Danuri, a Korean satellite orbiting the moon, captured the August 12, 2026, solar eclipse from the moon’s perspective. That’s the moon at upper right! Near the top of Earth, where it meets the moon, you can see a shadow where the total solar eclipse is crossing Greenland. Image via Danuri (KPLO)/ KARI.
The total solar eclipse captivated millions on August 12, 2026, as it crossed from Greenland to Iceland and then swept across Spain. We’ve seen stunning images of the event – both the partial and total phase – from EarthSky community members around the world. The images show the moon as it passed in front of the sun from Earth’s point of view. And now we’ve got another incredible perspective: that of the Korean Aerospace Research Institute’s lunar orbiter Danuri, as it looked back at Earth from lunar orbit.
Danuri, which launched to the moon in 2022, began orbiting the moon on December 26 of that year. The mission will continue operations until 2027. On August 12, 2026, the Danuri space probe was near the lunar south pole, heading from the moon’s far side to the near side when it caught Earth rising. And that was also the moment the moon’s shadow was crossing Earth in the vicinity of Greenland.
Solar eclipse from 236,000 miles (380,000 km) away
The Korea Aerospace Research Institute shared the image online and said:
In the early hours of August 13 [for Korea], the sun vanished from the skies over Europe.
This marked the first total solar eclipse visible from the Spanish mainland in 121 years, since 1905. Danuri captured this moment – which was not visible from Korea – from its orbit around the moon.
While moving from the far side to the near side of the moon and approaching the lunar south pole, Danuri photographed the moment the Earth rose above the lunar surface.
Do you see the dark patch cast upon the Earth in the photo?
That is the ‘moon’s shadow’ covering the Greenland region. Some parts of the shadow fell outside the field of view, obscured by the moon itself.
Even at this very moment, Danuri is recording the cosmos—views unseen from Earth.
Other eclipse views from space
This is not the first time we’ve seen eclipses from a vantage point in space. A weather satellite from the European Union also caught the August 12, 2026, eclipse.
During the 2024 total solar eclipse, astronauts aboard the International Space Station captured a view of Earth darkened by the moon’s shadow as well.
And in 2017, NASA’s Lunar Reconnaissance Orbiter caught the total solar eclipse from lunar orbit, but this view didn’t include the moon’s limb.
So the view of the total solar eclipse crossing Earth with the moon in the foreground is a truly unique view! Someday, perhaps an astronaut will capture a view of an eclipse on Earth with the lunar soil under their feet.
Bottom line: The Korean Aerospace Research Institute’s lunar orbiter, Danuri, captured a view of the solar eclipse on August 12, 2026. This unique perspective includes the moon’s limb in the foreground.
Danuri, a Korean satellite orbiting the moon, captured the August 12, 2026, solar eclipse from the moon’s perspective. That’s the moon at upper right! Near the top of Earth, where it meets the moon, you can see a shadow where the total solar eclipse is crossing Greenland. Image via Danuri (KPLO)/ KARI.
The total solar eclipse captivated millions on August 12, 2026, as it crossed from Greenland to Iceland and then swept across Spain. We’ve seen stunning images of the event – both the partial and total phase – from EarthSky community members around the world. The images show the moon as it passed in front of the sun from Earth’s point of view. And now we’ve got another incredible perspective: that of the Korean Aerospace Research Institute’s lunar orbiter Danuri, as it looked back at Earth from lunar orbit.
Danuri, which launched to the moon in 2022, began orbiting the moon on December 26 of that year. The mission will continue operations until 2027. On August 12, 2026, the Danuri space probe was near the lunar south pole, heading from the moon’s far side to the near side when it caught Earth rising. And that was also the moment the moon’s shadow was crossing Earth in the vicinity of Greenland.
Solar eclipse from 236,000 miles (380,000 km) away
The Korea Aerospace Research Institute shared the image online and said:
In the early hours of August 13 [for Korea], the sun vanished from the skies over Europe.
This marked the first total solar eclipse visible from the Spanish mainland in 121 years, since 1905. Danuri captured this moment – which was not visible from Korea – from its orbit around the moon.
While moving from the far side to the near side of the moon and approaching the lunar south pole, Danuri photographed the moment the Earth rose above the lunar surface.
Do you see the dark patch cast upon the Earth in the photo?
That is the ‘moon’s shadow’ covering the Greenland region. Some parts of the shadow fell outside the field of view, obscured by the moon itself.
Even at this very moment, Danuri is recording the cosmos—views unseen from Earth.
Other eclipse views from space
This is not the first time we’ve seen eclipses from a vantage point in space. A weather satellite from the European Union also caught the August 12, 2026, eclipse.
During the 2024 total solar eclipse, astronauts aboard the International Space Station captured a view of Earth darkened by the moon’s shadow as well.
And in 2017, NASA’s Lunar Reconnaissance Orbiter caught the total solar eclipse from lunar orbit, but this view didn’t include the moon’s limb.
So the view of the total solar eclipse crossing Earth with the moon in the foreground is a truly unique view! Someday, perhaps an astronaut will capture a view of an eclipse on Earth with the lunar soil under their feet.
Bottom line: The Korean Aerospace Research Institute’s lunar orbiter, Danuri, captured a view of the solar eclipse on August 12, 2026. This unique perspective includes the moon’s limb in the foreground.
View larger. | Artist’s concept of the super-Earth exoplanet LP 890-9 c. It orbits a red dwarf star 98 light-years from Earth. A new study suggests that super-Earths might be solid deep on the inside. This is due to minerals under extreme pressure and temperature – much more extreme than inside Earth – being compressed. Image via NASA/ JPL-Caltech/ Eos.
Super-Earths are rocky exoplanets, larger and more massive than Earth but smaller than Neptune. What are they like on the inside?
Researchers at Princeton University say in a new study that, surprisingly, super-Earths might be solid deep down in their mantles.
The study suggests the minerals inside these worlds would take on unusual forms due to the extreme heat and pressure deep down, meaning they would remain solid instead of melting.
Super-Earths are rocky exoplanets that are larger and more massive than Earth, but smaller than Neptune. Powerful telescopes have provided clues about what their atmospheres are like. But what are they like on the inside?
Some astronomers have suggested these worlds could contain oceans of magma. Now, a new study from researchers at Princeton University in New Jersey suggests something surprising; super-Earths might actually be solid deep inside their mantles. That’s because under the intense pressure and heat deep below the surface, some minerals could take unusual forms.
The researchers found these minerals could likely withstand the extremely high temperatures and pressures deep inside super-Earths – much hotter than inside Earth – and remain solid.
Nathaniel Scharping wrote about the new findings for Eos on August 6, 2026.
View larger. | Illustration depicting the size of a super-Earth called CoRoT-7b. Super-Earths are larger and more massive than Earth, but smaller and less massive than Neptune. Image via Aldaraon/ Wikimedia Commons.
Minerals take unusual forms
Scientists expect that some common minerals found inside Earth should be present within super-Earths as well. This includes substances like magnesium orthosilicate (Mg2SiO4). But the interiors of super-Earths have much more intense pressures and temperatures than inside Earth.
As noted in Eos, the atoms in the mineral would rearrange into different crystal structures. As explained in the article:
One of these high-pressure forms is called the spinel phase [spinel group], which is found in Earth’s mantle. At even higher pressures, this phase breaks down into two different minerals: bridgmanite, the most abundant mineral phase in Earth, and ferropericlase, a magnesium-rich oxide. However, under the far more extreme pressures expected inside massive rocky planets known as super-Earths, Mg2SiO4 becomes stable again in an entirely new crystal structure called post-post-spinel. Scientists predict that this ultrahigh-pressure phase of Mg2SiO4 is one of the dominant minerals in the deep mantles of super-Earths, making its melting behavior important for understanding how these planets form and evolve.
View larger. | This is an artist’s concept of a super-Earth with a deep magma ocean generating a magnetic field. The new study suggests that the deepest parts of these magma oceans in the mantle would remain solid instead of liquid. Image via University of Rochester Laboratory for Laser Energetics/ Michael Franchot/ University of Rochester.
Recreating conditions inside super-Earths
It is difficult to recreate these kinds of conditions in a lab. So the researchers did a computer model recreation instead. They used a technique called thermodynamic integration to study the melting curve of this mineral – the bizarrely named post-post-spinel Mg2SiO4 – at up to 1,300 gigapascals of pressure.
The post-post-spinel Mg2SiO4 is a refractory mineral. That means it can withstand extremely high temperatures before it begins to melt. Pressure plays a role, too. Depending on the pressure, it melts between 9,780 K (17,144 degrees Fahrenheit or 9,507 degrees Celsius) and 14,897 K (26,350 degrees Fahrenheit or 14,620 degrees Celsius). That is much hotter than temperatures at which related minerals melt, including bridgmanite and postperovskite (MgSiO3). Postperovskite is the high-pressure form of bridgmanite, which is stable near Earth’s core-mantle boundary.
In most exoplanets, iron would end up mixing with the post-post-spinel Mg2SiO4. The researchers found that even then, the melting point for post-post-spinel Mg2SiO4 remained above the temperatures estimated for the deep mantles of most rocky planets.
