View at EarthSky Community Photos. | Kannan A in Singapore wrote on April 19, 2021: “Upon a close look at the moon tonight, I realized that the Lunar X and Lunar V were clearly visible. These are transient lunar features visible on the lunar surface for about 4 hours once a month. They are most striking when they are visible on the shadow side of the terminator. But they will remain visible against the lunar surface even after the terminator has moved because they are brighter than the surrounding area.” Thank you, Kannan!
Have you heard of Lunar X and Lunar V? They are famous optical features on the moon, visible through telescopes. So, when the moon’s terminator – or line between light and dark on the moon – is located in just the right place, you can see a letter X and a letter V on the moon’s surface. Are they a sign of an alien visitation? No. Rather, Lunar X is a great example of how lighting and topography can combine on a planet or moon to produce a pattern that seems familiar to the human eye.
In reality, the illusion of Lunar X is created by sunlight falling on the rims/ridges between the craters La Caille, Bianchini and Purbach. The V is caused by light illuminating crater Ukert, along with several smaller craters.
View at EarthSky Community Photos. | Radu Anghel captured this image from Bacau, Romania, on April 27, 2023. Radu wrote: “X and V from tonight’s moon.” Thank you, Radu! Learn how to see Lunar X and V below.
When are they visible?
Basically, people see Lunar X and Lunar V at each cycle of the moon, but only for a short time. In fact, they’re observable for about four hours around the 1st quarter moon phase.
View at EarthSky Community Photos. | Matthew Chin from Hong Kong, China, shared this image of the moon, where Lunar X and Lunar V are visible, on January 18, 2024. Thank you, Matthew!
Bottom line: Lunar X and Lunar V are optical features on the moon. They are visible through a telescope for several hours around the time of the 1st quarter moon.
View at EarthSky Community Photos. | Kannan A in Singapore wrote on April 19, 2021: “Upon a close look at the moon tonight, I realized that the Lunar X and Lunar V were clearly visible. These are transient lunar features visible on the lunar surface for about 4 hours once a month. They are most striking when they are visible on the shadow side of the terminator. But they will remain visible against the lunar surface even after the terminator has moved because they are brighter than the surrounding area.” Thank you, Kannan!
Have you heard of Lunar X and Lunar V? They are famous optical features on the moon, visible through telescopes. So, when the moon’s terminator – or line between light and dark on the moon – is located in just the right place, you can see a letter X and a letter V on the moon’s surface. Are they a sign of an alien visitation? No. Rather, Lunar X is a great example of how lighting and topography can combine on a planet or moon to produce a pattern that seems familiar to the human eye.
In reality, the illusion of Lunar X is created by sunlight falling on the rims/ridges between the craters La Caille, Bianchini and Purbach. The V is caused by light illuminating crater Ukert, along with several smaller craters.
View at EarthSky Community Photos. | Radu Anghel captured this image from Bacau, Romania, on April 27, 2023. Radu wrote: “X and V from tonight’s moon.” Thank you, Radu! Learn how to see Lunar X and V below.
When are they visible?
Basically, people see Lunar X and Lunar V at each cycle of the moon, but only for a short time. In fact, they’re observable for about four hours around the 1st quarter moon phase.
View at EarthSky Community Photos. | Matthew Chin from Hong Kong, China, shared this image of the moon, where Lunar X and Lunar V are visible, on January 18, 2024. Thank you, Matthew!
Bottom line: Lunar X and Lunar V are optical features on the moon. They are visible through a telescope for several hours around the time of the 1st quarter moon.
View larger. | These are the 73 protoplanetary disks – or planet-forming disks – that ALMA observed in the Lupus region (2 of the images contain binary stars). New research shows that such disks – the birthplaces of new planets – come in a much wider range of sizes than previously thought. The size of Neptune’s orbit is shown at the bottom right for scale. AU means astronomical unit. One AU is the average distance from the sun to Earth. Image via Guerra-Alvarado et al./ Astronomie.nl.
Protoplanetary disks are huge rotating disks of gas and dust around newborn stars. They are the birthplaces of new planets.
Astronomers had thought almost all protoplanetary disks are big, about the size of our solar system or larger. But new observations show they come in a wide range of sizes.
About 2/3 of protoplanetary disks are much smaller than first thought. They tend to form around young red dwarf stars and also lack the gaps seen in larger disks, where giant planets form. This means our own solar system’s original disk was not typical of most stars.
What is a typical protoplanetary disk?
Planets are born in disks of dust and gas around newborn stars called protoplanetary disks. Many of those disks are immense, as large as our solar system or more. In fact, astronomers had thought that most, if not nearly all, such disks are this size. But a team of international astronomers said on March 26, 2025, that they’ve used the Atacama Large Millimeter/submillimeter Array (ALMA) to take a closer look at 73 protoplanetary disks in the Lupus star-forming region. And they found about 2/3 of those disks are much smaller than first thought. Unlike larger disks, the smaller ones don’t have gaps or rings. So what is a typical protoplanetary disk? Or is there no such thing?
The researchers’ new paper has been accepted for publication in Astronomy & Astrophysics. You can read a preprint version on arXiv submitted on March 25, 2025.
Planet-forming disks – or protoplanetary disks – are huge swirling disks of dust and gas around young stars. They are the birthplaces of new planets. Astronomers have imaged hundreds of them in recent years. How big are they? Until now, most of the disks that astronomers found have been enormous. If centered around our sun, they would extend past the orbit of Neptune.
Astronomers thought these were typical for protoplanetary disks. But that seems not to be the case after all.
Artist’s rendering of a protoplanetary (planet-forming) disk. Video via ESO/ L. Calçada.
Planet-forming disks come in many sizes, big and small
Only about 1/3 of the disks were of the gargantuan variety. The rest – 2/3 of the 73 disks – were much smaller. They would only extend about as far as the orbit of Jupiter, if placed around our sun. That’s about 6 astronomical units (AU). The smallest one was a scant 0.6 AU in size. One AU is the average distance from the sun to Earth, 93 million miles (150 million km). Guerra-Alvarado said:
These results completely change our view of what a ‘typical’ protoplanetary disk looks like. Only the brightest disks, which are the easiest to observe, show large-scale gaps, whereas compact disks without such substructures are actually much more common.
Notably, most of the smaller disks were around small stars called red dwarfs. In fact, these low-mass stars are the most common type of star in our Milky Way galaxy. This suggests there should be many more small disks waiting to be discovered.
