Astronomers Spot a 7-Billion-Year-Old Comet From Beyond the Solar System
Astronomers have their eyes on a mysterious object zipping through the Solar System, and if their hunch is right, it could be the oldest visitor humanity has ever observed.
Comet 31/ATLAS, first detected on July 1, has been identified as only the third confirmed interstellar object to pass through our solar neighborhood.
But what sets this icy traveler apart isn’t just its origins. It’s the staggering possibility that it may be 7 billion years old. That would make 31/ATLAS older than the Solar System itself.
Researchers believe the comet may have formed in the thick disk of the Milky Way, a region populated by some of the galaxy’s oldest stars. Unlike most comets, which are leftovers from the formation of nearby star systems, this one likely wandered the galaxy for billions of years before crossing paths with us.
If that’s true, 31/ATLAS could give scientists a rare glimpse into how the early Milky Way, and maybe even planetary systems, came together.
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While its exact origin remains unknown, researchers at the Royal Astronomical Society’s 2025 National Astronomy Meeting presented evidence showing the comet’s speed and orbit suggest an ancient, interstellar origin. They used data from ESA’s Gaia satellite to simulate the comet’s possible journey across the galaxy, analyzing the movements of over a billion stars to back up their findings.
Unlike its infamous predecessor ‘Oumuamua, which sparked alien theories back in 2017, or the comet 2I/Borisov spotted in 2019, 31/ATLAS appears to have been a frozen planetesimal—one of the original building blocks of planets.
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However, how it got here and why it’s moving the way it is remain open questions. Scientists hope further observations will reveal whether 31/ATLAS contains particles from some of the earliest stars in the galaxy, essentially making it a cosmic time capsule.
For now, the icy wanderer continues its journey past the Sun, carrying billions of years of galactic history along for the ride.
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