Have you ever wondered how many stars you can see in a dark sky?
How many stars can you see?
Imagine you’re under a dark sky far away from city lights, on a night with no moon, no clouds and no haze. How many stars could you see with your unaided eye? There’s really no definitive answer to this question, but astronomers use different numbers as theoretical estimates.
Considering all the stars visible in all directions around Earth, the upper end on the estimates is close to 10,000 visible stars. Here’s how one source, astronomytrek.com, came up with that number:
The brighter the star, the lower the apparent magnitude value assigned to it, with the most luminous given a negative number. In total there are 22 stars with magnitudes of between -1 and 1, making them the night sky’s brightest stars. In the meantime, there are 71 stars of 2nd magnitude, 190 stars of 3rd magnitude, 610 of 4th magnitude, 1,929 of 5th magnitude, and 5,946 of 6th magnitude. When we include another 3,150 stars at the limit of our visual acuity of magnitude +6.5, then this adds up to 9,096 stars that it is possible to see in the night sky from both the Northern and Southern Hemispheres with the unaided eye.
And there’s two hemispheres
But one person couldn’t see all those stars at once. For instance, in the Northern Hemisphere, many of the stars visible from the Southern Hemisphere will be hidden below your southern horizon. So, therefore, each hemisphere can only see about 5,000 stars. And, at any given time, half of Earth is in daylight. So only half the estimated number – perhaps 2,500 stars – would be visible from Earth’s night side. Plus, another fraction of those visible stars would be lost in the murk surrounding your horizon. That could bring you down to around 2,000, the most common number you’ll see for these estimates.
View at EarthSky Community Photos. | Jeremy Evans of California captured a Lyrid meteor zipping along the Milky way on April 22, 2025. Jeremy wrote: “Lyrids meteor shower, April 22nd at peak activity. It was a quiet shower this year. I had my camera going all night and only caught one meteor. This single frame is from an all-night 1,200 frame time lapse on my front deck, I’m very fortunate to live under dark Bortle 2 skies. The glow on the horizon is from the last quarter moon just before rising.” Thank you, Jeremy.
Factors that affect your seeing
Why can’t astronomers agree on the number of visible stars? It’s because we don’t all see the sky in the same way. And even under ideal conditions, there’s a fair amount of variation between how well people can see the stars. Some of the factors include the strength of your vision and your age. As you get older, your eyes become much less sensitive to faint light.
Plus, you have to take into account the brightness of your night sky. Even on a moonless night, the glow of lights from Earth’s surface brightens the sky.
Still, far from city lights – under absolutely perfect conditions of darkness and sky clarity – a young to middle-aged person with normal vision should be able to see thousands of stars.
The WyoAstro allsky camera recorded 2045 stars (see upper right) on the morning of August 20, 2026. This is approximately the same view an observer would see in a fairly dark sky. Image via WyoAstro allsky camera. Used with permission.
Bottom line: Have you ever wondered how many stars are visible on a given night? It depends on factors including how dark your sky is and what your age is.
Have you ever wondered how many stars you can see in a dark sky?
How many stars can you see?
Imagine you’re under a dark sky far away from city lights, on a night with no moon, no clouds and no haze. How many stars could you see with your unaided eye? There’s really no definitive answer to this question, but astronomers use different numbers as theoretical estimates.
Considering all the stars visible in all directions around Earth, the upper end on the estimates is close to 10,000 visible stars. Here’s how one source, astronomytrek.com, came up with that number:
The brighter the star, the lower the apparent magnitude value assigned to it, with the most luminous given a negative number. In total there are 22 stars with magnitudes of between -1 and 1, making them the night sky’s brightest stars. In the meantime, there are 71 stars of 2nd magnitude, 190 stars of 3rd magnitude, 610 of 4th magnitude, 1,929 of 5th magnitude, and 5,946 of 6th magnitude. When we include another 3,150 stars at the limit of our visual acuity of magnitude +6.5, then this adds up to 9,096 stars that it is possible to see in the night sky from both the Northern and Southern Hemispheres with the unaided eye.
And there’s two hemispheres
But one person couldn’t see all those stars at once. For instance, in the Northern Hemisphere, many of the stars visible from the Southern Hemisphere will be hidden below your southern horizon. So, therefore, each hemisphere can only see about 5,000 stars. And, at any given time, half of Earth is in daylight. So only half the estimated number – perhaps 2,500 stars – would be visible from Earth’s night side. Plus, another fraction of those visible stars would be lost in the murk surrounding your horizon. That could bring you down to around 2,000, the most common number you’ll see for these estimates.
View at EarthSky Community Photos. | Jeremy Evans of California captured a Lyrid meteor zipping along the Milky way on April 22, 2025. Jeremy wrote: “Lyrids meteor shower, April 22nd at peak activity. It was a quiet shower this year. I had my camera going all night and only caught one meteor. This single frame is from an all-night 1,200 frame time lapse on my front deck, I’m very fortunate to live under dark Bortle 2 skies. The glow on the horizon is from the last quarter moon just before rising.” Thank you, Jeremy.
Factors that affect your seeing
Why can’t astronomers agree on the number of visible stars? It’s because we don’t all see the sky in the same way. And even under ideal conditions, there’s a fair amount of variation between how well people can see the stars. Some of the factors include the strength of your vision and your age. As you get older, your eyes become much less sensitive to faint light.
Plus, you have to take into account the brightness of your night sky. Even on a moonless night, the glow of lights from Earth’s surface brightens the sky.
Still, far from city lights – under absolutely perfect conditions of darkness and sky clarity – a young to middle-aged person with normal vision should be able to see thousands of stars.
The WyoAstro allsky camera recorded 2045 stars (see upper right) on the morning of August 20, 2026. This is approximately the same view an observer would see in a fairly dark sky. Image via WyoAstro allsky camera. Used with permission.
Bottom line: Have you ever wondered how many stars are visible on a given night? It depends on factors including how dark your sky is and what your age is.
A queen angelfish, one of the colourful reef fish that inhabit coral reef ecosystems. Image via Pedro Lastra/ Wikipedia.
Motorboat noise could be doing more than just disturbing life beneath the ocean’s surface. New research from the University of Exeter, the University of Bristol and James Cook University suggests that repeated exposure to motorboat noise during early development can have lasting effects on reef fish, potentially affecting both their growth and their ability to respond to danger.
The findings reveal a hidden cost of boat traffic for reef ecosystems, with effects that can persist long after the boats have passed.
The researchers published their findings in the peer-reviewed journal Environmental Pollution on August 28, 2026.
Why reef fish are important
Reef fish are species that live in and around coral reefs, relying on these ecosystems for food, shelter and breeding grounds. Coral reefs support an extraordinary variety of marine life and provide habitats for thousands of fish species across tropical and subtropical waters.
But these ecosystems face pressure from many human activities, and underwater noise is one of the less visible disturbances. Motorboats can introduce persistent sounds into reef environments, potentially changing the conditions young fish experience during some of the most important stages of their development.
To investigate the longer-term effects of this noise, researchers from the University of Exeter, University of Bristol and James Cook University studied a species found on Australia’s Great Barrier Reef: the spiny chromis.
The spiny chromis (Acanthochromis polyacanthus) was the focus of research into how motorboat noise can affect young reef fish, from growth to the ability to escape predators. Image via Nikita/ Wikipedia.
Testing noise during early development
The researchers exposed the fish to recordings of either motorboat noise or natural reef sounds at two different stages of development: as embryos and shortly after hatching.
The researchers divided the fish into four groups. Some heard natural reef sounds before and after hatching, while others heard motorboat noise at both stages. The remaining two groups switched from one sound to the other after hatching.
The exposure lasted for up to 78 days. The researchers then stopped playing sounds 24 hours before testing the fish and kept the tanks silent during the test.
This allowed them to determine whether the noise had produced longer-lasting effects rather than simply distracting the fish while they were hearing the sound.
A royal angelfish, a striking coral reef species. Image via Diego Delso/ Wikipedia.
Noise changed their response to predators
The researchers wanted to know whether exposure to motorboat noise could affect one of the most important skills a young fish needs: escaping a predator.
The researchers simulated a predator attack by dropping a weight onto the surface of the water. For spiny chromis, the natural response to a threat is to bend the body into a “C” shape before rapidly swimming away from the danger.