Effects on super-Earths inside and out
In short, this means that many super-Earths likely have solid deep mantles. This can affect both convection inside the planet and magnetic fields outside the planet. Interestingly, another study from earlier this year found that super-Earths with powerful magnetic fields might be more likely to be able to support life.
Bottom line: Super-Earths might be solid in their deep insides, a new study says. Minerals might take unusual forms and remain solid despite the intense heat and pressure.
View larger. | Artist’s concept of the super-Earth exoplanet LP 890-9 c. It orbits a red dwarf star 98 light-years from Earth. A new study suggests that super-Earths might be solid deep on the inside. This is due to minerals under extreme pressure and temperature – much more extreme than inside Earth – being compressed. Image via NASA/ JPL-Caltech/ Eos.
Super-Earths are rocky exoplanets, larger and more massive than Earth but smaller than Neptune. What are they like on the inside?
Researchers at Princeton University say in a new study that, surprisingly, super-Earths might be solid deep down in their mantles.
The study suggests the minerals inside these worlds would take on unusual forms due to the extreme heat and pressure deep down, meaning they would remain solid instead of melting.
Super-Earths are rocky exoplanets that are larger and more massive than Earth, but smaller than Neptune. Powerful telescopes have provided clues about what their atmospheres are like. But what are they like on the inside?
Some astronomers have suggested these worlds could contain oceans of magma. Now, a new study from researchers at Princeton University in New Jersey suggests something surprising; super-Earths might actually be solid deep inside their mantles. That’s because under the intense pressure and heat deep below the surface, some minerals could take unusual forms.
The researchers found these minerals could likely withstand the extremely high temperatures and pressures deep inside super-Earths – much hotter than inside Earth – and remain solid.
Nathaniel Scharping wrote about the new findings for Eos on August 6, 2026.
View larger. | Illustration depicting the size of a super-Earth called CoRoT-7b. Super-Earths are larger and more massive than Earth, but smaller and less massive than Neptune. Image via Aldaraon/ Wikimedia Commons.
Minerals take unusual forms
Scientists expect that some common minerals found inside Earth should be present within super-Earths as well. This includes substances like magnesium orthosilicate (Mg2SiO4). But the interiors of super-Earths have much more intense pressures and temperatures than inside Earth.
As noted in Eos, the atoms in the mineral would rearrange into different crystal structures. As explained in the article:
One of these high-pressure forms is called the spinel phase [spinel group], which is found in Earth’s mantle. At even higher pressures, this phase breaks down into two different minerals: bridgmanite, the most abundant mineral phase in Earth, and ferropericlase, a magnesium-rich oxide. However, under the far more extreme pressures expected inside massive rocky planets known as super-Earths, Mg2SiO4 becomes stable again in an entirely new crystal structure called post-post-spinel. Scientists predict that this ultrahigh-pressure phase of Mg2SiO4 is one of the dominant minerals in the deep mantles of super-Earths, making its melting behavior important for understanding how these planets form and evolve.
View larger. | This is an artist’s concept of a super-Earth with a deep magma ocean generating a magnetic field. The new study suggests that the deepest parts of these magma oceans in the mantle would remain solid instead of liquid. Image via University of Rochester Laboratory for Laser Energetics/ Michael Franchot/ University of Rochester.
Recreating conditions inside super-Earths
It is difficult to recreate these kinds of conditions in a lab. So the researchers did a computer model recreation instead. They used a technique called thermodynamic integration to study the melting curve of this mineral – the bizarrely named post-post-spinel Mg2SiO4 – at up to 1,300 gigapascals of pressure.
The post-post-spinel Mg2SiO4 is a refractory mineral. That means it can withstand extremely high temperatures before it begins to melt. Pressure plays a role, too. Depending on the pressure, it melts between 9,780 K (17,144 degrees Fahrenheit or 9,507 degrees Celsius) and 14,897 K (26,350 degrees Fahrenheit or 14,620 degrees Celsius). That is much hotter than temperatures at which related minerals melt, including bridgmanite and postperovskite (MgSiO3). Postperovskite is the high-pressure form of bridgmanite, which is stable near Earth’s core-mantle boundary.
In most exoplanets, iron would end up mixing with the post-post-spinel Mg2SiO4. The researchers found that even then, the melting point for post-post-spinel Mg2SiO4 remained above the temperatures estimated for the deep mantles of most rocky planets.
Effects on super-Earths inside and out
In short, this means that many super-Earths likely have solid deep mantles. This can affect both convection inside the planet and magnetic fields outside the planet. Interestingly, another study from earlier this year found that super-Earths with powerful magnetic fields might be more likely to be able to support life.
Bottom line: Super-Earths might be solid in their deep insides, a new study says. Minerals might take unusual forms and remain solid despite the intense heat and pressure.
The 3 brightest stars in this image make up the asterism of the Summer Triangle, a giant triangle in the sky composed of the bright stars Vega (top left), Altair (lower middle) and Deneb (left center). Also in this image is the Great Rift, a dark band of interstellar clouds that passes right through the Milky Way and the Summer Triangle. Image via NASA/ A. Fujii/ ESA.
The Milky Way is the edgewise view into our home galaxy. It has an estimated 100 to 400 billion stars. So why does it contain a great dark patch?
The dark patch is a region of vast star-forming clouds called the Great Rift. This long swath of gaseous interstellar clouds darkens a stretch of the starry band of the Milky Way in our sky.
You need a dark sky to see the Great Rift. If you do see it, know that new stars are being born there, shrouded in their gas-and-dust cocoons.
The Great Rift: How to see it
A moonless night in August is an ideal time to look for the Great Rift in the starry band of the Milky Way. Under a dark sky, far from city lights, the Milky Way is easy to see stretching across the sky at this time of year. The Great Rift appears as dark lanes of dust running the length of the starlit Milky Way band.
You can see the Milky Way most easily in the evening from around June or July through about October. From a Northern Hemisphere location, you’ll see the thickest part of the Milky Way above the southern horizon. From the Southern Hemisphere, the thickest part of the Milky Way appears more overhead.
The Milky Way band looks milky white, which is where it gets its name. The skies aren’t black like ink between stars in the Milky Way. So you’ll know when you see the Great Rift, which looks as if someone took a marker and colored parts of the Milky Way darker.
View larger. | The Great Rift of the Milky Way passes through the constellation Cassiopeia and the Summer Triangle. Image via Wikimedia.
Constellations along the Great Rift
The Great Rift begins just above the constellation Sagittarius the Archer. Follow the Milky Way up until you see a black area in the Milky Way, just before you get to the constellation Cygnus the Swan. Cygnus is shaped like a cross. Deneb is the brightest star in Cygnus and part of the famous Summer Triangle asterism. You can see the Great Rift inside the Summer Triangle.
Be sure to keep your binoculars handy for any Milky Way viewing session. There are many interesting star-forming regions, star clusters and millions of stars that will capture your attention.
View at EarthSky Community Photos. | William Mathe made a 100-mile (160 km) drive to Last Chance, Colorado, for this scene on March 16, 2024. William wrote: “The ranch house is a bit of a fixer-upper. But it has spectacular views of the core of our little Milky Way galaxy.” Thank you, William!
The Great Rift is dark due to dust
Stars are formed from great clouds of gas and dust in our Milky Way galaxy and other galaxies. When we look up at the starry band of the Milky Way and see the Great Rift, we are looking into our galaxy’s star-forming regions. Imagine the vast number of new stars that will emerge, in time, from these clouds of dust.
Here’s the interaction between interstellar dust in the Milky Way and the structure of our galaxy’s magnetic field, as detected by ESA’s Planck satellite over the entire sky. Image via ESA.
Ancient cultures focused on dark areas, not light areas
You know those paintings where if you look at the light areas you see one thing, but in the dark areas you see something else?
The Great Rift is a bit like that. A few ancient cultures in Central and South America saw the dark areas of the Milky Way as constellations. These dark constellations had a variety of myths associated with them. For example, one important dark constellation was Yacana the Llama. It rises above Cuzco, the ancient city of the Incas, every year in November.
There are several Aboriginal Australian myths about the Great Rift. Some groups believe that ancestor spirits reside by this river in the sky, with the stars along its banks representing fish or their campfires. Others identify it with the Rainbow Serpent, often associated with water, life, and creation. Another interpretation involves the Emu in the Sky, a constellation formed by the dark patches of the Great Rift.
By the way, the other famous area of the sky that is obscured by molecular dust is visible from the Southern Hemisphere. It’s the famous Coalsack nebula near the Southern Cross, also known as the constellation Crux. The Coalsack is another region of star-forming activity in our night sky, much like the Great Rift.
Bottom line: The Great Rift or Dark Rift is a darkened swath of the Milky Way where new stars are forming. It’s best seen from a rural location away from light pollution.
The 3 brightest stars in this image make up the asterism of the Summer Triangle, a giant triangle in the sky composed of the bright stars Vega (top left), Altair (lower middle) and Deneb (left center). Also in this image is the Great Rift, a dark band of interstellar clouds that passes right through the Milky Way and the Summer Triangle. Image via NASA/ A. Fujii/ ESA.
The Milky Way is the edgewise view into our home galaxy. It has an estimated 100 to 400 billion stars. So why does it contain a great dark patch?