In addition, the researchers found these smaller disks should be ideal for super-Earth type exoplanets to form in. Those are rocky worlds larger and more massive than Earth, but smaller and less massive than Neptune. And, indeed, astronomers have found many super-Earths orbiting red dwarf stars. Sanchez said:
The observations also show that these compact discs could have optimal conditions for the formation of so-called super-Earths, as most of the dust is close to the star, where super-Earths are typically found.
The results also highlight a difference between our solar system and those that form from smaller protoplanetary disks. While our solar system has a wide range of planets, there is no super-Earth. Since the protoplanetary disk the solar system formed from was of the larger variety, there are now gas giant planets, but no super-Earths.
View larger. | Artist’s illustration of a large protoplanetary disk. The gaps are where new planets are forming. Image via ESO/ L. Calçada.
Missing gaps
The observations of the Lupus disks also provided another clue about planetary formation. Studies of full-grown stars have shown that most stars do not have giant gas planets. Smaller planets, like super-Earths and others, are more common. In fact, astronomers think super-Earths are the most common type of planet in our galaxy. This is also consistent with the new ALMA observations. Most of the smaller disks don’t have gaps in them. Those gaps are where new planets form. They gather surrounding material as they grow, clearing their orbit in the disk. This creates the gaps. As Van der Marel noted:
The discovery that the majority of the small disks do not show gaps, implies that the majority of stars do not host giant planets. This is consistent with what we see in exoplanet populations around full-grown stars. These observations link the disk population directly to the exoplanet population.
Not so typical after all
Overall, the observations show that the “typical” protoplanetary disks are not so typical after all. They are both big and small, with gaps and without gaps. Van der Marel said:
The research shows that we’ve been wrong for a long time about how a typical disk looks. Clearly, we’ve been biased toward the brightest and largest disks. Now we finally have a full overview of disks of all sizes.
Bottom line: Researchers using the ALMA observatory have found that protoplanetary disks – the birthplaces of new planets – vary in size much more than previously thought.
View larger. | These are the 73 protoplanetary disks – or planet-forming disks – that ALMA observed in the Lupus region (2 of the images contain binary stars). New research shows that such disks – the birthplaces of new planets – come in a much wider range of sizes than previously thought. The size of Neptune’s orbit is shown at the bottom right for scale. AU means astronomical unit. One AU is the average distance from the sun to Earth. Image via Guerra-Alvarado et al./ Astronomie.nl.
Protoplanetary disks are huge rotating disks of gas and dust around newborn stars. They are the birthplaces of new planets.
Astronomers had thought almost all protoplanetary disks are big, about the size of our solar system or larger. But new observations show they come in a wide range of sizes.
About 2/3 of protoplanetary disks are much smaller than first thought. They tend to form around young red dwarf stars and also lack the gaps seen in larger disks, where giant planets form. This means our own solar system’s original disk was not typical of most stars.
What is a typical protoplanetary disk?
Planets are born in disks of dust and gas around newborn stars called protoplanetary disks. Many of those disks are immense, as large as our solar system or more. In fact, astronomers had thought that most, if not nearly all, such disks are this size. But a team of international astronomers said on March 26, 2025, that they’ve used the Atacama Large Millimeter/submillimeter Array (ALMA) to take a closer look at 73 protoplanetary disks in the Lupus star-forming region. And they found about 2/3 of those disks are much smaller than first thought. Unlike larger disks, the smaller ones don’t have gaps or rings. So what is a typical protoplanetary disk? Or is there no such thing?
The researchers’ new paper has been accepted for publication in Astronomy & Astrophysics. You can read a preprint version on arXiv submitted on March 25, 2025.
Planet-forming disks – or protoplanetary disks – are huge swirling disks of dust and gas around young stars. They are the birthplaces of new planets. Astronomers have imaged hundreds of them in recent years. How big are they? Until now, most of the disks that astronomers found have been enormous. If centered around our sun, they would extend past the orbit of Neptune.
Astronomers thought these were typical for protoplanetary disks. But that seems not to be the case after all.
Artist’s rendering of a protoplanetary (planet-forming) disk. Video via ESO/ L. Calçada.
Planet-forming disks come in many sizes, big and small
Only about 1/3 of the disks were of the gargantuan variety. The rest – 2/3 of the 73 disks – were much smaller. They would only extend about as far as the orbit of Jupiter, if placed around our sun. That’s about 6 astronomical units (AU). The smallest one was a scant 0.6 AU in size. One AU is the average distance from the sun to Earth, 93 million miles (150 million km). Guerra-Alvarado said:
These results completely change our view of what a ‘typical’ protoplanetary disk looks like. Only the brightest disks, which are the easiest to observe, show large-scale gaps, whereas compact disks without such substructures are actually much more common.
Notably, most of the smaller disks were around small stars called red dwarfs. In fact, these low-mass stars are the most common type of star in our Milky Way galaxy. This suggests there should be many more small disks waiting to be discovered.
In addition, the researchers found these smaller disks should be ideal for super-Earth type exoplanets to form in. Those are rocky worlds larger and more massive than Earth, but smaller and less massive than Neptune. And, indeed, astronomers have found many super-Earths orbiting red dwarf stars. Sanchez said:
The observations also show that these compact discs could have optimal conditions for the formation of so-called super-Earths, as most of the dust is close to the star, where super-Earths are typically found.
The results also highlight a difference between our solar system and those that form from smaller protoplanetary disks. While our solar system has a wide range of planets, there is no super-Earth. Since the protoplanetary disk the solar system formed from was of the larger variety, there are now gas giant planets, but no super-Earths.
View larger. | Artist’s illustration of a large protoplanetary disk. The gaps are where new planets are forming. Image via ESO/ L. Calçada.
Missing gaps
The observations of the Lupus disks also provided another clue about planetary formation. Studies of full-grown stars have shown that most stars do not have giant gas planets. Smaller planets, like super-Earths and others, are more common. In fact, astronomers think super-Earths are the most common type of planet in our galaxy. This is also consistent with the new ALMA observations. Most of the smaller disks don’t have gaps in them. Those gaps are where new planets form. They gather surrounding material as they grow, clearing their orbit in the disk. This creates the gaps. As Van der Marel noted:
The discovery that the majority of the small disks do not show gaps, implies that the majority of stars do not host giant planets. This is consistent with what we see in exoplanet populations around full-grown stars. These observations link the disk population directly to the exoplanet population.
