our Milky Way. Image via ESA (artist’s impression and composition)/ Koppelman, Villalobos and Helmi (simulation)/ RAS.

Simulated galaxies with and without a flip

In the images below, we see two simulated galaxies. The first set of simulations are of a galaxy researchers call Halo 18. This galaxy underwent a disk flip. The one below it – simulated galaxy Halo 6 – did not have a collision or disk flip.

Views of a simulated galaxy the team calls Halo 18. After a head-on collision, the galaxy experiences a disk flip. You can see this by comparing the disk’s orientation at z=1.4 and z=0. The z and number at the bottom correspond to a redshift, which measures time. So z=0 is now, with larger numbers denoting events farther back in time. Each period of time illustrated in the simulation has a face-on and edge-on view. Image via Auriga Project/ RAS.

Views of simulated galaxy Halo 6. It undergoes neither a head-on collision or disk flip. Image via Auriga Project/ RAS.

Insight into galactic evolution and dark matter

A collision and disk flip gives astronomers more insight into the history of our own galaxy. And it also provides insight into other galaxies similar to ours. Batrakov said:

Because we live inside the Milky Way, we can study it in more detail than any other galaxy, which makes it a key testbed for understanding galaxies more broadly.

Not every galaxy experiences a disk flip. But now it seems the Milky Way experienced at least one in the past. Batrakov said:

Finding that its disk flipped adds a new chapter to that story, one we must account for when placing the Milky Way in a broader context of other galaxies. What excites me the most is that this complex history can be reconstructed just from present-day observations.

And the insight could extend to the elusive substance astronomers call dark matter. Astronomers have already known from earlier measurements of the movements of our galaxy that an invisible dark matter halo surrounds the Milky Way. In fact, dark matter makes up 90% of the mass of our galaxy.

The new study found that the starry halo rotating around the Milky Way is closely linked to the rotation of its dark matter halo. So this suggests that the Gaia Sausage remnants, along with other smaller galaxies that collided with us, may have evolved in step with the dark matter halo.

Bottom line: Our galaxy flipped after a collision with a dwarf galaxy 10 billion years ago, changing the Milky Way’s evolution, new simulations suggest.

Via Royal Astronomical Society

Read more: Did galaxy-killing wind shape the early universe?

Read more: The black hole or galaxy: Which came 1st?

The post Our galaxy flipped after a collision, say astronomers first appeared on EarthSky.

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Find M4: An easy to spot globular cluster near Antares

This chart shows the constellation Scorpius the Scorpion, holding the red star Antares at the its heart. Antares will lead you to a great globular cluster called Messier 4 (M4). It’s visible in the evenings for the next few months. Chart via EarthSky.

Bright red star Antares is easy to find in the prominent zodiacal constellation Scorpius the Scorpion. And if you look just slightly west of it through binoculars, you’ll see a small faint diffuse ball of light. Through a moderate-sized telescope, that fuzzy ball resolves into a tight collection of faint stars suspended in the darkness. That’s Messier 4, called M4 for short.

M4 is a globular star cluster. These balls of stars are some of the most ancient parts of our Milky Way galaxy.

M4 shines at magnitude +5.9, so it might just be visible to the unaided eye as a faint smudge on the sky under very dark skies.

Astronomer and photographer Fred Espenak captured this image of Messier 4, with Antares to its left, using a small telescope. Image via Fred Espenak. Used with permission.

Find M4 in binoculars first

If you’ve never found a deep-sky object on your own before, M4 is a great place to start. Northern Hemisphere summer evenings – or Southern Hemisphere winter evenings – are your best bet for catching M4. It’s easy to find, because it’s right next to the first-magnitude star Antares, the brightest star in the constellation Scorpius the Scorpion.

In early June, Antares is highest in the sky around midnight your local time (1 a.m. daylight saving time). That means it’s high in the south for Northern Hemisphere viewers, and overhead for Southern Hemisphere viewers. The stars return to the same place in the sky some two hours earlier every month. So, Antares is highest up around 10 p.m. (11 p.m. daylight saving time) in early July, and 8 p.m. (9 p.m. daylight saving time) in early August.

Antares and M4 fit inside the same binocular field of view, with M4 appearing a bit more than 1 degree to the west of Antares. For reference, a typical binocular field has a diameter of 5 to 6 degrees. M4 looks like a rather dim, hazy star in binoculars.

Once you spot it, you might begin longing for a telescope to be able to resolve this fuzzy cluster into a clump of starry pinpoints.

A star chart for Scorpius. Via IAU and Sky & Telescope/ Wikimedia Commons.

History of Messier 4

Swiss astronomer Jean-Philippe Loys de Chéseaux discovered M4 in 1746. However, it’s named after comet hunter Charles Messier (1730-1817). He listed M4 as object #4 in his famous Messier catalog. The catalog listed over 100 deep-sky objects that look like comets but really aren’t. Charles Messier wanted to steer comet hunters away from these faint fuzzies that masquerade as comets.

