This 1888 engraving – Empedocles Breaks through the Crystal Spheres – is reminiscent of the revolution in thought brought about by Nicolaus Copernicus, who was born 553 years ago today. The engraving 1st appeared in a book by Camille Flammarion with the caption: “A missionary of the Middle Ages tells that he had found the point where the sky and the Earth touch.” Image via Raven/ Wikimedia Commons (CC BY-SA 4.0).
Renaissance astronomer and mathematician Nicolaus Copernicus was born in Torun, Poland, 553 years ago today. At a time when deeply entrenched beliefs placed the Earth at the center of the universe – nested within crystal spheres – he proposed the revolutionary idea that Earth revolves around the sun. Can you picture the leap of imagination required for him to conceive of a sun-centered universe?
Copernicus’ famous book – “De revolutionibus orbium coelestium” (On the Revolutions of the Celestial Spheres) – was published just before his death in 1543. In fact, it set the stage for all of modern astronomy.
Nicolaus Copernicus – born on February 19, 1473 – started the scientific revolution with his novel ideas. Image via Wikimedia Commons.
Ancient Greek views of the universe
Copernicus wasn’t the first to conceive of a sun-centered universe, however. Early Greek and Mesopotamian philosophers also spoke of it.
It was the Greek philosopher Aristotle, however, who proposed that the heavens comprised 55 concentric, crystalline spheres. He said that celestial objects were attached to these spheres.
In Aristotle’s model, Earth lay at the center of these spheres.
So, Earth lay – fixed and enclosed – until Copernicus published his version of a heliocentric, or sun-centered, universe. Copernicus’s ideas and ground-shaking book moved the Earth and replaced it with the sun.
This 1888 engraving – Empedocles Breaks through the Crystal Spheres – is reminiscent of the revolution in thought brought about by Nicolaus Copernicus, who was born 553 years ago today. The engraving 1st appeared in a book by Camille Flammarion with the caption: “A missionary of the Middle Ages tells that he had found the point where the sky and the Earth touch.” Image via Raven/ Wikimedia Commons (CC BY-SA 4.0).
Renaissance astronomer and mathematician Nicolaus Copernicus was born in Torun, Poland, 553 years ago today. At a time when deeply entrenched beliefs placed the Earth at the center of the universe – nested within crystal spheres – he proposed the revolutionary idea that Earth revolves around the sun. Can you picture the leap of imagination required for him to conceive of a sun-centered universe?
Copernicus’ famous book – “De revolutionibus orbium coelestium” (On the Revolutions of the Celestial Spheres) – was published just before his death in 1543. In fact, it set the stage for all of modern astronomy.
Nicolaus Copernicus – born on February 19, 1473 – started the scientific revolution with his novel ideas. Image via Wikimedia Commons.
Ancient Greek views of the universe
Copernicus wasn’t the first to conceive of a sun-centered universe, however. Early Greek and Mesopotamian philosophers also spoke of it.
It was the Greek philosopher Aristotle, however, who proposed that the heavens comprised 55 concentric, crystalline spheres. He said that celestial objects were attached to these spheres.
In Aristotle’s model, Earth lay at the center of these spheres.
So, Earth lay – fixed and enclosed – until Copernicus published his version of a heliocentric, or sun-centered, universe. Copernicus’s ideas and ground-shaking book moved the Earth and replaced it with the sun.
This is Islas Ballestas off the coast of the Chincha and Pisco valleys of Peru. It is an important location for several seabird species. The white substance on the cliffs is bird guano. There is less of it today because seabird populations are in decline. Image via Jo Osborn/ University of Sydney.
The Chincha Kingdom in southern Peru, which existed 1,000 years ago, prospered because farmers used bird guano as fertilizer to grow high maize yields.
Scientists found high nitrogen levels in ancient maize, showing guano from the nearby Chincha Islands boosted crop production.
Increased food production created wealth, as well as strengthened trade and political power, helping the Chincha form alliances with the Inca Empire.
Bird guano boosted agricultural yields for Chincha Kingdom
The Chincha Kingdom was an ancient community that flourished in southern Peru from 900 CE to 1,450 CE (1,126 to 576 years ago). They were wealthy largely because farmers produced high maize yields, a primary food staple. On February 12, 2026, scientists at the University of Sydney said Chincha Kingdom farmers were able to get those high yields because they used bird guano (accumulated bird droppings) as fertilizer. The researchers discovered this when they ran chemical analyses on maize from ancient tombs, where they found high levels of nitrogen that could only have come from the guano.
Jacob Bongers, of the University of Sydney, is the lead author of the study. He said:
Seabird guano may seem trivial, yet our study suggests this potent resource could have significantly contributed to sociopolitical and economic change in the Peruvian Andes.
Guano dramatically boosted the production of maize (corn), and this agricultural surplus crucially helped fuel the Chincha Kingdom’s economy, driving their trade, wealth, population growth and regional influence, and shaped their strategic alliance with the Inca Empire.
In ancient Andean cultures, fertilizer was power.
The scientists published their study in the peer-reviewed journal PLOS One on February 11, 2026.
Jacob Bongers of the University of Sydney is the lead author of the new study. Image via Jacob Bongers/ Stefanie Zingsheim/ University of Sydney.
An ancient community of farmers and seafarers
The Chincha Valley, on the Pacific coast of Peru, was once home to about 100,000 people. Even though that region was largely arid, agriculture was possible because the Chincha River, originating from the Andes, flowed through the valley.
By the 11th century, the Chincha Kingdom had developed agricultural systems, including irrigation and field fertilization with bird guano. In addition, they were also a seafaring people who built large rafts with sails that carried cargo and people.
In 1534, Spanish conquerors came to Chincha Valley. Then, not long after, the Chincha population steeply declined over several decades, their demise mostly due to political turmoil and new diseases brought by the Spanish.
Uncovering the connection between agriculture and bird guano
The scientists studied the biochemical signatures in 35 samples of maize, found in burial tombs in the Chincha Valley. As a result, they found very high levels of nitrogen in the maize, far more than was naturally available in the soil.
Indeed, this finding proved that ancient Chincha Valley farmers fertilized their maize using seabird guano. That’s because guano is quite high in nitrogen, due to the seabirds’ fish diet.
Bongers said:
The guano was most likely harvested from the nearby Chincha Islands, renowned for their abundant and high-quality guano deposits. Colonial era writings we studied report that communities across coastal Peru and northern Chile sailed to several nearby islands on rafts to collect seabird droppings for fertilization.
Emily Milton of the Smithsonian Institution, a paper co-author, added:
The historical records documenting how bird guano was applied to maize fields helped us interpret the chemical data and understand the regional importance of this practice.
Our work extends the known geographic extent of guano fertilization, echoing recent findings in northern Chile, and suggests soil management began at least around 800 years ago in Peru.
Bird guano created power in an inhospitable region
Farming was not easy along the coast of Peru. That’s because conditions are very dry and irrigated soil can quickly lose nutrients. However, in the Chincha Valley, the irrigation system and fertilizing with guano enabled farmers to grow crops, especially their staple food, maize. Consequently, the ripple effect of an abundant maize supply supported other endeavors, such as trade and fishing.
Bongers commented:
We know the Chincha were extraordinarily wealthy and one of the most powerful coastal societies of their time. But what underpinned that prosperity? Previous research often pointed to spondylus shells, the spiny oyster, as the key driver of merchant wealth.
Our evidence suggests guano was central to the Chincha Kingdom’s success, with the Chincha’s maritime knowledge and access to the Chincha Islands likely reframing their strategic importance in the region.
Incas prized maize from the Chincha Valley
The Inca Empire, a highly developed civilization in the Andes Mountains, valued maize. They used it to make a ceremonial beer called chicha. However, they could not grow maize at their high altitude.
