Artist’s concept of the redoubtable Voyager 1 spacecraft — most distant human-made object from Earth. Humanity launched it in 1977. It officially left our solar system in 2012, becoming the first to exit the heliosphere, or sphere of our sun’s influence. NASA said that at 12:16:07 a.m. CST on November 18, 2026, Voyager 1 will reach a distance of 1 light-day from Earth. Image via Caltech/ NASA-JPL.
Voyager 1 to reach 1 light-day from Earth in November
Voyager 1 is the most distant human-made object from Earth. It launched into space on September 5, 1977, and visited Jupiter and Saturn before heading out of the solar system. It officially crossed out of our solar system, passing the heliopause – the sphere of the sun’s influence – back in 2012. And at 12:16:07 a.m. CST on November 18, 2026, NASA said that Voyager 1 will reach a major milestone: 1 light-day from Earth. That’s the distance it takes light to travel in 24 hours.
This historic milestone of 1 light-day is equal to about 16.1 billion miles (25.9 billion kilometers), or 173.14 astronomical units (AU). As of early October, the Voyager 1 spacecraft is about 15.98 billion miles (25.72 billion km) away from Earth. If we could peer at Voyager 1 through a telescope on Earth, the light we see left the spacecraft 23 hours, 52 minutes and 30 seconds ago. On November 18, it will breach the 24-hour mark.
And how long did it take Voyager 1 to travel 1 light-day? It took 49 years, 2 months, and 11 days to travel that distance from Earth. Keep on reading for how to celebrate this milestone.
Voyager 1 is now outside our solar system. On November 18, 2026, it will reach 1 light-day distant from Earth. Image via NASA/ JPL-Caltech.
Here’s how to celebrate!
To mark Voyager 1’s milestone of 1 light-day distant, NASA is organizing a worldwide Shine Bright celebration. After sunset on Tuesday, November 17, people can participate by pointing a flashlight, phone, glow stick or other light toward the sky and flashing the letters V-G-R for Voyager in Morse code.
So how do you spell V-G-R in Morse code? V is dot, dot, dot, dash. G is dash, dash, dot. And R is dot, dash, dot. If that’s too complicated, you can just NASA’s automated flasher here.
NASA hopes the worldwide light display will celebrate humanity’s remarkable achievement in sending a spacecraft farther into space than anything else they’ve ever built.
What about Voyager 2?
And where is Voyager 2? You might know that Voyager 2 actually launched a few weeks before its sister craft. But while Voyager 1 only visited Jupiter and Saturn, Voyager 2 took a Grand Tour, visiting all the gas giant planets: Jupiter, Saturn, Uranus and Neptune. So it’s not as far from Earth as Voyager 1.
But it’s not too far behind, relatively speaking. Voyager 2 is about 2 billion miles (3.2 billion km) closer to Earth than Voyager 1. It’s also moving a bit slower, so it can never catch up. Besides, Voyager 1 and 2 are not headed in the same direction anyway. Voyager 1 is headed “up” out of the solar plane, while Voyager 2 is headed “down.” Voyager 1 is moving toward the direction of the constellation Ophiuchus. And Voyager 2 is headed in the direction of the constellation Andromeda.
So when will Voyager 2 reach a distance of 1 light-day from us? NASA said not for nine more years, in November 2035.
Are the Voyager spacecraft still functioning?
Both Voyager spacecraft are still in communication with Earth, even though that process takes approximately a day for one-way messages. But most of the instruments on the Voyagers are no longer working. Over the years, NASA has turned off one system after another in order to save power. Just this year, in April 2026, NASA turned off the Low-Energy Charged Particle (LECP) instrument to save energy. This instrument was detecting electrons, ions and cosmic rays in the interstellar medium. But NASA could still turn it on at some point in the future for new measurements.
Both Voyager spacecraft carry a golden record that is etched with images and sounds to represent life on Earth. The golden records were a largely symbolic gesture meant to represent Earth in the wider universe and with the off-chance that an alien civilization would one day find them and learn something of their origins. As Carl Sagan said:
The spacecraft will be encountered and the record played only if there are advanced space-faring civilizations in interstellar space, but the launching of this ‘bottle’ into the cosmic ‘ocean’ says something very hopeful about life on this planet.
Bottom line: The Voyager 1 spacecraft — which launched from Earth in 1977 — will reach 1 light-day from Earth on November 18, 2026. It is the first human-made object to travel that far from Earth.
Artist’s concept of the redoubtable Voyager 1 spacecraft — most distant human-made object from Earth. Humanity launched it in 1977. It officially left our solar system in 2012, becoming the first to exit the heliosphere, or sphere of our sun’s influence. NASA said that at 12:16:07 a.m. CST on November 18, 2026, Voyager 1 will reach a distance of 1 light-day from Earth. Image via Caltech/ NASA-JPL.
Voyager 1 to reach 1 light-day from Earth in November
Voyager 1 is the most distant human-made object from Earth. It launched into space on September 5, 1977, and visited Jupiter and Saturn before heading out of the solar system. It officially crossed out of our solar system, passing the heliopause – the sphere of the sun’s influence – back in 2012. And at 12:16:07 a.m. CST on November 18, 2026, NASA said that Voyager 1 will reach a major milestone: 1 light-day from Earth. That’s the distance it takes light to travel in 24 hours.
This historic milestone of 1 light-day is equal to about 16.1 billion miles (25.9 billion kilometers), or 173.14 astronomical units (AU). As of early October, the Voyager 1 spacecraft is about 15.98 billion miles (25.72 billion km) away from Earth. If we could peer at Voyager 1 through a telescope on Earth, the light we see left the spacecraft 23 hours, 52 minutes and 30 seconds ago. On November 18, it will breach the 24-hour mark.
And how long did it take Voyager 1 to travel 1 light-day? It took 49 years, 2 months, and 11 days to travel that distance from Earth. Keep on reading for how to celebrate this milestone.
Voyager 1 is now outside our solar system. On November 18, 2026, it will reach 1 light-day distant from Earth. Image via NASA/ JPL-Caltech.
Here’s how to celebrate!
To mark Voyager 1’s milestone of 1 light-day distant, NASA is organizing a worldwide Shine Bright celebration. After sunset on Tuesday, November 17, people can participate by pointing a flashlight, phone, glow stick or other light toward the sky and flashing the letters V-G-R for Voyager in Morse code.
So how do you spell V-G-R in Morse code? V is dot, dot, dot, dash. G is dash, dash, dot. And R is dot, dash, dot. If that’s too complicated, you can just NASA’s automated flasher here.
NASA hopes the worldwide light display will celebrate humanity’s remarkable achievement in sending a spacecraft farther into space than anything else they’ve ever built.
What about Voyager 2?
And where is Voyager 2? You might know that Voyager 2 actually launched a few weeks before its sister craft. But while Voyager 1 only visited Jupiter and Saturn, Voyager 2 took a Grand Tour, visiting all the gas giant planets: Jupiter, Saturn, Uranus and Neptune. So it’s not as far from Earth as Voyager 1.
But it’s not too far behind, relatively speaking. Voyager 2 is about 2 billion miles (3.2 billion km) closer to Earth than Voyager 1. It’s also moving a bit slower, so it can never catch up. Besides, Voyager 1 and 2 are not headed in the same direction anyway. Voyager 1 is headed “up” out of the solar plane, while Voyager 2 is headed “down.” Voyager 1 is moving toward the direction of the constellation Ophiuchus. And Voyager 2 is headed in the direction of the constellation Andromeda.
So when will Voyager 2 reach a distance of 1 light-day from us? NASA said not for nine more years, in November 2035.
Are the Voyager spacecraft still functioning?
Both Voyager spacecraft are still in communication with Earth, even though that process takes approximately a day for one-way messages. But most of the instruments on the Voyagers are no longer working. Over the years, NASA has turned off one system after another in order to save power. Just this year, in April 2026, NASA turned off the Low-Energy Charged Particle (LECP) instrument to save energy. This instrument was detecting electrons, ions and cosmic rays in the interstellar medium. But NASA could still turn it on at some point in the future for new measurements.
Both Voyager spacecraft carry a golden record that is etched with images and sounds to represent life on Earth. The golden records were a largely symbolic gesture meant to represent Earth in the wider universe and with the off-chance that an alien civilization would one day find them and learn something of their origins. As Carl Sagan said:
The spacecraft will be encountered and the record played only if there are advanced space-faring civilizations in interstellar space, but the launching of this ‘bottle’ into the cosmic ‘ocean’ says something very hopeful about life on this planet.
Bottom line: The Voyager 1 spacecraft — which launched from Earth in 1977 — will reach 1 light-day from Earth on November 18, 2026. It is the first human-made object to travel that far from Earth.
View larger. | Artist’s concept of super-Earth TOI-561 b. New observations by NASA’s James Webb Space Telescope show again that this distant world has a dense atmosphere. The atmosphere of lava planet TOI-561 b is highly reflective, suggesting clouds or haze. Image via CryoDragon Inc./ University of Birmingham.
The super-Earth exoplanet TOI-561 b is hot and its surface is likely covered by molten lava. An atmosphere for this lava planet was an unexpected discovery.