Charles Messier (1730-1817), a French astronomer, compiled the Messier catalog of deep sky objects. Image via Wikipedia (public domain).

The science of M4

Today, we know that M4 is a globular star cluster. It’s a globe-shape stellar city packed with perhaps a hundred thousand stars. At about 5,500 light-years from Earth, M4 is the closest globular cluster to us. In comparison, most globulars in our galaxy reside tens of thousands of light-years away. The farthest globular cluster, M54, is about 87,000 light-years in distance.

Unlike open star clusters – such as the Pleiades and the Hyades – the Milky Way galaxy’s 150 or so known globular star clusters are not part of the galactic disk. Instead, globular clusters populate the galactic halo, the sphere-shaped region of the Milky Way circling above and below the galactic disk. There are likely more globular clusters hidden from view by the Milky Way’s central bulge and by clouds of dust and gas.

Difference between globular and open clusters

Globular clusters are tightly packed with tens to hundreds of thousands of stars, whereas open clusters are loosely-bound stellar groups with only a few hundred to a thousand stars. Globular clusters contain primitive stars that are billions of years old, and often almost as old as the universe itself. On the other hand, open clusters consist of young, hot stars that tend to disperse after hundreds of millions of years.

If you had a telescope like Hubble, it would allow you to see these ancient stars as shown in this animation.

M4’s position is at Right Ascension: 16h 23m 35s; Declination: -26° 31′ 33″

A Hubble Space Telescope image of the globular star cluster Messier 4. The cluster is a dense collection of several hundred thousand stars. Astronomers suspect that an intermediate-mass black hole, weighing as much as 800 times the mass of our sun, lurks unseen at its core. Image via ESA/ Hubble/ NASA.

Bottom line: Find M4, one of the easiest globular star clusters for beginners to spot. It’s located just next to reddish Antares, the brightest star in Scorpius the Scorpion.

The post Find M4: An easy to spot globular cluster near Antares first appeared on EarthSky.

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This chart shows the constellation Scorpius the Scorpion, holding the red star Antares at the its heart. Antares will lead you to a great globular cluster called Messier 4 (M4). It’s visible in the evenings for the next few months. Chart via EarthSky.

Bright red star Antares is easy to find in the prominent zodiacal constellation Scorpius the Scorpion. And if you look just slightly west of it through binoculars, you’ll see a small faint diffuse ball of light. Through a moderate-sized telescope, that fuzzy ball resolves into a tight collection of faint stars suspended in the darkness. That’s Messier 4, called M4 for short.

M4 is a globular star cluster. These balls of stars are some of the most ancient parts of our Milky Way galaxy.

M4 shines at magnitude +5.9, so it might just be visible to the unaided eye as a faint smudge on the sky under very dark skies.

Astronomer and photographer Fred Espenak captured this image of Messier 4, with Antares to its left, using a small telescope. Image via Fred Espenak. Used with permission.

Find M4 in binoculars first

If you’ve never found a deep-sky object on your own before, M4 is a great place to start. Northern Hemisphere summer evenings – or Southern Hemisphere winter evenings – are your best bet for catching M4. It’s easy to find, because it’s right next to the first-magnitude star Antares, the brightest star in the constellation Scorpius the Scorpion.

In early June, Antares is highest in the sky around midnight your local time (1 a.m. daylight saving time). That means it’s high in the south for Northern Hemisphere viewers, and overhead for Southern Hemisphere viewers. The stars return to the same place in the sky some two hours earlier every month. So, Antares is highest up around 10 p.m. (11 p.m. daylight saving time) in early July, and 8 p.m. (9 p.m. daylight saving time) in early August.

Antares and M4 fit inside the same binocular field of view, with M4 appearing a bit more than 1 degree to the west of Antares. For reference, a typical binocular field has a diameter of 5 to 6 degrees. M4 looks like a rather dim, hazy star in binoculars.

Once you spot it, you might begin longing for a telescope to be able to resolve this fuzzy cluster into a clump of starry pinpoints.

A star chart for Scorpius. Via IAU and Sky & Telescope/ Wikimedia Commons.

History of Messier 4

Swiss astronomer Jean-Philippe Loys de Chéseaux discovered M4 in 1746. However, it’s named after comet hunter Charles Messier (1730-1817). He listed M4 as object #4 in his famous Messier catalog. The catalog listed over 100 deep-sky objects that look like comets but really aren’t. Charles Messier wanted to steer comet hunters away from these faint fuzzies that masquerade as comets.

Charles Messier (1730-1817), a French astronomer, compiled the Messier catalog of deep sky objects. Image via Wikipedia (public domain).

The science of M4

Today, we know that M4 is a globular star cluster. It’s a globe-shape stellar city packed with perhaps a hundred thousand stars. At about 5,500 light-years from Earth, M4 is the closest globular cluster to us. In comparison, most globulars in our galaxy reside tens of thousands of light-years away. The farthest globular cluster, M54, is about 87,000 light-years in distance.