The dark patch is a region of vast star-forming clouds called the Great Rift. This long swath of gaseous interstellar clouds darkens a stretch of the starry band of the Milky Way in our sky.
You need a dark sky to see the Great Rift. If you do see it, know that new stars are being born there, shrouded in their gas-and-dust cocoons.
The Great Rift: How to see it
A moonless night in August is an ideal time to look for the Great Rift in the starry band of the Milky Way. Under a dark sky, far from city lights, the Milky Way is easy to see stretching across the sky at this time of year. The Great Rift appears as dark lanes of dust running the length of the starlit Milky Way band.
You can see the Milky Way most easily in the evening from around June or July through about October. From a Northern Hemisphere location, you’ll see the thickest part of the Milky Way above the southern horizon. From the Southern Hemisphere, the thickest part of the Milky Way appears more overhead.
The Milky Way band looks milky white, which is where it gets its name. The skies aren’t black like ink between stars in the Milky Way. So you’ll know when you see the Great Rift, which looks as if someone took a marker and colored parts of the Milky Way darker.
View larger. | The Great Rift of the Milky Way passes through the constellation Cassiopeia and the Summer Triangle. Image via Wikimedia.
Constellations along the Great Rift
The Great Rift begins just above the constellation Sagittarius the Archer. Follow the Milky Way up until you see a black area in the Milky Way, just before you get to the constellation Cygnus the Swan. Cygnus is shaped like a cross. Deneb is the brightest star in Cygnus and part of the famous Summer Triangle asterism. You can see the Great Rift inside the Summer Triangle.
Be sure to keep your binoculars handy for any Milky Way viewing session. There are many interesting star-forming regions, star clusters and millions of stars that will capture your attention.
View at EarthSky Community Photos. | William Mathe made a 100-mile (160 km) drive to Last Chance, Colorado, for this scene on March 16, 2024. William wrote: “The ranch house is a bit of a fixer-upper. But it has spectacular views of the core of our little Milky Way galaxy.” Thank you, William!
The Great Rift is dark due to dust
Stars are formed from great clouds of gas and dust in our Milky Way galaxy and other galaxies. When we look up at the starry band of the Milky Way and see the Great Rift, we are looking into our galaxy’s star-forming regions. Imagine the vast number of new stars that will emerge, in time, from these clouds of dust.
Here’s the interaction between interstellar dust in the Milky Way and the structure of our galaxy’s magnetic field, as detected by ESA’s Planck satellite over the entire sky. Image via ESA.
Ancient cultures focused on dark areas, not light areas
You know those paintings where if you look at the light areas you see one thing, but in the dark areas you see something else?
The Great Rift is a bit like that. A few ancient cultures in Central and South America saw the dark areas of the Milky Way as constellations. These dark constellations had a variety of myths associated with them. For example, one important dark constellation was Yacana the Llama. It rises above Cuzco, the ancient city of the Incas, every year in November.
There are several Aboriginal Australian myths about the Great Rift. Some groups believe that ancestor spirits reside by this river in the sky, with the stars along its banks representing fish or their campfires. Others identify it with the Rainbow Serpent, often associated with water, life, and creation. Another interpretation involves the Emu in the Sky, a constellation formed by the dark patches of the Great Rift.
By the way, the other famous area of the sky that is obscured by molecular dust is visible from the Southern Hemisphere. It’s the famous Coalsack nebula near the Southern Cross, also known as the constellation Crux. The Coalsack is another region of star-forming activity in our night sky, much like the Great Rift.
Bottom line: The Great Rift or Dark Rift is a darkened swath of the Milky Way where new stars are forming. It’s best seen from a rural location away from light pollution.
This starfield shows the newly discovered Milky Way satellite galaxy at the center. The point of light at left marked by the star shape indicates a star that was crucial in determining the distance to this little galaxy. Image via William Cerny/ Rubin Observatory/ arXiv.
This month, scientists using the preliminary data from the Vera C. Rubin Observatory said they had already discovered Rubin’s first ultra-faint satellite galaxy orbiting our home galaxy, the Milky Way. They’ve dubbed the new galaxy Aquarius IV. It’s one of the faintest of the roughly 60 little galaxies currently known to be orbiting (or closely associated with) the Milky Way.
The scientists say this discovery offers an early glimpse of the new observatory’s power to probe the universe.
The Vera C. Rubin Observatory – on the summit of Cerro Pachón in northern Chile – features a 3.2-gigapixel camera, roughly the size of a small car, making it the largest digital camera ever built for astronomy. This camera’s resolution is so high that displaying a single full-size image would require hundreds of 4K ultra-HD television screens. Using this camera, astronomers began a 10-year Legacy Survey of Space and Time (LSST) in June 2026.
The new satellite galaxy is one of the first of what scientists expect will be many discoveries. Researchers found the galaxy in Rubin’s Early Data Preview 2 dataset.
The researchers, led by William Cerny of Yale University, published their study in arXiv on August 4, 2026. This study has not yet been peer-reviewed.
Tiny galaxy hidden in Milky Way’s outskirts
Aquarius IV lies about 355,000 light-years from Earth, in the Milky Way’s outer halo. After detecting the galaxy in the Rubin data, the team confirmed the discovery in archival images from a second astronomical camera located in Chile, the Dark Energy Camera installed at the Victor M. Blanco 4-meter (13-foot) Telescope at Cerro Tololo.
Astronomers believe Aquarius IV is an ultra-faint dwarf galaxy. The paper said these types of galaxies:
… are the least luminous, least chemically enriched and most dark matter-dominated galaxies known, making them powerful probes of galaxy formation and dark matter physics.
Scientists found the first ultra-faint dwarf galaxy orbiting the Milky Way about 20 years ago. Today, there are roughly 60 other discoveries. But astronomers believe there are still hundreds of small galaxies near our Milky Way left to find.
And it’s already looking like Rubin will have a good chance of discovering them. The Early Data Preview 2 doesn’t even come from the start of the LSST survey. It came from a testing phase, before the survey began, between April 2025 and January 2026.
What else do we know about Aquarius IV?
Aquarius IV has an apparent magnitude of 18.3. That is incredibly faint, but – by stacking images and filtering out “noise” – the LSST survey can see even fainter objects. Still, galaxies like Aquarius IV are incredibly dim; they consist of diffuse stars of low luminosity. So they’re challenging to find!
The stars in Aquarius IV are poor in heavy elements, indicating that they are quite ancient, perhaps about 13 billion years old. That would mean they formed early in the universe’s history.
But the researchers caution that their classification of Aquarius IV as an ultra-faint dwarf galaxy is still preliminary. There is a chance it could be an unusually large globular cluster. The researchers said they need to do more observations to get spectroscopic measurements from more of its stars before they can confirm its true nature.
Artist’s concept of our Milky Way galaxy. The galaxy’s halo is a large sphere encompassing the entire Milky Way. Inside this sphere, astronomers said they have just discovered an ultra-faint satellite galaxy. Image via NASA.
Why ultra-faint galaxies matter
Ultra-faint dwarf galaxies are the least luminous and least chemically enriched (oldest) galaxies known. They are also believed to be the most dark matter-dominated. Dark matter is a mysterious substance believed to make up roughly 85% of all the universe’s matter (or 27% of the total universe). Dark energy, meanwhile, makes up the majority of the universe.
Astronomers study ultra-faint dwarf galaxies in part because they hold clues about how the first galaxies formed and how dark matter shaped the early universe.
Just the beginning for Rubin
Aquarius IV is already an exciting discovery using just the earliest observations from the Rubin Observatory. As the paper says:
Aquarius IV is among the faintest known Milky Way satellites in the distant halo, demonstrating Rubin’s ability to reveal ultra-faint satellites at the limits of existing surveys, even in its initial phases of operation. The sensitivity of Rubin LSST will steadily increase, and systems similar to Aquarius IV are expected to be detectable with more than 85% efficiency using the same search algorithm applied here. Rubin LSST thus stands poised to revolutionize the census of ultra-faint Milky Way satellites.
Bottom line: The Vera C. Rubin Observatory has only just begun its survey, yet it has already discovered Aquarius IV, an ultra-faint satellite galaxy of the Milky Way.
This starfield shows the newly discovered Milky Way satellite galaxy at the center. The point of light at left marked by the star shape indicates a star that was crucial in determining the distance to this little galaxy. Image via William Cerny/ Rubin Observatory/ arXiv.
This month, scientists using the preliminary data from the Vera C. Rubin Observatory said they had already discovered Rubin’s first ultra-faint satellite galaxy orbiting our home galaxy, the Milky Way. They’ve dubbed the new galaxy Aquarius IV. It’s one of the faintest of the roughly 60 little galaxies currently known to be orbiting (or closely associated with) the Milky Way.
The scientists say this discovery offers an early glimpse of the new observatory’s power to probe the universe.
The Vera C. Rubin Observatory – on the summit of Cerro Pachón in northern Chile – features a 3.2-gigapixel camera, roughly the size of a small car, making it the largest digital camera ever built for astronomy. This camera’s resolution is so high that displaying a single full-size image would require hundreds of 4K ultra-HD television screens. Using this camera, astronomers began a 10-year Legacy Survey of Space and Time (LSST) in June 2026.