Additional observations using the Webb space telescope have re-confirmed the existence of this world’s dense atmosphere.
The new observations also show that the atmosphere of TOI-561 b is highly reflective, with clouds or haze.
Surprising atmosphere of lava planet TOI-561 b re-confirmed by Webb
Last December, scientists at the Carnegie Institution for Science in Washington, D.C. said rocky exoplanet TOI-561 b was a scorching hot super-Earth — a lava planet — with a thick atmosphere. It was a surprise, because scientists had thought it was too small and too close to its star to hold an atmosphere.
TOI-561 b is located some 280.5 light-years from Earth, in the direction of our constellation Sextans. It orbits extremely near its host star, completing a single orbit (a full “year”) in under 10.5 hours. Surface temperatures are estimated to be over 2,000 K (around 3,100°F / 1,700°C). At these extreme temperatures, rock melts, creating a global ocean of molten lava on its dayside.
Now we have an update on this fascinating world. Some of the same researchers that conducted the earlier study — led this time by the University of Montreal in Canada — said on October 27, 2026, that they used the James Webb Space Telescope to re-observe TOI-561 b. Their observations showed that there are clouds or haze in the atmosphere of this world. They also suggest it reflects much of the heat coming from the planet’s star back into space.
The researchers published their peer-reviewed findings in The Astronomical Journal on September 29, 2026.
And Evan Gough wrote about the latest observations for Universe Today on October 27, 2026.
A surprising atmosphere
TOI-561 b is what scientists call an ultra-short period (USP) planet. Even though it is a super-Earth, scientists thought that it was too small — and hot — to hold on to any atmosphere, due to being so close to its star.
But it seems that TOI-561 b does have an atmosphere, and a thick one at that. The paper states:
Ultrashort period (USP) rocky planets are expected to be depleted of any substantial gaseous envelope due to the intense irradiation they receive from their host star, making the recent detection of an atmosphere around TOI-561 b particularly surprising. That finding was based on the planet’s bulk density and dayside emission spectrum, but full-orbit phase-curve observations offer a more comprehensive way to constrain the presence and characteristics of a planet’s atmosphere.
View larger. | Emission spectrum of TOI-561 b from the James Webb Space Telescope. The data are consistent with an atmosphere rich in volatiles like water, oxygen and carbon dioxide. The model shown here assumes an atmosphere that is composed of 100% water vapor. Image via NASA/ ESA/ CSA/ Ralf Crawford (STScI); Science: Johanna Teske (Carnegie Science Earth and Planets Laboratory)/ Anjali Piette (University of Birmingham)/ Tim Lichtenberg (Groningen)/ Nicole Wallack (Carnegie Science Earth and Planets Laboratory).
The atmosphere of the lava planet is highly reflective
The researchers used Webb to observe TOI-561 b for 37 hours. That worked out to seeing three orbits of the planet, at 10.5 hours per orbit. That is good, because the more orbits that can be observed, the better for gathering data.
The previous observations had also shown that TOI-561 b has an atmosphere. How did the researchers determine this?
The dayside of the planet was a lot cooler than expected. That shouldn’t be the case if the planet had no atmosphere.
There were two possible explanations. Either heat was being reflected back into space or the atmosphere transported it to the nightside. But the results showed the nightside wasn’t warm enough. The researchers estimated that about 3/4 of the planet’s heat must be reflected into space. The paper states:
We conclude from the GCM simulations that heat redistribution alone cannot match the observed dayside fluxes or amplitude of the phase curve, and a high-albedo source (Ab = 0.6) indicative of clouds or haze.
Co-author Lisa Dang is the project lead at the University of Waterloo, Ontario, Canada. She explained:
We measured how the planet’s brightness and heat changed throughout its orbit. This technique, known as a phase curve, revealed that the planet reflects a significant amount of light from its star, and that heat is being redistributed around the planet instead of only on the sunlit side. Together, these point to the presence of an atmosphere.
Multiple kinds of clouds
The researchers said that clouds or haze are likely reflecting the heat. Silicon dioxide (SiO2) and magnesium metasilicate (MgSiO3) are two of the most likely compositions of the clouds. The paper states that:
… multiple possible cloud species can form on the dayside, including MgSiO3 and SiO2.
View larger. | Another artist’s concept of scorching hot TOI-561 b and its sunlike star. New observations by NASA’s James Webb Space Telescope show again there is a dense atmosphere on the planet. Image via NASA/ ESA/ CSA/ Ralf Crawford (STScI).
Challenging current theories
The findings are surprising, and they also challenge current theories about rocky ultra-short period planets. Dang said:
Our discovery challenges current theories. We would expect a heavily irradiated rocky planet like TOI-561 b to have lost its atmosphere billions of years ago. Instead, the evidence suggests it still has a significant atmosphere today.
And the paper states:
Atmospheric-escape theory suggests that strongly irradiated super-Earths should be devoid of any volatile envelopes. This is particularly astonishing given that the current JWST census of rocky exoplanets has been interpreted as suggestive of a population of bare-rock planets …
It’s also notable that TOI-561 b orbits a sun-like star. Most ultra-short period planets orbit red dwarfs. And red dwarfs are known for their bursts of deadly radiation. That radiation can strip the atmospheres off planets that are too close.
Yet TOI-561 b receives more radiation from its star than typical red dwarfs. And it still has an atmosphere! How is that possible?
Lisa Dang at the University of Waterloo is the project lead for the new study of TOI-561 b. Image via University of Waterloo.
How is the atmosphere of lava planet TOI-561 b possible?
The researchers aren’t sure how TOI-561 b has been able to keep its atmosphere. But they have ideas.
It might have started out with an even much thicker primordial atmosphere, perhaps as a sub-Neptune (larger than a super-Earth). The radiation might have indeed stripped away most or all of that atmosphere. So what’s left now is a secondary atmosphere.
It’s also possible that the planet originated much farther out from its star than where it is now. That would be when the star was still young. At that time, it emitted even more radiation.
When the planet migrated closer to the star, the star was already “calming down” and emitting less radiation. As a result, the remaining atmosphere was spared from destruction.
Or it could be that the answer lies in both scenarios.
But there’s another possibility, too. The planet “consumed” its original atmosphere. In other words, the atmosphere became trapped in the interior of the planet.
Co-author Anjali Piette, Assistant Professor in Astronomy at the University of Birmingham, said:
Our discovery challenges current theories. We would expect a heavily irradiated rocky planet like TOI-561 b to have lost its atmosphere billions of years ago. Instead, the evidence suggests it still has a significant atmosphere today. This raises major questions such as whether the planet started with an unusually large supply of gases or if the ocean of molten rock covering its surface acts as a planet-wide volcano that is constantly feeding its atmosphere.
View larger. | Artist’s concept of a lava planet. TOI-561 b orbits so close to its star that its surface is likely covered in molten lava. Image via ESO/ Wikimedia Commons.
Venus or Io?
The researchers want to know if TOI-561 b is more similar to Venus or Jupiter’s volcanic moon Io. Dang said:
The next big question we will seek to answer is whether TOI-561 b’s atmosphere resembles Venus or an extreme version of lo. Observing the planet at longer wavelengths with the JWST could give us insights and help explain how a planet this hot has held on to an atmosphere for billions of years.
The unexpected atmosphere of lava world TOI-561 b was a big surprise to astronomers. But it will also provide valuable data for studying other rocky super-Earth planets. How many other also have atmospheres, and what kind?
Bottom line: More recent observations of hot super-Earth TOI-561 b by the Webb space telescope show again that the lava planet’s surprising atmosphere does exist. And it’s very reflective.
View larger. | Artist’s concept of super-Earth TOI-561 b. New observations by NASA’s James Webb Space Telescope show again that this distant world has a dense atmosphere. The atmosphere of lava planet TOI-561 b is highly reflective, suggesting clouds or haze. Image via CryoDragon Inc./ University of Birmingham.
The super-Earth exoplanet TOI-561 b is hot and its surface is likely covered by molten lava. An atmosphere for this lava planet was an unexpected discovery.
Additional observations using the Webb space telescope have re-confirmed the existence of this world’s dense atmosphere.
The new observations also show that the atmosphere of TOI-561 b is highly reflective, with clouds or haze.
Surprising atmosphere of lava planet TOI-561 b re-confirmed by Webb
Last December, scientists at the Carnegie Institution for Science in Washington, D.C. said rocky exoplanet TOI-561 b was a scorching hot super-Earth — a lava planet — with a thick atmosphere. It was a surprise, because scientists had thought it was too small and too close to its star to hold an atmosphere.
TOI-561 b is located some 280.5 light-years from Earth, in the direction of our constellation Sextans. It orbits extremely near its host star, completing a single orbit (a full “year”) in under 10.5 hours. Surface temperatures are estimated to be over 2,000 K (around 3,100°F / 1,700°C). At these extreme temperatures, rock melts, creating a global ocean of molten lava on its dayside.