Bongers said:
Guano was a highly sought-after resource the Incas would have wanted access to, playing an important role in the diplomatic arrangements between the Inca and the Chincha communities.
It expanded Chincha’s agricultural productivity and mercantile influence, leading to exchanges of resources and power.
Later, around 1480, the Chincha Kingdom became part of the Inca Empire.
Archaeological artifacts reflect Chincha Valley culture
The artwork of the Chincha people reflected strong ties to their livelihoods. For instance, pottery, ceramics and textiles featured sprouting maize, fish and seabirds.
The image on the left is a ceremonial digging stick. Next to it is a closeup of the handle. On this handle is a variety of artwork including seabirds and possible maize sprouting from abstracted fish. A Chincha artist created this ceremonial digging stick sometime between 1,200 CE and 1,535 CE. Image via The Metropolitan Museum of Art. (CC0)
Bongers observed:
Together, the chemical and material evidence we studied confirms earlier scholarship showing that guano was deliberately collected and used as a fertilizer.
But it also points to a deeper cultural significance, suggesting people recognized the exceptional power of this fertilizer and actively celebrated, protected and even ritualized the vital relationship between seabirds and agriculture.
Co-author Jo Osborn of Texas A&M University added:
The true power of the Chincha wasn’t just access to a resource; it was their mastery of a complex ecological system. They possessed the traditional knowledge to see the connection between marine and terrestrial life, and they turned that knowledge into the agricultural surplus that built their kingdom. Their art celebrates this connection, showing us that their power was rooted in ecological wisdom, not just gold or silver.
Bottom line: The ancient Chincha Kingdom of Peru prospered thanks to high maize yields, made possible by bird guano from nearby islands.
This is Islas Ballestas off the coast of the Chincha and Pisco valleys of Peru. It is an important location for several seabird species. The white substance on the cliffs is bird guano. There is less of it today because seabird populations are in decline. Image via Jo Osborn/ University of Sydney.
The Chincha Kingdom in southern Peru, which existed 1,000 years ago, prospered because farmers used bird guano as fertilizer to grow high maize yields.
Scientists found high nitrogen levels in ancient maize, showing guano from the nearby Chincha Islands boosted crop production.
Increased food production created wealth, as well as strengthened trade and political power, helping the Chincha form alliances with the Inca Empire.
Bird guano boosted agricultural yields for Chincha Kingdom
The Chincha Kingdom was an ancient community that flourished in southern Peru from 900 CE to 1,450 CE (1,126 to 576 years ago). They were wealthy largely because farmers produced high maize yields, a primary food staple. On February 12, 2026, scientists at the University of Sydney said Chincha Kingdom farmers were able to get those high yields because they used bird guano (accumulated bird droppings) as fertilizer. The researchers discovered this when they ran chemical analyses on maize from ancient tombs, where they found high levels of nitrogen that could only have come from the guano.
Jacob Bongers, of the University of Sydney, is the lead author of the study. He said:
Seabird guano may seem trivial, yet our study suggests this potent resource could have significantly contributed to sociopolitical and economic change in the Peruvian Andes.
Guano dramatically boosted the production of maize (corn), and this agricultural surplus crucially helped fuel the Chincha Kingdom’s economy, driving their trade, wealth, population growth and regional influence, and shaped their strategic alliance with the Inca Empire.
In ancient Andean cultures, fertilizer was power.
The scientists published their study in the peer-reviewed journal PLOS One on February 11, 2026.
Jacob Bongers of the University of Sydney is the lead author of the new study. Image via Jacob Bongers/ Stefanie Zingsheim/ University of Sydney.
An ancient community of farmers and seafarers
The Chincha Valley, on the Pacific coast of Peru, was once home to about 100,000 people. Even though that region was largely arid, agriculture was possible because the Chincha River, originating from the Andes, flowed through the valley.
By the 11th century, the Chincha Kingdom had developed agricultural systems, including irrigation and field fertilization with bird guano. In addition, they were also a seafaring people who built large rafts with sails that carried cargo and people.
In 1534, Spanish conquerors came to Chincha Valley. Then, not long after, the Chincha population steeply declined over several decades, their demise mostly due to political turmoil and new diseases brought by the Spanish.
Uncovering the connection between agriculture and bird guano
The scientists studied the biochemical signatures in 35 samples of maize, found in burial tombs in the Chincha Valley. As a result, they found very high levels of nitrogen in the maize, far more than was naturally available in the soil.
Indeed, this finding proved that ancient Chincha Valley farmers fertilized their maize using seabird guano. That’s because guano is quite high in nitrogen, due to the seabirds’ fish diet.
Bongers said:
The guano was most likely harvested from the nearby Chincha Islands, renowned for their abundant and high-quality guano deposits. Colonial era writings we studied report that communities across coastal Peru and northern Chile sailed to several nearby islands on rafts to collect seabird droppings for fertilization.
Emily Milton of the Smithsonian Institution, a paper co-author, added:
The historical records documenting how bird guano was applied to maize fields helped us interpret the chemical data and understand the regional importance of this practice.
Our work extends the known geographic extent of guano fertilization, echoing recent findings in northern Chile, and suggests soil management began at least around 800 years ago in Peru.
Bird guano created power in an inhospitable region
Farming was not easy along the coast of Peru. That’s because conditions are very dry and irrigated soil can quickly lose nutrients. However, in the Chincha Valley, the irrigation system and fertilizing with guano enabled farmers to grow crops, especially their staple food, maize. Consequently, the ripple effect of an abundant maize supply supported other endeavors, such as trade and fishing.
Bongers commented:
We know the Chincha were extraordinarily wealthy and one of the most powerful coastal societies of their time. But what underpinned that prosperity? Previous research often pointed to spondylus shells, the spiny oyster, as the key driver of merchant wealth.
Our evidence suggests guano was central to the Chincha Kingdom’s success, with the Chincha’s maritime knowledge and access to the Chincha Islands likely reframing their strategic importance in the region.
Incas prized maize from the Chincha Valley
The Inca Empire, a highly developed civilization in the Andes Mountains, valued maize. They used it to make a ceremonial beer called chicha. However, they could not grow maize at their high altitude.
Bongers said:
Guano was a highly sought-after resource the Incas would have wanted access to, playing an important role in the diplomatic arrangements between the Inca and the Chincha communities.
It expanded Chincha’s agricultural productivity and mercantile influence, leading to exchanges of resources and power.
Later, around 1480, the Chincha Kingdom became part of the Inca Empire.
Archaeological artifacts reflect Chincha Valley culture
The artwork of the Chincha people reflected strong ties to their livelihoods. For instance, pottery, ceramics and textiles featured sprouting maize, fish and seabirds.
The image on the left is a ceremonial digging stick. Next to it is a closeup of the handle. On this handle is a variety of artwork including seabirds and possible maize sprouting from abstracted fish. A Chincha artist created this ceremonial digging stick sometime between 1,200 CE and 1,535 CE. Image via The Metropolitan Museum of Art. (CC0)
Bongers observed:
Together, the chemical and material evidence we studied confirms earlier scholarship showing that guano was deliberately collected and used as a fertilizer.
But it also points to a deeper cultural significance, suggesting people recognized the exceptional power of this fertilizer and actively celebrated, protected and even ritualized the vital relationship between seabirds and agriculture.
Co-author Jo Osborn of Texas A&M University added:
The true power of the Chincha wasn’t just access to a resource; it was their mastery of a complex ecological system. They possessed the traditional knowledge to see the connection between marine and terrestrial life, and they turned that knowledge into the agricultural surplus that built their kingdom. Their art celebrates this connection, showing us that their power was rooted in ecological wisdom, not just gold or silver.
