Is This Comet the Oldest Thing in the Solar System?

On the discovery of the third interstellar comet

Not a comet, but this a very cool picture of the Cat’s Eye Nebula taken by the James Webb. Image credit: NASA, ESA, CSA, STScI.

Could it be the oldest object in the solar system?

In early July, astronomers announced the discovery of 3I/ATLAS, the third comet known to have entered our solar system from interstellar space. That is rare enough, but then, based on the direction it came from, astronomers announced an even more astonishing possibility. This comet could be, they say, a relic from an ancient solar system, and might have formed billions of years before our sun was born.

3I/ATLAS is currently close to the orbit of Jupiter. But it is travelling fast, moving at over two hundred thousand kilometres per hour. By October, it will have crossed the orbit of Mars, and will then make its closest approach to our star. The Earth, at that point, will be situated on the other side of the Sun. 3I/ATLAS will not be visible then, but afterwards, for a few weeks in November and December, it should be bright for small telescopes to pick it out.

Sadly, it will never shine strongly enough for the naked eye to see it. Yet, as the comet will pass fairly close to Mars, there is some possibility that our armada of probes and orbiters around the Red Planet might be able to see it. After December, however, it will be gone, fading as it once…