Unlike open star clusters – such as the Pleiades and the Hyades – the Milky Way galaxy’s 150 or so known globular star clusters are not part of the galactic disk. Instead, globular clusters populate the galactic halo, the sphere-shaped region of the Milky Way circling above and below the galactic disk. There are likely more globular clusters hidden from view by the Milky Way’s central bulge and by clouds of dust and gas.

Difference between globular and open clusters

Globular clusters are tightly packed with tens to hundreds of thousands of stars, whereas open clusters are loosely-bound stellar groups with only a few hundred to a thousand stars. Globular clusters contain primitive stars that are billions of years old, and often almost as old as the universe itself. On the other hand, open clusters consist of young, hot stars that tend to disperse after hundreds of millions of years.

If you had a telescope like Hubble, it would allow you to see these ancient stars as shown in this animation.

M4’s position is at Right Ascension: 16h 23m 35s; Declination: -26° 31′ 33″

A Hubble Space Telescope image of the globular star cluster Messier 4. The cluster is a dense collection of several hundred thousand stars. Astronomers suspect that an intermediate-mass black hole, weighing as much as 800 times the mass of our sun, lurks unseen at its core. Image via ESA/ Hubble/ NASA.

Bottom line: Find M4, one of the easiest globular star clusters for beginners to spot. It’s located just next to reddish Antares, the brightest star in Scorpius the Scorpion.

The post Find M4: An easy to spot globular cluster near Antares first appeared on EarthSky.

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Another new Psyche mission flyby image of Mars

What a cool composite! This image shows the view of a crescent Mars as the Psyche mission closed in for its flyby. The most distant and smallest image is at the center. The outer ring shows the last shot before Mars filled the field of view. Psyche took the images between May 2 and 15, 2026. The mission is on its way to the asteroid 16 Psyche. See a time lapse of the flyby below. Image via NASA/JPL-Caltech/ASU.

One more image from Mars!

On July 17, 2026, NASA released one more image – really a composite of 13 images – as the Psyche mission swung past Mars for a gravity assist. The Psyche mission, on its way to asteroid 16 Psyche, flew past Mars in May. The images above are a collection from between May 2 and 15, 2026, as the space probe grew nearer to the red planet. On Psyche’s approach, the angle of the sun meant the planet appeared as a lit crescent.

The team has also put together a time lapse of Psyche’s encounter with Mars. We get to see the approaching ruddy crescent, a view looking down at Martian craters, and then the red planet with its south polar ice cap recede from view as the space probe heads off toward the asteroid belt. It’s stunning! Watch it below.

Images of the Psyche mission flyby of Mars

The Psyche mission successfully completed its flyby of Mars on May 15, 2026. Mars gave the spacecraft a 1,000-mile-per-hour (1,600-km-per-hour) critical gravity assist.

It also moved its orbit by about 1 degree. So the spacecraft is now successfully it on track toward the asteroid 16 Psyche. See some of the new images of the flyby below.

Because of the angle of Psyche’s approach, Mars appeared first as a crescent. Then it saw a more fully lit Mars as it flew away.

The Psyche mission captured this view of a crescent Mars on May 15, 2026, at about 5:03 a.m. PDT (12:03 UTC). Psyche used Mars to adjust its orbit and get a gravity assist. NASA processed the image into a natural-color view using red, green and blue data acquired directly by the spacecraft’s multispectral imager. Image via NASA/ JPL-Caltech/ ASU.

The first view of a nearly “full Mars” from NASA’s Psyche spacecraft. This image is from shortly after its closest approach to the planet on May 15. The bright white spot is the south polar cap. Image via NASA/ JPL-Caltech/ ASU.

Psyche’s view of the Martian surface shows streaks from wind blowing over impact craters in the Syrtis Major region. The wind streaks extend to about 30 miles (50 km) long. And the large craters near center-bottom of the scene are around 30 miles in diameter. Image via NASA/ JPL-Caltech/ ASU.

An enhanced-color view of the heavily cratered southern highlands of Mars. Image via NASA/ JPL-Caltech/ ASU.

Psyche mission flyby of Mars

The Psyche spacecraft, launched in 2023, is headed toward a rare metal asteroid, also named Psyche (16 Psyche, the 16th known asteroid ever discovered). It will arrive in 2029. But in order to get out to the asteroid belt, the spacecraft made a close flyby of Mars to adjust its direction and pick up a boost of speed on May 15, 2026.

Psyche came within 2,800 miles (4,500 kilometers) of the red planet’s surface. That’s closer than Earth’s geostationary satellites. The spacecraft was traveling at 12,333 mph (19,848 kph).

The maneuver used Mars’ gravity as a “slingshot” to accelerate the probe and tilt its trajectory toward its final destination, the metal-rich asteroid 16 Psyche.