Bottom line: The ancient Chincha Kingdom of Peru prospered thanks to high maize yields, made possible by bird guano from nearby islands.
View at EarthSky Community Photos. | Paolo Palma in Naples, Italy, created this composite of the colors of the stars with images of individual stars taken over the course of 2 years, which he calls Kaleidocosmo. He captured all the stars he could see from Naples – up to +5 magnitude and brighter – some 1,250 stars! Then, he imaged each star out of focus to capture its color and created this composite, with the size of each star based on how bright it is. He wrote: “Kaleidocosmo can reveal how much the starry sky is more colorful than we imagine …” In addition, he also set his kaleidocosmo to music, which you can download here. Thank you, Paolo!
Tonight, go outside, and let your eyes adjust to the dark. Then note the subtle differences in the colors of the stars. Let’s explore some of the stars that you’ll see flickering against the black backdrop of night in winter. In fact, there’s a whole spectrum of star colors sparkling up there, from cool red stars to middle-range yellow stars to hot blue-white stars.
But in 2026, watch out for bright Jupiter among the stars of Gemini.
The colors of the stars
First, look high overhead in the winter evening sky for a bright star with the name of Capella. Capella’s nickname is the Little She-Goat, and it lies in the constellation Auriga the Charioteer.
So can you spot Capella? Once you find it, notice that it’s a golden star. The fact is, a star’s color indicates its spectral type. More about spectral types of stars below.
The bright star Capella in the constellation Auriga the Charioteer is overhead on winter evenings. To be certain you’ve found Capella, look for a little triangle of stars nearby. Capella is sometimes called the Goat Star, and the little triangle of stars is an asterism called The Kids.
Compare the different colors of the stars you see
Now try contrasting golden Capella with some of the stars in nearby Taurus the Bull. First, find the reddish star Aldebaran, the Eye of the Bull, and the bluish stars of the misty Pleiades cluster. Do you see the difference?
Taurus the Bull contains 2 star clusters that are easy to spot, the Pleiades and the Hyades. Aldebaran appears as part of the Hyades cluster.View at EarthSky Community Photos. | Jeremy Likness in Monroe, Washington, used a regular camera lens to capture this view of a bright red planet, Mars, on January 8, 2023. Plus he captured the reddish star Aldebaran in the Hyades star cluster (part of Taurus the Bull). And this photo shows the bluish, dipper-shaped Pleiades star cluster, also in Taurus. Thank you, Jeremy!
What about Sirius?
Sirius in the constellation Canis Major the Greater Dog is our sky’s brightest star, after the sun. It’s usually described as a white star.
So Capella is golden, and Sirius is white. Besides appearing so bright, Capella and Sirius often flicker deliriously when low in the sky. This effect has nothing to do with the colors of the stars themselves but rather is caused by Earth’s turbulent atmosphere. The twinkling effect is particularly prominent with the stars Capella and Sirius because they are so bright.
Sirius is the sky’s brightest star. You’ll always know it’s Sirius because Orion’s Belt – 3 stars in a short, straight row – points to it. Also, as seen from latitudes like those in Florida, Texas or southern California, Canopus – the 2nd-brightest star – arcs across the south below Sirius on February evenings. From farther south on the sky’s dome, Sirius and Canopus cross higher in the sky, like almost-twin diamonds. Chart via EarthSky.
Next, check out Orion
Orion the Hunter, a prominent constellation in the winter sky, sports a noticeably red star and a vivid blue star. The red star is Betelgeuse marking one shoulder, while the blue star is Rigel marking the opposite knee.
Notice the shades of red and orange of Betelgeuse in Paolo Palma’s creative collage below.
View at EarthSky Community Photos. | Amr Elsayed in Fayoum, Egypt, captured this image of Orion on December 6, 2024. Orion the Hunter is a great place to see the different colors of the stars. Rigel appears in the lower right of the constellation. Contrast its bluish-white light with that of reddish Betelgeuse in the upper left. Most of Orion’s stars are hot blue-white stars.View at EarthSky Community Photos. | Paolo Palma of Italy submitted this mosaic of the stars visible to the unaided eye in Orion and shot deliberately out of focus to capture their nuances and their apparent magnitude. Paolo wrote: “Orion the Hunter is probably the most beautiful constellation in the sky and its bright stars make it easily recognizable to anyone. This is how it would look if we could also see the colors of all the stars. Also shown are stars that can represent spectral classes, a beautiful color scale that can reveal the relationship between color and spectral class (temperature) of stars.” Thank you, Paolo!
The true colors of stars
And you don’t even have to know any star names or any constellations. Just glance around the sky, and notice the subtle color differences in the stars.
It’s helpful to know that a star’s true colors are more apparent as the star climbs higher in the sky, moving above the turbulence of Earth’s atmosphere. So, if you have good eyesight and a dark, clear sky, you should be able to detect hints of color within the brighter stars.
And if you have difficulty discerning star colors with the unaided eye, look at the bright stars through binoculars. A useful trick is to put the star out of focus in your binoculars so the color will become more obvious.
Why do stars have different colors?
The light of a star reveals many things, including the star’s surface temperature. The yellowish color of Capella indicates a mid-range surface temperature, much like our sun. The red of Aldebaran is typical of the lower surface temperature of an older star, whereas the blue of the Pleiades reveals their high surface temperatures and young age.
In fact, the surface temperature – or color – of a star determines its spectral class. On the Hertzsprung-Russell diagram below, you can see the different spectral classes listed across the bottom of the chart with temperatures going from hottest to coolest. Also, it shows the colors of stars associated with each spectral class and temperature.
So what are the spectral classes of Capella, Aldebaran, Sirius, Betelgeuse, Rigel and the Pleiades? Capella is a G star. Our sun is also a G star. Both our sun and Capella shine with a golden light. Aldebaran and Betelgeuse are cool stars and appear reddish. Aldebaran is a K type star and Betelgeuse is an M type star. Sirius is an A type star and appears white. Rigel and the stars of Pleiades are type B stars.
View larger. | A star that is blue or blue-white in color, such as Spica at the upper left, has a high surface temperature. In contrast, a red-colored star (such as Antares and Betelgeuse at the upper right), has a lower surface temperature. Image of Hertzsprung-Russell diagram via Chandra/ NASA.
Bottom line: Winter is the perfect season for noticing the colors of the stars. Have you ever noticed them? By all means, go check them out tonight! And now you also can tell the temperature of a star by its color.
View at EarthSky Community Photos. | Paolo Palma in Naples, Italy, created this composite of the colors of the stars with images of individual stars taken over the course of 2 years, which he calls Kaleidocosmo. He captured all the stars he could see from Naples – up to +5 magnitude and brighter – some 1,250 stars! Then, he imaged each star out of focus to capture its color and created this composite, with the size of each star based on how bright it is. He wrote: “Kaleidocosmo can reveal how much the starry sky is more colorful than we imagine …” In addition, he also set his kaleidocosmo to music, which you can download here. Thank you, Paolo!
Tonight, go outside, and let your eyes adjust to the dark. Then note the subtle differences in the colors of the stars. Let’s explore some of the stars that you’ll see flickering against the black backdrop of night in winter. In fact, there’s a whole spectrum of star colors sparkling up there, from cool red stars to middle-range yellow stars to hot blue-white stars.
But in 2026, watch out for bright Jupiter among the stars of Gemini.
The colors of the stars
First, look high overhead in the winter evening sky for a bright star with the name of Capella. Capella’s nickname is the Little She-Goat, and it lies in the constellation Auriga the Charioteer.