Among fish that had experienced natural reef sounds during at least one stage of development, around 80% responded to the simulated attack. However, about 20% of those fish made a fatal mistake: they swam towards the predator instead of away from it.
The results were more concerning among fish exposed to motorboat noise during both stages of early development. Only 68% responded to the simulated attack, and 40% of those responders swam towards the predator.
Because the researchers did not expose the fish to any sound during the test itself, the results suggest that the effects were not simply an immediate reaction to the noise. Instead, early exposure appeared to have changed how the fish responded to danger later on.
This is an emperor angelfish, a reef-dwelling fish found across the Indo-Pacific. Image via Francois Libert/ Wikipedia.
Motorboat noise can affect growth
The researchers also found a clear difference in body size among fish exposed to boat noise after hatching. On average, those fish were 7% shorter than fish exposed to natural reef sounds.
The researchers suggest that several mechanisms could contribute to this effect. Notably, previous research has shown that motorboat noise can alter parental care behavior. Sophie Nedelec, a senior research fellow at the University of Exeter, said:
We know from previous research that motorboat noise affects parental care behavior, including oxygenating eggs by fanning during the embryonic phase, which is linked with their survival.
She added:
[Exposure to motorboat noise] could cause stress or affect feeding, creating cumulative effects that lead to poor assessment of risk and decision making, and smaller body size.
A mandarinfish, a small reef fish known for its intricate patterns. Image via Luc Viatour/ Wikipedia.
Effects that can persist beyond the noise
The findings suggest that noise pollution can influence young reef fish even when the source of the disturbance is no longer present. Nedelec said:
Our results show that exposure to motorboat noise during early development can affect growth and disrupt the escape response of juveniles, even when the escape occurs in relatively quiet conditions.
The combination of reduced growth and poorer predator responses could be particularly important in the wild, where young fish already face intense pressure from predators and must make rapid decisions to survive.
Here’s a moorish idol, a distinctive reef fish with a long, pointed snout. Image via Diego Delso/ Wikipedia.
Could limiting boat traffic help?
The researchers suggest that limiting motorboat traffic close to reefs during the breeding season could help protect young reef fish from these effects. Nedelec explained that:
Limiting motorboat traffic close to reefs during the breeding season may reduce these effects and protect reef fish – thereby helping to preserve coral reefs, which are valuable and vulnerable ecosystems worldwide.
For these young fish, motorboat noise is not simply an annoyance. It can affect their growth and their ability to escape danger, two factors that can make the difference between surviving and becoming prey.
A queen triggerfish, a distinctive inhabitant of tropical coral reefs. Image via Francois Libert/ iNaturalist.
Bottom line: Reef fish exposed to motorboat noise can end up smaller and struggle to escape predators, says new research into dangerous underwater noise.
A queen angelfish, one of the colourful reef fish that inhabit coral reef ecosystems. Image via Pedro Lastra/ Wikipedia.
Motorboat noise could be doing more than just disturbing life beneath the ocean’s surface. New research from the University of Exeter, the University of Bristol and James Cook University suggests that repeated exposure to motorboat noise during early development can have lasting effects on reef fish, potentially affecting both their growth and their ability to respond to danger.
The findings reveal a hidden cost of boat traffic for reef ecosystems, with effects that can persist long after the boats have passed.
The researchers published their findings in the peer-reviewed journal Environmental Pollution on August 28, 2026.
Why reef fish are important
Reef fish are species that live in and around coral reefs, relying on these ecosystems for food, shelter and breeding grounds. Coral reefs support an extraordinary variety of marine life and provide habitats for thousands of fish species across tropical and subtropical waters.
But these ecosystems face pressure from many human activities, and underwater noise is one of the less visible disturbances. Motorboats can introduce persistent sounds into reef environments, potentially changing the conditions young fish experience during some of the most important stages of their development.
To investigate the longer-term effects of this noise, researchers from the University of Exeter, University of Bristol and James Cook University studied a species found on Australia’s Great Barrier Reef: the spiny chromis.
The spiny chromis (Acanthochromis polyacanthus) was the focus of research into how motorboat noise can affect young reef fish, from growth to the ability to escape predators. Image via Nikita/ Wikipedia.
Testing noise during early development
The researchers exposed the fish to recordings of either motorboat noise or natural reef sounds at two different stages of development: as embryos and shortly after hatching.
The researchers divided the fish into four groups. Some heard natural reef sounds before and after hatching, while others heard motorboat noise at both stages. The remaining two groups switched from one sound to the other after hatching.
The exposure lasted for up to 78 days. The researchers then stopped playing sounds 24 hours before testing the fish and kept the tanks silent during the test.
This allowed them to determine whether the noise had produced longer-lasting effects rather than simply distracting the fish while they were hearing the sound.
A royal angelfish, a striking coral reef species. Image via Diego Delso/ Wikipedia.
Noise changed their response to predators
The researchers wanted to know whether exposure to motorboat noise could affect one of the most important skills a young fish needs: escaping a predator.
The researchers simulated a predator attack by dropping a weight onto the surface of the water. For spiny chromis, the natural response to a threat is to bend the body into a “C” shape before rapidly swimming away from the danger.
Among fish that had experienced natural reef sounds during at least one stage of development, around 80% responded to the simulated attack. However, about 20% of those fish made a fatal mistake: they swam towards the predator instead of away from it.
The results were more concerning among fish exposed to motorboat noise during both stages of early development. Only 68% responded to the simulated attack, and 40% of those responders swam towards the predator.
Because the researchers did not expose the fish to any sound during the test itself, the results suggest that the effects were not simply an immediate reaction to the noise. Instead, early exposure appeared to have changed how the fish responded to danger later on.
This is an emperor angelfish, a reef-dwelling fish found across the Indo-Pacific. Image via Francois Libert/ Wikipedia.
Motorboat noise can affect growth
The researchers also found a clear difference in body size among fish exposed to boat noise after hatching. On average, those fish were 7% shorter than fish exposed to natural reef sounds.
The researchers suggest that several mechanisms could contribute to this effect. Notably, previous research has shown that motorboat noise can alter parental care behavior. Sophie Nedelec, a senior research fellow at the University of Exeter, said:
We know from previous research that motorboat noise affects parental care behavior, including oxygenating eggs by fanning during the embryonic phase, which is linked with their survival.
She added:
[Exposure to motorboat noise] could cause stress or affect feeding, creating cumulative effects that lead to poor assessment of risk and decision making, and smaller body size.
A mandarinfish, a small reef fish known for its intricate patterns. Image via Luc Viatour/ Wikipedia.
Effects that can persist beyond the noise
The findings suggest that noise pollution can influence young reef fish even when the source of the disturbance is no longer present. Nedelec said:
Our results show that exposure to motorboat noise during early development can affect growth and disrupt the escape response of juveniles, even when the escape occurs in relatively quiet conditions.
The combination of reduced growth and poorer predator responses could be particularly important in the wild, where young fish already face intense pressure from predators and must make rapid decisions to survive.
Here’s a moorish idol, a distinctive reef fish with a long, pointed snout. Image via Diego Delso/ Wikipedia.
Could limiting boat traffic help?
The researchers suggest that limiting motorboat traffic close to reefs during the breeding season could help protect young reef fish from these effects. Nedelec explained that:
Limiting motorboat traffic close to reefs during the breeding season may reduce these effects and protect reef fish – thereby helping to preserve coral reefs, which are valuable and vulnerable ecosystems worldwide.
For these young fish, motorboat noise is not simply an annoyance. It can affect their growth and their ability to escape danger, two factors that can make the difference between surviving and becoming prey.
A queen triggerfish, a distinctive inhabitant of tropical coral reefs. Image via Francois Libert/ iNaturalist.
Bottom line: Reef fish exposed to motorboat noise can end up smaller and struggle to escape predators, says new research into dangerous underwater noise.
View larger. | Here’s a view of Earth on September 21, 2005, showing the entire region of Antarctica with land ice and its seasonal sea ice. Now, researchers have found microbes in Antarctica that don’t live anywhere else on Earth. Image via Andrzej 22/ NASA/ Wikimedia Commons.
Antarctica is home to a variety of plant and animal life, despite the extreme cold. What about microbes?
Researchers at University of Colorado have discovered microbes in Antarctica soil that are not known to exist anywhere else on Earth.
