Introduction to the Oldest Comet
A mysterious interstellar object discovered by British astronomers is likely the oldest comet that has ever been seen. The "water-rich" visitor, named 3i/Atlas, is the first object to reach us from a completely different region of our galaxy.
Origin and Age
Only two other objects have entered our solar system from elsewhere. In contrast to its predecessors, 3i/Atlas seems to travel on a steep path that indicates it comes from the "thick disc" of the Milky Way, an area of old stars that circle above and below the thin level where most stars are located. According to researcher Matthew Hopkins, all non-interlocking comets, such as Halley’s Comet, which were formed with our solar system, are up to 4.5 billion years old. However, interstellar visitors have the potential to be far older, and statistical methods suggest that 3i/Atlas is very likely the oldest comet we have ever seen.
Estimated Age and Discovery
3i/Atlas could be about three billion years older than our solar system. It was first discovered on July 1, 2025, by the Atlas survey telescope in Chile when it was about 670 million kilometers from the sun. The Earth is 149 million km from the sun.
Visibility and Observation
When 3i/Atlas gets closer to the sun, the sunlight heats its surface and triggers the outgassing of steam and dust that creates the bright tail of a comet. Members of the public could be able to take a look at 3i/Atlas in the coming months, as researchers say it should be visible in late 2025 and early 2026 with adequate amateur telescopes.
Significance and Research
Professor Chris Lintott, co-author of the study, said, "This is an object from a part of the galaxy that we have never seen nearby. We believe there is a two-thirds chance that this comet is older than the solar system and has been traveling through interstellar space since then." The discovery of 3i/Atlas provides a unique opportunity for researchers to study an object from a distant region of the galaxy, offering insomnia into the formation and evolution of our solar system and beyond.