So can you spot Capella? Once you find it, notice that it’s a golden star. The fact is, a star’s color indicates its spectral type. More about spectral types of stars below.
The bright star Capella in the constellation Auriga the Charioteer is overhead on winter evenings. To be certain you’ve found Capella, look for a little triangle of stars nearby. Capella is sometimes called the Goat Star, and the little triangle of stars is an asterism called The Kids.
Compare the different colors of the stars you see
Now try contrasting golden Capella with some of the stars in nearby Taurus the Bull. First, find the reddish star Aldebaran, the Eye of the Bull, and the bluish stars of the misty Pleiades cluster. Do you see the difference?
Taurus the Bull contains 2 star clusters that are easy to spot, the Pleiades and the Hyades. Aldebaran appears as part of the Hyades cluster.View at EarthSky Community Photos. | Jeremy Likness in Monroe, Washington, used a regular camera lens to capture this view of a bright red planet, Mars, on January 8, 2023. Plus he captured the reddish star Aldebaran in the Hyades star cluster (part of Taurus the Bull). And this photo shows the bluish, dipper-shaped Pleiades star cluster, also in Taurus. Thank you, Jeremy!
What about Sirius?
Sirius in the constellation Canis Major the Greater Dog is our sky’s brightest star, after the sun. It’s usually described as a white star.
So Capella is golden, and Sirius is white. Besides appearing so bright, Capella and Sirius often flicker deliriously when low in the sky. This effect has nothing to do with the colors of the stars themselves but rather is caused by Earth’s turbulent atmosphere. The twinkling effect is particularly prominent with the stars Capella and Sirius because they are so bright.
Sirius is the sky’s brightest star. You’ll always know it’s Sirius because Orion’s Belt – 3 stars in a short, straight row – points to it. Also, as seen from latitudes like those in Florida, Texas or southern California, Canopus – the 2nd-brightest star – arcs across the south below Sirius on February evenings. From farther south on the sky’s dome, Sirius and Canopus cross higher in the sky, like almost-twin diamonds. Chart via EarthSky.
Next, check out Orion
Orion the Hunter, a prominent constellation in the winter sky, sports a noticeably red star and a vivid blue star. The red star is Betelgeuse marking one shoulder, while the blue star is Rigel marking the opposite knee.
Notice the shades of red and orange of Betelgeuse in Paolo Palma’s creative collage below.
View at EarthSky Community Photos. | Amr Elsayed in Fayoum, Egypt, captured this image of Orion on December 6, 2024. Orion the Hunter is a great place to see the different colors of the stars. Rigel appears in the lower right of the constellation. Contrast its bluish-white light with that of reddish Betelgeuse in the upper left. Most of Orion’s stars are hot blue-white stars.View at EarthSky Community Photos. | Paolo Palma of Italy submitted this mosaic of the stars visible to the unaided eye in Orion and shot deliberately out of focus to capture their nuances and their apparent magnitude. Paolo wrote: “Orion the Hunter is probably the most beautiful constellation in the sky and its bright stars make it easily recognizable to anyone. This is how it would look if we could also see the colors of all the stars. Also shown are stars that can represent spectral classes, a beautiful color scale that can reveal the relationship between color and spectral class (temperature) of stars.” Thank you, Paolo!
The true colors of stars
And you don’t even have to know any star names or any constellations. Just glance around the sky, and notice the subtle color differences in the stars.
It’s helpful to know that a star’s true colors are more apparent as the star climbs higher in the sky, moving above the turbulence of Earth’s atmosphere. So, if you have good eyesight and a dark, clear sky, you should be able to detect hints of color within the brighter stars.
And if you have difficulty discerning star colors with the unaided eye, look at the bright stars through binoculars. A useful trick is to put the star out of focus in your binoculars so the color will become more obvious.
Why do stars have different colors?
The light of a star reveals many things, including the star’s surface temperature. The yellowish color of Capella indicates a mid-range surface temperature, much like our sun. The red of Aldebaran is typical of the lower surface temperature of an older star, whereas the blue of the Pleiades reveals their high surface temperatures and young age.
In fact, the surface temperature – or color – of a star determines its spectral class. On the Hertzsprung-Russell diagram below, you can see the different spectral classes listed across the bottom of the chart with temperatures going from hottest to coolest. Also, it shows the colors of stars associated with each spectral class and temperature.
So what are the spectral classes of Capella, Aldebaran, Sirius, Betelgeuse, Rigel and the Pleiades? Capella is a G star. Our sun is also a G star. Both our sun and Capella shine with a golden light. Aldebaran and Betelgeuse are cool stars and appear reddish. Aldebaran is a K type star and Betelgeuse is an M type star. Sirius is an A type star and appears white. Rigel and the stars of Pleiades are type B stars.
View larger. | A star that is blue or blue-white in color, such as Spica at the upper left, has a high surface temperature. In contrast, a red-colored star (such as Antares and Betelgeuse at the upper right), has a lower surface temperature. Image of Hertzsprung-Russell diagram via Chandra/ NASA.
Bottom line: Winter is the perfect season for noticing the colors of the stars. Have you ever noticed them? By all means, go check them out tonight! And now you also can tell the temperature of a star by its color.
NOAA’s Storm Prediction Center has issued its fire weather outlook for Wednesday, February 18, 2026, and Thursday, February 19, 2026. Large swaths of the central United States face critical conditions due to gusty winds and low relative humidity. Image via NOAA.
Fire weather continues for much of the central US
Much of the central United States has experienced an early spring warm-up over the past few days. But with the added warmth came gusty winds and low relative humidity, a perfect recipe for fire weather. NOAA’s Storm Prediction Center issued areas of critical and elevated fire weather on February 18, 2026, for much of the high Southern Plains and most of Iowa including parts of the surrounding states. The panhandle of Oklahoma and across the border into Kansas already battled wildfires for most of the day on Tuesday.
Wildfires can start in various ways, and one thing you can do to help over the next few days is to delay any burning. One of the fires in the Southern Plains on Tuesday started after a seven-vehicle crash, while another appeared to have started from power lines that blew down in heavy winds.
Farmers were plowing fire lines in Oklahoma in an attempt to protect their livestock.
For the high Southern Plains, NOAA said on Wednesday morning:
As downslope flow peaks in intensity by mid to late afternoon, widespread 25 mph sustained westerly surface winds, with higher gusts, will overlap with 10-15% relative humidity (perhaps lower in some locales). The best chance for these conditions will be over northeast New Mexico into the Texas Panhandle and immediate surrounding areas.
Given very receptive fuels, high-end Critical conditions, supporting dangerous/rapid wildfire-spread potential, are expected. While Extremely Critical conditions are not expected to be widespread like the yesterday, spotty Extremely Critical conditions may be observed.
Otherwise, 15-20% relative humidity will overlap with 15-20 mph sustained west-southwesterly winds for several hours across much of the southern High Plains, warranting broad Elevated/Critical highlights.
For portions of the Midwest, NOAA said:
Before the surface low undergoes significant weakening, strong gradient flow will persist during the afternoon, when boundary-layer mixing will support a belt of overlapping 25 mph sustained westerly surface winds and 15-25% relative humidity for at least a few hours. These conditions will most likely be observed over central Iowa and immediate surrounding areas.
Such conditions are high-end Critical for the Midwest, especially when considering that yesterday’s precipitation has not yielded meaningful accumulations, which have also been lacking in the past few weeks.
Rapid, dangerous wildfire spread is possible wherever dry fuel beds exist, and a sparse instance of Extremely Critical conditions cannot be ruled out.
Stay weather aware and keep up to date with your local National Weather Service office for changing conditions.
Bottom line: Critical fire weather will threaten much of the central United States on Wednesday and Thursday. Wildfires were already plaguing areas in Oklahoma and Kansas on Tuesday.