Not so typical after all
Overall, the observations show that the “typical” protoplanetary disks are not so typical after all. They are both big and small, with gaps and without gaps. Van der Marel said:
The research shows that we’ve been wrong for a long time about how a typical disk looks. Clearly, we’ve been biased toward the brightest and largest disks. Now we finally have a full overview of disks of all sizes.
Bottom line: Researchers using the ALMA observatory have found that protoplanetary disks – the birthplaces of new planets – vary in size much more than previously thought.
On March 20, 2025, NOAA’s South Pole Atmospheric Baseline Observatory saw the final glimpse of sunlight before 6 months of darkness. In this image, a wave of snow frames Dark Sector telescopes. Image via Ian Crocker/ NOAA.
Earth passed the March equinox on March 20, 2025. The Northern Hemisphere is beginning spring while the Southern Hemisphere is entering autumn.
The South Pole saw the sunset on the March equinox. For the next six months, Antarctica will undergo a perpetual night.
Over the course of a year, there is only one sunrise and one sunset for the South Pole. As a result, researchers who do one-year tours of duty will spend half the time in daylight and half in darkness.
In the Northern Hemisphere, March 20 signals the start of spring. It’s the start of fall in the Southern Hemisphere, where researchers and staff at NOAA’s South Pole Observatory recently witnessed the fading light of the sun and the start of six months of darkness. Ian Crocker, a South Pole station technician with NOAA’s Global Monitoring Laboratory, said:
As the sun gets low on the horizon and temperatures continue to drop, the sky transitions from the bright, crisp blue we had seen since our arrival many months ago, to slowly reveal shades of green and orange, pink and violet.
Crocker and his colleagues will help continue NOAA’s mission at the observatory throughout the 2025 Antarctic winter, including taking measurements of ozone, greenhouse gases, aerosols and solar radiation.
NOAA’s South Pole Observatory is part of the National Science Foundation’s Amundsen-Scott South Pole Station. It’s located at the geographic South Pole on the Antarctic plateau at an elevation of 2,837 meters (9,307 ft) above sea level. For nine months each year, no flights go in or out of the research station because aircraft systems don’t work in such cold conditions.
GML staff members have a one-year tour of duty at the observatory. However, they experience just one sunrise and one sunset. So consequently, they won’t see the sun rise for six months.
Crocker shares what that experience means to him:
The stark, surreal beauty of this place and this time of transition is unlike any other. It elicits feelings of wondrous awe, deep gratitude, a contemplative curiosity about the dark months ahead and knowing that this experience will leave an imprint on our lives forever.
A green sky and nearly full moon above the Dark Sector and Ceremonial South Pole, on March 17, 2025. The Dark Sector is a designated area where light and electromagnetic interference are minimized to support sensitive scientific instruments. Image via Ian Crocker/ NOAA.
Bottom line: On the March equinox, researchers at the South Pole saw the sunset and entered into six months of darkness. During their one year in Antarctica, they will only see one sunrise and one sunset.
On March 20, 2025, NOAA’s South Pole Atmospheric Baseline Observatory saw the final glimpse of sunlight before 6 months of darkness. In this image, a wave of snow frames Dark Sector telescopes. Image via Ian Crocker/ NOAA.
Earth passed the March equinox on March 20, 2025. The Northern Hemisphere is beginning spring while the Southern Hemisphere is entering autumn.
The South Pole saw the sunset on the March equinox. For the next six months, Antarctica will undergo a perpetual night.
Over the course of a year, there is only one sunrise and one sunset for the South Pole. As a result, researchers who do one-year tours of duty will spend half the time in daylight and half in darkness.
In the Northern Hemisphere, March 20 signals the start of spring. It’s the start of fall in the Southern Hemisphere, where researchers and staff at NOAA’s South Pole Observatory recently witnessed the fading light of the sun and the start of six months of darkness. Ian Crocker, a South Pole station technician with NOAA’s Global Monitoring Laboratory, said:
As the sun gets low on the horizon and temperatures continue to drop, the sky transitions from the bright, crisp blue we had seen since our arrival many months ago, to slowly reveal shades of green and orange, pink and violet.
Crocker and his colleagues will help continue NOAA’s mission at the observatory throughout the 2025 Antarctic winter, including taking measurements of ozone, greenhouse gases, aerosols and solar radiation.
NOAA’s South Pole Observatory is part of the National Science Foundation’s Amundsen-Scott South Pole Station. It’s located at the geographic South Pole on the Antarctic plateau at an elevation of 2,837 meters (9,307 ft) above sea level. For nine months each year, no flights go in or out of the research station because aircraft systems don’t work in such cold conditions.
GML staff members have a one-year tour of duty at the observatory. However, they experience just one sunrise and one sunset. So consequently, they won’t see the sun rise for six months.
Crocker shares what that experience means to him:
The stark, surreal beauty of this place and this time of transition is unlike any other. It elicits feelings of wondrous awe, deep gratitude, a contemplative curiosity about the dark months ahead and knowing that this experience will leave an imprint on our lives forever.
A green sky and nearly full moon above the Dark Sector and Ceremonial South Pole, on March 17, 2025. The Dark Sector is a designated area where light and electromagnetic interference are minimized to support sensitive scientific instruments. Image via Ian Crocker/ NOAA.
Bottom line: On the March equinox, researchers at the South Pole saw the sunset and entered into six months of darkness. During their one year in Antarctica, they will only see one sunrise and one sunset.
Star-hopping is going from stars you know … to stars you don’t know. On April evenings, you can look west after sunset to star-hop from the constellation Orion the Hunter to Sirius. Chart via EarthSky.
Star-hop from Orion to Sirius
One very easy constellation to find at this time of the year is the magnificent Orion the Hunter, now descending in the west after sunset. It’s easy because Orion contains a very noticeable pattern of three medium-bright stars in a short straight row. These stars are known as Orion’s Belt. Find Orion, and continue the line of his belt to star-hop to Sirius. Found in the constellation Canis Major, this is the sky’s brightest star!
As Earth revolves around the sun, both the constellation Orion and the star Sirius are about to disappear for a while. They always drop into the sun’s glare shortly after this time of the year, as Earth’s motion brings the sun between us and them. So be sure to look for them while you can, soon after the sun goes down. We’ll see them again in the east before dawn, beginning around late July or early August.
People learning to recognize the stars often use star-hopping – going from stars and constellations they know to ones they don’t know – to find and recognize new stars and constellations. The use of Orion’s Belt to find Sirius is one of the best-known star-hops in the sky, because the stars are so bright and the pattern is so definite.