Now we have an update on this fascinating world. Some of the same researchers that conducted the earlier study — led this time by the University of Montreal in Canada — said on October 27, 2026, that they used the James Webb Space Telescope to re-observe TOI-561 b. Their observations showed that there are clouds or haze in the atmosphere of this world. They also suggest it reflects much of the heat coming from the planet’s star back into space.
The researchers published their peer-reviewed findings in The Astronomical Journal on September 29, 2026.
And Evan Gough wrote about the latest observations for Universe Today on October 27, 2026.
A surprising atmosphere
TOI-561 b is what scientists call an ultra-short period (USP) planet. Even though it is a super-Earth, scientists thought that it was too small — and hot — to hold on to any atmosphere, due to being so close to its star.
But it seems that TOI-561 b does have an atmosphere, and a thick one at that. The paper states:
Ultrashort period (USP) rocky planets are expected to be depleted of any substantial gaseous envelope due to the intense irradiation they receive from their host star, making the recent detection of an atmosphere around TOI-561 b particularly surprising. That finding was based on the planet’s bulk density and dayside emission spectrum, but full-orbit phase-curve observations offer a more comprehensive way to constrain the presence and characteristics of a planet’s atmosphere.
View larger. | Emission spectrum of TOI-561 b from the James Webb Space Telescope. The data are consistent with an atmosphere rich in volatiles like water, oxygen and carbon dioxide. The model shown here assumes an atmosphere that is composed of 100% water vapor. Image via NASA/ ESA/ CSA/ Ralf Crawford (STScI); Science: Johanna Teske (Carnegie Science Earth and Planets Laboratory)/ Anjali Piette (University of Birmingham)/ Tim Lichtenberg (Groningen)/ Nicole Wallack (Carnegie Science Earth and Planets Laboratory).
The atmosphere of the lava planet is highly reflective
The researchers used Webb to observe TOI-561 b for 37 hours. That worked out to seeing three orbits of the planet, at 10.5 hours per orbit. That is good, because the more orbits that can be observed, the better for gathering data.
The previous observations had also shown that TOI-561 b has an atmosphere. How did the researchers determine this?
The dayside of the planet was a lot cooler than expected. That shouldn’t be the case if the planet had no atmosphere.
There were two possible explanations. Either heat was being reflected back into space or the atmosphere transported it to the nightside. But the results showed the nightside wasn’t warm enough. The researchers estimated that about 3/4 of the planet’s heat must be reflected into space. The paper states:
We conclude from the GCM simulations that heat redistribution alone cannot match the observed dayside fluxes or amplitude of the phase curve, and a high-albedo source (Ab = 0.6) indicative of clouds or haze.
Co-author Lisa Dang is the project lead at the University of Waterloo, Ontario, Canada. She explained:
We measured how the planet’s brightness and heat changed throughout its orbit. This technique, known as a phase curve, revealed that the planet reflects a significant amount of light from its star, and that heat is being redistributed around the planet instead of only on the sunlit side. Together, these point to the presence of an atmosphere.
Multiple kinds of clouds
The researchers said that clouds or haze are likely reflecting the heat. Silicon dioxide (SiO2) and magnesium metasilicate (MgSiO3) are two of the most likely compositions of the clouds. The paper states that:
… multiple possible cloud species can form on the dayside, including MgSiO3 and SiO2.
View larger. | Another artist’s concept of scorching hot TOI-561 b and its sunlike star. New observations by NASA’s James Webb Space Telescope show again there is a dense atmosphere on the planet. Image via NASA/ ESA/ CSA/ Ralf Crawford (STScI).
Challenging current theories
The findings are surprising, and they also challenge current theories about rocky ultra-short period planets. Dang said:
Our discovery challenges current theories. We would expect a heavily irradiated rocky planet like TOI-561 b to have lost its atmosphere billions of years ago. Instead, the evidence suggests it still has a significant atmosphere today.
And the paper states:
Atmospheric-escape theory suggests that strongly irradiated super-Earths should be devoid of any volatile envelopes. This is particularly astonishing given that the current JWST census of rocky exoplanets has been interpreted as suggestive of a population of bare-rock planets …
It’s also notable that TOI-561 b orbits a sun-like star. Most ultra-short period planets orbit red dwarfs. And red dwarfs are known for their bursts of deadly radiation. That radiation can strip the atmospheres off planets that are too close.
Yet TOI-561 b receives more radiation from its star than typical red dwarfs. And it still has an atmosphere! How is that possible?
Lisa Dang at the University of Waterloo is the project lead for the new study of TOI-561 b. Image via University of Waterloo.
How is the atmosphere of lava planet TOI-561 b possible?
The researchers aren’t sure how TOI-561 b has been able to keep its atmosphere. But they have ideas.
It might have started out with an even much thicker primordial atmosphere, perhaps as a sub-Neptune (larger than a super-Earth). The radiation might have indeed stripped away most or all of that atmosphere. So what’s left now is a secondary atmosphere.
It’s also possible that the planet originated much farther out from its star than where it is now. That would be when the star was still young. At that time, it emitted even more radiation.
When the planet migrated closer to the star, the star was already “calming down” and emitting less radiation. As a result, the remaining atmosphere was spared from destruction.
Or it could be that the answer lies in both scenarios.
But there’s another possibility, too. The planet “consumed” its original atmosphere. In other words, the atmosphere became trapped in the interior of the planet.
Co-author Anjali Piette, Assistant Professor in Astronomy at the University of Birmingham, said:
Our discovery challenges current theories. We would expect a heavily irradiated rocky planet like TOI-561 b to have lost its atmosphere billions of years ago. Instead, the evidence suggests it still has a significant atmosphere today. This raises major questions such as whether the planet started with an unusually large supply of gases or if the ocean of molten rock covering its surface acts as a planet-wide volcano that is constantly feeding its atmosphere.
View larger. | Artist’s concept of a lava planet. TOI-561 b orbits so close to its star that its surface is likely covered in molten lava. Image via ESO/ Wikimedia Commons.
Venus or Io?
The researchers want to know if TOI-561 b is more similar to Venus or Jupiter’s volcanic moon Io. Dang said:
The next big question we will seek to answer is whether TOI-561 b’s atmosphere resembles Venus or an extreme version of lo. Observing the planet at longer wavelengths with the JWST could give us insights and help explain how a planet this hot has held on to an atmosphere for billions of years.
The unexpected atmosphere of lava world TOI-561 b was a big surprise to astronomers. But it will also provide valuable data for studying other rocky super-Earth planets. How many other also have atmospheres, and what kind?
Bottom line: More recent observations of hot super-Earth TOI-561 b by the Webb space telescope show again that the lava planet’s surprising atmosphere does exist. And it’s very reflective.
The Summer Triangle is a famous asterism, consisting of 3 bright stars. These stars are overhead in summer. But you can also easily see them through the northern autumn. Chart via EarthSky.
The Summer Triangle in autumn
The Summer Triangle isn’t a constellation. It’s an asterism, an obvious pattern or group of stars with a popular name. The Summer Triangle consists of three bright stars in three separate constellations.
The Summer Triangle is the signature star formation in the Northern Hemisphere’s summer sky. However, as the Septemberequinox comes and goes – and as the weeks of autumn begin to slide by – you’ll continue to notice this famous trio of stars.
You’ll find the Summer Triangle in November and December. Look for it tonight in the early evening. Look west!
In early November, the Summer Triangle is high in the western sky around mid-evening. Image via WyoAstro All-sky camera.
The 3 stars of the Summer Triangle
The brightest of the three stars is Vega is in the constellation Lyra the Harp. It’s the 5th-brightest star in our night sky. You’ll recognize Vega for its blue-white color. This star is located 25 light-years away.
Next in brightness is the star Altair is in Aquila the Eagle. Its only 16.7 light-years away. You’ll recognize Altair becuase it’s flanked closely by two fainter stars.
Deneb — in Cygnus the Swan — is the faintest of the Summer Triangle stars. But it has good reason to be faintest to our eye, because Deneb is one of the most distant stars we see with the unaided eye. It’s a luminous supergiant star, located roughly 1,400 to 2,600 light–years from Earth.
When is it visible in the evening sky
In the month of June – around the June solstice – the Summer Triangle pops out in the east as darkness falls and shines all night long. But now – after sunset in November – the Summer Triangle appears high in the western evening sky. As evening deepens, the Summer Triangle descends westward, with all three of its stars staying above the horizon until mid-to-late evening.
Altair – the Summer Triangle’s southernmost star – will set around 10 to 11 p.m. in November at mid-northern latitudes. Notice where you see the Summer Triangle at a given time this evening. The Summer Triangle will return to this same place in the sky some four minutes earlier with each passing day, or two hours earlier with each passing month.
Bottom line: Look westward this evening for the three brilliant stars of the Summer Triangle: Vega, Deneb and Altair.
The Summer Triangle is a famous asterism, consisting of 3 bright stars. These stars are overhead in summer. But you can also easily see them through the northern autumn. Chart via EarthSky.
The Summer Triangle in autumn
The Summer Triangle isn’t a constellation. It’s an asterism, an obvious pattern or group of stars with a popular name. The Summer Triangle consists of three bright stars in three separate constellations.