NOAA’s Storm Prediction Center has issued its fire weather outlook for Wednesday, February 18, 2026, and Thursday, February 19, 2026. Large swaths of the central United States face critical conditions due to gusty winds and low relative humidity. Image via NOAA.
Fire weather continues for much of the central US
Much of the central United States has experienced an early spring warm-up over the past few days. But with the added warmth came gusty winds and low relative humidity, a perfect recipe for fire weather. NOAA’s Storm Prediction Center issued areas of critical and elevated fire weather on February 18, 2026, for much of the high Southern Plains and most of Iowa including parts of the surrounding states. The panhandle of Oklahoma and across the border into Kansas already battled wildfires for most of the day on Tuesday.
Wildfires can start in various ways, and one thing you can do to help over the next few days is to delay any burning. One of the fires in the Southern Plains on Tuesday started after a seven-vehicle crash, while another appeared to have started from power lines that blew down in heavy winds.
Farmers were plowing fire lines in Oklahoma in an attempt to protect their livestock.
For the high Southern Plains, NOAA said on Wednesday morning:
As downslope flow peaks in intensity by mid to late afternoon, widespread 25 mph sustained westerly surface winds, with higher gusts, will overlap with 10-15% relative humidity (perhaps lower in some locales). The best chance for these conditions will be over northeast New Mexico into the Texas Panhandle and immediate surrounding areas.
Given very receptive fuels, high-end Critical conditions, supporting dangerous/rapid wildfire-spread potential, are expected. While Extremely Critical conditions are not expected to be widespread like the yesterday, spotty Extremely Critical conditions may be observed.
Otherwise, 15-20% relative humidity will overlap with 15-20 mph sustained west-southwesterly winds for several hours across much of the southern High Plains, warranting broad Elevated/Critical highlights.
For portions of the Midwest, NOAA said:
Before the surface low undergoes significant weakening, strong gradient flow will persist during the afternoon, when boundary-layer mixing will support a belt of overlapping 25 mph sustained westerly surface winds and 15-25% relative humidity for at least a few hours. These conditions will most likely be observed over central Iowa and immediate surrounding areas.
Such conditions are high-end Critical for the Midwest, especially when considering that yesterday’s precipitation has not yielded meaningful accumulations, which have also been lacking in the past few weeks.
Rapid, dangerous wildfire spread is possible wherever dry fuel beds exist, and a sparse instance of Extremely Critical conditions cannot be ruled out.
Stay weather aware and keep up to date with your local National Weather Service office for changing conditions.
Bottom line: Critical fire weather will threaten much of the central United States on Wednesday and Thursday. Wildfires were already plaguing areas in Oklahoma and Kansas on Tuesday.
Simulated movement and speed (indicated by the length of the arrows) of objects surrounding the Local Group of galaxies, which is in the center of the image. The Milky Way and Andromeda galaxies are the main players in our Local Group. Scientists said our Local Group sits in a sheet of dark matter with voids on either side. These voids allow more distant galaxies to move away from our pull of gravity. Image via Ewoud Wempe and collaborators/ University of Groningen.
According to a team of scientists led by the University of Groningen, in the Netherlands, this 32-million-light-year-long sheet of dark matter encases both our home galaxy and the entire nearby Local Group of galaxies.
The scientists said on January 27, 2026, that they used a detailed computer simulation of local gravity conditions to uncover the structure of this sheet. They found that two huge voids sandwich the mass of dark matter. And this structure seems to explain why nearby large galaxies – other than Andromeda – are fleeing the Milky Way, instead of being pulled toward us.
When accounting for all the mass in the universe, 85% of it is dark matter, while just 15% of it is normal matter (that which we can see). Dark matter doesn’t reflect light, but it does interact gravitationally with itself and with regular matter and energy. So that means that where it clumps and gathers at high or low densities shapes the underlying geometry of the universe.
The authors argue their computer simulation of gravitational conditions from the Big Bang to the present results in a dark matter distribution that carries almost all other galaxies away from the Local Group. Astronomers call this expansion of the universe the Hubble flow. At the same time, the model shows why the Milky Way and Andromeda galaxies appear to be on a collision course. From the paper:
…The observed quiet local Hubble flow can be consistent with the halo masses implied for Andromeda and the Milky Way … only if the mass distribution is strongly concentrated in a sheet out to at least 10 megaparsecs (32 million light-years), with substantially underdense regions both above and below this Supergalactic Plane.
Edwin Hubble and the expanding universe
In the early 20th century, astronomer Edwin Hubble discovered the Milky Way is just one of many galaxies in the universe. He also found that almost all galaxies are moving away from us. This outward flow was a key clue that the cosmos began with the Big Bang and has been expanding ever since.
However, the Andromeda Galaxy was and remains an exception. It, the Milky Way and the dozens of other smaller members of the Local Group, seemed immune to the force pushing the rest of the cosmos apart. Now a group of European astrophysicists claim to have cracked this mystery. Lead author Ewoud Wempe of the University of Groningen said it’s the first time anyone has attempted such an elaborate computer simulation of the evolving universe. Wempe said:
We are exploring all possible local configurations of the early universe that ultimately could lead to the Local Group. It is great that we now have a model that is consistent with the current cosmological model on the one hand, and with the dynamics of our local environment on the other.
A simulation starting with Cosmic Microwave Background
The computer started its simulation with the early universe. It began with tiny deviations that statistically matched the oldest light we can detect, the Cosmic Microwave Background. The areas chosen for the simulation eventually transformed into galaxy formations that match our local conditions of distance and speed. But these areas also had to move like the Local Group does with respect to more distant galaxies.
The computer found hundreds of matches for the Milky Way-Andromeda system. Inside these areas, a reduced Hubble flow allows and encourages galaxy clusters like the Local Group. Yet outside them – at much larger distances – galaxies rush away, sometimes at speeds exceeding the Hubble flow.
By combining the hundreds of simulations of dark matter distributions resulting in systems matching the Milky Way and Andromeda, the researchers created the best fit for what we actually see around us. The end result is a dark matter environment in the form of a sheet matching the distribution of the galaxies in the Local Group.
Left: A top-down view of the Local Group simulation, with the Milky Way and Andromeda as the brightest blobs. Light blue dots are 31 nearby galaxies. The pinkish-purple color represents the distribution of dark matter. Arrows show the velocity of dark matter relative to a uniformly expanding universe. Right: A side view of the Local Group, revealing the sheet structure. Image via Max Planck Institute.
Milky Way and Andromeda vs. the universe
In our cosmic neighborhood, the simulations resulted in predictions of dark matter concentrated into a sheet extending well beyond the region of the Local Group. It didn’t stop there. The simulation even showed there must be large low-density regions on either flattened side of the dark matter sheet. These areas do exist and are known as the Local Voids.
The simulation even predicted the flattened distribution of far more distant galaxies in the Local Supercluster without knowing of its existence.
Researchers created a virtual twin of the Local Group that explains how the universe came to look the way it does. Also, they’ve answered a question that’s excited and perplexed astronomers for the better part of a century. As co-author Amina Helmi of the University of Groningen explained:
I am excited to see that, based purely on the motions of galaxies, we can determine a mass distribution that corresponds to the positions of galaxies within and just outside the Local Group.
Bottom line: A new computer simulation shows the Milky Way Galaxy is inside an enormous dark matter sheet. This sheet lies between two voids. The geometry explains our Local Group and why more distant galaxies aren’t pulled in toward us.