An early Psyche image of Mars was the one below, from May 3. In the image, Psyche was still about 3 million miles (4.8 million km) away.

This was the Psyche spacecraft’s view of Mars on May 3, 2026. Image via NASA/ JPL-Caltech/ ASU.

Does Mars have a ring?

Astronomers think Mars might have a faint, dusty ring. The ring would be the result of micrometeorites striking Mars’ two moons, Phobos and Deimos, and ejecting dust into orbit around Mars. So there’s a chance data from Psyche could reveal this dusty ring around Mars. The sun-Mars-Psyche alignment might allow the sun striking the particles to scatter light, and image processing could pick up the ring.

Colorized version of Psyche’s image of Mars from May 3, 2026. Image via NASA/ JPL-Caltech/ ASU.

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Why fly past Mars?

While most flybys are planned to give a spacecraft a boost of speed, this flyby is also important to slightly change the spacecraft’s trajectory. The orbit of asteroid Psyche is skewed by about 3 degrees from the plane of the solar system. So in order to get to the asteroid Psyche, the Psyche mission must adjust its trajectory by a little bit.

In this diagram of the planets in our solar system, you can see Psyche’s orbit (green) is slightly tilted compared to the solar system’s plane. Image via In-the-Sky.org. Visit the interactive diagram here.

More about the Psyche mission and asteroid

Some scientists think the asteroid Psyche is a failed planet. Perhaps, as the nascent planet formed, something struck it and stripped off the outer layers, leaving behind the metallic core. If so, then some estimates put the massive, metal-rich object’s worth at $10,000 quadrillion. That’s more than the entire economy of Earth.

However, a 2021 study from the University of Arizona said asteroid Psyche might not be as metallic or dense as scientists once thought. Instead, these scientists said:

Rather than being an intact exposed core of an early planet, it might actually be closer to a rubble pile.

Who’s right? That’s what the Psyche mission hopes to discover when it arrives at the asteroid in 2029.

Artist’s concept of asteroid Psyche. Image via Maxar/ ASU/ P. Rubin/ NASA/ JPL-Caltech.

Bottom line: NASA released a composite image of Mars lit like a crescent as the Psyche mission flew by for a gravity assist. You can also watch a stunning time lapse of the whole flyby here.

Via NASA

Read more: Ancient lake on Mars? Rover finds strong new evidence

Read more: New meteor shower from an asteroid being eroded by the sun

The post Another new Psyche mission flyby image of Mars first appeared on EarthSky.

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What a cool composite! This image shows the view of a crescent Mars as the Psyche mission closed in for its flyby. The most distant and smallest image is at the center. The outer ring shows the last shot before Mars filled the field of view. Psyche took the images between May 2 and 15, 2026. The mission is on its way to the asteroid 16 Psyche. See a time lapse of the flyby below. Image via NASA/JPL-Caltech/ASU.

One more image from Mars!

On July 17, 2026, NASA released one more image – really a composite of 13 images – as the Psyche mission swung past Mars for a gravity assist. The Psyche mission, on its way to asteroid 16 Psyche, flew past Mars in May. The images above are a collection from between May 2 and 15, 2026, as the space probe grew nearer to the red planet. On Psyche’s approach, the angle of the sun meant the planet appeared as a lit crescent.

The team has also put together a time lapse of Psyche’s encounter with Mars. We get to see the approaching ruddy crescent, a view looking down at Martian craters, and then the red planet with its south polar ice cap recede from view as the space probe heads off toward the asteroid belt. It’s stunning! Watch it below.

Images of the Psyche mission flyby of Mars

The Psyche mission successfully completed its flyby of Mars on May 15, 2026. Mars gave the spacecraft a 1,000-mile-per-hour (1,600-km-per-hour) critical gravity assist.

It also moved its orbit by about 1 degree. So the spacecraft is now successfully it on track toward the asteroid 16 Psyche. See some of the new images of the flyby below.

Because of the angle of Psyche’s approach, Mars appeared first as a crescent. Then it saw a more fully lit Mars as it flew away.

The Psyche mission captured this view of a crescent Mars on May 15, 2026, at about 5:03 a.m. PDT (12:03 UTC). Psyche used Mars to adjust its orbit and get a gravity assist. NASA processed the image into a natural-color view using red, green and blue data acquired directly by the spacecraft’s multispectral imager. Image via NASA/ JPL-Caltech/ ASU.

The first view of a nearly “full Mars” from NASA’s Psyche spacecraft. This image is from shortly after its closest approach to the planet on May 15. The bright white spot is the south polar cap. Image via NASA/ JPL-Caltech/ ASU.

Psyche’s view of the Martian surface shows streaks from wind blowing over impact craters in the Syrtis Major region. The wind streaks extend to about 30 miles (50 km) long. And the large craters near center-bottom of the scene are around 30 miles in diameter. Image via NASA/ JPL-Caltech/ ASU.