Another great star-hop to try is using the Big Dipper to find Polaris, the North Star. If you’re in the Northern Hemisphere, this star-hop will allow you to always find north!
Look for the Big and Little Dipper high in the northern sky on spring evenings. This view is for the Northern Hemisphere. The 2 outer stars in the bowl of the Dipper point to Polaris, the North Star. Polaris marks the end of the handle of the Little Dipper. Chart via EarthSky.View at EarthSky Community Photos. | Cecille Kennedy in Oregon shared this image with us on March 13, 2024. Cecille wrote: “Before midnight, pointing the camera straight up into the night sky, there is the Big Dipper and the Little Dipper. When you are looking at Polaris, you are facing north. While other constellations move around, Polaris stays still as it’s found at the north celestial pole. Thus Polaris is a very useful star for navigators and sailors. The 2 front stars in the asterism of the Big Dipper are called Pointers because they point to the North Star or Polaris.” Thank you, Cecille!
Bottom line: Star-hopping is going from stars you know to stars you don’t know. Star-hop from the constellation Orion the Hunter to Sirius, the sky’s brightest star, before they’re gone!
Star-hopping is going from stars you know … to stars you don’t know. On April evenings, you can look west after sunset to star-hop from the constellation Orion the Hunter to Sirius. Chart via EarthSky.
Star-hop from Orion to Sirius
One very easy constellation to find at this time of the year is the magnificent Orion the Hunter, now descending in the west after sunset. It’s easy because Orion contains a very noticeable pattern of three medium-bright stars in a short straight row. These stars are known as Orion’s Belt. Find Orion, and continue the line of his belt to star-hop to Sirius. Found in the constellation Canis Major, this is the sky’s brightest star!
As Earth revolves around the sun, both the constellation Orion and the star Sirius are about to disappear for a while. They always drop into the sun’s glare shortly after this time of the year, as Earth’s motion brings the sun between us and them. So be sure to look for them while you can, soon after the sun goes down. We’ll see them again in the east before dawn, beginning around late July or early August.
People learning to recognize the stars often use star-hopping – going from stars and constellations they know to ones they don’t know – to find and recognize new stars and constellations. The use of Orion’s Belt to find Sirius is one of the best-known star-hops in the sky, because the stars are so bright and the pattern is so definite.
Another great star-hop to try is using the Big Dipper to find Polaris, the North Star. If you’re in the Northern Hemisphere, this star-hop will allow you to always find north!
Look for the Big and Little Dipper high in the northern sky on spring evenings. This view is for the Northern Hemisphere. The 2 outer stars in the bowl of the Dipper point to Polaris, the North Star. Polaris marks the end of the handle of the Little Dipper. Chart via EarthSky.View at EarthSky Community Photos. | Cecille Kennedy in Oregon shared this image with us on March 13, 2024. Cecille wrote: “Before midnight, pointing the camera straight up into the night sky, there is the Big Dipper and the Little Dipper. When you are looking at Polaris, you are facing north. While other constellations move around, Polaris stays still as it’s found at the north celestial pole. Thus Polaris is a very useful star for navigators and sailors. The 2 front stars in the asterism of the Big Dipper are called Pointers because they point to the North Star or Polaris.” Thank you, Cecille!
Bottom line: Star-hopping is going from stars you know to stars you don’t know. Star-hop from the constellation Orion the Hunter to Sirius, the sky’s brightest star, before they’re gone!
Watch this video of some of our editor’s pics for the best deep-sky photos of March 2025, and then see more below!
Stunning deep-sky photos from our community
The EarthSky community has many talented astrophotographers who capture stunning images of the deep sky. We gathered some of our favorite deep-sky photos we received in March 2025 for you to enjoy. Do you have some of your own images to share? You can submit them to us here. We love to see them!
View at EarthSky Community Photos. | Scott Smith in Palmetto, Florida, captured the Trifid nebula on March 27, 2025. Scott wrote: “The Trifid nebula illustrates 3 different types of astronomical nebulae in a single deep-sky object. A red emission nebula (light from hydrogen atoms), a blue reflection nebula (dust reflected by starlight), and dark nebula, with dense dust that silhouettes the light beneath it. The Trifid nebula (catalogued as Messier 20 or M20 and as NGC 6514) lies in the northwest of Sagittarius. Charles Messier discovered it on June 5, 1764.” Thank you, Scott!
Deep-sky photos of open star clusters
View at EarthSky Community Photos. | Our own Marcy Curran from EarthSky, in Cheyenne, Wyoming, captured open clusters Messier 36, Messier 37 and Messier 38 on March 26, 2025. Marcy wrote: “Auriga is a constellation prominent in the winter months of the Northern Hemisphere. It contains 3 bright Messier objects, all of them are open star clusters. M38 (the Starfish cluster) is about 4,200 light-years away and lies almost in the middle of the constellation. M36 (the Pinwheel cluster) is next in line to M38 and lies about 4,100 light-years distant. Next is M37, the brightest, richest and largest of the 3 open clusters. It’s about 4,500 light-years away.” Thank you, Marcy!View at EarthSky Community Photos. | Muhammad Alaa in Sanabu, Assiut, Egypt, captured the Pleiades in the constellation Taurus the Bull on March 20, 2025. Thank you, Muhammad!
Globular star clusters
View at EarthSky Community Photos. | Scott Smith in Palmetto, Florida, captured Omega Centauri on March 3, 2025. Scott wrote: “Omega Centauri is a globular cluster in the constellation of Centaurus. Located at a distance of 17,090 light-years, it is the largest known globular cluster in the Milky Way, at a diameter of roughly 150 light-years. It contains approximately 10 million stars, making it the most massive known globular cluster in the Milky Way.” Thank you, Scott!View at EarthSky Community Photos. | Tom Cofer in Lakewood Ranch, Florida, captured this telescopic view of Messier 13, the Hercules Cluster, on March 14, 2025. Tom wrote: “A snow globe of stars!” Thank you, Tom!