The microbes are uniquely adapted to the extreme conditions in Antarctica.
Antarctica is a unique environment on Earth, with its own plant and animal life such as penguins. But what about microbes? We think of microbes as being everywhere. That is, the same types of microbes all over the planet. But it turns out that Antarctica is unique that way, too. On August 31, 2026, researchers at CIRES at University of Colorado Boulder said that they’ve discovered microbes in Antarctica that are found nowhere else on Earth. And indeed, the microbial critters are uniquely adapted to the extreme conditions in Antarctica.
Notably, these are specific microbes, not all microbes in Antarctica. But it shows that some life in Antarctica can be different from the rest of the world.
The researchers published the new peer-reviewed findings in Proceedings of the National Academy of Sciences (PNAS) on August 31, 2026.
Microbes found in Antarctica's soil are unique to the continent. In a new study, the researchers analyzed soil samples from Antarctica and similar cold, dry environments like the Tibetan Plateau, Svalbard in the Arctic, and Chile’s Atacama Desert. @pnas.bsky buff.ly/Ds9MBDm
We know that microbes can be found virtually everywhere on Earth. Even Antarctica. But there’s a misperception that the same microbes are everywhere.
Nick Dragone at University of Colorado Boulder led the new study. He said:
There is a long-standing assumption in microbiology that ‘everything is everywhere.’ Antarctica has often been viewed as a possible exception, and our findings support that idea. Some Antarctic soil microbes appear to be distinct from those found in soils elsewhere around the world.
And finding microbes that are endemic – living naturally in only one specific geographic location – in Antarctica has implications for how scientists think microbial life spreads around the planet. Microbes can disperse great distances on winds or ocean currents.
Co-author and CIRES Fellow and Director of the Center for Microbial Exploration Noah Fierer added:
If we do find we’re looking for endemic microorganisms, a good place to start is Antarctica, because it’s an entire continent that is geographically isolated. It also has unique conditions not typically found in other soil environments. Cold is the obvious one, but also super dry; Antarctica is a desert.
Scanning electron image of Arthrobacter bacteria cells. Image via United States Department of Energy/ Wikipedia.
The search is on
The team searched for and collected soil samples from across Antarctica, which was essential to the study.
The researchers tested the soil samples from Antarctica and similar cold, dry environments such as the Tibetan Plateau, Svalbard in the Arctic and Chile’s Atacama Desert. Overall, this included over 100 Antarctic strains in the Arthrobacter group and nearly 500 strains from other locations worldwide. These particular strains are common in soils from Antarctica to Colorado to the tropics. Co-author Byron Adams at Brigham Young University said:
Arthrobacter as a group may be found all over the planet, but when we look closely at individual strains, just like penguins, Antarctica clearly has its own distinctive biological history.
Fierer said:
We already knew that a broad diversity of microbes can survive the inhospitable conditions of Antarctica. Now we know that some of those microbes are also unique to Antarctica and are uniquely adapted to life on the southern continent.
View larger. | Antarctica is home to some plants and animals, including penguins. And microbes. Image via Roux/ Wikipedia.
Genomes and simulating Antarctica
The researchers conducted the laboratory studies in two steps. First they sequenced the genomes – the genetic information of organisms – of the Arthrobacter strains. They compared the genomic traits of the bacteria to other samples collected from around the world. It was the genomic traits that showed that these specific microbes were unique to Antarctica. In fact, 90% of the strains are found nowhere else on Earth.
The team then simulated the conditions of Antarctica in the lab, such as the extreme cold and dryness. Then, they grew strains of Arthrobacter in Petri dishes. These strains tended to grow more slowly than the other test strains. But they did survive and grew.
Nicholas Dragone at CIRES/ University of Colorado Boulder led the new study about microbes in Antarctica. Image via CIRES Center for Education, Engagement and Evaluation/ University of Colorado Boulder/ RECCS.
Ancient birds in Antarctica
Speaking of life in Antarctica, last year scientists said that the fossil of an ancient bird called Vegavis iaai showed how many birds survived the asteroid impact that killed off the dinosaurs about 66 million years ago. The great distance from the impact site in Mexico and Antarctica could have allowed some birds to survive the upheaval.
At the time, Antarctica was ice-free and had a temperate climate with forests of conifers, cycads and ferns. So Vegavis lived among a diverse fauna of other birds, non-avian dinosaurs, insects, reptiles, pterosaurs and small early mammals.
Bottom line: Researchers have discovered that some microbes in Antarctica are unique to the icy continent and are found nowhere else on Earth.
View larger. | Here’s a view of Earth on September 21, 2005, showing the entire region of Antarctica with land ice and its seasonal sea ice. Now, researchers have found microbes in Antarctica that don’t live anywhere else on Earth. Image via Andrzej 22/ NASA/ Wikimedia Commons.
Antarctica is home to a variety of plant and animal life, despite the extreme cold. What about microbes?
Researchers at University of Colorado have discovered microbes in Antarctica soil that are not known to exist anywhere else on Earth.
The microbes are uniquely adapted to the extreme conditions in Antarctica.
Antarctica is a unique environment on Earth, with its own plant and animal life such as penguins. But what about microbes? We think of microbes as being everywhere. That is, the same types of microbes all over the planet. But it turns out that Antarctica is unique that way, too. On August 31, 2026, researchers at CIRES at University of Colorado Boulder said that they’ve discovered microbes in Antarctica that are found nowhere else on Earth. And indeed, the microbial critters are uniquely adapted to the extreme conditions in Antarctica.
Notably, these are specific microbes, not all microbes in Antarctica. But it shows that some life in Antarctica can be different from the rest of the world.
The researchers published the new peer-reviewed findings in Proceedings of the National Academy of Sciences (PNAS) on August 31, 2026.
Microbes found in Antarctica's soil are unique to the continent. In a new study, the researchers analyzed soil samples from Antarctica and similar cold, dry environments like the Tibetan Plateau, Svalbard in the Arctic, and Chile’s Atacama Desert. @pnas.bsky buff.ly/Ds9MBDm
We know that microbes can be found virtually everywhere on Earth. Even Antarctica. But there’s a misperception that the same microbes are everywhere.
Nick Dragone at University of Colorado Boulder led the new study. He said:
There is a long-standing assumption in microbiology that ‘everything is everywhere.’ Antarctica has often been viewed as a possible exception, and our findings support that idea. Some Antarctic soil microbes appear to be distinct from those found in soils elsewhere around the world.
And finding microbes that are endemic – living naturally in only one specific geographic location – in Antarctica has implications for how scientists think microbial life spreads around the planet. Microbes can disperse great distances on winds or ocean currents.
Co-author and CIRES Fellow and Director of the Center for Microbial Exploration Noah Fierer added:
If we do find we’re looking for endemic microorganisms, a good place to start is Antarctica, because it’s an entire continent that is geographically isolated. It also has unique conditions not typically found in other soil environments. Cold is the obvious one, but also super dry; Antarctica is a desert.
Scanning electron image of Arthrobacter bacteria cells. Image via United States Department of Energy/ Wikipedia.
The search is on
The team searched for and collected soil samples from across Antarctica, which was essential to the study.
The researchers tested the soil samples from Antarctica and similar cold, dry environments such as the Tibetan Plateau, Svalbard in the Arctic and Chile’s Atacama Desert. Overall, this included over 100 Antarctic strains in the Arthrobacter group and nearly 500 strains from other locations worldwide. These particular strains are common in soils from Antarctica to Colorado to the tropics. Co-author Byron Adams at Brigham Young University said:
Arthrobacter as a group may be found all over the planet, but when we look closely at individual strains, just like penguins, Antarctica clearly has its own distinctive biological history.
Fierer said:
We already knew that a broad diversity of microbes can survive the inhospitable conditions of Antarctica. Now we know that some of those microbes are also unique to Antarctica and are uniquely adapted to life on the southern continent.
View larger. | Antarctica is home to some plants and animals, including penguins. And microbes. Image via Roux/ Wikipedia.
Genomes and simulating Antarctica
The researchers conducted the laboratory studies in two steps. First they sequenced the genomes – the genetic information of organisms – of the Arthrobacter strains. They compared the genomic traits of the bacteria to other samples collected from around the world. It was the genomic traits that showed that these specific microbes were unique to Antarctica. In fact, 90% of the strains are found nowhere else on Earth.