An enhanced-color view of the heavily cratered southern highlands of Mars. Image via NASA/ JPL-Caltech/ ASU.

Psyche mission flyby of Mars

The Psyche spacecraft, launched in 2023, is headed toward a rare metal asteroid, also named Psyche (16 Psyche, the 16th known asteroid ever discovered). It will arrive in 2029. But in order to get out to the asteroid belt, the spacecraft made a close flyby of Mars to adjust its direction and pick up a boost of speed on May 15, 2026.

Psyche came within 2,800 miles (4,500 kilometers) of the red planet’s surface. That’s closer than Earth’s geostationary satellites. The spacecraft was traveling at 12,333 mph (19,848 kph).

The maneuver used Mars’ gravity as a “slingshot” to accelerate the probe and tilt its trajectory toward its final destination, the metal-rich asteroid 16 Psyche.

An early Psyche image of Mars was the one below, from May 3. In the image, Psyche was still about 3 million miles (4.8 million km) away.

This was the Psyche spacecraft’s view of Mars on May 3, 2026. Image via NASA/ JPL-Caltech/ ASU.

Does Mars have a ring?

Astronomers think Mars might have a faint, dusty ring. The ring would be the result of micrometeorites striking Mars’ two moons, Phobos and Deimos, and ejecting dust into orbit around Mars. So there’s a chance data from Psyche could reveal this dusty ring around Mars. The sun-Mars-Psyche alignment might allow the sun striking the particles to scatter light, and image processing could pick up the ring.

Colorized version of Psyche’s image of Mars from May 3, 2026. Image via NASA/ JPL-Caltech/ ASU.

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.

Why fly past Mars?

While most flybys are planned to give a spacecraft a boost of speed, this flyby is also important to slightly change the spacecraft’s trajectory. The orbit of asteroid Psyche is skewed by about 3 degrees from the plane of the solar system. So in order to get to the asteroid Psyche, the Psyche mission must adjust its trajectory by a little bit.

In this diagram of the planets in our solar system, you can see Psyche’s orbit (green) is slightly tilted compared to the solar system’s plane. Image via In-the-Sky.org. Visit the interactive diagram here.

More about the Psyche mission and asteroid

Some scientists think the asteroid Psyche is a failed planet. Perhaps, as the nascent planet formed, something struck it and stripped off the outer layers, leaving behind the metallic core. If so, then some estimates put the massive, metal-rich object’s worth at $10,000 quadrillion. That’s more than the entire economy of Earth.

However, a 2021 study from the University of Arizona said asteroid Psyche might not be as metallic or dense as scientists once thought. Instead, these scientists said:

Rather than being an intact exposed core of an early planet, it might actually be closer to a rubble pile.

Who’s right? That’s what the Psyche mission hopes to discover when it arrives at the asteroid in 2029.

Artist’s concept of asteroid Psyche. Image via Maxar/ ASU/ P. Rubin/ NASA/ JPL-Caltech.

Bottom line: NASA released a composite image of Mars lit like a crescent as the Psyche mission flew by for a gravity assist. You can also watch a stunning time lapse of the whole flyby here.

Via NASA

Read more: Ancient lake on Mars? Rover finds strong new evidence

Read more: New meteor shower from an asteroid being eroded by the sun

The post Another new Psyche mission flyby image of Mars first appeared on EarthSky.

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1st atmosphere detected on Earth-like, habitable-zone world

Atmosphere detected! For the 1st time, astronomers have detected an atmosphere on a rocky exoplanet in the habitable zone of its star. This is an artist’s concept of the planet in question, LHS 1140 b. Image via Melissa Weiss/ CfA.

• LHS 1140 b is a super-Earth exoplanet 48 light-years away. It orbits in the habitable zone of its red dwarf star.
• Scientists have just found evidence that this world has an atmosphere. The evidence comes from helium leaking from the planet into space.
• The researchers estimate the atmosphere is over 3 billion years old. More observations are needed to know the atmosphere’s composition.

Millions come to EarthSky for night sky news and trusted science. Your donations keep us free and accessible for all.

1st detection of atmosphere on rocky exoplanet

For the first time, astronomers have found strong evidence for an atmosphere on a rocky exoplanet in the habitable zone of its star.

The planet, LHS 1140 b, is a super-Earth planet about 48 light-years from us. LHS 1140 b orbits a red dwarf star within the so-called habitable zone. Being in this zone doesn’t necessarily make a planet fit for life. The habitable zone is simply the region around a star where temperatures would allow water to remain liquid, which is crucial for life as we know it.

The researchers, led by the Center for Astrophysics | Harvard & Smithsonian in Cambridge, Massachusetts, said on July 16, 2026, that they detected helium escaping from LHS 1140 b. And this kind of helium escape also happens in the atmospheres of Earth and other planets.