The Summer Triangle is the signature star formation in the Northern Hemisphere’s summer sky. However, as the Septemberequinox comes and goes – and as the weeks of autumn begin to slide by – you’ll continue to notice this famous trio of stars.
You’ll find the Summer Triangle in November and December. Look for it tonight in the early evening. Look west!
In early November, the Summer Triangle is high in the western sky around mid-evening. Image via WyoAstro All-sky camera.
The 3 stars of the Summer Triangle
The brightest of the three stars is Vega is in the constellation Lyra the Harp. It’s the 5th-brightest star in our night sky. You’ll recognize Vega for its blue-white color. This star is located 25 light-years away.
Next in brightness is the star Altair is in Aquila the Eagle. Its only 16.7 light-years away. You’ll recognize Altair becuase it’s flanked closely by two fainter stars.
Deneb — in Cygnus the Swan — is the faintest of the Summer Triangle stars. But it has good reason to be faintest to our eye, because Deneb is one of the most distant stars we see with the unaided eye. It’s a luminous supergiant star, located roughly 1,400 to 2,600 light–years from Earth.
When is it visible in the evening sky
In the month of June – around the June solstice – the Summer Triangle pops out in the east as darkness falls and shines all night long. But now – after sunset in November – the Summer Triangle appears high in the western evening sky. As evening deepens, the Summer Triangle descends westward, with all three of its stars staying above the horizon until mid-to-late evening.
Altair – the Summer Triangle’s southernmost star – will set around 10 to 11 p.m. in November at mid-northern latitudes. Notice where you see the Summer Triangle at a given time this evening. The Summer Triangle will return to this same place in the sky some four minutes earlier with each passing day, or two hours earlier with each passing month.
Bottom line: Look westward this evening for the three brilliant stars of the Summer Triangle: Vega, Deneb and Altair.
Rubin Observatory has discovered a retrograde object, currently labeled R631. It orbits the sun beyond the orbit of the 8th planet, Neptune, at a steep inclination. Simulation via Tony Dunn.
Rubin finds retrograde object past Neptune
The new Rubin Observatory in Chile has found an object beyond Neptune that follows a retrograde orbit. Most other other planets, moons and asteroids orbit our sun in a more or less flat plane. They generally move in the same direction, counterclockwise as seen from earthly north.
This object’s orbit is highly inclined, slicing through at a severe angle.
When we hear the word retrograde, we tend to think of an object moving backward in its orbit, against the direction of most planets, and many asteroids and moons. But in astronomy, retrograde has a more precise meaning. Any object whose orbit is tilted more than 90 degrees relative to the plane of the solar system is considered to be in retrograde motion.
This newly discovered object, currently designated R631 in the Rubin data, has an orbital inclination of 142 degrees. So its orbit is tilted beyond perpendicular, and it is moving in the opposite direction from most planets.
The designation R631 is only temporary. The object will soon get an official designation from the Minor Planet Center. Astronomers and citizens alike who monitor Rubin’s alert stream noticed this object, which has appeared over four months in the data. Rubin’s observations of the retrograde object are from December 2025 through March 2026.
R631 is located 32 astronomical units (AU) from our sun. That’s 30 times the Earth-sun distance. And it would place the object just beyond the orbit of Neptune, which is 30 AU from the sun. The object R631 will reach its closest point to the sun, or perihelion, on October 31, 2047, at a distance of 24 AU.
If this orbit is correct, it will take object R631 some 547.84 Earth-years to make one full orbit of the sun.
Physicist and astronomer Marshall Eubanks said on Minor Planet Mailing List that the object could be 62 miles (100 km) in diameter. He said it might be akin to giant Comet Bernardinelli–Bernstein (comet C/2014 UN271), the largest known Oort cloud comet.
If R631 is cometary in nature, it might show some activity (such as outgassing) around the time of its 2047 perihelion. In June 2025, we reported that Comet Bernardinelli–Bernstein has been belching jets from a distance of 16.6 AU from our sun.
Why does R631 orbit in retrograde motion?
Why do objects in our solar system tend to orbit the sun in the same direction? And why might this object be orbiting differently from other objects?
Our solar system is thought to have been formed from a spinning cloud of gas and dust in space. The central concentration of mass pulled itself inward through gravity to form the sun. The rest of the dust and gas went on to clump together and eventually form planets, with crumbs left over as objects such as asteroids, moons and comets.
So there are several ways R631 might have developed a retrograde orbit. It might have been born in another solar system — flung out of its that system, perhaps when the system brushed too close to ours — and ultimately was pulled into the sun’s gravity well.
Alternatively, it might have begun life in our solar system, in an ordinary prograde orbit, like Earth’s. It might then have passed too close to a large object, say Jupiter or a passing star, which flung it into a retrograde path.
Sam Deen, an amateur astronomer who finds lost objects such as asteroids and comets in archival data, said the retrograde object is likely from the Kuiper belt and became destabilized when it passed too close to Neptune sometime in the past billion years.
Is R631 related to the Kreutz sungrazers?
This is not the first object discovered with a retrograde orbit. In fact, there was another famous object that had a 142-degree inclination: the Great Comet of 1882.
This comet was bright. It might have been the brightest natural object in the sky in recorded history. It was visible in daylight, reaching what some say was a magnitude of -17. That’s in contrast to our sun, which has a magnitude of -26. The Great Comet of 1882 came so close to our sun that it broke into fragments. Its highly inclined orbit matched that of the Kreutz sungrazer family of comets, a group of comets that follow remarkably similar orbits, bringing them extremely close to the sun at their nearest approach.
Comet Ikeya-Seki was another Kreutz sungrazer that had an inclination of about 142 degrees. It had a spectacular encounter with the sun in October 1965. Although it survived its extremely close passage, its nucleus broke apart into several pieces. Those fragments gradually faded as they traveled away from the sun.
Scientists think the Kreutz sungrazer comets are all remnants of a single, massive ancient comet that fragmented hundreds or thousands of years ago.
If you’re curious — like I was — if R631 could be from that same object, Tony Dunn ran a simulation of the Kreutz sungrazers versus R631 and the rest of the solar system. His simulation makes it clear that R631 is unrelated.
The retrograde object R631 has a 142 degree inclination from the plane of our solar system. The Kreutz sungrazing comets also have a 142 degree inclination, but they take starkly different paths from R631. R631 is in green, and the Kreutz sungrazers are in white. Simulation via Tony Dunn.
Bottom line: The Rubin Observatory in Chile has discovered a retrograde object in our solar system. It circles the sun in a highly inclined orbit beyond Neptune.
Rubin Observatory has discovered a retrograde object, currently labeled R631. It orbits the sun beyond the orbit of the 8th planet, Neptune, at a steep inclination. Simulation via Tony Dunn.
Rubin finds retrograde object past Neptune
The new Rubin Observatory in Chile has found an object beyond Neptune that follows a retrograde orbit. Most other other planets, moons and asteroids orbit our sun in a more or less flat plane. They generally move in the same direction, counterclockwise as seen from earthly north.
This object’s orbit is highly inclined, slicing through at a severe angle.
When we hear the word retrograde, we tend to think of an object moving backward in its orbit, against the direction of most planets, and many asteroids and moons. But in astronomy, retrograde has a more precise meaning. Any object whose orbit is tilted more than 90 degrees relative to the plane of the solar system is considered to be in retrograde motion.
This newly discovered object, currently designated R631 in the Rubin data, has an orbital inclination of 142 degrees. So its orbit is tilted beyond perpendicular, and it is moving in the opposite direction from most planets.
The designation R631 is only temporary. The object will soon get an official designation from the Minor Planet Center. Astronomers and citizens alike who monitor Rubin’s alert stream noticed this object, which has appeared over four months in the data. Rubin’s observations of the retrograde object are from December 2025 through March 2026.
R631 is located 32 astronomical units (AU) from our sun. That’s 30 times the Earth-sun distance. And it would place the object just beyond the orbit of Neptune, which is 30 AU from the sun. The object R631 will reach its closest point to the sun, or perihelion, on October 31, 2047, at a distance of 24 AU.
If this orbit is correct, it will take object R631 some 547.84 Earth-years to make one full orbit of the sun.
Physicist and astronomer Marshall Eubanks said on Minor Planet Mailing List that the object could be 62 miles (100 km) in diameter. He said it might be akin to giant Comet Bernardinelli–Bernstein (comet C/2014 UN271), the largest known Oort cloud comet.
If R631 is cometary in nature, it might show some activity (such as outgassing) around the time of its 2047 perihelion. In June 2025, we reported that Comet Bernardinelli–Bernstein has been belching jets from a distance of 16.6 AU from our sun.
Why does R631 orbit in retrograde motion?
Why do objects in our solar system tend to orbit the sun in the same direction? And why might this object be orbiting differently from other objects?
Our solar system is thought to have been formed from a spinning cloud of gas and dust in space. The central concentration of mass pulled itself inward through gravity to form the sun. The rest of the dust and gas went on to clump together and eventually form planets, with crumbs left over as objects such as asteroids, moons and comets.