The new satellite galaxy is one of the first of what scientists expect will be many discoveries. Researchers found the galaxy in Rubin’s Early Data Preview 2 dataset.
The researchers, led by William Cerny of Yale University, published their study in arXiv on August 4, 2026. This study has not yet been peer-reviewed.
Tiny galaxy hidden in Milky Way’s outskirts
Aquarius IV lies about 355,000 light-years from Earth, in the Milky Way’s outer halo. After detecting the galaxy in the Rubin data, the team confirmed the discovery in archival images from a second astronomical camera located in Chile, the Dark Energy Camera installed at the Victor M. Blanco 4-meter (13-foot) Telescope at Cerro Tololo.
Astronomers believe Aquarius IV is an ultra-faint dwarf galaxy. The paper said these types of galaxies:
… are the least luminous, least chemically enriched and most dark matter-dominated galaxies known, making them powerful probes of galaxy formation and dark matter physics.
Scientists found the first ultra-faint dwarf galaxy orbiting the Milky Way about 20 years ago. Today, there are roughly 60 other discoveries. But astronomers believe there are still hundreds of small galaxies near our Milky Way left to find.
And it’s already looking like Rubin will have a good chance of discovering them. The Early Data Preview 2 doesn’t even come from the start of the LSST survey. It came from a testing phase, before the survey began, between April 2025 and January 2026.
What else do we know about Aquarius IV?
Aquarius IV has an apparent magnitude of 18.3. That is incredibly faint, but – by stacking images and filtering out “noise” – the LSST survey can see even fainter objects. Still, galaxies like Aquarius IV are incredibly dim; they consist of diffuse stars of low luminosity. So they’re challenging to find!
The stars in Aquarius IV are poor in heavy elements, indicating that they are quite ancient, perhaps about 13 billion years old. That would mean they formed early in the universe’s history.
But the researchers caution that their classification of Aquarius IV as an ultra-faint dwarf galaxy is still preliminary. There is a chance it could be an unusually large globular cluster. The researchers said they need to do more observations to get spectroscopic measurements from more of its stars before they can confirm its true nature.
Artist’s concept of our Milky Way galaxy. The galaxy’s halo is a large sphere encompassing the entire Milky Way. Inside this sphere, astronomers said they have just discovered an ultra-faint satellite galaxy. Image via NASA.
Why ultra-faint galaxies matter
Ultra-faint dwarf galaxies are the least luminous and least chemically enriched (oldest) galaxies known. They are also believed to be the most dark matter-dominated. Dark matter is a mysterious substance believed to make up roughly 85% of all the universe’s matter (or 27% of the total universe). Dark energy, meanwhile, makes up the majority of the universe.
Astronomers study ultra-faint dwarf galaxies in part because they hold clues about how the first galaxies formed and how dark matter shaped the early universe.
Just the beginning for Rubin
Aquarius IV is already an exciting discovery using just the earliest observations from the Rubin Observatory. As the paper says:
Aquarius IV is among the faintest known Milky Way satellites in the distant halo, demonstrating Rubin’s ability to reveal ultra-faint satellites at the limits of existing surveys, even in its initial phases of operation. The sensitivity of Rubin LSST will steadily increase, and systems similar to Aquarius IV are expected to be detectable with more than 85% efficiency using the same search algorithm applied here. Rubin LSST thus stands poised to revolutionize the census of ultra-faint Milky Way satellites.
Bottom line: The Vera C. Rubin Observatory has only just begun its survey, yet it has already discovered Aquarius IV, an ultra-faint satellite galaxy of the Milky Way.
The Cassini spacecraft orbited Saturn from 2004 to 2017. This image stemmed from a Cassini highlight, when it executed a fantastic series of maneuvers, diving repeatedly between the planet’s outer atmosphere and inner rings. The image is from high above Saturn, looking down toward its north pole. Image via software engineer Gordan Ugarkovic/ NASA.
In mid-August 2026, Saturn is rising in the middle of the night. Watch for it around midnight, ascending at the sunrise point in your sky. It’ll look like a bright golden “star.” By dawn, Saturn – still on the sun’s path – will be at its highest in your sky. Or watch for Saturn near the moon on August 29 and 30.
Saturn is the 6th planet outward from the sun and the farthest planet easily visible to the unaided eye. It’s the faintest and slowest-moving of the bright planets. You need a telescope to see the planet’s rings, but Saturn is also fun to watch with the eye alone. You’ll find it shining with a steady light, in a creamy golden color.
Saturn takes almost 30 years to orbit the sun. So it moves more slowly than the other bright planets in front of the fixed stars. The ancient Assyrians called Saturn Lubad-sag-uš, often translated as the oldest of the old sheep. It’s easy to imagine why, if you consider Saturn’s slow movement in front of the stars. Because of its nearly 30-year orbit, it takes nearly 30 years to complete one journey our sky, traveling through all the constellations of the zodiac. It really does seem to amble across the sky like an old sheep.
And, unlike the other bright planets, Saturn isn’t showy to the eye alone. It’s the hardest bright planet to recognize.
But moon is a handy tool. Look for the moon near Saturn on August 29 and 30, 2026. And it’ll be near the full moon again on September 27, and every month it is visible. To find Saturn near the moon every month of the year (except when it is behind the sun), visit EarthSky’s night sky guide.
And keep reading to learn the best time of 2026 to look for Saturn.
The waning gibbous moon joins Saturn on the evenings of August 29 and 30. You can catch them until dawn. Chart via EarthSky.
Saturn closest, brightest, opposite sun on October 4
The best time of year to see an outer planet, like Saturn, are the months around that planet’s yearly opposition. That’s when Earth will go between the sun and that outer world. The planet will appear opposite the sun in our sky, rising into view at a convenient hour for viewing.
In 2026, Saturn will come to opposition on October 4. So the months around October are best for viewing the planet this year.
Because we’re going between Saturn and the sun then, October 4 – the opposition date – will feature the ringed planet approximately at its closest to Earth. Because it’s closest, it’ll appear at its brightest in our sky. Saturn is the faintest of the bright planets. It’s still pretty bright, but, normally, you wouldn’t pick it out from among the stars.
But around September, October and November, you can view Saturn fairly easily, because Saturn will appear as bright as the brightest stars.
Since we pass Saturn – the 6th planet outward from the sun – from an inside track around the sun, the ringed planet will look as if it’s going backward (retrograde) for a time, in front of the fixed stars of the zodiac. In 2026, Saturn retrogrades from July 27 until December 11. That’s when it moves westward in front of the stars, in contrast to its regular motion, toward the east in front of the stars.
When Saturn started its retrograde (westward) movement in front of the backdrop stars of the zodiac on July 27, it was among the stars of Aquarius the Water Bearer. By the end of Saturn’s retrograde on December 11, it’ll lie among the stars of Cetus the Whale. It’ll remain in Cetus the rest of 2026.
Saturn’s yearly opposition happens about two weeks later with each passing year. The 2024 opposition happened on September 8. The 2025 opposition happened on September 21. And the 2026 opposition will be on October 4. And next year? Opposition for Saturn in 2027 will take place October 18.
So you see that Saturn – like most objects in the heavens – is really very orderly in its comings and goings in our sky. Once you learn to identify it, you can recognize it from year to year.
Opposition happens when Earth flies between an outer planet, like Saturn, and the sun. In 2026, Saturn’s opposition comes on October 4. Illustration via Heavens-Above. Used with permission.
But how can you recognize it?
Like all planets, Saturn is lovely to gaze upon and think about. It’s a real place, after all, not just a light in the sky. Plus, Saturn’s brightness waxes and wanes in a subtle way throughout every year, making it fun to watch. But how can you recognize Saturn?
As we said above, the best way is to start with the nights when the moon will be passing near. To find out when this will be: visit EarthSky’s night sky guide.
But what if you can’t wait for the moon? Here are some tips:
Think about the path the sun travels across your sky. That path is called the ecliptic. On EarthSky charts, we nearly always represent that path by a green line. So – wherever you are on Earth – you will look along the sun’s path for Saturn.
Look along that path for bright lights. Saturn may be the faintest of the bright planets, but it’s as bright as the brightest stars.
Notice the twinkling of the stars. Stars twinkle because they are so far away. Through earthly telescopes, even, unless some special technique is being used, stars look like pinpoints. But Saturn is vastly closer than the stars. Through telescopes it looks like a golden (ring-encircled) disk. Light waves from one side of that disk cancel out light waves from the other side. So Saturn shines steadily!
Watch for its golden color. Yes. Saturn appears golden to the eye. A golden, steady light – located along the sun’s path across the sky – is likely Saturn.
Can you see the rings of Saturn if you look with the eye alone? No, you need a small telescope to see the rings. But Saturn is still beautiful to the eye. Once you learn to spot it, you’ll find a great source of contentment in recognizing it year after year.
The Cassini spacecraft ended its mission in 2017. This Cassini image is from December 18, 2016. It shows a level of detail in Saturn’s rings twice as high as had ever been observed before. Wow! Image via NASA. Read more about Cassini’s epic final year at Saturn.