LHS 1140 b is 1.73 times the radius of Earth and 5.6 times Earth’s mass. The researchers say that’s consistent with an Earth-like bulk along with a lower-density part, such as an atmosphere or a high abundance of water.

The planet has an estimated equilibrium temperature of 116 degrees Fahrenheit (47 degrees Celsius).

The researchers published their exciting peer-reviewed results in Science on July 16, 2026.

A major milestone

The discovery is a major milestone in the study of rocky exoplanets. That’s because an atmosphere is essential for life as we understand it. Lead author Collin Cherubim at Harvard University said:

An atmosphere is essential for a planet to support life as we know it. This is the first time anyone has found an atmosphere on a rocky planet in the habitable zone of another star.

Co-author Robin Wordsworth added:

20 years ago we wondered whether other terrestrial-type planets even existed. Then we learned they’re common, and found some in the habitable zone. The next question was whether any of them had managed to keep an atmosphere. Now we know at least one has.

Cherubim and his colleagues were testing their theoretical model of LHS 1140 b. The model predicted that the planet would have an atmosphere, with helium escaping from the upper atmosphere into space. The researchers used the Warm Infrared Echelle (WINERED) Spectrograph on the Magellan Clay Telescope at Las Campanas Observatory in Chile for their observations of LHS 1140 b.

And, in fact, they observed both known planets of the star LHS 1140. Both LHS 1140 b and LHS 1140 c transited their star on the same night. The researchers saw no evidence of an atmosphere on LHS 1140 c, which is smaller and more heavily irradiated by its star. But LHS 1140 b was a different story.

View larger. | This is an artist’s concept of Kepler-62f, a super-Earth planet in the habitable zone of its star. Image via NASA.

Escaping helium points to an atmosphere

The researchers found helium escaping from LHS 1140 b. This kind of helium escape has been seen before on some planets, including Earth. Helium, a very light gas, will move to the top of an atmosphere, where it will start leaking into space. And the data was solid. David Charbonneau, head of the Harvard Department of Astronomy and astronomer in the Center for Astrophysics | Harvard & Smithsonian, said:

Collin analyzed the planets we knew about and predicted that this one would have a helium atmosphere. Then he organized telescope time, got the data and the detection was statistically rock solid.

The X-ray data from Magellan Clay explained the rate at which the planet lost its helium. This is due to X-ray radiation from the host star. Therefore, the X-ray data proved the rocky object must be replenishing its supply of helium. If it wasn’t, there would be no helium remaining in the planet’s atmosphere.

Notably, the researchers detected the helium escape in 2024 but not in 2025. This indicates that the atmospheric escape process is variable. It also means the atmosphere likely no longer contains any primordial hydrogen in its atmosphere. That’s good, since it hints that the atmosphere is more complex and evolved, like on rocky planets in our solar system, including Earth. Other gases and water would be below the top helium layer.

An ancient atmosphere

The researchers say that the atmosphere has likely survived for more than 3 billion years.

Astronomers had found that some other rocky exoplanets don’t have atmospheres. This was cause for a bit of pessimism among scientists. As Jason Dittmann at the University of Florida noted:

We were getting to the point in the field where maybe all of these planets don’t have an atmosphere, and we need to look at ones around sun-like stars instead of smaller stars. And then finally here is actually one with an atmosphere, and it happens to be the one that I had spent so many hours working on.

LHS 1140b is one of the current selected targets under the Rocky Worlds Director’s Discretionary Time (DDT) Program. Rocky Worlds DDT is a joint program for the James Webb Space Telescope and the Hubble Space Telescope that is dedicated to finding evidence of atmospheres on rocky exoplanets orbiting dwarf stars.

We still don’t know what the rest of the atmosphere, below the upper helium layer, is composed of. That will require additional observations to figure out. As Cherubim noted:

This has been a model validation, and hopefully it’s just the first of many more observations to come.

Robin Wordsworth, Collin Cherubim (lead author) and David Charbonneau at Harvard University. Image via Center for Astrophysics | Harvard & Smithsonian.

Bottom line: Scientists have found an atmosphere on rocky exoplanet LHS 1140 b. The super-Earth planet, 48 light-years away, is in the habitable zone of its red dwarf star.

Source: Helium escaping from the atmosphere of a nearby rocky exoplanet orbiting in a habitable zone

Via Center for Astrophysics | Harvard & Smithsonian

Via University of Florida

Read more: New habitable exoplanets model narrows down search for life

Read more: Habitable exoplanets could exist around nearby stars

The post 1st atmosphere detected on Earth-like, habitable-zone world first appeared on EarthSky.

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Atmosphere detected! For the 1st time, astronomers have detected an atmosphere on a rocky exoplanet in the habitable zone of its star. This is an artist’s concept of the planet in question, LHS 1140 b. Image via Melissa Weiss/ CfA.