Galaxies in the deep-sky
View at EarthSky Community Photos. | Gwen Forrester in DeKalb County, Tennessee, captured Messier 81, a bright galaxy in the constellation Ursa Major, on March 26, 2025. Gwen wrote: “Messier 81, Bode’s Galaxy, a grand design spiral galaxy 12 million light-years away.” Thank you, Gwen!View at EarthSky Community Photos. | David Hoskin in Halifax, Nova Scotia, Canada, captured this telescopic view of Messier 82 on March 4, 2025. David wrote: “Messier 82, the Cigar Galaxy, lies in the constellation Ursa Major and is about 12 million light-years from Earth. Stars are forming at a high rate in this galaxy.” Thank you, David!View at EarthSky Community Photos. | Josh Wright in Cleethorpes, England, captured Messier 51 in the constellation Canes Venatici on March 19, 2025. Josh wrote: “The Whirlpool Galaxy, an interacting grand-design spiral galaxy 31 million light-years away. Taken with my smart telescope from my back garden.” Thank you, Josh!View at EarthSky Community Photos. | Steven Bellavia in Staunton River State Park, Virginia, captured NGC 3628, the Hamburger Galaxy, in the constellation Leo, on March 26, 2025. Steven wrote: “This is the fainter sibling of the Leo Triplet, which contains M65 and M66, which are not in this close-up image. It is an unbarred spiral galaxy about 35 million light-years away, discovered by William Herschel in 1784.” Thank you, Steven!
Messier 101, the Pinwheel Galaxy
View at EarthSky Community Photos. | Andy Dungan near Cotopaxi, Colorado, captured Messier 101, the Pinwheel Galaxy in the constellation Ursa Major, on March 2, 2025. Andy wrote: “I never would have imagined how much more detail I could get from data using PI (PixInsight). The difference is astonishing. Imagine how much better I can get when I have some real understanding of PixInsight. This experience has proved to me that software is as important if not more important than the hardware.” Wonderful image. Thank you, Andy!View at EarthSky Community Photos. | Muhammad Alaa in Sanabu, Assiut, Egypt, captured the Pinwheel Galaxy on March 25, 2025. Muhammad wrote: “The Pinwheel Galaxy is one of the most beautiful spiral galaxies. It lies in the Ursa Major constellation, about 21 million light-years from Earth.” Thank you, Muhammad!View at EarthSky Community Photos. | Jelieta Walinski at Desert Bloom Observatory in St. David, Arizona, captured the Pinwheel Galaxy on March 3, 2025. Jelieta wrote: “Marvel at the breathtaking beauty of the Pinwheel Galaxy. This celestial wonder is home to hundreds of billions of stars, with estimates suggesting around 100 billion stellar inhabitants. As we gaze upon this cosmic masterpiece, we’re reminded of the awe-inspiring beauty and mystery that awaits us in the vast expanse of the universe. Don’t forget to look up!” Thank you, Jelieta!
Bottom line: Enjoy this gallery of deep-sky photos for March 2025 from our EarthSky community. If you have a great photo to share, send it in, too. We love to see them!
Watch this video of some of our editor’s pics for the best deep-sky photos of March 2025, and then see more below!
Stunning deep-sky photos from our community
The EarthSky community has many talented astrophotographers who capture stunning images of the deep sky. We gathered some of our favorite deep-sky photos we received in March 2025 for you to enjoy. Do you have some of your own images to share? You can submit them to us here. We love to see them!
View at EarthSky Community Photos. | Scott Smith in Palmetto, Florida, captured the Trifid nebula on March 27, 2025. Scott wrote: “The Trifid nebula illustrates 3 different types of astronomical nebulae in a single deep-sky object. A red emission nebula (light from hydrogen atoms), a blue reflection nebula (dust reflected by starlight), and dark nebula, with dense dust that silhouettes the light beneath it. The Trifid nebula (catalogued as Messier 20 or M20 and as NGC 6514) lies in the northwest of Sagittarius. Charles Messier discovered it on June 5, 1764.” Thank you, Scott!
Deep-sky photos of open star clusters
View at EarthSky Community Photos. | Our own Marcy Curran from EarthSky, in Cheyenne, Wyoming, captured open clusters Messier 36, Messier 37 and Messier 38 on March 26, 2025. Marcy wrote: “Auriga is a constellation prominent in the winter months of the Northern Hemisphere. It contains 3 bright Messier objects, all of them are open star clusters. M38 (the Starfish cluster) is about 4,200 light-years away and lies almost in the middle of the constellation. M36 (the Pinwheel cluster) is next in line to M38 and lies about 4,100 light-years distant. Next is M37, the brightest, richest and largest of the 3 open clusters. It’s about 4,500 light-years away.” Thank you, Marcy!View at EarthSky Community Photos. | Muhammad Alaa in Sanabu, Assiut, Egypt, captured the Pleiades in the constellation Taurus the Bull on March 20, 2025. Thank you, Muhammad!
Globular star clusters
View at EarthSky Community Photos. | Scott Smith in Palmetto, Florida, captured Omega Centauri on March 3, 2025. Scott wrote: “Omega Centauri is a globular cluster in the constellation of Centaurus. Located at a distance of 17,090 light-years, it is the largest known globular cluster in the Milky Way, at a diameter of roughly 150 light-years. It contains approximately 10 million stars, making it the most massive known globular cluster in the Milky Way.” Thank you, Scott!View at EarthSky Community Photos. | Tom Cofer in Lakewood Ranch, Florida, captured this telescopic view of Messier 13, the Hercules Cluster, on March 14, 2025. Tom wrote: “A snow globe of stars!” Thank you, Tom!
Galaxies in the deep-sky
View at EarthSky Community Photos. | Gwen Forrester in DeKalb County, Tennessee, captured Messier 81, a bright galaxy in the constellation Ursa Major, on March 26, 2025. Gwen wrote: “Messier 81, Bode’s Galaxy, a grand design spiral galaxy 12 million light-years away.” Thank you, Gwen!View at EarthSky Community Photos. | David Hoskin in Halifax, Nova Scotia, Canada, captured this telescopic view of Messier 82 on March 4, 2025. David wrote: “Messier 82, the Cigar Galaxy, lies in the constellation Ursa Major and is about 12 million light-years from Earth. Stars are forming at a high rate in this galaxy.” Thank you, David!View at EarthSky Community Photos. | Josh Wright in Cleethorpes, England, captured Messier 51 in the constellation Canes Venatici on March 19, 2025. Josh wrote: “The Whirlpool Galaxy, an interacting grand-design spiral galaxy 31 million light-years away. Taken with my smart telescope from my back garden.” Thank you, Josh!View at EarthSky Community Photos. | Steven Bellavia in Staunton River State Park, Virginia, captured NGC 3628, the Hamburger Galaxy, in the constellation Leo, on March 26, 2025. Steven wrote: “This is the fainter sibling of the Leo Triplet, which contains M65 and M66, which are not in this close-up image. It is an unbarred spiral galaxy about 35 million light-years away, discovered by William Herschel in 1784.” Thank you, Steven!