From the Northern Hemisphere, the sun’s path arcs across the southern sky. But, from the Southern Hemisphere, you will look north rather than south to follow the sun and planets along the ecliptic. How high the sun’s path appears to you depends on your latitude, and on which part of the ecliptic you’re looking toward.
From Twizel, New Zealand, at about 44 degrees south latitude, different parts of the ecliptic can reach anywhere from about 23 degrees to nearly 70 degrees above the northern horizon as they cross the meridian. Farther north, from Auckland or much of Australia, parts of the ecliptic can climb higher still.
As Saturn spends nearly 30 years moving around our sky, it gradually passes through sections of the ecliptic that appear higher or lower in our sky. At its 2026 opposition, Saturn will reach about 44 degrees high from Twizel, 51 degrees from Auckland and 54 degrees from Sydney, comfortably above the horizon and offering good views through a telescope.
So, for much of the Southern Hemisphere, Saturn will be reasonably high above the northern horizon around its October 2026 opposition. It will rise around sunset in the east-northeast, climb across the northern sky and culminate (reach its highest point) due north around midnight, before heading toward the west-northwest.
Over the decades, Saturn’s altitude at opposition gradually changes as it makes its long journey through the zodiac, a planetary cycle you can watch unfold over a lifetime.
Where will Saturn be in the last few months of 2026?
Saturn is nearly always somewhere in our sky, for most of every year. In the second half 2026, as Earth moves away from Saturn in its orbit, we’ll see Saturn shift its location in our evening sky, rising earlier each night.
After Saturn’s opposition in October 2026, Saturn will appear farther to the west as darkness falls each month thereafter.
Finally, in March of 2027, Saturn will disappear in the western twilight after sunset.
One last thing, for you telescope users: the south side of Saturn’s rings are facing in Earth’s direction. They’ll have a -7.5-degree tilt around opposition.
View at EarthSky Community Photos. | John Nelson of Puget Sound, Washington, submitted this composite image and wrote: “A composite of some of my images of Saturn over the last 6 years showing how the angle of Saturn’s rings to Earth have been slowly decreasing. Saturn’s ring angle toward Earth cycles over a 13- to 15-year period going from nearly fully open to edge on then back again.” Thank you, John.
Bottom line: The best time for viewing the planet Saturn in 2026 is here. The ringed planet will be at its brightest and in the sky all night, or nearly so. Why? Because we’ll pass between Saturn and the sun on October 4.
The Cassini spacecraft orbited Saturn from 2004 to 2017. This image stemmed from a Cassini highlight, when it executed a fantastic series of maneuvers, diving repeatedly between the planet’s outer atmosphere and inner rings. The image is from high above Saturn, looking down toward its north pole. Image via software engineer Gordan Ugarkovic/ NASA.
In mid-August 2026, Saturn is rising in the middle of the night. Watch for it around midnight, ascending at the sunrise point in your sky. It’ll look like a bright golden “star.” By dawn, Saturn – still on the sun’s path – will be at its highest in your sky. Or watch for Saturn near the moon on August 29 and 30.
Saturn is the 6th planet outward from the sun and the farthest planet easily visible to the unaided eye. It’s the faintest and slowest-moving of the bright planets. You need a telescope to see the planet’s rings, but Saturn is also fun to watch with the eye alone. You’ll find it shining with a steady light, in a creamy golden color.
Saturn takes almost 30 years to orbit the sun. So it moves more slowly than the other bright planets in front of the fixed stars. The ancient Assyrians called Saturn Lubad-sag-uš, often translated as the oldest of the old sheep. It’s easy to imagine why, if you consider Saturn’s slow movement in front of the stars. Because of its nearly 30-year orbit, it takes nearly 30 years to complete one journey our sky, traveling through all the constellations of the zodiac. It really does seem to amble across the sky like an old sheep.
And, unlike the other bright planets, Saturn isn’t showy to the eye alone. It’s the hardest bright planet to recognize.
But moon is a handy tool. Look for the moon near Saturn on August 29 and 30, 2026. And it’ll be near the full moon again on September 27, and every month it is visible. To find Saturn near the moon every month of the year (except when it is behind the sun), visit EarthSky’s night sky guide.
And keep reading to learn the best time of 2026 to look for Saturn.
The waning gibbous moon joins Saturn on the evenings of August 29 and 30. You can catch them until dawn. Chart via EarthSky.
Saturn closest, brightest, opposite sun on October 4
The best time of year to see an outer planet, like Saturn, are the months around that planet’s yearly opposition. That’s when Earth will go between the sun and that outer world. The planet will appear opposite the sun in our sky, rising into view at a convenient hour for viewing.
In 2026, Saturn will come to opposition on October 4. So the months around October are best for viewing the planet this year.
Because we’re going between Saturn and the sun then, October 4 – the opposition date – will feature the ringed planet approximately at its closest to Earth. Because it’s closest, it’ll appear at its brightest in our sky. Saturn is the faintest of the bright planets. It’s still pretty bright, but, normally, you wouldn’t pick it out from among the stars.
But around September, October and November, you can view Saturn fairly easily, because Saturn will appear as bright as the brightest stars.
Since we pass Saturn – the 6th planet outward from the sun – from an inside track around the sun, the ringed planet will look as if it’s going backward (retrograde) for a time, in front of the fixed stars of the zodiac. In 2026, Saturn retrogrades from July 27 until December 11. That’s when it moves westward in front of the stars, in contrast to its regular motion, toward the east in front of the stars.
When Saturn started its retrograde (westward) movement in front of the backdrop stars of the zodiac on July 27, it was among the stars of Aquarius the Water Bearer. By the end of Saturn’s retrograde on December 11, it’ll lie among the stars of Cetus the Whale. It’ll remain in Cetus the rest of 2026.
Saturn’s yearly opposition happens about two weeks later with each passing year. The 2024 opposition happened on September 8. The 2025 opposition happened on September 21. And the 2026 opposition will be on October 4. And next year? Opposition for Saturn in 2027 will take place October 18.
So you see that Saturn – like most objects in the heavens – is really very orderly in its comings and goings in our sky. Once you learn to identify it, you can recognize it from year to year.
Opposition happens when Earth flies between an outer planet, like Saturn, and the sun. In 2026, Saturn’s opposition comes on October 4. Illustration via Heavens-Above. Used with permission.
But how can you recognize it?
Like all planets, Saturn is lovely to gaze upon and think about. It’s a real place, after all, not just a light in the sky. Plus, Saturn’s brightness waxes and wanes in a subtle way throughout every year, making it fun to watch. But how can you recognize Saturn?
As we said above, the best way is to start with the nights when the moon will be passing near. To find out when this will be: visit EarthSky’s night sky guide.
But what if you can’t wait for the moon? Here are some tips:
Think about the path the sun travels across your sky. That path is called the ecliptic. On EarthSky charts, we nearly always represent that path by a green line. So – wherever you are on Earth – you will look along the sun’s path for Saturn.
Look along that path for bright lights. Saturn may be the faintest of the bright planets, but it’s as bright as the brightest stars.
Notice the twinkling of the stars. Stars twinkle because they are so far away. Through earthly telescopes, even, unless some special technique is being used, stars look like pinpoints. But Saturn is vastly closer than the stars. Through telescopes it looks like a golden (ring-encircled) disk. Light waves from one side of that disk cancel out light waves from the other side. So Saturn shines steadily!
Watch for its golden color. Yes. Saturn appears golden to the eye. A golden, steady light – located along the sun’s path across the sky – is likely Saturn.
Can you see the rings of Saturn if you look with the eye alone? No, you need a small telescope to see the rings. But Saturn is still beautiful to the eye. Once you learn to spot it, you’ll find a great source of contentment in recognizing it year after year.
The Cassini spacecraft ended its mission in 2017. This Cassini image is from December 18, 2016. It shows a level of detail in Saturn’s rings twice as high as had ever been observed before. Wow! Image via NASA. Read more about Cassini’s epic final year at Saturn.
From the Northern Hemisphere, the sun’s path arcs across the southern sky. But, from the Southern Hemisphere, you will look north rather than south to follow the sun and planets along the ecliptic. How high the sun’s path appears to you depends on your latitude, and on which part of the ecliptic you’re looking toward.
From Twizel, New Zealand, at about 44 degrees south latitude, different parts of the ecliptic can reach anywhere from about 23 degrees to nearly 70 degrees above the northern horizon as they cross the meridian. Farther north, from Auckland or much of Australia, parts of the ecliptic can climb higher still.
As Saturn spends nearly 30 years moving around our sky, it gradually passes through sections of the ecliptic that appear higher or lower in our sky. At its 2026 opposition, Saturn will reach about 44 degrees high from Twizel, 51 degrees from Auckland and 54 degrees from Sydney, comfortably above the horizon and offering good views through a telescope.
So, for much of the Southern Hemisphere, Saturn will be reasonably high above the northern horizon around its October 2026 opposition. It will rise around sunset in the east-northeast, climb across the northern sky and culminate (reach its highest point) due north around midnight, before heading toward the west-northwest.
Over the decades, Saturn’s altitude at opposition gradually changes as it makes its long journey through the zodiac, a planetary cycle you can watch unfold over a lifetime.
