The thick disk is a band of our galaxy’s most ancient stars that sandwiches the thin disk, which formed more recently and contains our relatively young star, the sun, and the solar system.

“This is an object from a part of the galaxy we’ve never seen up close before,” University of Oxford astrophysicist Chris Lintott said. “We think there’s a two-thirds chance this comet is older than the solar system, and that it’s been drifting through interstellar space ever since.”

If 3I/ATLAS originates from the Milky Way’s thick stellar disk, and thus formed around an ancient star, this also has implications for its chemical composition. Hopkins and crew suggest the interstellar interloper may be rich in water ice.