The team then simulated the conditions of Antarctica in the lab, such as the extreme cold and dryness. Then, they grew strains of Arthrobacter in Petri dishes. These strains tended to grow more slowly than the other test strains. But they did survive and grew.
Nicholas Dragone at CIRES/ University of Colorado Boulder led the new study about microbes in Antarctica. Image via CIRES Center for Education, Engagement and Evaluation/ University of Colorado Boulder/ RECCS.
Ancient birds in Antarctica
Speaking of life in Antarctica, last year scientists said that the fossil of an ancient bird called Vegavis iaai showed how many birds survived the asteroid impact that killed off the dinosaurs about 66 million years ago. The great distance from the impact site in Mexico and Antarctica could have allowed some birds to survive the upheaval.
At the time, Antarctica was ice-free and had a temperate climate with forests of conifers, cycads and ferns. So Vegavis lived among a diverse fauna of other birds, non-avian dinosaurs, insects, reptiles, pterosaurs and small early mammals.
Bottom line: Researchers have discovered that some microbes in Antarctica are unique to the icy continent and are found nowhere else on Earth.
A super-closeup view of Mars meteorite ALH84001, found in Antarctica. What is that famous sub-micron-scale wormlike structure? If we ever do confirm life beyond Earth, how might the worlds’ nations respond? Experts think there are 3 possibilities. Image via NASA/ Wikimedia Commons.
Finding microbial life beyond Earth would be more than a scientific breakthrough. It has the potential to change how humanity thinks about itself.
Experts see three possible responses: nations could cooperate on research and regulation, or they could compete for scientific and economic advantages, or they could isolate themselves because of biosecurity concerns.
Policymakers can prepare now by using scenario planning to consider these possibilities, because the discovery of extraterrestrial life has the potential to bring both unprecedented cooperation and new forms of rivalry.
If we find life beyond Earth, how will nations respond?
Microbes from space have fueled the plots of science fiction mainstays like Project Hail Mary and The Andromeda Strain. But with more space missions launching each year, finding extraterrestrial life in a microbial form is becoming more plausible. What will the response be back here on Earth if – or when – scientists discover extraterrestrial microbes? Will the international policy and security communities be prepared for the fallout?
When you hear about extraterrestrial life, your mind may go to intelligent life, like the kind present in a lot of Hollywood science fiction. But even the confirmation of microbial life that originated somewhere other than on Earth – which is much more likely – would be a paradigm-shifting event. Thinking about what these consequences might look like early on can help nations and the international community prepare.
This is the famous Martian meteorite ALH84001. Found in Antarctica, scientists for a time thought the meteorite from Mars showed evidence of life. Image via NASA/ Lunar and Planetary Institute.
Preparing for the possibility of life beyond Earth
Our team is interested in this question. We’re made up of a full professor of international affairs, who earned a Ph.D. in chemistry, and whose expertise is on how emerging science and technologies could affect global conflict and cooperation, as well as an emerging scholar in space policy and security and an expert on social and political implications of frontier technologies, such as AI, space, quantum and energy sources.
Scientists are searching for life in space using what they know about life on Earth. But what will happen if or when they find something?
A governance challenge
The discovery of microbial life would expose significant gaps in international governance related to space.
While there are some existing international agreements, including the Outer Space Treaty, that provide space law guidelines, these are ill-equipped to address the complexities posed by extraterrestrial biology.
However, it doesn’t have much to say about who can own extraterrestrial organisms or what to do about biosecurity risks. It doesn’t have direction for who can use, preserve or destroy living things, such as bacteria or fungi, that may be discovered in space.
While people have yet to discover extraterrestrial life of any kind, there are some major geopolitical events that can help researchers understand what the consequences might look like.
While the space race of the 1950s and ’60s led to exploration of the moon, it was driven by a Cold War power struggle between two nations back on Earth. Instead of coming together to explore space, both countries experienced a renewed sense of nationalism. They used the new discoveries that came from the space race to invest in their military capabilities.
On the other hand, researchers can look at how states respond to asteroid threats. Since an asteroid could pose a truly existential threat from space, preventing the worst-case scenario requires cooperation and thinking ahead.
Astronomers have built a global, collaborative network to monitor for and sound the alarm about any potential threats. This network has shown that nations can put aside terrestrial rivalries to work together if they perceive something from space as a truly existential threat.
The International Space Station is another example showing how nations that are competing great powers on Earth work together to cooperate in space. Countries have collaborated to solve issues on the International Space Station that have specific, short-term and clearly identified goals.
These examples show a range of possible reactions to the discovery of space microbes. The situation could renew space races between competing countries and lead to militarization, or it could create unprecedented cooperation.
Read on for the three main possible outcomes we’ve identified to the discovery of microbial extraterrestrial life.
The ISS is an example of countries cooperating in space research. Image via NASA/ Roscosmos.
Cooperation
First, there’s a cooperative outcome, reminiscent of the asteroid threat network or the International Space Station. Here, nations collaborate to regulate research, share data, protect the planet or advance specific interests they share.
This pathway isn’t inherently benign or malignant. It could entail expanding the roles of international organizations or creating new legal instruments.
Competition
Second there’s a competitive outcome, characterized by strategic rivalry between countries. Like in the space race, nations could fight to be technologically superior. They might try to monopolize access to the extraterrestrial microbes or to leverage biological discoveries from the microbes for their own economic or military advantage.
Scientific breakthroughs derived from extraterrestrial organisms could lead to innovations in medicine, agriculture, energy and beyond. However, the organisms could also be weaponized, intentionally or otherwise, which would amplify biosecurity risks. In this sense, the discovery of microbial life could create a new form of technological competition, one that merges space exploration with biological research and development.
For example, around 60% of all satellites currently orbiting the Earth belong to SpaceX’s Starlink subsidiary. The company can – and has – chosen to block access selectively, in alignment with its political priorities. When commercial interests and national priorities diverge, who has access versus who is denied access can be uncertain.
Research around biopiracy may come into play. Biopiracy is a term that applies to two primary issues: the patenting of indigenous knowledge or the patenting of natural resources, such as microbes, for profit. The Budapest Treaty prohibits claiming ownership of a naturally occurring microbe on Earth, but there’s no equivalent for microbes in space.
Isolation
Third is an isolationist outcome, in which states could sever their involvement in international cooperation due to biosecurity concerns or political distrust. The potential for unknown biological risks, however minimal, could trigger precautionary restrictions on data sharing, which limits international collaboration.
Countries may lose or gain allies as they grapple with whether the microbe could cause harm to humans or the environment, or be developed into a biological weapon.
Countries will have to prepare not only for the scientific implications of discovery but also for its societal and political reverberations. The politicization of scientific discoveries from the microbes could complicate or change how countries respond domestically and at the international scale. Misinformation about the microbes could shape policy and public response.
Preparing for the unprecedented
The discovery of extraterrestrial microbial life would not merely mark a scientific milestone. It would be a geopolitical event.
Rather than attempting to predict a singular outcome, policymakers could adopt scenario-based planning approaches in the meantime to anticipate and prepare for a range of possibilities. In these approaches, participants explore multiple futures through structured activities similar to professional or military wargaming or path games, in which they explore multiple outcomes systematically to test strategies, to plan and to analyze potential outcomes under realistic uncertainty.
In our view, the question is not whether humanity will discover life beyond Earth, but whether it is prepared for the consequences when it does.
Bottom line: If we ever find life beyond Earth, how will the nations of the world respond? A group of experts say there are three possibilities: cooperation, competition and isolation.
A super-closeup view of Mars meteorite ALH84001, found in Antarctica. What is that famous sub-micron-scale wormlike structure? If we ever do confirm life beyond Earth, how might the worlds’ nations respond? Experts think there are 3 possibilities. Image via NASA/ Wikimedia Commons.
Finding microbial life beyond Earth would be more than a scientific breakthrough. It has the potential to change how humanity thinks about itself.
Experts see three possible responses: nations could cooperate on research and regulation, or they could compete for scientific and economic advantages, or they could isolate themselves because of biosecurity concerns.
Policymakers can prepare now by using scenario planning to consider these possibilities, because the discovery of extraterrestrial life has the potential to bring both unprecedented cooperation and new forms of rivalry.
If we find life beyond Earth, how will nations respond?