Where will Saturn be in the last few months of 2026?
Saturn is nearly always somewhere in our sky, for most of every year. In the second half 2026, as Earth moves away from Saturn in its orbit, we’ll see Saturn shift its location in our evening sky, rising earlier each night.
After Saturn’s opposition in October 2026, Saturn will appear farther to the west as darkness falls each month thereafter.
Finally, in March of 2027, Saturn will disappear in the western twilight after sunset.
One last thing, for you telescope users: the south side of Saturn’s rings are facing in Earth’s direction. They’ll have a -7.5-degree tilt around opposition.
View at EarthSky Community Photos. | John Nelson of Puget Sound, Washington, submitted this composite image and wrote: “A composite of some of my images of Saturn over the last 6 years showing how the angle of Saturn’s rings to Earth have been slowly decreasing. Saturn’s ring angle toward Earth cycles over a 13- to 15-year period going from nearly fully open to edge on then back again.” Thank you, John.
Bottom line: The best time for viewing the planet Saturn in 2026 is here. The ringed planet will be at its brightest and in the sky all night, or nearly so. Why? Because we’ll pass between Saturn and the sun on October 4.
If you’re in the Northern Hemisphere, look southward on your summer evenings for mighty Ophiuchus the Serpent Bearer. It’s surrounded by the constellations Serpens Cauda and Serpens Caput. Chart via EarthSky.
Ophiuchus, the unofficial 13th constellation of the zodiac
If you were born somewhere between November 30 and December 18, chances are the sun was in the constellation Ophiuchus the Serpent Bearer. Therefore, your “sign” should be Ophiuchus. But, of course, Ophiuchus is not an official constellation of the zodiac, nor will you find it in horoscopes. Ophiuchus the Serpent Bearer is a large constellation that you can spot near the southern horizon from the Northern Hemisphere during July, August and September evenings. The Serpent Bearer is standing on the Scorpion and its red star Antares.
From the Southern Hemisphere, Ophiuchus is closer to overhead. Ophiuchus’ brightest star is Rasalhague.
The official boundary lines for all 88 constellations were drawn up by the International Astronomical Union (IAU) in the 1930s.
Signs versus constellations
Poor Ophiuchus. Nobody ever claims him as a birth sign, despite the fact that the ecliptic runs across him, too. After all, the band of the zodiac extends some 8 degrees north and south of the ecliptic, spanning a total of 16 degrees in width. And the constellations are not evenly spaced along this band in our sky. The signs of the zodiac are familiar to all who read online astrology advice. There are 12 familiar signs of the zodiac, but no Ophiuchus.
Yet the moon and planets do regularly move within the boundaries of Ophiuchus. And so does the sun. The sun is in front of Ophiuchus from about November 30 to December 18 each year.
The sun is said to enter the sign Sagittarius around November 21, or whenever the sun is precisely 30 degrees west of the December solstice point. And then the sun then enters the sign Capricorn on the December 21 solstice. So the sun passes through the “sign” Sagittarius for the period before and up to the December solstice, irrespective of the fact that the sun is actually shining in front of the constellation Ophiuchus from November 30 to December 18.
By the way, the December solstice point moves one degree westward in front of the zodiacal constellations – or backdrop stars – in about 72 years. This means that the December solstice point will finally move into the constellation Ophiuchus by the year 2269.
Ophiuchus holding the serpent, Serpens, as depicted in Urania’s Mirror, a set of constellation cards published in London circa 1825. Image via Adam Cuerden/ Wikipedia.
When and where to locate Ophiuchus
The best time to observe Ophiuchus is during a Northern Hemisphere summer (Southern Hemisphere winter). From the Northern Hemisphere, late July and early August present this constellation high in the southern sky at nightfall and early evening. It’s in the southwest sky on autumn evenings in the Northern Hemisphere.
This rather large constellation fills the area of sky to the north of the constellation Scorpius the Scorpion and to the south of the constellation Hercules the Strongman. If you’re familiar with Scorpius’ brightest star Antares, try star-hopping to Ophiuchus from this ruddy gem of a star. The head of Ophiuchus is marked by the star Rasalhague (Alpha Ophiuchi).
Ophiuchus is joined in legend and in the sky to the constellation of the Serpent. If you have a dark sky, you might find this is one constellation that looks like what it’s supposed to be: a big guy holding a snake. The name Ophiuchus comes from two Greek words meaning serpent and holding.
Deep-sky objects in Ophiuchus
On a night when the moon is absent, take your binoculars and use them to scan Ophiuchus, which lies near the band of the Milky Way and so has many deep-sky wonders. Ophiuchus boasts of numerous globular clusters, for example. The two easiest globular clusters to see with ordinary binoculars are M10 and M12, as shown on the above chart. Through binoculars, they look like faint puffs of light, but with the telescope, you begin to see these globular clusters for what they really are. They are immense stellar cities spanning a hundred to a few hundred light-years in diameter, teeming with hundreds of thousands of stars.
Another big deep-sky favorite is the Pipe Nebula, a vast interstellar cloud of gas and dust sweeping across about 7 degrees of sky. At arm’s length, that’s about the width of three to four fingers. This dark nebula resides at a distance of 600 to 700 light-years in southern Ophiuchus. You can see it with the unaided eye in a dark, transparent sky. The Pipe Nebula is due east of the star Antares and due north of the stars Shaula and Lesath. These two stars (but not the Pipe Nebula) are shown on the above chart.
Ophiuchus in myth and star lore
In Greek sky lore, Ophiuchus represents Asclepius, Greek god of medicine and doctors. He is always holding a great serpent or snake. And, depending on how it’s used, a snake’s venom can either kill or cure. It’s said that Asclepius concocted a healing potion from the venom of Serpens the Serpent, mixing it with a Gorgon’s blood and an unknown herb. This potion gave humans access to immortality, until the god of the underworld, Pluto, appealed to the king of the gods. Pluto asked Zeus to reconsider the ramifications of the death of death.
We hardly know how Pluto made his appeal. Perhaps he said only that which never lives never dies, and that no mortal can have one without the other. Sophocles may have expressed the myth’s inherent message when saying:
Better to die, and sleep the never-waking sleep, than linger on and dare to live when the soul’s life is gone.
Possibly, the poet T.S. Eliot echoed the theme of the ever-living story in his Four Quartets:
We die with the dying:
See, they depart, and we go with them.
We are born with the dead:
See, they return, and bring us with them.
In any event, according to the myth, Zeus confiscated the potion, removed Asclepius from Earth and placed the gifted physician into the starry heavens. Today, the Staff of Asclepius – symbol of the World Health Organization and other medical organizations – pays tribute to this story and echoes the mighty celestial shape of the constellation Ophiuchus the Serpent Bearer.
Ophiuchus in history and science
It’s been more than 400 years since anyone has seen a supernova explosion of a star within our own Milky Way galaxy. But in the year 1604, a supernova known as Kepler’s Supernova exploded onto the scene, attaining unaided-eye visibility for 18 months. It shone in southern Ophiuchus, not all that far from the Pipe Nebula.
Kepler’s Supernova in 1604 came upon the heels of Tycho’s Supernova that lit up Cassiopeia in 1572. These supernovae sent shock waves into the intelligentsia of Europe, which firmly believed in the Aristotelian notion of an immutable universe outside the orbit of the moon. Tycho Brahe took a parallax measurement of the 1572 supernova, proving that it could not be an atmospheric phenomenon. In fact, the supernova shone well beyond the moon’s orbit. Shortly thereafter, Kepler’s Supernova in 1604 seemed to drive home the point all over again.
Moreover, Tycho Brahe measured the distance of a comet in 1577, also finding it to be farther away than the moon. Aristotelians wanted to believe comets were gases burning in the atmosphere, but once again, Tycho threw cold water on the idea of Aristotle’s immutable universe.
Bottom line: The sun lies within the boundaries of the constellation Ophiuchus the Serpent Bearer for about two weeks of every year. Thus, Ophiuchus is an unofficial member of the zodiac. Learn the difference between constellations and signs, and how to locate Ophiuchus.
If you’re in the Northern Hemisphere, look southward on your summer evenings for mighty Ophiuchus the Serpent Bearer. It’s surrounded by the constellations Serpens Cauda and Serpens Caput. Chart via EarthSky.
Ophiuchus, the unofficial 13th constellation of the zodiac
If you were born somewhere between November 30 and December 18, chances are the sun was in the constellation Ophiuchus the Serpent Bearer. Therefore, your “sign” should be Ophiuchus. But, of course, Ophiuchus is not an official constellation of the zodiac, nor will you find it in horoscopes. Ophiuchus the Serpent Bearer is a large constellation that you can spot near the southern horizon from the Northern Hemisphere during July, August and September evenings. The Serpent Bearer is standing on the Scorpion and its red star Antares.
From the Southern Hemisphere, Ophiuchus is closer to overhead. Ophiuchus’ brightest star is Rasalhague.
The official boundary lines for all 88 constellations were drawn up by the International Astronomical Union (IAU) in the 1930s.
