A billion-year journey from another star system to our own
In short: For a brief window in 2025, Earth's most powerful telescopes turned toward a visitor from the deep void. Comet 3I/ATLAS is not a local resident; it is an interstellar traveler carrying secrets from a solar system we have never seen.
Discovered on July 1, 2025, by the ATLAS survey telescope in Chile, 3I/ATLAS is only the third known interstellar object ever observed. It follows the path of 1I/ʻOumuamua and 2I/Borisov. Unlike local comets that follow closed orbits around our Sun, 3I/ATLAS moves on a hyperbolic trajectory, meaning it originated from outside our solar system and will eventually leave it forever.
The object is characterized as an icy body releasing dust and gas, creating tails of charged particles. Its extreme speed—roughly 250,000 km/h at its closest approach to the Sun—suggests it is billions of years old, having drifted through the vacuum of space for eons before entering our celestial neighborhood. This makes it a 'true outsider,' providing a rare chemical and physical snapshot of world formation in a distant star system.
While it captured global attention, 3I/ATLAS posed no threat to Earth. On 19 December 2025, the object neared our world at approximately 270 million kilometres (which equals nearly 1.8 times the gap between the Sun and Earth). Because it passed so close to the Sun in late October 2025, it became invisible to ground-based telescopes for a period before reappearing in early December for renewed study.
The naming convention reflects its unique status: 'I' stands for interstellar, '3' marks its sequence as the third such discovery, and 'ATLAS' credits the program that first spotted it. Scientists continue to use data from NASA's Hubble Space Telescope and various orbiters to investigate its physical properties and size.
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Sources
- Summary by Intellect · source: What The News Should Have Told You About 3I Atlas
- Also: Comet 3I/ATLAS - NASA Science
- Also: Comet 3I/ATLAS – frequently asked questions
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