So there are several ways R631 might have developed a retrograde orbit. It might have been born in another solar system — flung out of its that system, perhaps when the system brushed too close to ours — and ultimately was pulled into the sun’s gravity well.
Alternatively, it might have begun life in our solar system, in an ordinary prograde orbit, like Earth’s. It might then have passed too close to a large object, say Jupiter or a passing star, which flung it into a retrograde path.
Sam Deen, an amateur astronomer who finds lost objects such as asteroids and comets in archival data, said the retrograde object is likely from the Kuiper belt and became destabilized when it passed too close to Neptune sometime in the past billion years.
Is R631 related to the Kreutz sungrazers?
This is not the first object discovered with a retrograde orbit. In fact, there was another famous object that had a 142-degree inclination: the Great Comet of 1882.
This comet was bright. It might have been the brightest natural object in the sky in recorded history. It was visible in daylight, reaching what some say was a magnitude of -17. That’s in contrast to our sun, which has a magnitude of -26. The Great Comet of 1882 came so close to our sun that it broke into fragments. Its highly inclined orbit matched that of the Kreutz sungrazer family of comets, a group of comets that follow remarkably similar orbits, bringing them extremely close to the sun at their nearest approach.
Comet Ikeya-Seki was another Kreutz sungrazer that had an inclination of about 142 degrees. It had a spectacular encounter with the sun in October 1965. Although it survived its extremely close passage, its nucleus broke apart into several pieces. Those fragments gradually faded as they traveled away from the sun.
Scientists think the Kreutz sungrazer comets are all remnants of a single, massive ancient comet that fragmented hundreds or thousands of years ago.
If you’re curious — like I was — if R631 could be from that same object, Tony Dunn ran a simulation of the Kreutz sungrazers versus R631 and the rest of the solar system. His simulation makes it clear that R631 is unrelated.
The retrograde object R631 has a 142 degree inclination from the plane of our solar system. The Kreutz sungrazing comets also have a 142 degree inclination, but they take starkly different paths from R631. R631 is in green, and the Kreutz sungrazers are in white. Simulation via Tony Dunn.
Bottom line: The Rubin Observatory in Chile has discovered a retrograde object in our solar system. It circles the sun in a highly inclined orbit beyond Neptune.
Tomorrow would have been Carl Sagan’s 92nd birthday. The astronomer and science popularizer became famous through his books and the 1980 television series Cosmos. He also made major contributions to planetary science and the American space program.
Carl Edward Sagan was born on November 9, 1934, in Brooklyn, New York. He studied physics at the University of Chicago and earned his doctorate in astronomy and astrophysics in 1960.
In the 1960s, one of Sagan’s earliest works in professional astronomical research shed light on the atmospheres of our solar system’s planets, for example Mars and Venus. In Sagan’s day, scientists were still trying to understand how Mars could be so cold while Venus is so hot. Sagan successfully argued that Venus could be a greenhouse furnace by using data from tables for steam boiler engineering.
It was Carl Sagan who said, “We’re made of starstuff. We are a way for the cosmos to know itself.” Image via NASA/ Planetary Society/ Wikimedia Commons.
Carl Sagan and the search for extraterrestrial intelligence
Around this same time, Sagan became interested in the search for extraterrestrial intelligence (SETI) and contributed to those programs. He showed that the building blocks of life could be easily created by exposing simple chemicals to UV light. In 1966, he helped I. S. Shklovskii, a Soviet astronomer and astrophysicist, revise and expand his classic book on extraterrestrial life, Intelligent Life in the Universe.
In 1968, Harvard University denied Sagan tenure; some speculated it was due to his controversial opinions on extraterrestrial intelligence. He went on to become a professor at Cornell University in Ithaca, New York, where he spent the rest of his professional career.
Also, Sagan contributed to the U.S. space program. Among other things, he briefed astronauts before their trip to the moon, and he was part of the Mariner, Viking, Galileo, and Voyager space missions. In the Viking missions, for example — two probes sent to explore Mars in the 1970s — he collaborated on choosing ideal landing sites.
But in addition to his books and the “Cosmos” television series, it’s Sagan’s actual messages to the cosmos — placed aboard the first spacecraft designed to leave our solar system, the Pioneer and Voyager missions — that may be his greatest legacy.
Carl Sagan poses with a model of the Viking lander in Death Valley, California. Image via NASA.
Messages to the stars: Pioneer
The original idea for the Pioneer plaques — a pair of gold-anodized aluminum plaques carrying messages from humankind, placed aboard the 1972 Pioneer 10 and 1973 Pioneer 11 spacecraft — came from journalist and consultant Eric Burgess. He approached Sagan about it, and NASA agreed to it and gave Sagan three weeks to prepare a message.
Together with astronomer Frank Drake, who formulated the famous Drake Equation (a way of estimating the number of intelligent civilizations in our Milky Way galaxy), Sagan designed the plaque, with artwork prepared by his wife at the time, Linda Salzman Sagan.
The Pioneers and their plaques are now billions of miles from Earth. Both spacecraft are coasting toward interstellar space, carrying messages from Earth into the distant future.
A Pioneer plaque, which Carl Sagan helped create for the first two spacecraft designed to leave our solar system, image via NASA/ Wikimedia Commons.
Later in that same decade, Sagan and his wife-to-be, Ann Druyan, contributed to the design of yet another message from humankind to outer space. The Voyager probes launched in 1977. They both carry what is known as a Voyager Golden Record. Each Golden Record contains 116 images that depict historical scientific works and humans performing mundane activities, plus music from artists such as Bach, Mozart, and Chuck Berry, an hour-long record of Ann Druyan’s brainwaves, and greetings in 55 languages.
The Voyagers launched later, but traveled faster than the Pioneers. Voyager 1 and 2 have reached interstellar space. Voyager 1 is the farthest human-made object from Earth. Voyager 1 is expected to reach 1 light-day from Earth on November 18, 2026. Voyager 2 is closer than Voyager 1 but farther away than Pioneer 10.
During the 1980s, Sagan encouraged nuclear disarmament and was one of the five authors of the concept of nuclear winter, which describes the aftermath of a nuclear war. Moreover, the work showed that, in a nuclear war, no one would win. It’s hard to estimate the importance of this work to the global consciousness of the time, but it’s perhaps no accident that the Cold War ended not long afterward.
Carl Sagan remained at Cornell until his death on December 20, 1996, at age 62 from pneumonia.
Over the course of his life, Carl Sagan published more than 600 scientific papers and articles, and wrote, co-wrote or edited more than 20 books. He was an inspiration to many, and continues to inspire many young scientists to tread the path of astronomy and astronomical communication. Plus, he encouraged scientific responsibility by promoting nuclear disarmament. Equally important, his work in science outreach encouraged science literacy not only among Americans, but around the world. He was very quotable and said, among many other wonderful things:
The nitrogen in our DNA, the calcium in our teeth, the iron in our blood, the carbon in our apple pies were made in the interiors of collapsing stars. We are made of starstuff.
Do you remember him? Do you remember his words and the sound of his voice? Listen and remember, via the video below.
Bottom line: Carl Sagan was born on November 9, 1934. He is most remembered for his efforts in popularizing science through his books, for his television series “Cosmos” and for his messages to the cosmos placed on the Pioneer and Voyager spacecraft.
Tomorrow would have been Carl Sagan’s 92nd birthday. The astronomer and science popularizer became famous through his books and the 1980 television series Cosmos. He also made major contributions to planetary science and the American space program.
Carl Edward Sagan was born on November 9, 1934, in Brooklyn, New York. He studied physics at the University of Chicago and earned his doctorate in astronomy and astrophysics in 1960.
In the 1960s, one of Sagan’s earliest works in professional astronomical research shed light on the atmospheres of our solar system’s planets, for example Mars and Venus. In Sagan’s day, scientists were still trying to understand how Mars could be so cold while Venus is so hot. Sagan successfully argued that Venus could be a greenhouse furnace by using data from tables for steam boiler engineering.
It was Carl Sagan who said, “We’re made of starstuff. We are a way for the cosmos to know itself.” Image via NASA/ Planetary Society/ Wikimedia Commons.
Carl Sagan and the search for extraterrestrial intelligence
Around this same time, Sagan became interested in the search for extraterrestrial intelligence (SETI) and contributed to those programs. He showed that the building blocks of life could be easily created by exposing simple chemicals to UV light. In 1966, he helped I. S. Shklovskii, a Soviet astronomer and astrophysicist, revise and expand his classic book on extraterrestrial life, Intelligent Life in the Universe.
In 1968, Harvard University denied Sagan tenure; some speculated it was due to his controversial opinions on extraterrestrial intelligence. He went on to become a professor at Cornell University in Ithaca, New York, where he spent the rest of his professional career.
Also, Sagan contributed to the U.S. space program. Among other things, he briefed astronauts before their trip to the moon, and he was part of the Mariner, Viking, Galileo, and Voyager space missions. In the Viking missions, for example — two probes sent to explore Mars in the 1970s — he collaborated on choosing ideal landing sites.