Signs versus constellations
Poor Ophiuchus. Nobody ever claims him as a birth sign, despite the fact that the ecliptic runs across him, too. After all, the band of the zodiac extends some 8 degrees north and south of the ecliptic, spanning a total of 16 degrees in width. And the constellations are not evenly spaced along this band in our sky. The signs of the zodiac are familiar to all who read online astrology advice. There are 12 familiar signs of the zodiac, but no Ophiuchus.
Yet the moon and planets do regularly move within the boundaries of Ophiuchus. And so does the sun. The sun is in front of Ophiuchus from about November 30 to December 18 each year.
The sun is said to enter the sign Sagittarius around November 21, or whenever the sun is precisely 30 degrees west of the December solstice point. And then the sun then enters the sign Capricorn on the December 21 solstice. So the sun passes through the “sign” Sagittarius for the period before and up to the December solstice, irrespective of the fact that the sun is actually shining in front of the constellation Ophiuchus from November 30 to December 18.
By the way, the December solstice point moves one degree westward in front of the zodiacal constellations – or backdrop stars – in about 72 years. This means that the December solstice point will finally move into the constellation Ophiuchus by the year 2269.
Ophiuchus holding the serpent, Serpens, as depicted in Urania’s Mirror, a set of constellation cards published in London circa 1825. Image via Adam Cuerden/ Wikipedia.
When and where to locate Ophiuchus
The best time to observe Ophiuchus is during a Northern Hemisphere summer (Southern Hemisphere winter). From the Northern Hemisphere, late July and early August present this constellation high in the southern sky at nightfall and early evening. It’s in the southwest sky on autumn evenings in the Northern Hemisphere.
This rather large constellation fills the area of sky to the north of the constellation Scorpius the Scorpion and to the south of the constellation Hercules the Strongman. If you’re familiar with Scorpius’ brightest star Antares, try star-hopping to Ophiuchus from this ruddy gem of a star. The head of Ophiuchus is marked by the star Rasalhague (Alpha Ophiuchi).
Ophiuchus is joined in legend and in the sky to the constellation of the Serpent. If you have a dark sky, you might find this is one constellation that looks like what it’s supposed to be: a big guy holding a snake. The name Ophiuchus comes from two Greek words meaning serpent and holding.
Deep-sky objects in Ophiuchus
On a night when the moon is absent, take your binoculars and use them to scan Ophiuchus, which lies near the band of the Milky Way and so has many deep-sky wonders. Ophiuchus boasts of numerous globular clusters, for example. The two easiest globular clusters to see with ordinary binoculars are M10 and M12, as shown on the above chart. Through binoculars, they look like faint puffs of light, but with the telescope, you begin to see these globular clusters for what they really are. They are immense stellar cities spanning a hundred to a few hundred light-years in diameter, teeming with hundreds of thousands of stars.
Another big deep-sky favorite is the Pipe Nebula, a vast interstellar cloud of gas and dust sweeping across about 7 degrees of sky. At arm’s length, that’s about the width of three to four fingers. This dark nebula resides at a distance of 600 to 700 light-years in southern Ophiuchus. You can see it with the unaided eye in a dark, transparent sky. The Pipe Nebula is due east of the star Antares and due north of the stars Shaula and Lesath. These two stars (but not the Pipe Nebula) are shown on the above chart.
Ophiuchus in myth and star lore
In Greek sky lore, Ophiuchus represents Asclepius, Greek god of medicine and doctors. He is always holding a great serpent or snake. And, depending on how it’s used, a snake’s venom can either kill or cure. It’s said that Asclepius concocted a healing potion from the venom of Serpens the Serpent, mixing it with a Gorgon’s blood and an unknown herb. This potion gave humans access to immortality, until the god of the underworld, Pluto, appealed to the king of the gods. Pluto asked Zeus to reconsider the ramifications of the death of death.
We hardly know how Pluto made his appeal. Perhaps he said only that which never lives never dies, and that no mortal can have one without the other. Sophocles may have expressed the myth’s inherent message when saying:
Better to die, and sleep the never-waking sleep, than linger on and dare to live when the soul’s life is gone.
Possibly, the poet T.S. Eliot echoed the theme of the ever-living story in his Four Quartets:
We die with the dying:
See, they depart, and we go with them.
We are born with the dead:
See, they return, and bring us with them.
In any event, according to the myth, Zeus confiscated the potion, removed Asclepius from Earth and placed the gifted physician into the starry heavens. Today, the Staff of Asclepius – symbol of the World Health Organization and other medical organizations – pays tribute to this story and echoes the mighty celestial shape of the constellation Ophiuchus the Serpent Bearer.
Ophiuchus in history and science
It’s been more than 400 years since anyone has seen a supernova explosion of a star within our own Milky Way galaxy. But in the year 1604, a supernova known as Kepler’s Supernova exploded onto the scene, attaining unaided-eye visibility for 18 months. It shone in southern Ophiuchus, not all that far from the Pipe Nebula.
Kepler’s Supernova in 1604 came upon the heels of Tycho’s Supernova that lit up Cassiopeia in 1572. These supernovae sent shock waves into the intelligentsia of Europe, which firmly believed in the Aristotelian notion of an immutable universe outside the orbit of the moon. Tycho Brahe took a parallax measurement of the 1572 supernova, proving that it could not be an atmospheric phenomenon. In fact, the supernova shone well beyond the moon’s orbit. Shortly thereafter, Kepler’s Supernova in 1604 seemed to drive home the point all over again.
Moreover, Tycho Brahe measured the distance of a comet in 1577, also finding it to be farther away than the moon. Aristotelians wanted to believe comets were gases burning in the atmosphere, but once again, Tycho threw cold water on the idea of Aristotle’s immutable universe.
Bottom line: The sun lies within the boundaries of the constellation Ophiuchus the Serpent Bearer for about two weeks of every year. Thus, Ophiuchus is an unofficial member of the zodiac. Learn the difference between constellations and signs, and how to locate Ophiuchus.
Asaph Hall discovered Phobos, a moon for Mars, on August 17, 1877. This image of the large crater Stickney on the Martian moon Phobos is color-enhanced. The crater is 5.6 miles (9 km) in diameter, so it covers a substantial proportion of Phobos’ surface. The impact almost destroyed the small moon! Notice the smaller crater within Stickney, about 1.2 miles (2 km) in diameter, resulting from a later impact. Image via HiRISE/ MRO/ LPL (U. Arizona)/ NASA.
August 17, 1877: Asaph Hall discovers a moon for Mars
On August 17 149 years ago, American astronomer Asaph Hall discovered the first known moon for our neighboring planet, Mars. Later that year, he found a second Martian moon. Today, we call the first and larger moon Phobos. And we call the second and smaller one Deimos.
To date, Phobos and Deimos remain the only known moons of Mars.
Both Phobos and Deimos are potato-shaped. They look more like asteroids than like Earth’s much-larger companion moon. In fact, it’s likely that Mars captured these little worlds that now orbit the red planet. Studies have indicated that – millions of years from now – Phobos will shatter and form a ring around Mars. Some astronomers think Phobos alternates between being a planetary ring, then clumping up again to form a moon. More about ring theories of Phobos below.
The names Phobos and Deimos mean fear and terror, respectively. Their names refer to the sons of the war god Ares in Greek mythology. Ares was the Greek counterpart to the Roman war god Mars.
Although it’s the larger of Mars’ two moons, Phobos is tiny. It has a mean diameter of only about 14 miles (22.5 km). But it’s seven times more massive than Deimos, which has a mean diameter of about 7.7 miles (12.4 km). For these moons, we’re speaking in terms of a mean diameter because both moons are oblong in shape and not spherical. In contrast, Earth’s moon is nearly round, since it’s large enough for its gravity to have pulled it into a spherical shape.
Earth’s moon is also much larger (2,159 miles or 3,475 km in diameter). Since both Phobos and Deimos are so tiny, they have very weak gravity. And that means they don’t have enough gravity to make them round.
Mariner 9 was 1st to see them close
During Mariner 9’s mission to Mars in 1971 and 1972, scientists got their first closeup look at Phobos. Just like asteroids, its oblong surface shows many small craters. But one large crater stood out as much bigger than the rest. Astronomers named it Stickney Crater, for Angeline Stickney: an American academic, suffragist and mathematician, and Asaph Hall’s wife.
Stickney looks like a giant hole on one end of Phobos. Whatever rocky body created it was almost big enough to have shattered the moon. It’s thought that, whenever the impact occurred, Phobos barely survived.
Viking I image of Phobos and its large crater Stickney. The spacecraft captured this image in June 1977, 100 years after the discovery of Phobos. Image via NASA/ ESA.A closer view of the grooves on Phobos. Image via NASA/ JPL-Caltech/ University of Arizona.The Viking orbiter obtained this global map of Phobos. Image via NASA/ Astrogeology Science Center/ Planetary Data System/ Phil Stooke.
Was Phobos once a ring? Will it be again?
Phobos has long, shallow grooves running across its surface, radiating away from Stickney. Many planetary scientists believe these grooves are early signs of eventual structural failure in the moon. They say it’s possible that – some 50 million years from now – Phobos will break apart, forming a ring around Mars.