• LHS 1140 b is a super-Earth exoplanet 48 light-years away. It orbits in the habitable zone of its red dwarf star.
• Scientists have just found evidence that this world has an atmosphere. The evidence comes from helium leaking from the planet into space.
• The researchers estimate the atmosphere is over 3 billion years old. More observations are needed to know the atmosphere’s composition.

Millions come to EarthSky for night sky news and trusted science. Your donations keep us free and accessible for all.

1st detection of atmosphere on rocky exoplanet

For the first time, astronomers have found strong evidence for an atmosphere on a rocky exoplanet in the habitable zone of its star.

The planet, LHS 1140 b, is a super-Earth planet about 48 light-years from us. LHS 1140 b orbits a red dwarf star within the so-called habitable zone. Being in this zone doesn’t necessarily make a planet fit for life. The habitable zone is simply the region around a star where temperatures would allow water to remain liquid, which is crucial for life as we know it.

The researchers, led by the Center for Astrophysics | Harvard & Smithsonian in Cambridge, Massachusetts, said on July 16, 2026, that they detected helium escaping from LHS 1140 b. And this kind of helium escape also happens in the atmospheres of Earth and other planets.

LHS 1140 b is 1.73 times the radius of Earth and 5.6 times Earth’s mass. The researchers say that’s consistent with an Earth-like bulk along with a lower-density part, such as an atmosphere or a high abundance of water.

The planet has an estimated equilibrium temperature of 116 degrees Fahrenheit (47 degrees Celsius).

The researchers published their exciting peer-reviewed results in Science on July 16, 2026.

A major milestone

The discovery is a major milestone in the study of rocky exoplanets. That’s because an atmosphere is essential for life as we understand it. Lead author Collin Cherubim at Harvard University said:

An atmosphere is essential for a planet to support life as we know it. This is the first time anyone has found an atmosphere on a rocky planet in the habitable zone of another star.

Co-author Robin Wordsworth added:

20 years ago we wondered whether other terrestrial-type planets even existed. Then we learned they’re common, and found some in the habitable zone. The next question was whether any of them had managed to keep an atmosphere. Now we know at least one has.

Cherubim and his colleagues were testing their theoretical model of LHS 1140 b. The model predicted that the planet would have an atmosphere, with helium escaping from the upper atmosphere into space. The researchers used the Warm Infrared Echelle (WINERED) Spectrograph on the Magellan Clay Telescope at Las Campanas Observatory in Chile for their observations of LHS 1140 b.

And, in fact, they observed both known planets of the star LHS 1140. Both LHS 1140 b and LHS 1140 c transited their star on the same night. The researchers saw no evidence of an atmosphere on LHS 1140 c, which is smaller and more heavily irradiated by its star. But LHS 1140 b was a different story.

View larger. | This is an artist’s concept of Kepler-62f, a super-Earth planet in the habitable zone of its star. Image via NASA.

Escaping helium points to an atmosphere

The researchers found helium escaping from LHS 1140 b. This kind of helium escape has been seen before on some planets, including Earth. Helium, a very light gas, will move to the top of an atmosphere, where it will start leaking into space. And the data was solid. David Charbonneau, head of the Harvard Department of Astronomy and astronomer in the Center for Astrophysics | Harvard & Smithsonian, said:

Collin analyzed the planets we knew about and predicted that this one would have a helium atmosphere. Then he organized telescope time, got the data and the detection was statistically rock solid.

The X-ray data from Magellan Clay explained the rate at which the planet lost its helium. This is due to X-ray radiation from the host star. Therefore, the X-ray data proved the rocky object must be replenishing its supply of helium. If it wasn’t, there would be no helium remaining in the planet’s atmosphere.

Notably, the researchers detected the helium escape in 2024 but not in 2025. This indicates that the atmospheric escape process is variable. It also means the atmosphere likely no longer contains any primordial hydrogen in its atmosphere. That’s good, since it hints that the atmosphere is more complex and evolved, like on rocky planets in our solar system, including Earth. Other gases and water would be below the top helium layer.

An ancient atmosphere

The researchers say that the atmosphere has likely survived for more than 3 billion years.

Astronomers had found that some other rocky exoplanets don’t have atmospheres. This was cause for a bit of pessimism among scientists. As Jason Dittmann at the University of Florida noted:

We were getting to the point in the field where maybe all of these planets don’t have an atmosphere, and we need to look at ones around sun-like stars instead of smaller stars. And then finally here is actually one with an atmosphere, and it happens to be the one that I had spent so many hours working on.

LHS 1140b is one of the current selected targets under the Rocky Worlds Director’s Discretionary Time (DDT) Program. Rocky Worlds DDT is a joint program for the James Webb Space Telescope and the Hubble Space Telescope that is dedicated to finding evidence of atmospheres on rocky exoplanets orbiting dwarf stars.

We still don’t know what the rest of the atmosphere, below the upper helium layer, is composed of. That will require additional observations to figure out. As Cherubim noted:

This has been a model validation, and hopefully it’s just the first of many more observations to come.