Simulated movement and speed (indicated by the length of the arrows) of objects surrounding the Local Group of galaxies, which is in the center of the image. The Milky Way and Andromeda galaxies are the main players in our Local Group. Scientists said our Local Group sits in a sheet of dark matter with voids on either side. These voids allow more distant galaxies to move away from our pull of gravity. Image via Ewoud Wempe and collaborators/ University of Groningen.
According to a team of scientists led by the University of Groningen, in the Netherlands, this 32-million-light-year-long sheet of dark matter encases both our home galaxy and the entire nearby Local Group of galaxies.
The scientists said on January 27, 2026, that they used a detailed computer simulation of local gravity conditions to uncover the structure of this sheet. They found that two huge voids sandwich the mass of dark matter. And this structure seems to explain why nearby large galaxies – other than Andromeda – are fleeing the Milky Way, instead of being pulled toward us.
When accounting for all the mass in the universe, 85% of it is dark matter, while just 15% of it is normal matter (that which we can see). Dark matter doesn’t reflect light, but it does interact gravitationally with itself and with regular matter and energy. So that means that where it clumps and gathers at high or low densities shapes the underlying geometry of the universe.
The authors argue their computer simulation of gravitational conditions from the Big Bang to the present results in a dark matter distribution that carries almost all other galaxies away from the Local Group. Astronomers call this expansion of the universe the Hubble flow. At the same time, the model shows why the Milky Way and Andromeda galaxies appear to be on a collision course. From the paper:
…The observed quiet local Hubble flow can be consistent with the halo masses implied for Andromeda and the Milky Way … only if the mass distribution is strongly concentrated in a sheet out to at least 10 megaparsecs (32 million light-years), with substantially underdense regions both above and below this Supergalactic Plane.
Edwin Hubble and the expanding universe
In the early 20th century, astronomer Edwin Hubble discovered the Milky Way is just one of many galaxies in the universe. He also found that almost all galaxies are moving away from us. This outward flow was a key clue that the cosmos began with the Big Bang and has been expanding ever since.
However, the Andromeda Galaxy was and remains an exception. It, the Milky Way and the dozens of other smaller members of the Local Group, seemed immune to the force pushing the rest of the cosmos apart. Now a group of European astrophysicists claim to have cracked this mystery. Lead author Ewoud Wempe of the University of Groningen said it’s the first time anyone has attempted such an elaborate computer simulation of the evolving universe. Wempe said:
We are exploring all possible local configurations of the early universe that ultimately could lead to the Local Group. It is great that we now have a model that is consistent with the current cosmological model on the one hand, and with the dynamics of our local environment on the other.
A simulation starting with Cosmic Microwave Background
The computer started its simulation with the early universe. It began with tiny deviations that statistically matched the oldest light we can detect, the Cosmic Microwave Background. The areas chosen for the simulation eventually transformed into galaxy formations that match our local conditions of distance and speed. But these areas also had to move like the Local Group does with respect to more distant galaxies.
The computer found hundreds of matches for the Milky Way-Andromeda system. Inside these areas, a reduced Hubble flow allows and encourages galaxy clusters like the Local Group. Yet outside them – at much larger distances – galaxies rush away, sometimes at speeds exceeding the Hubble flow.
By combining the hundreds of simulations of dark matter distributions resulting in systems matching the Milky Way and Andromeda, the researchers created the best fit for what we actually see around us. The end result is a dark matter environment in the form of a sheet matching the distribution of the galaxies in the Local Group.
Left: A top-down view of the Local Group simulation, with the Milky Way and Andromeda as the brightest blobs. Light blue dots are 31 nearby galaxies. The pinkish-purple color represents the distribution of dark matter. Arrows show the velocity of dark matter relative to a uniformly expanding universe. Right: A side view of the Local Group, revealing the sheet structure. Image via Max Planck Institute.
Milky Way and Andromeda vs. the universe
In our cosmic neighborhood, the simulations resulted in predictions of dark matter concentrated into a sheet extending well beyond the region of the Local Group. It didn’t stop there. The simulation even showed there must be large low-density regions on either flattened side of the dark matter sheet. These areas do exist and are known as the Local Voids.
The simulation even predicted the flattened distribution of far more distant galaxies in the Local Supercluster without knowing of its existence.
Researchers created a virtual twin of the Local Group that explains how the universe came to look the way it does. Also, they’ve answered a question that’s excited and perplexed astronomers for the better part of a century. As co-author Amina Helmi of the University of Groningen explained:
I am excited to see that, based purely on the motions of galaxies, we can determine a mass distribution that corresponds to the positions of galaxies within and just outside the Local Group.
Bottom line: A new computer simulation shows the Milky Way Galaxy is inside an enormous dark matter sheet. This sheet lies between two voids. The geometry explains our Local Group and why more distant galaxies aren’t pulled in toward us.
You can find Cassiopeia the Queen in the northwest in the evening around the month of February. It’s one of the easiest constellations to spot! It has the shape of an M or W. If you have a dark sky, you can also look above Cassiopeia for a famous binocular object, the Double Cluster in Perseus. Chart via EarthSky.
Cassiopeia the Queen in late winter and early spring
On late northern winter evenings and throughout spring, Cassiopeia the Queen descends in her throne in the northwest after nightfall. Cassiopeia is one of the easiest constellations to spot because of its distinctive shape. Cassiopeia looks like the letter W or M. Look for the Queen as your sky gets dark in February and March. She’ll be lower in the northwest as spring begins to unfold. For those in the northern U.S. and Canada, Cassiopeia is circumpolar, or above the horizon all night every night.
The stars of Cassiopeia
Cassiopeia is home to five bright stars that form the W shape. Some describe these stars as outlining the chair – or throne – she sits upon. If you’re viewing Cassiopeia as the letter W, the stars, from left to right, are Segin, Ruchbah, Gamma Cassiopeiae, Schedar and Caph.
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 prominently again in the evening sky, Cassiopeia is descending in the northwest.
The Big Dipper and Cassiopeia circle around Polaris, the North Star, completing one rotation in 23 hours and 56 minutes. Both constellations are circumpolar at 41° north latitude and all latitudes farther north. Image via Mjchael/ Wikipedia (CC BY-SA 2.5).
Neighboring star clusters
If you have a dark sky, look across the border of Cassiopeia into Perseus the Hero for a famous binocular object. It’s the Double Cluster in Perseus. They are open star clusters, each of which consists of young stars still moving together from the primordial cloud of gas and dust that gave birth to them.
In fact, these clusters have a unique set of mismatched names: H and Chi Persei. 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 – the cluster on the top – 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.
Upside-down Cassiopeia, as depicted on Mercator celestial globe in 1551. Image via Harvard Map Collection/ Wikipedia (public domain).
Lore of the Queen
In sky lore and in Greek mythology, Cassiopeia was 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.
Her boast angered Poseidon, god of the sea, who sent a sea monster (Cetus the Whale) to ravage the kingdom. To pacify the monster, Cassiopeia’s daughter, Princess Andromeda, was left tied to a rock by the sea. Then, when Cetus was about to devour her, Perseus the Hero happened by on Pegasus the Winged Horse.
Then, 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. Meanwhile, at other times of the 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 she is sometimes called – is upside-down and 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.
Bottom line: The constellation Cassiopeia the Queen has the distinct shape of a W or M. You’ll find her descending in her throne on late northern winter evenings and throughout spring nights.
You can find Cassiopeia the Queen in the northwest in the evening around the month of February. It’s one of the easiest constellations to spot! It has the shape of an M or W. If you have a dark sky, you can also look above Cassiopeia for a famous binocular object, the Double Cluster in Perseus. Chart via EarthSky.