Microbes from space have fueled the plots of science fiction mainstays like Project Hail Mary and The Andromeda Strain. But with more space missions launching each year, finding extraterrestrial life in a microbial form is becoming more plausible. What will the response be back here on Earth if – or when – scientists discover extraterrestrial microbes? Will the international policy and security communities be prepared for the fallout?
When you hear about extraterrestrial life, your mind may go to intelligent life, like the kind present in a lot of Hollywood science fiction. But even the confirmation of microbial life that originated somewhere other than on Earth – which is much more likely – would be a paradigm-shifting event. Thinking about what these consequences might look like early on can help nations and the international community prepare.
This is the famous Martian meteorite ALH84001. Found in Antarctica, scientists for a time thought the meteorite from Mars showed evidence of life. Image via NASA/ Lunar and Planetary Institute.
Preparing for the possibility of life beyond Earth
Our team is interested in this question. We’re made up of a full professor of international affairs, who earned a Ph.D. in chemistry, and whose expertise is on how emerging science and technologies could affect global conflict and cooperation, as well as an emerging scholar in space policy and security and an expert on social and political implications of frontier technologies, such as AI, space, quantum and energy sources.
Scientists are searching for life in space using what they know about life on Earth. But what will happen if or when they find something?
A governance challenge
The discovery of microbial life would expose significant gaps in international governance related to space.
While there are some existing international agreements, including the Outer Space Treaty, that provide space law guidelines, these are ill-equipped to address the complexities posed by extraterrestrial biology.
However, it doesn’t have much to say about who can own extraterrestrial organisms or what to do about biosecurity risks. It doesn’t have direction for who can use, preserve or destroy living things, such as bacteria or fungi, that may be discovered in space.
While people have yet to discover extraterrestrial life of any kind, there are some major geopolitical events that can help researchers understand what the consequences might look like.
While the space race of the 1950s and ’60s led to exploration of the moon, it was driven by a Cold War power struggle between two nations back on Earth. Instead of coming together to explore space, both countries experienced a renewed sense of nationalism. They used the new discoveries that came from the space race to invest in their military capabilities.
On the other hand, researchers can look at how states respond to asteroid threats. Since an asteroid could pose a truly existential threat from space, preventing the worst-case scenario requires cooperation and thinking ahead.
Astronomers have built a global, collaborative network to monitor for and sound the alarm about any potential threats. This network has shown that nations can put aside terrestrial rivalries to work together if they perceive something from space as a truly existential threat.
The International Space Station is another example showing how nations that are competing great powers on Earth work together to cooperate in space. Countries have collaborated to solve issues on the International Space Station that have specific, short-term and clearly identified goals.
These examples show a range of possible reactions to the discovery of space microbes. The situation could renew space races between competing countries and lead to militarization, or it could create unprecedented cooperation.
Read on for the three main possible outcomes we’ve identified to the discovery of microbial extraterrestrial life.
The ISS is an example of countries cooperating in space research. Image via NASA/ Roscosmos.
Cooperation
First, there’s a cooperative outcome, reminiscent of the asteroid threat network or the International Space Station. Here, nations collaborate to regulate research, share data, protect the planet or advance specific interests they share.
This pathway isn’t inherently benign or malignant. It could entail expanding the roles of international organizations or creating new legal instruments.
Competition
Second there’s a competitive outcome, characterized by strategic rivalry between countries. Like in the space race, nations could fight to be technologically superior. They might try to monopolize access to the extraterrestrial microbes or to leverage biological discoveries from the microbes for their own economic or military advantage.
Scientific breakthroughs derived from extraterrestrial organisms could lead to innovations in medicine, agriculture, energy and beyond. However, the organisms could also be weaponized, intentionally or otherwise, which would amplify biosecurity risks. In this sense, the discovery of microbial life could create a new form of technological competition, one that merges space exploration with biological research and development.
For example, around 60% of all satellites currently orbiting the Earth belong to SpaceX’s Starlink subsidiary. The company can – and has – chosen to block access selectively, in alignment with its political priorities. When commercial interests and national priorities diverge, who has access versus who is denied access can be uncertain.
Research around biopiracy may come into play. Biopiracy is a term that applies to two primary issues: the patenting of indigenous knowledge or the patenting of natural resources, such as microbes, for profit. The Budapest Treaty prohibits claiming ownership of a naturally occurring microbe on Earth, but there’s no equivalent for microbes in space.
Isolation
Third is an isolationist outcome, in which states could sever their involvement in international cooperation due to biosecurity concerns or political distrust. The potential for unknown biological risks, however minimal, could trigger precautionary restrictions on data sharing, which limits international collaboration.
Countries may lose or gain allies as they grapple with whether the microbe could cause harm to humans or the environment, or be developed into a biological weapon.
Countries will have to prepare not only for the scientific implications of discovery but also for its societal and political reverberations. The politicization of scientific discoveries from the microbes could complicate or change how countries respond domestically and at the international scale. Misinformation about the microbes could shape policy and public response.
Preparing for the unprecedented
The discovery of extraterrestrial microbial life would not merely mark a scientific milestone. It would be a geopolitical event.
Rather than attempting to predict a singular outcome, policymakers could adopt scenario-based planning approaches in the meantime to anticipate and prepare for a range of possibilities. In these approaches, participants explore multiple futures through structured activities similar to professional or military wargaming or path games, in which they explore multiple outcomes systematically to test strategies, to plan and to analyze potential outcomes under realistic uncertainty.
In our view, the question is not whether humanity will discover life beyond Earth, but whether it is prepared for the consequences when it does.
Bottom line: If we ever find life beyond Earth, how will the nations of the world respond? A group of experts say there are three possibilities: cooperation, competition and isolation.
Octans and Apus (the Octant and the Bird of Paradise, respectively) lie far south. In fact, Octans is home to the south celestial pole. Be sure to look for them from the Southern Hemisphere on September evenings. Chart via EarthSky.
Octans and Apus
Octans the Octant and Apus the Bird of Paradise circle the south celestial pole. If you want to see them, you’ll have to be in the Southern Hemisphere. In fact, the south celestial pole lies inside the constellation boundary for Octans.
Both of these constellations are south circumpolar constellations. Of course, the north has circumpolar constellations too. Constellations such as Ursa Minor, Ursa Major and Draco can be seen any night of the year from the Northern Hemisphere. Octans and Apus are two constellations that Southern Hemisphere observers can view on any clear evening.
Octans the Octant
And Octans is a key constellation for another reason. When we look in its direction in space, we are looking toward Earth’s south celestial pole. Polaris is the famous star marking the location of the north celestial pole. But the Southern Hemisphere has no bright star near its celestial pole. That is why you might hear astronomers say there’s no pole star for the Southern Hemisphere sky.
There is an extremely dim galaxy that’s nearly at the location of the south celestial pole. And that galaxy has the fitting name of Polarissima Australis. It shines much too dimly to be viewed without optical aid, at magnitude 13.5.
The brightest star in Octans is only moderately bright at +3.7 magnitude. It is Nu Octantis, a double star, located some 69 light-years away. The star is home to a confirmed super-Jovian exoplanet. So far, no other planets have been found in the Nu Octantis system.
Star chart for Octans the Octant. The location where all the lines converge marks the south celestial pole. Chart via IAU/ Sky and Telescope/ Wikimedia Commons.
Apus the Bird of Paradise
Then, next to Octans, is Apus the Bird of Paradise. It’s small and ranked 67th in size out of the 88 constellations. It lies between Octans and Triangulum Australe the Southern Triangle. The stars in Apus are quite dim. The brightest member of the constellation is Alpha Apodis at magnitude 3.83. Alpha Apodis lies about 430 light-years from Earth. Slightly fainter is Gamma Apodis at magnitude 3.86 and 150 light-years distant. This star is a strong source of X-rays.
Star chart for Apus the Bird of Paradise. Chart via IAU/ Sky and Telescope/ Wikimedia Commons.
Bottom line: Octans and Apus are two constellations that you have to be in the Southern Hemisphere to see. Plus, Octans is home to the south celestial pole.
Octans and Apus (the Octant and the Bird of Paradise, respectively) lie far south. In fact, Octans is home to the south celestial pole. Be sure to look for them from the Southern Hemisphere on September evenings. Chart via EarthSky.