But in addition to his books and the “Cosmos” television series, it’s Sagan’s actual messages to the cosmos — placed aboard the first spacecraft designed to leave our solar system, the Pioneer and Voyager missions — that may be his greatest legacy.
Carl Sagan poses with a model of the Viking lander in Death Valley, California. Image via NASA.
Messages to the stars: Pioneer
The original idea for the Pioneer plaques — a pair of gold-anodized aluminum plaques carrying messages from humankind, placed aboard the 1972 Pioneer 10 and 1973 Pioneer 11 spacecraft — came from journalist and consultant Eric Burgess. He approached Sagan about it, and NASA agreed to it and gave Sagan three weeks to prepare a message.
Together with astronomer Frank Drake, who formulated the famous Drake Equation (a way of estimating the number of intelligent civilizations in our Milky Way galaxy), Sagan designed the plaque, with artwork prepared by his wife at the time, Linda Salzman Sagan.
The Pioneers and their plaques are now billions of miles from Earth. Both spacecraft are coasting toward interstellar space, carrying messages from Earth into the distant future.
A Pioneer plaque, which Carl Sagan helped create for the first two spacecraft designed to leave our solar system, image via NASA/ Wikimedia Commons.
Later in that same decade, Sagan and his wife-to-be, Ann Druyan, contributed to the design of yet another message from humankind to outer space. The Voyager probes launched in 1977. They both carry what is known as a Voyager Golden Record. Each Golden Record contains 116 images that depict historical scientific works and humans performing mundane activities, plus music from artists such as Bach, Mozart, and Chuck Berry, an hour-long record of Ann Druyan’s brainwaves, and greetings in 55 languages.
The Voyagers launched later, but traveled faster than the Pioneers. Voyager 1 and 2 have reached interstellar space. Voyager 1 is the farthest human-made object from Earth. Voyager 1 is expected to reach 1 light-day from Earth on November 18, 2026. Voyager 2 is closer than Voyager 1 but farther away than Pioneer 10.
During the 1980s, Sagan encouraged nuclear disarmament and was one of the five authors of the concept of nuclear winter, which describes the aftermath of a nuclear war. Moreover, the work showed that, in a nuclear war, no one would win. It’s hard to estimate the importance of this work to the global consciousness of the time, but it’s perhaps no accident that the Cold War ended not long afterward.
Carl Sagan remained at Cornell until his death on December 20, 1996, at age 62 from pneumonia.
Over the course of his life, Carl Sagan published more than 600 scientific papers and articles, and wrote, co-wrote or edited more than 20 books. He was an inspiration to many, and continues to inspire many young scientists to tread the path of astronomy and astronomical communication. Plus, he encouraged scientific responsibility by promoting nuclear disarmament. Equally important, his work in science outreach encouraged science literacy not only among Americans, but around the world. He was very quotable and said, among many other wonderful things:
The nitrogen in our DNA, the calcium in our teeth, the iron in our blood, the carbon in our apple pies were made in the interiors of collapsing stars. We are made of starstuff.
Do you remember him? Do you remember his words and the sound of his voice? Listen and remember, via the video below.
Bottom line: Carl Sagan was born on November 9, 1934. He is most remembered for his efforts in popularizing science through his books, for his television series “Cosmos” and for his messages to the cosmos placed on the Pioneer and Voyager spacecraft.
Everyone on Earth sees essentially the same moon phase at the same time. But the moon can look different depending on where you are. Its orientation changes with your location and even over the course of a single night.
Why does this happen? It comes down to Earth’s rotation and our different perspectives on the sky.
The moon appears to change its angle in the sky as the night goes on. That’s because Earth rotates, changing our view of the moon. Like the sun and stars, the moon appears to travel in an arc across the sky.
The illustration below shows the curved line traveled by the stars and the moon, as they traverse sky’s dome each night (or day). And that is because Earth’s rotation under the sky causes the stars and moon to move westward throughout the night. However, the moon’s motion in its orbit around Earth each day is eastward, in front of the background stars.
Each night, the stars and moon travel along curved lines moving westward across the sky dome. That’s why the moon’s orientation with respect to your horizon changes throughout the night. On the other hand, the moon’s orbit around Earth results in the moon moving eastward relative to the background stars each day. Chart via Marcy Curran.
How the moon changes over hours
Overnight — or even in a few hours — you can notice that the appearance of the moon changes.
View at EarthSky Community Photos. | Meiying Lee in Taipei, Taiwan, captured these images and made this composite chart of the moon over a single evening in July. It shows how the angle of the waxing gibbous moon — and the color of both the moon itself and the background sky — change from when you might first spy it in late afternoon until after midnight, when it sets. Thank you, Meiying!
View at EarthSky Community Photos. | This is a crop of an image taken by Andy Bentley in Mountain View, California, showing the moon on a single night in February. See the full image here. We all see the same moon phase. But, as the image shows, the moon’s orientation to your horizon changes throughout the night, or as you move northward or southward on Earth’s globe. Thanks, Andy!
How the moon changes between hemispheres
So, why do people in different parts of the globe see the same moon phase, but it appears different? People in the Northern and Southern Hemispheres see the moon oriented differently from one another. It’s not a change in phase. It’s a change in the orientation of the moon with respect to your horizon. The differences can be hard to comprehend!
For one thing, observers in the Northern and Southern Hemispheres see the moon apparently upside down with respect to each other. You can see that if you scrutinize the moon’s features in the image below.
From Earth’s Northern Hemisphere, the moon’s north pole appears at the top. From Earth’s Southern Hemisphere, the moon’s south pole appears at the top. It’s all a matter of perspective! Image and caption via The Planetary Society. Used with permission.
Also, notice that from the Northern Hemisphere, a waxing moon (from new moon to full moon) increases its phase from right to left. Meanwhile, from the Southern Hemisphere, a waxing moon increases its phase from left to right.
Have you ever been to the southern hemisphere Ashes?? Ever see the Southern Cross? Sigma Octantis? The sun moving from right to left each day? The stars moving clockwise each night? The moon phases move from left to right over 28 days?#SouthernHemisphereDisprovesFlatEarthpic.twitter.com/pfESD411yH
Why so different? Think of the moon’s path across your sky. Just picture yourself standing there, looking at it. From the Northern Hemisphere, we look generally southward to see the moon (or sun) crossing our sky. From the Southern Hemisphere, people look generally northward to see the moon (or sun) crossing the sky.
Can you see why that shift in your orientation on the globe would cause you to see the moon differently?
A final thought
What we on Earth call moon phases are really about sunrise/set on the moon. Astronomers call the line between light and dark on the moon the terminator. That’s the line of sunrise or sunset on the moon, and it shifts, just as the line of sunrise and sunset on Earth is constantly shifting.
Also, Earth spins relatively fast, approximately once every 24 hours. The moon spins on its axis only about once a month, and its line of sunrise/set moves slowly. It’s wonderful fun to beg or borrow a telescope for a night when the moon is up … and watch for yourself over several hours. The shadows slowly shift on the moon, as the lunar sunrise or sunset slowly creeps across the moon’s face.
Of course, it’s also a great way to clear the mind!
View at EarthSky Community Photos. | Meiying Lee submitted this composite image of moon phases and wrote: “The photos of the moon were taken from August 15th, through September 10th. On September 11th, typhoon #14 Chanthu began to hit Taiwan and interrupted the progress. A friend Bob in Phoenix, Arizona agreed to complete the last three moon phase photographs that ended on September 13th. Through the cooperation of Taiwan and USA, the month-long moon phases documentation finally completes.” Thank you, Meiying!
Bottom line: The moon shows one phase to the Earth at the same time, but our different perspectives due to where we are on the globe can make the moon appear differently in our sky.
Everyone on Earth sees essentially the same moon phase at the same time. But the moon can look different depending on where you are. Its orientation changes with your location and even over the course of a single night.
Why does this happen? It comes down to Earth’s rotation and our different perspectives on the sky.
The moon appears to change its angle in the sky as the night goes on. That’s because Earth rotates, changing our view of the moon. Like the sun and stars, the moon appears to travel in an arc across the sky.
The illustration below shows the curved line traveled by the stars and the moon, as they traverse sky’s dome each night (or day). And that is because Earth’s rotation under the sky causes the stars and moon to move westward throughout the night. However, the moon’s motion in its orbit around Earth each day is eastward, in front of the background stars.
Each night, the stars and moon travel along curved lines moving westward across the sky dome. That’s why the moon’s orientation with respect to your horizon changes throughout the night. On the other hand, the moon’s orbit around Earth results in the moon moving eastward relative to the background stars each day. Chart via Marcy Curran.
How the moon changes over hours
Overnight — or even in a few hours — you can notice that the appearance of the moon changes.
View at EarthSky Community Photos. | Meiying Lee in Taipei, Taiwan, captured these images and made this composite chart of the moon over a single evening in July. It shows how the angle of the waxing gibbous moon — and the color of both the moon itself and the background sky — change from when you might first spy it in late afternoon until after midnight, when it sets. Thank you, Meiying!
View at EarthSky Community Photos. | This is a crop of an image taken by Andy Bentley in Mountain View, California, showing the moon on a single night in February. See the full image here. We all see the same moon phase. But, as the image shows, the moon’s orientation to your horizon changes throughout the night, or as you move northward or southward on Earth’s globe. Thanks, Andy!