Messier 101, the Pinwheel Galaxy
View at EarthSky Community Photos. | Andy Dungan near Cotopaxi, Colorado, captured Messier 101, the Pinwheel Galaxy in the constellation Ursa Major, on March 2, 2025. Andy wrote: “I never would have imagined how much more detail I could get from data using PI (PixInsight). The difference is astonishing. Imagine how much better I can get when I have some real understanding of PixInsight. This experience has proved to me that software is as important if not more important than the hardware.” Wonderful image. Thank you, Andy!View at EarthSky Community Photos. | Muhammad Alaa in Sanabu, Assiut, Egypt, captured the Pinwheel Galaxy on March 25, 2025. Muhammad wrote: “The Pinwheel Galaxy is one of the most beautiful spiral galaxies. It lies in the Ursa Major constellation, about 21 million light-years from Earth.” Thank you, Muhammad!View at EarthSky Community Photos. | Jelieta Walinski at Desert Bloom Observatory in St. David, Arizona, captured the Pinwheel Galaxy on March 3, 2025. Jelieta wrote: “Marvel at the breathtaking beauty of the Pinwheel Galaxy. This celestial wonder is home to hundreds of billions of stars, with estimates suggesting around 100 billion stellar inhabitants. As we gaze upon this cosmic masterpiece, we’re reminded of the awe-inspiring beauty and mystery that awaits us in the vast expanse of the universe. Don’t forget to look up!” Thank you, Jelieta!
Bottom line: Enjoy this gallery of deep-sky photos for March 2025 from our EarthSky community. If you have a great photo to share, send it in, too. We love to see them!
The April birthstone is the diamond. And a diamond solitaire ring is a popular choice for engagement rings. Image via EarthSky’s Marcy Curran.
The April birthstone
The April birthstone is the diamond. It’s treasured for its exceptional hardness and purity of color. Although the diamond is not the rarest of gems, it’s still one of the most popular gemstones.
As a result of a diamonds’ cold, sparkling fire, it’s held us spellbound for centuries. What’s more, it’s inspired rich, passionate myths of romance, intrigue, power, greed and magic. Today, the diamond is a symbol of enduring love, and often graces engagement rings.
Ancient Hindus, finding diamonds washed out of the ground after thunderstorms, believed bolts of lightning created them.
Of course, we know different now. In fact, diamonds are the rich cousins of graphite. Both are crystalline forms of pure carbon. But the enormous differences in their properties are a result of the way the carbon atoms bond together. In graphite, carbon atoms form in sheets that easily slide past each other, which makes graphite ideal as a lubricant and, of course, as pencil lead. On the other hand, diamond crystals are a tight-fisted network of carbon atoms securely bound in four directions. Thus, making diamonds the hardest naturally-occurring substance in the world.
So to achieve such a compact and strongly-held network of carbon atoms, it’s believed that diamonds crystallized deep under the Earth’s surface. At these depths – 90 to 120 miles deep (145 – 193 km) – the proper conditions for the formation of diamonds exist. That’s because pressures are more than 65,000 times that of the atmosphere at the Earth’s surface, with temperatures exceeding 2,700 degrees Fahrenheit (1,500 degrees Celsius). And as a matter of fact, such pressures and temperatures are reproduced in laboratories successfully creating synthetic diamonds.
This is the typical shape of a rough diamond crystal. Its lustrous faces also indicate that this crystal is from a primary deposit. Image via Géry Parent/ Wikipedia (Public domain).
The quality of diamonds
There are many kinds of diamonds: transparent, translucent, or opaque; ranging from colorless to sooty black, with many colors in between. Mostly transparent diamonds, those that are colorless or tinted, end up in jewelry. And then lower grade diamonds are for industrial use.
The color of a diamond depends on the kind of impurities embedded inside it. For example, yellow diamonds betray minute quantities of nitrogen, while boron imparts a bluish hue. As a matter of fact, some inclusions in diamonds have great scientific value. That’s because they are time capsules containing valuable information about conditions deep in the Earth’s upper mantle where diamonds form. Additionally, they offer clues to the formation and age of the diamond.
Different types of rough diamonds. Image via James St. John/ Wikipedia (CC BY 2.0).
Sources of the April birthstone
Diamonds are found in alluvial deposits or gravel swept away by streams, rivers, glaciers and ocean currents. Also, they are in sedimentary rock where gravel deposits and organic material are compressed into rock. Diamonds are in some samples of kimberlite, a type of volcanic rock first identified in Kimberley, South Africa. Also, the diamonds in kimberlite may be very old, perhaps as much as three billion years old. And even meteorites – bits of rocky space debris that land on Earth – often contain tiny flecks of diamonds.
Diamonds are crystals. Crystals are the ultimate form of symmetry in nature. Their shape reflects the internal orderly arrangement of atoms within the crystal. In diamonds, atoms of carbon are held tightly by covalent bonding, where two neighboring atoms share an electron, endowing the diamond crystal with great strength. But despite that hardness, diamonds can be cut with saws and polished with grinding wheels coated with tiny industrial diamond fragments. In their natural form, diamonds can appear quite unimpressive. But they are cut and polished by skilled craftsmen in a pattern that reflects and refracts the light among their facets to reveal the hidden beauty of the stone.
One of the most famous diamonds, the Hope Diamond, shown here in the National Museum of Natural History in Washington, D.C. Image via David Bjorgen/ Wikipedia (CC BY-SA 3.0).
Diamond lore
Some diamonds seem to have lived lives of their own. One legendary stone in the diamond hall of fame is the Koh-i-noor (“Mountain of Light”). The Koh-i-noor diamond is believed to be 5,000 years old, and was featured in the great Sanskrit epic The Mahabharata.
Originally owned by the Rajah of Malwa in India, the Koh-i-noor has since been a player in victories and defeats spanning India, Persia and Afghanistan. It was in the possession of the great Mogul dynasty from 1526 to 1739. Its owners included Shah Jehan, who built the Taj Mahal in memory of his queen Mumtaz. The Persian invader Nadir Shah briefly possessed it until his assassination in 1747. The jewel then fell into the hands of Afghan rulers who eventually surrendered it to the Rajah of Punjab, Ranjit Singh.
Two years after Ranjit Singh’s death in 1839, Punjab became part of India under British rule and they presented the stone to Queen Victoria. Then she had it cut from its original 187 carats to 108 carats to further enhance its beauty. After her death, the diamond became part of the British crown jewels. Queen Elizabeth (later the Queen Mother) wore it in her crown at her 1937 coronation. However, Camilla chose to wear another crown to Charles III coronation in 2023.