Octans and Apus
Octans the Octant and Apus the Bird of Paradise circle the south celestial pole. If you want to see them, you’ll have to be in the Southern Hemisphere. In fact, the south celestial pole lies inside the constellation boundary for Octans.
Both of these constellations are south circumpolar constellations. Of course, the north has circumpolar constellations too. Constellations such as Ursa Minor, Ursa Major and Draco can be seen any night of the year from the Northern Hemisphere. Octans and Apus are two constellations that Southern Hemisphere observers can view on any clear evening.
Octans the Octant
And Octans is a key constellation for another reason. When we look in its direction in space, we are looking toward Earth’s south celestial pole. Polaris is the famous star marking the location of the north celestial pole. But the Southern Hemisphere has no bright star near its celestial pole. That is why you might hear astronomers say there’s no pole star for the Southern Hemisphere sky.
There is an extremely dim galaxy that’s nearly at the location of the south celestial pole. And that galaxy has the fitting name of Polarissima Australis. It shines much too dimly to be viewed without optical aid, at magnitude 13.5.
The brightest star in Octans is only moderately bright at +3.7 magnitude. It is Nu Octantis, a double star, located some 69 light-years away. The star is home to a confirmed super-Jovian exoplanet. So far, no other planets have been found in the Nu Octantis system.
Star chart for Octans the Octant. The location where all the lines converge marks the south celestial pole. Chart via IAU/ Sky and Telescope/ Wikimedia Commons.
Apus the Bird of Paradise
Then, next to Octans, is Apus the Bird of Paradise. It’s small and ranked 67th in size out of the 88 constellations. It lies between Octans and Triangulum Australe the Southern Triangle. The stars in Apus are quite dim. The brightest member of the constellation is Alpha Apodis at magnitude 3.83. Alpha Apodis lies about 430 light-years from Earth. Slightly fainter is Gamma Apodis at magnitude 3.86 and 150 light-years distant. This star is a strong source of X-rays.
Star chart for Apus the Bird of Paradise. Chart via IAU/ Sky and Telescope/ Wikimedia Commons.
Bottom line: Octans and Apus are two constellations that you have to be in the Southern Hemisphere to see. Plus, Octans is home to the south celestial pole.
View larger. | Cutaway view of Mars showing the interior of the planet. Researchers have discovered evidence for excess heat in Mars’ southern hemisphere, deep below the surface. Image via NASA/ Theophilus Britt Griswold.
Mars is a cold world, with ice caps and lots of ice below the surface.
But new research has discovered strange excess heat deep below the surface of southern hemisphere.
Explanations range from a giant impact releasing thermal energy to thick geological features trapping heat.
Mars’ southern hemisphere is unexpectedly hot deep below the surface
Mars is a very cold planet on the surface. Like Earth, it gradually gets warmer the deeper you go into its interior. But now, researchers at Caltech in California have found an unusual anomaly. They said on August 26, 2026, that there’s a huge excess of heat deep below Mars’ surface in the southern hemisphere. In fact, the region is about 200-400 degrees Celsius (290-750 degrees Fahrenheit) hotter than expected.
The heat anomaly seems to mirror the north-south asymmetry of Mars. The planet’s northern hemisphere is mostly flat lowlands, while the southern hemisphere is covered by craters and mountains. Because of this, Mars sometimes is referred to as as being “two-faced.” Now it seems that rather than being simply a surface feature, that characteristic runs deep into the inside of the planet as well.
How did the researchers discover this anomaly? Caltech alumnus Alexander Berne led the new study. Berne and his team used data collected over decades from three different Mars missions: Mars Global Surveyor, Mars Odyssey and Mars Reconnaissance Orbiter. The team measured tiny variations in the spacecrafts’ velocities and then used them to reconstruct the gravitational field around Mars.
Using a technique called tidal tomography, or planetary tomography, the researchers measured how those gravitational signatures vary over time. This enabled the team to create a model of the planet’s interior. As Berne explained:
Scientists usually assume that the interiors of planetary bodies are generally spherically symmetric, but this is not necessarily true. As we get more gravity data, we can determine the three-dimensional intricacies of a planet’s interior structure. These inferences in turn give us a blueprint for designing future missions and scientific exploration of these worlds. Understanding the interior structure of planetary bodies helps us unravel the processes that shaped their formation and evolution.
View larger. | This diagram depicts the cold interior of the northern hemisphere and the warm interior of the southern hemisphere. Image via Berne et al./ Nature.View larger. | Map showing Mars’ topography. The planet’s northern and southern hemispheres are very different; the north is mostly flat lowlands, while the south is covered in craters and mountains. Image via NASA/ JPL/ USGS/ Wikipedia.
An unbalanced interior
Like Earth, Mars isn’t perfectly spherical. The northern lowlands are mostly quite flat, while the southern hemisphere has mountains and many deep craters. And this is where the thermal anomaly comes in. The interior of the southern hemisphere is much hotter than the north, by about 200-400 degrees Celsius (290-750 degrees Fahrenheit). At those temperatures, the rock is partially molten.
What could explain Mars’ southern hemisphere anomaly?
The researchers have proposed a few hypotheses to explain the anomaly. One is a giant impact that released heat from the northern hemisphere.
Another possibility is spontaneous convection – the movement of heat through fluids – in the southern mantle.
Finally, it could be caused by thick geological features in the southern hemisphere that trap excess heat from escaping.
The findings also have implications for the geological history of Mars and its habitability billions of years ago. Co-author Amirhossein Bagheri, a postdoctoral scholar at Caltech, said:
The dichotomy that we see between north and south is important to understand because it gives information about processes that may have influenced the hydrology of Mars, including the formation of basins that may have held water.
Bottom line: A new study from Caltech shows that Mars’ southern hemisphere is much hotter than expected deep below the surface. Why is that?
View larger. | Cutaway view of Mars showing the interior of the planet. Researchers have discovered evidence for excess heat in Mars’ southern hemisphere, deep below the surface. Image via NASA/ Theophilus Britt Griswold.
Mars is a cold world, with ice caps and lots of ice below the surface.
But new research has discovered strange excess heat deep below the surface of southern hemisphere.
Explanations range from a giant impact releasing thermal energy to thick geological features trapping heat.
Mars’ southern hemisphere is unexpectedly hot deep below the surface
Mars is a very cold planet on the surface. Like Earth, it gradually gets warmer the deeper you go into its interior. But now, researchers at Caltech in California have found an unusual anomaly. They said on August 26, 2026, that there’s a huge excess of heat deep below Mars’ surface in the southern hemisphere. In fact, the region is about 200-400 degrees Celsius (290-750 degrees Fahrenheit) hotter than expected.
The heat anomaly seems to mirror the north-south asymmetry of Mars. The planet’s northern hemisphere is mostly flat lowlands, while the southern hemisphere is covered by craters and mountains. Because of this, Mars sometimes is referred to as as being “two-faced.” Now it seems that rather than being simply a surface feature, that characteristic runs deep into the inside of the planet as well.
How did the researchers discover this anomaly? Caltech alumnus Alexander Berne led the new study. Berne and his team used data collected over decades from three different Mars missions: Mars Global Surveyor, Mars Odyssey and Mars Reconnaissance Orbiter. The team measured tiny variations in the spacecrafts’ velocities and then used them to reconstruct the gravitational field around Mars.
Using a technique called tidal tomography, or planetary tomography, the researchers measured how those gravitational signatures vary over time. This enabled the team to create a model of the planet’s interior. As Berne explained:
Scientists usually assume that the interiors of planetary bodies are generally spherically symmetric, but this is not necessarily true. As we get more gravity data, we can determine the three-dimensional intricacies of a planet’s interior structure. These inferences in turn give us a blueprint for designing future missions and scientific exploration of these worlds. Understanding the interior structure of planetary bodies helps us unravel the processes that shaped their formation and evolution.
View larger. | This diagram depicts the cold interior of the northern hemisphere and the warm interior of the southern hemisphere. Image via Berne et al./ Nature.View larger. | Map showing Mars’ topography. The planet’s northern and southern hemispheres are very different; the north is mostly flat lowlands, while the south is covered in craters and mountains. Image via NASA/ JPL/ USGS/ Wikipedia.