Cassiopeia the Queen in late winter and early spring
On late northern winter evenings and throughout spring, Cassiopeia the Queen descends in her throne in the northwest after nightfall. Cassiopeia is one of the easiest constellations to spot because of its distinctive shape. Cassiopeia looks like the letter W or M. Look for the Queen as your sky gets dark in February and March. She’ll be lower in the northwest as spring begins to unfold. For those in the northern U.S. and Canada, Cassiopeia is circumpolar, or above the horizon all night every night.
The stars of Cassiopeia
Cassiopeia is home to five bright stars that form the W shape. Some describe these stars as outlining the chair – or throne – she sits upon. If you’re viewing Cassiopeia as the letter W, the stars, from left to right, are Segin, Ruchbah, Gamma Cassiopeiae, Schedar and Caph.
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 prominently again in the evening sky, Cassiopeia is descending in the northwest.
The Big Dipper and Cassiopeia circle around Polaris, the North Star, completing one rotation in 23 hours and 56 minutes. Both constellations are circumpolar at 41° north latitude and all latitudes farther north. Image via Mjchael/ Wikipedia (CC BY-SA 2.5).
Neighboring star clusters
If you have a dark sky, look across the border of Cassiopeia into Perseus the Hero for a famous binocular object. It’s the Double Cluster in Perseus. They are open star clusters, each of which consists of young stars still moving together from the primordial cloud of gas and dust that gave birth to them.
In fact, these clusters have a unique set of mismatched names: H and Chi Persei. 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 – the cluster on the top – 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.
Upside-down Cassiopeia, as depicted on Mercator celestial globe in 1551. Image via Harvard Map Collection/ Wikipedia (public domain).
Lore of the Queen
In sky lore and in Greek mythology, Cassiopeia was 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.
Her boast angered Poseidon, god of the sea, who sent a sea monster (Cetus the Whale) to ravage the kingdom. To pacify the monster, Cassiopeia’s daughter, Princess Andromeda, was left tied to a rock by the sea. Then, when Cetus was about to devour her, Perseus the Hero happened by on Pegasus the Winged Horse.
Then, 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. Meanwhile, at other times of the 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 she is sometimes called – is upside-down and 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.
Bottom line: The constellation Cassiopeia the Queen has the distinct shape of a W or M. You’ll find her descending in her throne on late northern winter evenings and throughout spring nights.
View original. | The Mars Curiosity rover captured this image of the drill hole in the Cumberland mudstone that it first investigated back in 2013. A new study from NASA suggests the long-chain organic molecules it found in the rock – thought to have likely come from fatty acids and/or alkanes – can’t be explained by non-biological processes alone. Are these organics on Mars evidence of past life? Image via NASA/ JPL-Caltech/ MSSS.
NASA’s Curiosity rover found complex organic molecules on Mars. Scientists think they are the remains of fatty acids. Could ancient life have produced them?
The organics were surprisingly abundant in the mudstone before radiation began to destroy them, a new NASA-led study shows.
Non-biological sources don’t fully explain the abundance and complexity of the organics, the study says. But more work is needed to understand their origin.
Almost a year ago, NASA’s Curiosity rover found something quite intriguing: long-chain organic molecules that scientists said could have come from fatty acids and/or alkanes. Fatty acids are common in life on Earth. Could they be evidence for ancient martian life? That possibility just got another boost from an international team of researchers led by NASA’s Goddard Space Flight Center in Maryland. The researchers said on February 6, 2026, that additional studies of the data from Curiosity show that non-biological sources they had considered don’t fully explain the organics. They conclude, therefore, that a biological source is a reasonable hypothesis.
The paper proposes two possible explanations: hydrothermal synthesis of the molecules or an ancient biosphere of microorganisms.
Curiosity found the complex organics – long-chain fatty acids and/or alkanes – in mudstone rocks in Gale Crater. Curiosity has been exploring this crater since 2012. The crater used to hold a lake or series of lakes billions of years ago.
This still isn’t proof of past life on Mars. But it certainly adds to the growing hints that Mars might have once been home to microbial life (and still could be).
The researchers published their peer-reviewed findings in a new hypothesis paper in the journal Astrobiology on February 4, 2026.
NASA Study: Non-biologic Processes Don't Fully Explain Mars Organicsastrobiology.com/2026/02/nasa… #astrobiology #Mars
NASA first reported the tantalizing finding back in March 2025. The rover found small amounts of the long-chain organic molecules decane, undecane and dodecane in the mudstone samples it analyzed. The samples came from a fine-grained sedimentary mudstone rock nicknamed Cumberland. They were the largest organics that any Mars mission had discovered so far. The rover’s onboard lab analysis suggested they were likely the remains of fatty acids and/or alkanes.
That’s significant, because on Earth, fatty acids are mostly produced by living organisms. Geological process can create them too, though.
NASA’s Curiosity rover found the largest organic molecules on Mars yet. Did ancient life produce them? Video via NASA Goddard.
Rewinding the clock
The researchers wanted to know how much organic material was present in the rock before radiation from the sun destroyed it while hitting the surface. That would provide clues as to whether it was small amounts from sources such as meteorites or dust or larger amounts that would be more difficult to explain without biology.
The researchers used a combination of lab radiation experiments, mathematical modeling and data from Curiosity itself. This allowed them to “rewind the clock” about 80 million years. That’s how long the rock would have been exposed on the martian surface.
View larger. | Graphic depicting the long-chain organic molecules decane, undecane and dodecane. Image via NASA/ Dan Gallagher.
An abundance of organics on Mars
Intriguingly, the results showed the rock had an abundance of the organic molecules before radiation began to destroy them. That is difficult to explain without biology. The press release said:
As the non-biological sources they considered could not fully explain the abundance of organic compounds, it is therefore reasonable to hypothesize that living things could have formed them.
The measured abundance of long-chain alkanes and their possible carboxylic acid precursors found in the ancient Cumberland mudstone in Gale Crater would have been substantially higher before the onset of exposure to ionizing radiation approximately 80 million years ago. Based on recent radiolysis experiments, we estimate conservatively that the Cumberland mudstone would have contained 120–7700 ppm of long-chain alkanes and/or fatty acids before ionizing radiation exposure. Such a high concentration of large organic molecules in martian sedimentary rocks cannot be readily explained by the accretion of organics from carbon-rich interplanetary dust particles and meteorites, nor by the deposition of hypothetical haze-derived organics from an ancient martian atmosphere.
Hydrothermal activity or biology?
The study focuses on two primary possibilities. One is that the organics were formed by hydrothermal activity. However, analysis of the mudstone rock itself showed it had not experienced the high temperatures associated with hydrothermal activity. The researchers also considered serpentinization, a low-temperature metamorphic and hydration process where water reacts with ultramafic, olivine- and pyroxene-rich rocks from the Earth’s mantle, transforming them into serpentinite. But the rover didn’t find any telltale serpentine minerals in the rock. Also, if either of those two processes formed the organics, it must have occurred elsewhere, with water later transporting the organics to the Cumberland location.
It would also imply that there were abundant organics in the surrounding early Noachian (early Mars) rocks of Gale Crater. But only trace amounts have ever been detected so far.
The other, more exciting, possibility is that the organics, such as the former fatty acids, were the products of life, just as most of them on Earth are. The long-chain molecules are suggestive of an ancient martian biosphere of microorganisms. It is hard to assess that, however, because the parameters of the experiments with the Sample Analysis at Mars (SAM) instrument on Curiosity made it difficult to detect both shorter and even longer-chain molecules. Scientists would need to compare them to the known long-chain molecules to more accurately assess their abundance.
View larger. | This Mastcam image from Curiosity shows the drilling target at the Cumberland mudstone on May 15, 2013. Image via NASA/ JPL-Caltech.