Find out about the birthstones for the other months of the year.
The April birthstone is the diamond. And a diamond solitaire ring is a popular choice for engagement rings. Image via EarthSky’s Marcy Curran.
The April birthstone
The April birthstone is the diamond. It’s treasured for its exceptional hardness and purity of color. Although the diamond is not the rarest of gems, it’s still one of the most popular gemstones.
As a result of a diamonds’ cold, sparkling fire, it’s held us spellbound for centuries. What’s more, it’s inspired rich, passionate myths of romance, intrigue, power, greed and magic. Today, the diamond is a symbol of enduring love, and often graces engagement rings.
Ancient Hindus, finding diamonds washed out of the ground after thunderstorms, believed bolts of lightning created them.
Of course, we know different now. In fact, diamonds are the rich cousins of graphite. Both are crystalline forms of pure carbon. But the enormous differences in their properties are a result of the way the carbon atoms bond together. In graphite, carbon atoms form in sheets that easily slide past each other, which makes graphite ideal as a lubricant and, of course, as pencil lead. On the other hand, diamond crystals are a tight-fisted network of carbon atoms securely bound in four directions. Thus, making diamonds the hardest naturally-occurring substance in the world.
So to achieve such a compact and strongly-held network of carbon atoms, it’s believed that diamonds crystallized deep under the Earth’s surface. At these depths – 90 to 120 miles deep (145 – 193 km) – the proper conditions for the formation of diamonds exist. That’s because pressures are more than 65,000 times that of the atmosphere at the Earth’s surface, with temperatures exceeding 2,700 degrees Fahrenheit (1,500 degrees Celsius). And as a matter of fact, such pressures and temperatures are reproduced in laboratories successfully creating synthetic diamonds.
This is the typical shape of a rough diamond crystal. Its lustrous faces also indicate that this crystal is from a primary deposit. Image via Géry Parent/ Wikipedia (Public domain).
The quality of diamonds
There are many kinds of diamonds: transparent, translucent, or opaque; ranging from colorless to sooty black, with many colors in between. Mostly transparent diamonds, those that are colorless or tinted, end up in jewelry. And then lower grade diamonds are for industrial use.
The color of a diamond depends on the kind of impurities embedded inside it. For example, yellow diamonds betray minute quantities of nitrogen, while boron imparts a bluish hue. As a matter of fact, some inclusions in diamonds have great scientific value. That’s because they are time capsules containing valuable information about conditions deep in the Earth’s upper mantle where diamonds form. Additionally, they offer clues to the formation and age of the diamond.
Different types of rough diamonds. Image via James St. John/ Wikipedia (CC BY 2.0).
Sources of the April birthstone
Diamonds are found in alluvial deposits or gravel swept away by streams, rivers, glaciers and ocean currents. Also, they are in sedimentary rock where gravel deposits and organic material are compressed into rock. Diamonds are in some samples of kimberlite, a type of volcanic rock first identified in Kimberley, South Africa. Also, the diamonds in kimberlite may be very old, perhaps as much as three billion years old. And even meteorites – bits of rocky space debris that land on Earth – often contain tiny flecks of diamonds.
Diamonds are crystals. Crystals are the ultimate form of symmetry in nature. Their shape reflects the internal orderly arrangement of atoms within the crystal. In diamonds, atoms of carbon are held tightly by covalent bonding, where two neighboring atoms share an electron, endowing the diamond crystal with great strength. But despite that hardness, diamonds can be cut with saws and polished with grinding wheels coated with tiny industrial diamond fragments. In their natural form, diamonds can appear quite unimpressive. But they are cut and polished by skilled craftsmen in a pattern that reflects and refracts the light among their facets to reveal the hidden beauty of the stone.
One of the most famous diamonds, the Hope Diamond, shown here in the National Museum of Natural History in Washington, D.C. Image via David Bjorgen/ Wikipedia (CC BY-SA 3.0).
Diamond lore
Some diamonds seem to have lived lives of their own. One legendary stone in the diamond hall of fame is the Koh-i-noor (“Mountain of Light”). The Koh-i-noor diamond is believed to be 5,000 years old, and was featured in the great Sanskrit epic The Mahabharata.
Originally owned by the Rajah of Malwa in India, the Koh-i-noor has since been a player in victories and defeats spanning India, Persia and Afghanistan. It was in the possession of the great Mogul dynasty from 1526 to 1739. Its owners included Shah Jehan, who built the Taj Mahal in memory of his queen Mumtaz. The Persian invader Nadir Shah briefly possessed it until his assassination in 1747. The jewel then fell into the hands of Afghan rulers who eventually surrendered it to the Rajah of Punjab, Ranjit Singh.
Two years after Ranjit Singh’s death in 1839, Punjab became part of India under British rule and they presented the stone to Queen Victoria. Then she had it cut from its original 187 carats to 108 carats to further enhance its beauty. After her death, the diamond became part of the British crown jewels. Queen Elizabeth (later the Queen Mother) wore it in her crown at her 1937 coronation. However, Camilla chose to wear another crown to Charles III coronation in 2023.
Find out about the birthstones for the other months of the year.
View larger. | Artist’s concept of a collision between 2 rocky bodies in the early solar system. A new study suggests an event like this, although with more similarly sized bodies, created Mercury. Image via NASA/ JPL-Caltech/ Wikimedia Commons (Public domain).
How did planet Mercury form? Scientists have been pondering this question for a long time.
According to new research, Mercury originated from the massive grazing collision of 2 similarly-sized bodies.
Collisions like this one were common in the early solar system billions of years ago. In fact, they likely accounted for about 1/3 of all impacts.
Mercury is the smallest and innermost planet in our solar system. It looks a lot like our moon at first glance, but it’s its own world, with unique geology and history. Scientists have been trying to figure out how it formed for a long time. And now, a new study from researchers in Brazil, Germany and France has shed some new light on the question. In a new preprint paper published on March 4, 2025, they said that a grazing giant collision between two similar-sized rocky bodies likely created Mercury a few billion years ago.
Mark Thompson wrote about the latest findings in Universe Today on March 25, 2025.
Despite its superficial resemblance to our moon, Mercury is a unique and strange world. Researchers have found evidence for a possible 10-mile-thick (16 km) layer of diamonds between the core and mantle of this planet, along with salty glaciers that could even be habitable.