Robin Wordsworth, Collin Cherubim (lead author) and David Charbonneau at Harvard University. Image via Center for Astrophysics | Harvard & Smithsonian.

Bottom line: Scientists have found an atmosphere on rocky exoplanet LHS 1140 b. The super-Earth planet, 48 light-years away, is in the habitable zone of its red dwarf star.

Source: Helium escaping from the atmosphere of a nearby rocky exoplanet orbiting in a habitable zone

Via Center for Astrophysics | Harvard & Smithsonian

Via University of Florida

Read more: New habitable exoplanets model narrows down search for life

Read more: Habitable exoplanets could exist around nearby stars

The post 1st atmosphere detected on Earth-like, habitable-zone world first appeared on EarthSky.

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Summer Triangle star: Altair is variable and spins fast!

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

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

First, Altair rotates rapidly

Incredibly, this star requires only about 10 hours to spin once on its axis. That’s in contrast to about 27 days for our sun! And, of course, Earth takes 24 hours to spin once, so Altair rotates over twice as fast as our planet.

This speedy spin tends to flatten the star a bit, much as a pizza dough flattens as it spins. Rough estimates are that Altair’s flattening is about 14%. Our sun is also slightly flattened, although this flattening is difficult to measure because its slow rotation produces only a very small deformation.

In 2007, University of Michigan astronomers combined light from four widely separated telescopes to produce the 1st picture showing surface details on Altair. The researchers, led by John Monnier, used optical interferometry to get this image. Read more about the study at SpaceDaily.com.

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

— Sarah Salviander (@sarahsalviander) September 25, 2019

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

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

Altair compared with our sun

If Altair took the place of our sun, life on Earth would be doomed. That’s because Altair is over 10 times more luminous than our sun.

As you might have guessed, Altair is a more massive star than our sun, with about 1.8 times the sun’s mass. Its diameter is estimated to be between 1.6 to 2 times that of the sun. And its surface temperature is between 11,960 degrees F (6,620 C) and 14,840 F (8,230 C), compared to about 10,000F (5,800 C) on our sun.

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

The star is classified as a Delta Scuti variable star since it shows slight changes in luminosity. It has three dim companion stars visible through telescopes.

And not only is Altair a fast spinner, but it also moves quickly in front of its background stars. In fact, it’ll move about a full degree on our sky over the next 5,000 years.

How to see Altair from the Northern Hemisphere

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

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

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

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

Altair in culture, history and myth

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

The name Altair is Arabic in origin, and means “eagle”. Interestingly, its constellation’s name, Aquila, is the Latin word for eagle.

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

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

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

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

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

Altair’s position

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

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

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

Our Summer Triangle series also includes:

Vega is bright and blue-white

Deneb is distant and very luminous

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

from EarthSky https://ift.tt/fU7Lski

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

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

First, Altair rotates rapidly

Incredibly, this star requires only about 10 hours to spin once on its axis. That’s in contrast to about 27 days for our sun! And, of course, Earth takes 24 hours to spin once, so Altair rotates over twice as fast as our planet.

This speedy spin tends to flatten the star a bit, much as a pizza dough flattens as it spins. Rough estimates are that Altair’s flattening is about 14%. Our sun is also slightly flattened, although this flattening is difficult to measure because its slow rotation produces only a very small deformation.

In 2007, University of Michigan astronomers combined light from four widely separated telescopes to produce the 1st picture showing surface details on Altair. The researchers, led by John Monnier, used optical interferometry to get this image. Read more about the study at SpaceDaily.com.

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

— Sarah Salviander (@sarahsalviander) September 25, 2019

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

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

Altair compared with our sun

If Altair took the place of our sun, life on Earth would be doomed. That’s because Altair is over 10 times more luminous than our sun.

As you might have guessed, Altair is a more massive star than our sun, with about 1.8 times the sun’s mass. Its diameter is estimated to be between 1.6 to 2 times that of the sun. And its surface temperature is between 11,960 degrees F (6,620 C) and 14,840 F (8,230 C), compared to about 10,000F (5,800 C) on our sun.

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

The star is classified as a Delta Scuti variable star since it shows slight changes in luminosity. It has three dim companion stars visible through telescopes.

And not only is Altair a fast spinner, but it also moves quickly in front of its background stars. In fact, it’ll move about a full degree on our sky over the next 5,000 years.

How to see Altair from the Northern Hemisphere

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

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

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

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

Altair in culture, history and myth

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

The name Altair is Arabic in origin, and means “eagle”. Interestingly, its constellation’s name, Aquila, is the Latin word for eagle.

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

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

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

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

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

Altair’s position

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

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

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

Our Summer Triangle series also includes:

Vega is bright and blue-white

Deneb is distant and very luminous

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

from EarthSky https://ift.tt/fU7Lski