More study needed
A lot more study is required to further determine whether these organics really could be evidence of past life. For now, the paper concludes:
We agree with Carl Sagan’s claim that extraordinary claims require extraordinary evidence and understand that any purported detection of life on Mars will necessarily be met with intense scrutiny. In addition, in practice with established norms in the field of astrobiology, we note that the certainty of a life detection beyond Earth will require multiple lines of evidence. Nevertheless, our approach has led us to estimate that the Cumberland mudstone conservatively contained 120–7700 ppm of long-chain alkanes and/or fatty acids before exposure to ionizing radiation. We argue that such high concentrations of long-chain alkanes are inconsistent with a few known abiotic sources of organic molecules on ancient Mars.
To improve the ability to predict the types and concentrations of organic molecules that could have been preserved in ancient sedimentary rocks exposed to ionizing radiation at the martian surface – regardless of their origin – we recommend experimental studies that determine the radiolytic degradation rates of kerogens, alkanes and fatty acids in Cumberland-like Mars analogs under Mars-like conditions.
Bottom line: NASA’s Curiosity rover found complex organics on Mars, possibly remains of fatty acids. A new NASA study suggests they are difficult to explain without life.
View original. | The Mars Curiosity rover captured this image of the drill hole in the Cumberland mudstone that it first investigated back in 2013. A new study from NASA suggests the long-chain organic molecules it found in the rock – thought to have likely come from fatty acids and/or alkanes – can’t be explained by non-biological processes alone. Are these organics on Mars evidence of past life? Image via NASA/ JPL-Caltech/ MSSS.
NASA’s Curiosity rover found complex organic molecules on Mars. Scientists think they are the remains of fatty acids. Could ancient life have produced them?
The organics were surprisingly abundant in the mudstone before radiation began to destroy them, a new NASA-led study shows.
Non-biological sources don’t fully explain the abundance and complexity of the organics, the study says. But more work is needed to understand their origin.
Almost a year ago, NASA’s Curiosity rover found something quite intriguing: long-chain organic molecules that scientists said could have come from fatty acids and/or alkanes. Fatty acids are common in life on Earth. Could they be evidence for ancient martian life? That possibility just got another boost from an international team of researchers led by NASA’s Goddard Space Flight Center in Maryland. The researchers said on February 6, 2026, that additional studies of the data from Curiosity show that non-biological sources they had considered don’t fully explain the organics. They conclude, therefore, that a biological source is a reasonable hypothesis.
The paper proposes two possible explanations: hydrothermal synthesis of the molecules or an ancient biosphere of microorganisms.
Curiosity found the complex organics – long-chain fatty acids and/or alkanes – in mudstone rocks in Gale Crater. Curiosity has been exploring this crater since 2012. The crater used to hold a lake or series of lakes billions of years ago.
This still isn’t proof of past life on Mars. But it certainly adds to the growing hints that Mars might have once been home to microbial life (and still could be).
The researchers published their peer-reviewed findings in a new hypothesis paper in the journal Astrobiology on February 4, 2026.
NASA Study: Non-biologic Processes Don't Fully Explain Mars Organicsastrobiology.com/2026/02/nasa… #astrobiology #Mars
NASA first reported the tantalizing finding back in March 2025. The rover found small amounts of the long-chain organic molecules decane, undecane and dodecane in the mudstone samples it analyzed. The samples came from a fine-grained sedimentary mudstone rock nicknamed Cumberland. They were the largest organics that any Mars mission had discovered so far. The rover’s onboard lab analysis suggested they were likely the remains of fatty acids and/or alkanes.
That’s significant, because on Earth, fatty acids are mostly produced by living organisms. Geological process can create them too, though.
NASA’s Curiosity rover found the largest organic molecules on Mars yet. Did ancient life produce them? Video via NASA Goddard.
Rewinding the clock
The researchers wanted to know how much organic material was present in the rock before radiation from the sun destroyed it while hitting the surface. That would provide clues as to whether it was small amounts from sources such as meteorites or dust or larger amounts that would be more difficult to explain without biology.
The researchers used a combination of lab radiation experiments, mathematical modeling and data from Curiosity itself. This allowed them to “rewind the clock” about 80 million years. That’s how long the rock would have been exposed on the martian surface.
View larger. | Graphic depicting the long-chain organic molecules decane, undecane and dodecane. Image via NASA/ Dan Gallagher.
An abundance of organics on Mars
Intriguingly, the results showed the rock had an abundance of the organic molecules before radiation began to destroy them. That is difficult to explain without biology. The press release said:
As the non-biological sources they considered could not fully explain the abundance of organic compounds, it is therefore reasonable to hypothesize that living things could have formed them.
The measured abundance of long-chain alkanes and their possible carboxylic acid precursors found in the ancient Cumberland mudstone in Gale Crater would have been substantially higher before the onset of exposure to ionizing radiation approximately 80 million years ago. Based on recent radiolysis experiments, we estimate conservatively that the Cumberland mudstone would have contained 120–7700 ppm of long-chain alkanes and/or fatty acids before ionizing radiation exposure. Such a high concentration of large organic molecules in martian sedimentary rocks cannot be readily explained by the accretion of organics from carbon-rich interplanetary dust particles and meteorites, nor by the deposition of hypothetical haze-derived organics from an ancient martian atmosphere.
Hydrothermal activity or biology?
The study focuses on two primary possibilities. One is that the organics were formed by hydrothermal activity. However, analysis of the mudstone rock itself showed it had not experienced the high temperatures associated with hydrothermal activity. The researchers also considered serpentinization, a low-temperature metamorphic and hydration process where water reacts with ultramafic, olivine- and pyroxene-rich rocks from the Earth’s mantle, transforming them into serpentinite. But the rover didn’t find any telltale serpentine minerals in the rock. Also, if either of those two processes formed the organics, it must have occurred elsewhere, with water later transporting the organics to the Cumberland location.
It would also imply that there were abundant organics in the surrounding early Noachian (early Mars) rocks of Gale Crater. But only trace amounts have ever been detected so far.
The other, more exciting, possibility is that the organics, such as the former fatty acids, were the products of life, just as most of them on Earth are. The long-chain molecules are suggestive of an ancient martian biosphere of microorganisms. It is hard to assess that, however, because the parameters of the experiments with the Sample Analysis at Mars (SAM) instrument on Curiosity made it difficult to detect both shorter and even longer-chain molecules. Scientists would need to compare them to the known long-chain molecules to more accurately assess their abundance.
View larger. | This Mastcam image from Curiosity shows the drilling target at the Cumberland mudstone on May 15, 2013. Image via NASA/ JPL-Caltech.
More study needed
A lot more study is required to further determine whether these organics really could be evidence of past life. For now, the paper concludes:
We agree with Carl Sagan’s claim that extraordinary claims require extraordinary evidence and understand that any purported detection of life on Mars will necessarily be met with intense scrutiny. In addition, in practice with established norms in the field of astrobiology, we note that the certainty of a life detection beyond Earth will require multiple lines of evidence. Nevertheless, our approach has led us to estimate that the Cumberland mudstone conservatively contained 120–7700 ppm of long-chain alkanes and/or fatty acids before exposure to ionizing radiation. We argue that such high concentrations of long-chain alkanes are inconsistent with a few known abiotic sources of organic molecules on ancient Mars.
To improve the ability to predict the types and concentrations of organic molecules that could have been preserved in ancient sedimentary rocks exposed to ionizing radiation at the martian surface – regardless of their origin – we recommend experimental studies that determine the radiolytic degradation rates of kerogens, alkanes and fatty acids in Cumberland-like Mars analogs under Mars-like conditions.
Bottom line: NASA’s Curiosity rover found complex organics on Mars, possibly remains of fatty acids. A new NASA study suggests they are difficult to explain without life.