And until now, scientists haven’t fully understood how Mercury formed. Surrounding its iron core is a relatively thin silicate mantle. In fact, the solid inner core and the molten outer core together take up nearly 85% of the planet’s radius. That’s much more than any of the other rocky planets. This posed a mystery. As the paper states:
The origin of Mercury still remains poorly understood compared to the other rocky planets of the solar system. One of the most relevant constraints that any formation model has to fulfill refers to its internal structure, with a predominant iron core covered by a thin silicate layer.
View larger. | Diagram depicting the interior structure of Mercury as currently understood. The overall core is nearly 85% of the planet’s radius, much more than other rocky planets in our solar system. This supports the theory that Mercury formed from the grazing impact of 2 similarly-sized bodies. Image via NASA/ Goddard Space Flight Center.
Collisions in the early solar system
The early solar system was a chaotic place, with frequent collisions between rocky bodies. And Mercury’s strangely large core has led scientists to hypothesize that a giant collision with a much larger body might have stripped away its outer layers.
But simulations of the early solar system have found colossal impacts between very differently sized objects to be relatively rare. On the other hand, recent simulations suggest that grazing ‘hit-and-run’ collisions between similarly-sized bodies are much more common. In fact, they likely accounted for about 1/3 of all impacts in the early solar system. And this, the new study says, is how Mercury likely formed.
One of the newest images of Mercury, from the 3rd flyby of the BepiColombo spacecraft on June 19, 2023. Image via ESA/ BepiColombo/ MTM.
Did a massive collision create Mercury?
Patrick Franco at the National Observatory in Brazil led the new study into whether two similar-sized rocky bodies could form a planet similar to Mercury.
Their study used a main body – a proto-Mercury – with a mass just over 10% of Earth’s, and a 30% iron makeup. In the simulations, the researchers experimented with variously sized secondary bodies, with varying amounts of iron.
They also varied the impact velocities between the two bodies, from 2.8 to 3.8 times the mutual escape velocity. The escape velocity is the minimum speed needed for an object to escape the orbit of or contact with a primary body.
Within these parameters, the researchers experimented with collision scenarios that could have occurred billions of years ago in the early solar system.
And they eventually found a setup in which Mercury grazed a similarly sized rocky object in a hit-and-run collision, leading it to lose much of its outer material. This scenario produced a planet that matched Mercury’s mass with a 5% margin, and left a core of 65-75% iron, matching Mercury’s current value of 70%. It’s strong evidence, they said, that a collision like this produced the planet we know today.
Patrick Franco at the National Observatory in Brazil is the lead author of the new Mercury study. Image via LinkedIn.
Bottom line: A new study says Mercury was formed from a huge collision between 2 similarly-sized rocky bodies.
View larger. | Artist’s concept of a collision between 2 rocky bodies in the early solar system. A new study suggests an event like this, although with more similarly sized bodies, created Mercury. Image via NASA/ JPL-Caltech/ Wikimedia Commons (Public domain).
How did planet Mercury form? Scientists have been pondering this question for a long time.
According to new research, Mercury originated from the massive grazing collision of 2 similarly-sized bodies.
Collisions like this one were common in the early solar system billions of years ago. In fact, they likely accounted for about 1/3 of all impacts.
Mercury is the smallest and innermost planet in our solar system. It looks a lot like our moon at first glance, but it’s its own world, with unique geology and history. Scientists have been trying to figure out how it formed for a long time. And now, a new study from researchers in Brazil, Germany and France has shed some new light on the question. In a new preprint paper published on March 4, 2025, they said that a grazing giant collision between two similar-sized rocky bodies likely created Mercury a few billion years ago.
Mark Thompson wrote about the latest findings in Universe Today on March 25, 2025.
Despite its superficial resemblance to our moon, Mercury is a unique and strange world. Researchers have found evidence for a possible 10-mile-thick (16 km) layer of diamonds between the core and mantle of this planet, along with salty glaciers that could even be habitable.
And until now, scientists haven’t fully understood how Mercury formed. Surrounding its iron core is a relatively thin silicate mantle. In fact, the solid inner core and the molten outer core together take up nearly 85% of the planet’s radius. That’s much more than any of the other rocky planets. This posed a mystery. As the paper states:
The origin of Mercury still remains poorly understood compared to the other rocky planets of the solar system. One of the most relevant constraints that any formation model has to fulfill refers to its internal structure, with a predominant iron core covered by a thin silicate layer.
View larger. | Diagram depicting the interior structure of Mercury as currently understood. The overall core is nearly 85% of the planet’s radius, much more than other rocky planets in our solar system. This supports the theory that Mercury formed from the grazing impact of 2 similarly-sized bodies. Image via NASA/ Goddard Space Flight Center.
Collisions in the early solar system
The early solar system was a chaotic place, with frequent collisions between rocky bodies. And Mercury’s strangely large core has led scientists to hypothesize that a giant collision with a much larger body might have stripped away its outer layers.
But simulations of the early solar system have found colossal impacts between very differently sized objects to be relatively rare. On the other hand, recent simulations suggest that grazing ‘hit-and-run’ collisions between similarly-sized bodies are much more common. In fact, they likely accounted for about 1/3 of all impacts in the early solar system. And this, the new study says, is how Mercury likely formed.
One of the newest images of Mercury, from the 3rd flyby of the BepiColombo spacecraft on June 19, 2023. Image via ESA/ BepiColombo/ MTM.
Did a massive collision create Mercury?
Patrick Franco at the National Observatory in Brazil led the new study into whether two similar-sized rocky bodies could form a planet similar to Mercury.
Their study used a main body – a proto-Mercury – with a mass just over 10% of Earth’s, and a 30% iron makeup. In the simulations, the researchers experimented with variously sized secondary bodies, with varying amounts of iron.
They also varied the impact velocities between the two bodies, from 2.8 to 3.8 times the mutual escape velocity. The escape velocity is the minimum speed needed for an object to escape the orbit of or contact with a primary body.
Within these parameters, the researchers experimented with collision scenarios that could have occurred billions of years ago in the early solar system.
And they eventually found a setup in which Mercury grazed a similarly sized rocky object in a hit-and-run collision, leading it to lose much of its outer material. This scenario produced a planet that matched Mercury’s mass with a 5% margin, and left a core of 65-75% iron, matching Mercury’s current value of 70%. It’s strong evidence, they said, that a collision like this produced the planet we know today.
Patrick Franco at the National Observatory in Brazil is the lead author of the new Mercury study. Image via LinkedIn.
Bottom line: A new study says Mercury was formed from a huge collision between 2 similarly-sized rocky bodies.
