A mystery interstellar object discovered last week is likely to be the oldest comet ever seen—possibly predating our solar system by more than 3 billion years, researchers say.

I/ATLAS isn't just fascinating because it is the third interstellar visitor found in the solar system; new research suggests it's also the oldest comet ever seen, at over 7 billion years old.

The ATLAS (short for Asteroid Terrestrial-impact Last Alert System) is a NASA-funded program developed by the University of Hawaii. It incorporates data from four ground-based telescopes, two in Hawaii, one in Chile, and one in South Africa, to scan the entire sky twice a night, looking for asteroids and other impactors.