How the moon changes between hemispheres
So, why do people in different parts of the globe see the same moon phase, but it appears different? People in the Northern and Southern Hemispheres see the moon oriented differently from one another. It’s not a change in phase. It’s a change in the orientation of the moon with respect to your horizon. The differences can be hard to comprehend!
For one thing, observers in the Northern and Southern Hemispheres see the moon apparently upside down with respect to each other. You can see that if you scrutinize the moon’s features in the image below.
From Earth’s Northern Hemisphere, the moon’s north pole appears at the top. From Earth’s Southern Hemisphere, the moon’s south pole appears at the top. It’s all a matter of perspective! Image and caption via The Planetary Society. Used with permission.
Also, notice that from the Northern Hemisphere, a waxing moon (from new moon to full moon) increases its phase from right to left. Meanwhile, from the Southern Hemisphere, a waxing moon increases its phase from left to right.
Have you ever been to the southern hemisphere Ashes?? Ever see the Southern Cross? Sigma Octantis? The sun moving from right to left each day? The stars moving clockwise each night? The moon phases move from left to right over 28 days?#SouthernHemisphereDisprovesFlatEarthpic.twitter.com/pfESD411yH
Why so different? Think of the moon’s path across your sky. Just picture yourself standing there, looking at it. From the Northern Hemisphere, we look generally southward to see the moon (or sun) crossing our sky. From the Southern Hemisphere, people look generally northward to see the moon (or sun) crossing the sky.
Can you see why that shift in your orientation on the globe would cause you to see the moon differently?
A final thought
What we on Earth call moon phases are really about sunrise/set on the moon. Astronomers call the line between light and dark on the moon the terminator. That’s the line of sunrise or sunset on the moon, and it shifts, just as the line of sunrise and sunset on Earth is constantly shifting.
Also, Earth spins relatively fast, approximately once every 24 hours. The moon spins on its axis only about once a month, and its line of sunrise/set moves slowly. It’s wonderful fun to beg or borrow a telescope for a night when the moon is up … and watch for yourself over several hours. The shadows slowly shift on the moon, as the lunar sunrise or sunset slowly creeps across the moon’s face.
Of course, it’s also a great way to clear the mind!
View at EarthSky Community Photos. | Meiying Lee submitted this composite image of moon phases and wrote: “The photos of the moon were taken from August 15th, through September 10th. On September 11th, typhoon #14 Chanthu began to hit Taiwan and interrupted the progress. A friend Bob in Phoenix, Arizona agreed to complete the last three moon phase photographs that ended on September 13th. Through the cooperation of Taiwan and USA, the month-long moon phases documentation finally completes.” Thank you, Meiying!
Bottom line: The moon shows one phase to the Earth at the same time, but our different perspectives due to where we are on the globe can make the moon appear differently in our sky.
View larger. | Color-coded topographic map of the Alba Mons volcano (center) and surrounding region. Many cracks in the surface are visible around the volcano. The European Space Agency’s Trace Gas Orbiter (TGO) detected the gas hydrogen chloride coming from some of the cracks. Are they evidence of active volcanoes on Mars? Image via NASA/ JPL-Caltech/ Arizona State University/ Wikimedia Commons.
Are there still active volcanoes on Mars? The planet’s volcanoes are no longer erupting, but there could still be flowing magma underground.
The European Space Agency’s Trace Gas Orbiter has detected hydrogen chloride coming out of cracks in the surface in the Alba Mons volcano region.
The noxious gas is often produced by hot magma moving below the surface on Earth.
Mars’ enormous volcanoes — including Olympus Mons, the largest in the solar system — are remnants of an active volcanic past. But, unlike Earth, Mars has no moving tectonic plates to continually reshape its surface. And so, for much of the space age, Mars has been considered a largely dormant world.
But that picture has been changing. NASA’s InSight lander detected more than 1,300 seismic events, revealing that Mars still experiences marsquakes. And evidence of relatively recent volcanic activity has been accumulating, too.
Now, an international team of researchers says it has found perhaps the strongest evidence yet that Mars might still be volcanically active, with magma moving beneath its surface.
The researchers said on November 4, 2026, that the European Space Agency’s Trace Gas Orbiter (TGO) has detected the gas hydrogen chloride (HCl) above cracks in the Martian surface in the region of the Alba Mons volcano. Alba Mons is northeast of Olympus Mons.
On Earth, magmatism — the movement of hot magma below the surface — often produces hydrogen chloride. It is a minor volcanic gas compared to water vapor, carbon dioxide, and sulfur dioxide from earthly volcanoes. But, on Mars, hydrogen chloride might be a major volcanic gas, according to scientists.
The detection adds to previous evidence for active volcanism still occurring on Mars today. Even though Mars’ volcanoes are no long erupting, magma could still flow deeper down.
The researchers published their new peer-reviewed findings in Science Advances on November 4, 2026.
Mars may not be geologically dead after all. ? Our ExoMars Trace Gas Orbiter has detected hydrogen chloride above volcanic fissures in the Alba Mons region, which scientists suggest could be linked to dormant volcanic activity beneath the surface. Read more: new.esa.int/articles/new…
Traces of noxious gas point to possible active volcanoes on Mars
Trace Gas Orbiter detected the traces of hydrogen chloride above geologically fresh cracks in the surface in the Alba Mons region. The gas was at parts-per-billion levels, but still higher than expected (if future studies confirm it is there at all). The paper states:
Detections of hydrogen chloride at low altitudes, unexplained by observed atmospheric state and models, together with the geological context of the region, hint at an igneous origin of this gas.
Mars is reputed to lack ongoing volcanic activity. However, marsquakes were revealed recently, and clues to volcanism younger than tens of million years have accumulated. While sulfur dioxide, so far undetected, could testify to ongoing eruptive activity, evidence of active magma chambers may be better identified by seepage of halogen gases, such as hydrogen chloride.
Co-lead author Daniel Mège at the Space Research Center of the Polish Academy of Sciences said:
Our findings suggest that Mars has retained enough internal heat to support volcanic activity until recently, and possibly still does.
The Trace Gas Orbiter was able to find the smoking gun. It was like looking for a needle in a haystack. It’s truly amazing that it spotted a handful of molecules from a perhaps intermittent source, whilst moving continuously along its orbit to monitor the whole martian atmosphere,
A huge part of the work consisted of examining all the possible chemical processes going on in the martian atmosphere. We needed to be rigorous, critical and creative to explain the presence of hydrogen chloride. The data were complex, but also excellent brain food.
View larger. | This Mars Express spacecraft view shows Olympus Mons on Mars, the largest volcano in the solar system. Mars’ volcanoes might no longer be erupting, but it seems there may still be magma flowing beneath the surface. If so, Mars could still have active volcanic systems deep underground. Image via ESA/ DLR/ FU Berlin/ J. Cowart.
Aerosols and seepage
Hydrogen chloride can be found virtually everywhere in the Martian atmosphere. But those observations are typically during warmer seasons, when the hydrogen chloride behaves as an aerosol. Aerosols are fine solid particles or liquid droplets in the atmosphere.
This gas isn’t seen as much during Mars’ colder seasons because its molecules are quickly “absorbed” by water ice crystals and disappear from the observations. But the detections at Alba Mons were during the cold season. And the levels were much higher than anticipated. The gas was detected above geologically fresh new cracks in the surface around the volcano. The cracks were several hundred meters long, and tens of centimeters wide.
The researchers said it’s likely that the hydrogen chloride seeped into Mars’ atmosphere from these cracks. That would make it volcanic in origin. The paper states:
Observations by Atmospheric Chemistry Suite led to the widespread observations of hydrogen chloride at part-per-billion levels in the atmosphere of Mars during the warm perihelion period [when Mars was closest to the sun in its 2-year orbit], attributed to aerosol-atmospheric sources. Here, we report hydrogen chloride detections during the cold aphelion season [when Mars is farthest from the sun] that are isolated in the Alba Mons region.
We also identify fresh and narrow (<1 meter) fissures in this area, which we interpret to be potential hydrogen chloride pathways rooted into magmatic bodies at depth. Our results are best explained by ongoing igneous processes in the Martian interior.
A supplementary to the main paper (pdf download) also states:
Localized aphelion detections of HCl at low altitudes, together with the geological context of the area, suggests an igneous origin of this gas and that the detections are made above the seepage.
Icy buffer zone
It’s possible that the hydrogen chloride doesn’t come straight from the magma. It might come from a buffer zone, a layer of permafrost above the magma.
In the cold winter, the ice traps the hydrogen chloride molecules. But when the temperatures get a bit warmer in spring, the ice sublimates and release the gas into the atmosphere.
If there is a permanent source of hydrogen chloride in the surface “soil,” this could explain the seasonality of the observations and their binding to a certain area.
View larger. | The possible chlorine cycle on Mars, including hydrogen chloride. Image via ESA.