An unbalanced interior
Like Earth, Mars isn’t perfectly spherical. The northern lowlands are mostly quite flat, while the southern hemisphere has mountains and many deep craters. And this is where the thermal anomaly comes in. The interior of the southern hemisphere is much hotter than the north, by about 200-400 degrees Celsius (290-750 degrees Fahrenheit). At those temperatures, the rock is partially molten.
What could explain Mars’ southern hemisphere anomaly?
The researchers have proposed a few hypotheses to explain the anomaly. One is a giant impact that released heat from the northern hemisphere.
Another possibility is spontaneous convection – the movement of heat through fluids – in the southern mantle.
Finally, it could be caused by thick geological features in the southern hemisphere that trap excess heat from escaping.
The findings also have implications for the geological history of Mars and its habitability billions of years ago. Co-author Amirhossein Bagheri, a postdoctoral scholar at Caltech, said:
The dichotomy that we see between north and south is important to understand because it gives information about processes that may have influenced the hydrology of Mars, including the formation of basins that may have held water.
Bottom line: A new study from Caltech shows that Mars’ southern hemisphere is much hotter than expected deep below the surface. Why is that?
Any late summer evening and throughout northern autumn, Cassiopeia the Queen will be ascending in the northeast after nightfall. The shape of this constellation makes Cassiopeia’s stars very noticeable. Cassiopeia looks like the letter W (or M).
Look for the Queen at nightfall in September, and notice how she gets higher in the northeast with each day as northern autumn unfolds.
For those at the latitudes of the northern U.S. and Canada, Cassiopeia is circumpolar. That means the constellation stays above the horizon all night, every night.
How to see Cassiopeia
Cassiopeia represents an ancient queen of Ethiopia. You still sometimes hear the old name for this constellation: Cassiopeia’s Chair. And some old star maps depict the queen sitting on the chair, marked by five stars.
These stars – the brightest ones in Cassiopeia – are Schedar, Caph, Gamma Cassiopeiae, Ruchbah and Segin.
Around the middle of the night during the autumn months, Cassiopeia swings above Polaris, the North Star.
Before dawn, look in the northwest.
You can find Cassiopeia the Queen in the northeast around the month of September. If you have a dark sky, look below Cassiopeia for a famous binocular object. This object is called the Double Cluster in Perseus. Chart via EarthSky.
Opposite the Big Dipper
Cassiopeia is opposite the Big Dipper in the northern sky.
That is, the two constellations lie on opposite sides of the pole star, Polaris.
So when Cassiopeia is high in the sky, as it is on evenings from about September through February, the Big Dipper is low in the sky. Every March, when the Dipper is ascending in the northeast, getting ready to appear prominent again in the evening sky, Cassiopeia is descending in the northwest.
The Big Dipper and the W-shaped constellation Cassiopeia circle around Polaris, the North Star, in a period of 23 hours and 56 minutes. The Dipper is circumpolar at 41 degrees north latitude, and all latitudes farther north. Image via Mjchael/ Wikipedia.
These are two open star clusters. Each consists of young stars still moving together from the primordial cloud of gas and dust that gave birth to them.
These two clusters are familiarly known to stargazers as H and Chi Persei.
Interestingly, their names are from two different alphabets, the Greek and the Roman. Stars have Greek letter names, but most star clusters don’t. Johann Bayer (1572-1625) gave Chi Persei its Greek letter name. Then, it’s said, he ran out of Greek letters. That’s when he used a Roman letter – the letter H – to name the other cluster.
Charts for Cassiopeia
In the 1930s, the International Astronomical Union (IAU) – an organization of professional astronomers – decided to define boundaries and officially name 88 constellations. This is the realm of night sky they identified as Cassiopeia. Read more about the constellations. Image via IAU.Cassiopeia as Johannes Hevelius depicted it in the 1600s. Image via Wikimedia Commons.
Lore of Cassiopeia
In skylore and in Greek mythology, Cassiopeia is a beautiful and vain queen of Ethiopia. It’s said that she committed the sin of pride by boasting that both she and her daughter Andromeda were more beautiful than Nereids, or sea nymphs. Pridefulness, in mythology, is never wise.
Since her boast angered Poseidon, God of the Sea, he sent a sea monster (Cetus the Whale) to ravage the kingdom. So to pacify the monster, Cassiopeia’s daughter, Princess Andromeda, was left tied to a rock by the sea. Cetus was about to devour her when Perseus the Hero happened by on Pegasus, the Flying Horse.
Perseus rescued the princess, and all lived happily … and the gods were pleased, so all of these characters were elevated to the heavens as stars.
But – because of her vanity – Cassiopeia suffered an indignity. At some times of the night or year, this constellation has more the shape of the letter M, and you might imagine the Queen reclining on her starry throne.
At other times of year or night – as in the wee hours between midnight and dawn in February and March – Cassiopeia’s Chair dips below the celestial pole. And then this constellation appears to us on Earth more like the letter W. That’s when the Lady of the Chair, as astronomers sometimes call her, is said to hang on for dear life. If Cassiopeia the Queen lets go, she will drop from the sky into the ocean below, where the Nereids must still be waiting.
Cassiopeia by our EarthSky Community
View at EarthSky Community Photos. | Enrico Modica captured this photo on August 13, 2026, in Italy. Enrico wrote: “This image shows the Plemmirio Lighthouse near Syracuse, Sicily, beneath the summer night sky, with the constellations of Andromeda, Cassiopeia, and Perseus, as well as the Andromeda Galaxy (M31), approximately 2.5 million light-years away. A Perseid meteor is also visible on the left side of the frame right by Cassiopeia.” Thank you, Enrico!View at EarthSky Community Photos. | V. Liard Photography in Champagne, France, took this wonderful image on July 22, 2023. It features the W-shaped constellation Cassiopeia the Queen. Thank you, V. Liard! Cassiopeia is a great constellation to come to know, especially if you have a dark sky. That’s because it points to our neighbor, the Andromeda galaxy.
Bottom line: Cassiopeia the Queen is an easy-to-find constellation. It has the shape of a W or M. Look for it in the north-northeast sky on September and October evenings.
Any late summer evening and throughout northern autumn, Cassiopeia the Queen will be ascending in the northeast after nightfall. The shape of this constellation makes Cassiopeia’s stars very noticeable. Cassiopeia looks like the letter W (or M).
Look for the Queen at nightfall in September, and notice how she gets higher in the northeast with each day as northern autumn unfolds.
For those at the latitudes of the northern U.S. and Canada, Cassiopeia is circumpolar. That means the constellation stays above the horizon all night, every night.
How to see Cassiopeia
Cassiopeia represents an ancient queen of Ethiopia. You still sometimes hear the old name for this constellation: Cassiopeia’s Chair. And some old star maps depict the queen sitting on the chair, marked by five stars.
These stars – the brightest ones in Cassiopeia – are Schedar, Caph, Gamma Cassiopeiae, Ruchbah and Segin.
Around the middle of the night during the autumn months, Cassiopeia swings above Polaris, the North Star.
Before dawn, look in the northwest.
You can find Cassiopeia the Queen in the northeast around the month of September. If you have a dark sky, look below Cassiopeia for a famous binocular object. This object is called the Double Cluster in Perseus. Chart via EarthSky.
Opposite the Big Dipper
Cassiopeia is opposite the Big Dipper in the northern sky.
That is, the two constellations lie on opposite sides of the pole star, Polaris.
So when Cassiopeia is high in the sky, as it is on evenings from about September through February, the Big Dipper is low in the sky. Every March, when the Dipper is ascending in the northeast, getting ready to appear prominent again in the evening sky, Cassiopeia is descending in the northwest.
The Big Dipper and the W-shaped constellation Cassiopeia circle around Polaris, the North Star, in a period of 23 hours and 56 minutes. The Dipper is circumpolar at 41 degrees north latitude, and all latitudes farther north. Image via Mjchael/ Wikipedia.
These are two open star clusters. Each consists of young stars still moving together from the primordial cloud of gas and dust that gave birth to them.
These two clusters are familiarly known to stargazers as H and Chi Persei.
Interestingly, their names are from two different alphabets, the Greek and the Roman. Stars have Greek letter names, but most star clusters don’t. Johann Bayer (1572-1625) gave Chi Persei its Greek letter name. Then, it’s said, he ran out of Greek letters. That’s when he used a Roman letter – the letter H – to name the other cluster.