A study in 2018 suggested that rolling boulders created the grooves, spraying across the surface during impact. As Ken Ramsley, a planetary science researcher at Brown University who led the work, explained:
These grooves are a distinctive feature of Phobos, and planetary scientists have been debating how they formed for 40 years. We think this study is another step toward zeroing in on an explanation.
More ring theories
In 2017, a new theory by Purdue University scientists suggested Phobos might not only break apart and form a ring around the planet but also suggests this ring formation happened before.
David Minton, a professor, and Andrew Hesselbrock, a doctoral student, both at Purdue, developed a computer model showing debris ejected into space from an asteroid or other body slamming into Mars. This event – some 4.3 billion years ago – would cause the material to subsequently alternate between becoming a planetary ring and clumping up again to form the moon Phobos.
Size and visual comparison of Phobos (left) and Deimos (right). Image via NASA.
In the next 20-40 million years Mars’ largest moon Phobos will be torn apart by gravitational forces leading to the creation of a ring that could last up to 100 million years#NFTs#Moon#Spacepic.twitter.com/IIYHCkgDhf
Another study, from scientists at Purdue and the SETI Institute in June 2020, also concluded that Mars used to have a ring or series of rings. The scientists based that study on an analysis of the orbit of the other Martian moon, Deimos.
Deimos is smaller than Phobos. And it has an orbit that’s tilted with respect to Mars’ equator by about 2 degrees. Meanwhile, Phobos’ orbit isn’t inclined as much. The larger moon is inclined to Mars’ equator by only about 1 degree. The scientists said in a statement:
These orbital resonances are picky but predictable … We can tell that only an outward-moving moon could have strongly affected Deimos, which means that Mars must have had a ring pushing the inner moon outward … This moon may have been 20 times as massive as Phobos, and may have been its ‘grandparent’ existing just over 3 billion years ago … [It] was followed by two more ring-moon cycles, with the latest moon being Phobos.
So, basically, there may have been a moon about 20 times more massive than Phobos, and Mars’ rings pushed it outward. And at least two times since then, that moon broke apart and then formed a new ring, before the material coalesced together again to form a new moon. Phobos is now that current moon. The scientists say it will eventually break apart to form a new ring, thus continuing the cycle.
Scientists also now know Phobos is much younger than Deimos – perhaps only 200 million years old – which would fit the moon/ring scenario. The Phobos we see today is simply a newer and smaller version of its original self.
Eclipsing moons
Asaph Hall probably never imagined the idea of Phobos breaking apart and forming a ring around Mars. And he couldn’t possibly have imagined the video below, which was acquired by NASA’s Mars rover Curiosity on August 1, 2013. This video shows both moons, Phobos and Deimos, as you might see them while standing on the surface of Mars. You can clearly see some of the large craters on Phobos in these images.
This was the first time that images taken from Mars’ surface caught one moon eclipsing the other … but probably not the last.
Bottom line: On this date in 1877, American astronomer Asaph Hall discovered a moon for Mars: Phobos, the larger of Mars’ two moons. He discovered the other moon, Deimos, later that year.
Asaph Hall discovered Phobos, a moon for Mars, on August 17, 1877. This image of the large crater Stickney on the Martian moon Phobos is color-enhanced. The crater is 5.6 miles (9 km) in diameter, so it covers a substantial proportion of Phobos’ surface. The impact almost destroyed the small moon! Notice the smaller crater within Stickney, about 1.2 miles (2 km) in diameter, resulting from a later impact. Image via HiRISE/ MRO/ LPL (U. Arizona)/ NASA.
August 17, 1877: Asaph Hall discovers a moon for Mars
On August 17 149 years ago, American astronomer Asaph Hall discovered the first known moon for our neighboring planet, Mars. Later that year, he found a second Martian moon. Today, we call the first and larger moon Phobos. And we call the second and smaller one Deimos.
To date, Phobos and Deimos remain the only known moons of Mars.
Both Phobos and Deimos are potato-shaped. They look more like asteroids than like Earth’s much-larger companion moon. In fact, it’s likely that Mars captured these little worlds that now orbit the red planet. Studies have indicated that – millions of years from now – Phobos will shatter and form a ring around Mars. Some astronomers think Phobos alternates between being a planetary ring, then clumping up again to form a moon. More about ring theories of Phobos below.
The names Phobos and Deimos mean fear and terror, respectively. Their names refer to the sons of the war god Ares in Greek mythology. Ares was the Greek counterpart to the Roman war god Mars.
Although it’s the larger of Mars’ two moons, Phobos is tiny. It has a mean diameter of only about 14 miles (22.5 km). But it’s seven times more massive than Deimos, which has a mean diameter of about 7.7 miles (12.4 km). For these moons, we’re speaking in terms of a mean diameter because both moons are oblong in shape and not spherical. In contrast, Earth’s moon is nearly round, since it’s large enough for its gravity to have pulled it into a spherical shape.
Earth’s moon is also much larger (2,159 miles or 3,475 km in diameter). Since both Phobos and Deimos are so tiny, they have very weak gravity. And that means they don’t have enough gravity to make them round.
Mariner 9 was 1st to see them close
During Mariner 9’s mission to Mars in 1971 and 1972, scientists got their first closeup look at Phobos. Just like asteroids, its oblong surface shows many small craters. But one large crater stood out as much bigger than the rest. Astronomers named it Stickney Crater, for Angeline Stickney: an American academic, suffragist and mathematician, and Asaph Hall’s wife.
Stickney looks like a giant hole on one end of Phobos. Whatever rocky body created it was almost big enough to have shattered the moon. It’s thought that, whenever the impact occurred, Phobos barely survived.
Viking I image of Phobos and its large crater Stickney. The spacecraft captured this image in June 1977, 100 years after the discovery of Phobos. Image via NASA/ ESA.A closer view of the grooves on Phobos. Image via NASA/ JPL-Caltech/ University of Arizona.The Viking orbiter obtained this global map of Phobos. Image via NASA/ Astrogeology Science Center/ Planetary Data System/ Phil Stooke.
Was Phobos once a ring? Will it be again?
Phobos has long, shallow grooves running across its surface, radiating away from Stickney. Many planetary scientists believe these grooves are early signs of eventual structural failure in the moon. They say it’s possible that – some 50 million years from now – Phobos will break apart, forming a ring around Mars.
A study in 2018 suggested that rolling boulders created the grooves, spraying across the surface during impact. As Ken Ramsley, a planetary science researcher at Brown University who led the work, explained:
These grooves are a distinctive feature of Phobos, and planetary scientists have been debating how they formed for 40 years. We think this study is another step toward zeroing in on an explanation.
More ring theories
In 2017, a new theory by Purdue University scientists suggested Phobos might not only break apart and form a ring around the planet but also suggests this ring formation happened before.
David Minton, a professor, and Andrew Hesselbrock, a doctoral student, both at Purdue, developed a computer model showing debris ejected into space from an asteroid or other body slamming into Mars. This event – some 4.3 billion years ago – would cause the material to subsequently alternate between becoming a planetary ring and clumping up again to form the moon Phobos.
Size and visual comparison of Phobos (left) and Deimos (right). Image via NASA.
In the next 20-40 million years Mars’ largest moon Phobos will be torn apart by gravitational forces leading to the creation of a ring that could last up to 100 million years#NFTs#Moon#Spacepic.twitter.com/IIYHCkgDhf
Another study, from scientists at Purdue and the SETI Institute in June 2020, also concluded that Mars used to have a ring or series of rings. The scientists based that study on an analysis of the orbit of the other Martian moon, Deimos.
Deimos is smaller than Phobos. And it has an orbit that’s tilted with respect to Mars’ equator by about 2 degrees. Meanwhile, Phobos’ orbit isn’t inclined as much. The larger moon is inclined to Mars’ equator by only about 1 degree. The scientists said in a statement:
These orbital resonances are picky but predictable … We can tell that only an outward-moving moon could have strongly affected Deimos, which means that Mars must have had a ring pushing the inner moon outward … This moon may have been 20 times as massive as Phobos, and may have been its ‘grandparent’ existing just over 3 billion years ago … [It] was followed by two more ring-moon cycles, with the latest moon being Phobos.
So, basically, there may have been a moon about 20 times more massive than Phobos, and Mars’ rings pushed it outward. And at least two times since then, that moon broke apart and then formed a new ring, before the material coalesced together again to form a new moon. Phobos is now that current moon. The scientists say it will eventually break apart to form a new ring, thus continuing the cycle.
Scientists also now know Phobos is much younger than Deimos – perhaps only 200 million years old – which would fit the moon/ring scenario. The Phobos we see today is simply a newer and smaller version of its original self.
Eclipsing moons
Asaph Hall probably never imagined the idea of Phobos breaking apart and forming a ring around Mars. And he couldn’t possibly have imagined the video below, which was acquired by NASA’s Mars rover Curiosity on August 1, 2013. This video shows both moons, Phobos and Deimos, as you might see them while standing on the surface of Mars. You can clearly see some of the large craters on Phobos in these images.
This was the first time that images taken from Mars’ surface caught one moon eclipsing the other … but probably not the last.
Bottom line: On this date in 1877, American astronomer Asaph Hall discovered a moon for Mars: Phobos, the larger of Mars’ two moons. He discovered the other moon, Deimos, later that year.
