A very old visitor
The interstellar comet 3I/Atlas, the third object from beyond our Solar System ever spotted passing through it, may be nearly 12 billion years old. That would make it only slightly younger than the Milky Way, which formed about 13 billion years ago. In other words, the comet may be so ancient that the star system where it was born no longer exists. Cosmology does enjoy a dramatic reveal.
The finding comes from a study led by NASA’s Goddard Space Flight Center and currently posted on arXiv, where scientific papers go before the wider community has had a chance to pick them apart. The work also includes participation from the Near-Earth Object Coordination Centre (Neocc) in Frascati, near Rome, the European Space Agency unit that tracks asteroids and other objects and assesses whether they pose any risk to Earth.
Why researchers think it is older than first estimated
A previous study published in The Astrophysical Journal Letters had used the comet’s high speed, about 58 kilometers per second, to estimate an age somewhere between 3 billion and 11 billion years. That was a wide range, which is a polite scientific way of saying “we are not entirely sure.”
The new work, led by Martin Cordiner, narrows the estimate toward the older end of that spectrum.
What they looked at
The researchers based their conclusion on the comet’s chemical composition, focusing in particular on the presence of specific isotopes of carbon and hydrogen. Isotopes are atoms of the same element with the same number of protons but a different number of neutrons in the nucleus.
To do this, they used data gathered by the James Webb Space Telescope, a joint mission involving NASA, ESA and the Canadian Space Agency. Those observations suggest that 3I/Atlas formed in a part of the galaxy far from our own region and did so a very long time ago, during the early history of the Milky Way.
What it could tell us
If the analysis holds up, 3I/Atlas may be a relic of one of the first planetary systems in our galaxy. That would make it more than just a rare interstellar passerby. It could preserve clues about ancient planets and the environment in which the earliest systems formed.
For now, the comet remains a remote and unusually old messenger from a part of the galaxy we do not get to visit, at least not yet, and probably not with current budgets.
