Space photo of the day: Brilliant comet shines at sunset over observatory in Chile
A brilliant comet lights up the night sky over Chile's Atacama Desert in this stunning image captured by a photographer with the European Southern Observatory in January 2025.
What you're seeing here is the Great Comet C/2024 G3 (ATLAS), a comet discovered in 2024 that lit up the night sky late in that year and early 2025, and was the brightest comet in 18 years when it was visible to stargazers throughout January 2025. The comet was first discovered in April 2024 by the Asteroid Terrestrial-impact Last Alert System (or ATLAS) using a nearly 20-inch (0.5 meters) telescope in Rio Hurtado, Chile. It soon became one of the most anticipated skywatching targets of early 2025.
For several days in January, it was visible to the unaided eye for stargazers with clear and dark skies, was even visible in the daytime, a rarity among comets.
This image shows comet C/2024 G3 (ATLAS) from the European Southern Observatory near its Very Large Telescope (which is visible on the mountaintop of Cerro Paranal at left) as seen by ESO photographer Florentin Millour on Jan. 21, 2025. ESO shared the image to the public today, March 17.
ESO's observatories in Chile's Atacama Desert operate under extremely dark conditions. Unlike in the Northern Hemisphere, where the comet was only visible for a short week, it was visible for much longer in the Southern Hemisphere, home to ESO and other observatories.
Comets that are visible to the unaided eye are an extremely exciting sight. They are icy wanderers from the outer solar system left over from the formation of the sun its planets, including Earth.
Because comets like C/2024 G3 (ATLAS) are made mostly of water ice, as they approach the inner solar system, that ice sublimates into a gas as it nears the sun to create a vast, willowy tail. In Millour's photo, you can see that tail blowing out, away from the sun just after sunset, from the comet's head (called the nucleus) on the horizon. The solar wind also blows ions of the comet, creating second ion tail.
The fact that C/2024 G3 (ATLAS) was briefly visible during daytime hours is a rare sight indeed. Even astronauts in space observed the comet!
If you're looking to learn more, check out our feature on the discovery of comet C/2024 G3 (ATLAS) by skywatching columnist Joe Rao. He also has this retrospective on C/2024 G3 (ATLAS) that explains why it will go down as one of the great comets of the 21st century.
We also have a deep guide on how comets work, as well as a guide on how to observe and photograph comets in the night sky.
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