The chlorine cycle
On both Earth and Mars, there was a chlorine cycle initiated by degassing while the planets were still forming. In other words, as molten rock cooled and solidified, it released gases from the planets’ interiors into their atmospheres.The paper states:
On Mars, as on Earth, the chlorine cycle initiated by volcanic degassing from the deep interior upon planetary accretion was fed by the subsequent volcanic eruptions, and, because of its high mobility and solubility, chlorine has been continuously recycled in water, sediments, permafrost, and ice clouds. However, contrary to Earth, the absence of recycling due to plate tectonics probably make the volcanic source the main input to the surface-atmosphere system on Mars. The topic addressed here is volcanism still contributing to this cycle on Mars today?
The more we know about Mars, the more we learn that it’s not as cold and dead as we thought it was. While the surface is a cold desert, there might still be heat deeper down. Heat from flowing magma that just might be able to melt ice and support life.
Co-lead author Daniel Mège at the Space Research Center of the Polish Academy of Sciences. Image via Daniel Mège.
Habitats for life?
Plus, hot magma deeper down could heat ice and create groundwater. So could there still be active hydrothermal systems, too? If so, they might provide habitable conditions for microbes below the surface. Mège said:
Looking for Martian life in the seeping fissures of the Alba Mons region would make a lot of sense. If hydrothermal systems are active, they could contain the ingredients and energy needed for microorganisms to develop, and shield microorganisms from the hostile and changing environment above the surface.
Bottom line: Are there still active volcanoes on Mars? New detections of hydrogen chloride from below the surface suggest flowing magma.
View larger. | Color-coded topographic map of the Alba Mons volcano (center) and surrounding region. Many cracks in the surface are visible around the volcano. The European Space Agency’s Trace Gas Orbiter (TGO) detected the gas hydrogen chloride coming from some of the cracks. Are they evidence of active volcanoes on Mars? Image via NASA/ JPL-Caltech/ Arizona State University/ Wikimedia Commons.
Are there still active volcanoes on Mars? The planet’s volcanoes are no longer erupting, but there could still be flowing magma underground.
The European Space Agency’s Trace Gas Orbiter has detected hydrogen chloride coming out of cracks in the surface in the Alba Mons volcano region.
The noxious gas is often produced by hot magma moving below the surface on Earth.
Mars’ enormous volcanoes — including Olympus Mons, the largest in the solar system — are remnants of an active volcanic past. But, unlike Earth, Mars has no moving tectonic plates to continually reshape its surface. And so, for much of the space age, Mars has been considered a largely dormant world.
But that picture has been changing. NASA’s InSight lander detected more than 1,300 seismic events, revealing that Mars still experiences marsquakes. And evidence of relatively recent volcanic activity has been accumulating, too.
Now, an international team of researchers says it has found perhaps the strongest evidence yet that Mars might still be volcanically active, with magma moving beneath its surface.
The researchers said on November 4, 2026, that the European Space Agency’s Trace Gas Orbiter (TGO) has detected the gas hydrogen chloride (HCl) above cracks in the Martian surface in the region of the Alba Mons volcano. Alba Mons is northeast of Olympus Mons.
On Earth, magmatism — the movement of hot magma below the surface — often produces hydrogen chloride. It is a minor volcanic gas compared to water vapor, carbon dioxide, and sulfur dioxide from earthly volcanoes. But, on Mars, hydrogen chloride might be a major volcanic gas, according to scientists.
The detection adds to previous evidence for active volcanism still occurring on Mars today. Even though Mars’ volcanoes are no long erupting, magma could still flow deeper down.
The researchers published their new peer-reviewed findings in Science Advances on November 4, 2026.
Mars may not be geologically dead after all. ? Our ExoMars Trace Gas Orbiter has detected hydrogen chloride above volcanic fissures in the Alba Mons region, which scientists suggest could be linked to dormant volcanic activity beneath the surface. Read more: new.esa.int/articles/new…
Traces of noxious gas point to possible active volcanoes on Mars
Trace Gas Orbiter detected the traces of hydrogen chloride above geologically fresh cracks in the surface in the Alba Mons region. The gas was at parts-per-billion levels, but still higher than expected (if future studies confirm it is there at all). The paper states:
Detections of hydrogen chloride at low altitudes, unexplained by observed atmospheric state and models, together with the geological context of the region, hint at an igneous origin of this gas.
Mars is reputed to lack ongoing volcanic activity. However, marsquakes were revealed recently, and clues to volcanism younger than tens of million years have accumulated. While sulfur dioxide, so far undetected, could testify to ongoing eruptive activity, evidence of active magma chambers may be better identified by seepage of halogen gases, such as hydrogen chloride.
Co-lead author Daniel Mège at the Space Research Center of the Polish Academy of Sciences said:
Our findings suggest that Mars has retained enough internal heat to support volcanic activity until recently, and possibly still does.
The Trace Gas Orbiter was able to find the smoking gun. It was like looking for a needle in a haystack. It’s truly amazing that it spotted a handful of molecules from a perhaps intermittent source, whilst moving continuously along its orbit to monitor the whole martian atmosphere,
A huge part of the work consisted of examining all the possible chemical processes going on in the martian atmosphere. We needed to be rigorous, critical and creative to explain the presence of hydrogen chloride. The data were complex, but also excellent brain food.
View larger. | This Mars Express spacecraft view shows Olympus Mons on Mars, the largest volcano in the solar system. Mars’ volcanoes might no longer be erupting, but it seems there may still be magma flowing beneath the surface. If so, Mars could still have active volcanic systems deep underground. Image via ESA/ DLR/ FU Berlin/ J. Cowart.
Aerosols and seepage
Hydrogen chloride can be found virtually everywhere in the Martian atmosphere. But those observations are typically during warmer seasons, when the hydrogen chloride behaves as an aerosol. Aerosols are fine solid particles or liquid droplets in the atmosphere.
This gas isn’t seen as much during Mars’ colder seasons because its molecules are quickly “absorbed” by water ice crystals and disappear from the observations. But the detections at Alba Mons were during the cold season. And the levels were much higher than anticipated. The gas was detected above geologically fresh new cracks in the surface around the volcano. The cracks were several hundred meters long, and tens of centimeters wide.
The researchers said it’s likely that the hydrogen chloride seeped into Mars’ atmosphere from these cracks. That would make it volcanic in origin. The paper states:
Observations by Atmospheric Chemistry Suite led to the widespread observations of hydrogen chloride at part-per-billion levels in the atmosphere of Mars during the warm perihelion period [when Mars was closest to the sun in its 2-year orbit], attributed to aerosol-atmospheric sources. Here, we report hydrogen chloride detections during the cold aphelion season [when Mars is farthest from the sun] that are isolated in the Alba Mons region.
We also identify fresh and narrow (<1 meter) fissures in this area, which we interpret to be potential hydrogen chloride pathways rooted into magmatic bodies at depth. Our results are best explained by ongoing igneous processes in the Martian interior.
A supplementary to the main paper (pdf download) also states:
Localized aphelion detections of HCl at low altitudes, together with the geological context of the area, suggests an igneous origin of this gas and that the detections are made above the seepage.
Icy buffer zone
It’s possible that the hydrogen chloride doesn’t come straight from the magma. It might come from a buffer zone, a layer of permafrost above the magma.
In the cold winter, the ice traps the hydrogen chloride molecules. But when the temperatures get a bit warmer in spring, the ice sublimates and release the gas into the atmosphere.
If there is a permanent source of hydrogen chloride in the surface “soil,” this could explain the seasonality of the observations and their binding to a certain area.
View larger. | The possible chlorine cycle on Mars, including hydrogen chloride. Image via ESA.
The chlorine cycle
On both Earth and Mars, there was a chlorine cycle initiated by degassing while the planets were still forming. In other words, as molten rock cooled and solidified, it released gases from the planets’ interiors into their atmospheres.The paper states:
On Mars, as on Earth, the chlorine cycle initiated by volcanic degassing from the deep interior upon planetary accretion was fed by the subsequent volcanic eruptions, and, because of its high mobility and solubility, chlorine has been continuously recycled in water, sediments, permafrost, and ice clouds. However, contrary to Earth, the absence of recycling due to plate tectonics probably make the volcanic source the main input to the surface-atmosphere system on Mars. The topic addressed here is volcanism still contributing to this cycle on Mars today?
The more we know about Mars, the more we learn that it’s not as cold and dead as we thought it was. While the surface is a cold desert, there might still be heat deeper down. Heat from flowing magma that just might be able to melt ice and support life.
Co-lead author Daniel Mège at the Space Research Center of the Polish Academy of Sciences. Image via Daniel Mège.
Habitats for life?
Plus, hot magma deeper down could heat ice and create groundwater. So could there still be active hydrothermal systems, too? If so, they might provide habitable conditions for microbes below the surface. Mège said:
Looking for Martian life in the seeping fissures of the Alba Mons region would make a lot of sense. If hydrothermal systems are active, they could contain the ingredients and energy needed for microorganisms to develop, and shield microorganisms from the hostile and changing environment above the surface.
Bottom line: Are there still active volcanoes on Mars? New detections of hydrogen chloride from below the surface suggest flowing magma.