Charts for Cassiopeia
In the 1930s, the International Astronomical Union (IAU) – an organization of professional astronomers – decided to define boundaries and officially name 88 constellations. This is the realm of night sky they identified as Cassiopeia. Read more about the constellations. Image via IAU.Cassiopeia as Johannes Hevelius depicted it in the 1600s. Image via Wikimedia Commons.
Lore of Cassiopeia
In skylore and in Greek mythology, Cassiopeia is a beautiful and vain queen of Ethiopia. It’s said that she committed the sin of pride by boasting that both she and her daughter Andromeda were more beautiful than Nereids, or sea nymphs. Pridefulness, in mythology, is never wise.
Since her boast angered Poseidon, God of the Sea, he sent a sea monster (Cetus the Whale) to ravage the kingdom. So to pacify the monster, Cassiopeia’s daughter, Princess Andromeda, was left tied to a rock by the sea. Cetus was about to devour her when Perseus the Hero happened by on Pegasus, the Flying Horse.
Perseus rescued the princess, and all lived happily … and the gods were pleased, so all of these characters were elevated to the heavens as stars.
But – because of her vanity – Cassiopeia suffered an indignity. At some times of the night or year, this constellation has more the shape of the letter M, and you might imagine the Queen reclining on her starry throne.
At other times of year or night – as in the wee hours between midnight and dawn in February and March – Cassiopeia’s Chair dips below the celestial pole. And then this constellation appears to us on Earth more like the letter W. That’s when the Lady of the Chair, as astronomers sometimes call her, is said to hang on for dear life. If Cassiopeia the Queen lets go, she will drop from the sky into the ocean below, where the Nereids must still be waiting.
Cassiopeia by our EarthSky Community
View at EarthSky Community Photos. | Enrico Modica captured this photo on August 13, 2026, in Italy. Enrico wrote: “This image shows the Plemmirio Lighthouse near Syracuse, Sicily, beneath the summer night sky, with the constellations of Andromeda, Cassiopeia, and Perseus, as well as the Andromeda Galaxy (M31), approximately 2.5 million light-years away. A Perseid meteor is also visible on the left side of the frame right by Cassiopeia.” Thank you, Enrico!View at EarthSky Community Photos. | V. Liard Photography in Champagne, France, took this wonderful image on July 22, 2023. It features the W-shaped constellation Cassiopeia the Queen. Thank you, V. Liard! Cassiopeia is a great constellation to come to know, especially if you have a dark sky. That’s because it points to our neighbor, the Andromeda galaxy.
Bottom line: Cassiopeia the Queen is an easy-to-find constellation. It has the shape of a W or M. Look for it in the north-northeast sky on September and October evenings.
View larger. | This view of Mercury from the BepiColombo spacecraft came from its 3rd flyby of the planet on June 19, 2023. BepiColombo’s propulsion system will separate from its 2 orbiters on September 3, 2026. Then the 2 spacecraft will enter orbit around Mercury on November 21, 2026. Image via ESA/ BepiColombo/ MTM.
BepiColombo mission to arrive at Mercury in November
Today, on September 3, 2026, ESA’s BepiColombo spacecraft is moving one crucial step closer to entering Mercury’s orbit.
Bepicolombo launched to space way back October 20, 2018, from Kourou, French Guiana. The spacecraft has spent eight years maneuvering into position so that it can orbit Mercury, the closest planet to the sun. Orbiting Mercury is a true engineering challenge, because the spacecraft picks up speed as it nears the massive sun. But it must slow down to enter Mercury’s orbit and not fly straight past.
So, during its journey, BepiColombo has made flybys of Earth, Venus and Mercury to help put on the brakes. And on September 3, 2026, Bepicolombo’s Mercury Transfer Module (the spacecraft’s propulsion unit) will separate from the science orbiters, Mercury Planetary Orbiter (MPO) and Mercury Magnetospheric Orbiter (MMO). These two spacecraft will then enter orbit around Mercury on November 21, 2026.
On December 9-10, the two orbiters will separate from each other. Finally, science operations will begin in April 2027.
BepiColombo’s flybys
BepiColombo has made one Earth flyby, two Venus flybys, and six Mercury flybys since its launch in 2018. Click the links below to learn more about the flybys.
View larger. | The European Space Agency’s BepiColombo spacecraft, heading toward Mercury, caught this fleeting image of Venus on October 15, 2020. You can see the terminator line, or dividing line between light and dark on Venus, pass from right to left, causing Venus to change phase as the spacecraft swept past. Image via ESA/ BepiColombo/ MTM.
What scientists hope to learn at Mercury
Mercury is currently the least-understood planet in the inner solar system. In fact, before BepiColombo, the only spacecraft to have visited Mercury were NASA’s Mariner 10 and MESSENGER missions.
Now, scientists hope to solve five mysteries with BepiColombo:
Where did Mercury come from?
Is there really water on Mercury?
Is Mercury dead or alive?
Why is Mercury so dark?
Why does Mercury have a magnetic field?
To answer these questions, BepiColombo will spend at least one year orbiting Mercury. The mission will use its high-resolution instruments to learn about the mineralogical and elemental composition of Mercury’s surface. Plus, it will scan polar regions for ice. BepiColombo will look for anything that looks like it has changed on Mercury since MESSENGER visited 10 years earlier. And the two orbiters will travel through different areas of the planet’s magnetosphere to measure how it changes and interacts with the sun.
Bottom line: The BepiColombo mission has been maneuvering its way into orbit around Mercury for eight years. On September 3, it will release two orbiters in Mercury orbit.
View larger. | This view of Mercury from the BepiColombo spacecraft came from its 3rd flyby of the planet on June 19, 2023. BepiColombo’s propulsion system will separate from its 2 orbiters on September 3, 2026. Then the 2 spacecraft will enter orbit around Mercury on November 21, 2026. Image via ESA/ BepiColombo/ MTM.
BepiColombo mission to arrive at Mercury in November
Today, on September 3, 2026, ESA’s BepiColombo spacecraft is moving one crucial step closer to entering Mercury’s orbit.
Bepicolombo launched to space way back October 20, 2018, from Kourou, French Guiana. The spacecraft has spent eight years maneuvering into position so that it can orbit Mercury, the closest planet to the sun. Orbiting Mercury is a true engineering challenge, because the spacecraft picks up speed as it nears the massive sun. But it must slow down to enter Mercury’s orbit and not fly straight past.
So, during its journey, BepiColombo has made flybys of Earth, Venus and Mercury to help put on the brakes. And on September 3, 2026, Bepicolombo’s Mercury Transfer Module (the spacecraft’s propulsion unit) will separate from the science orbiters, Mercury Planetary Orbiter (MPO) and Mercury Magnetospheric Orbiter (MMO). These two spacecraft will then enter orbit around Mercury on November 21, 2026.
On December 9-10, the two orbiters will separate from each other. Finally, science operations will begin in April 2027.
BepiColombo’s flybys
BepiColombo has made one Earth flyby, two Venus flybys, and six Mercury flybys since its launch in 2018. Click the links below to learn more about the flybys.
View larger. | The European Space Agency’s BepiColombo spacecraft, heading toward Mercury, caught this fleeting image of Venus on October 15, 2020. You can see the terminator line, or dividing line between light and dark on Venus, pass from right to left, causing Venus to change phase as the spacecraft swept past. Image via ESA/ BepiColombo/ MTM.
What scientists hope to learn at Mercury
Mercury is currently the least-understood planet in the inner solar system. In fact, before BepiColombo, the only spacecraft to have visited Mercury were NASA’s Mariner 10 and MESSENGER missions.
Now, scientists hope to solve five mysteries with BepiColombo:
Where did Mercury come from?
Is there really water on Mercury?
Is Mercury dead or alive?
Why is Mercury so dark?
Why does Mercury have a magnetic field?
To answer these questions, BepiColombo will spend at least one year orbiting Mercury. The mission will use its high-resolution instruments to learn about the mineralogical and elemental composition of Mercury’s surface. Plus, it will scan polar regions for ice. BepiColombo will look for anything that looks like it has changed on Mercury since MESSENGER visited 10 years earlier. And the two orbiters will travel through different areas of the planet’s magnetosphere to measure how it changes and interacts with the sun.
Bottom line: The BepiColombo mission has been maneuvering its way into orbit around Mercury for eight years. On September 3, it will release two orbiters in Mercury orbit.
