Our Third Interstellar Visitor Might Be 8 Billion Years Old

The interstellar entities currently traversing our solar system may include one of the oldest comets ever observed.

Comet 3I/Atlas was identified earlier this month near Jupiter’s orbit, moving at approximately 60 km per second and estimated to be about 20 km in size. It is the third recognized interstellar object in our solar system, having passed near Mars in October before entering the solar orbit.

Matthew Hopkins from Oxford University and his team utilized data from the ESA Gaia spacecraft, which cataloged billions of stars in our galaxy, to simulate the comet’s speed and trajectory, revealing its point of origin. It seems to have emerged from an area close to our galaxy, which is about 13 billion years old, specifically from what is referred to as a thick disk.

“Objects from the thicker disk tend to be quicker,” explains Hopkins, noting that the previous two identified interstellar objects (Oumuamua in 2017 and Comet Borisov in 2019) exhibited a decline in speed. “Their velocities aligned with expectations for thin disk objects.”

Modeling by the team indicates that 3I/Atlas may have originated from a star nearly 8 billion years old, potentially twice the age of our sun, hinting at it being one of the oldest comets ever witnessed. “This might be the oldest comet I’ve encountered,” Hopkins states. Interstellar objects are typically ejected early during a star’s lifecycle and are often propelled by interactions with massive planets.

Hopkins mentioned that ancient stars are likely to possess lower metallicity compared to our sun, implying that these comets might have a higher water content. If this hypothesis holds, we may witness significant water activity from the comet as it nears the sun in the upcoming months.

This could be our first interaction with another star, providing insights into pristine materials that have existed for billions of years, unaltered since before Earth’s formation. “I believe many interstellar objects we’ve encountered are our first meetings with stars, even those that are 8 billion years old,” Hopkins asserts. “They have likely traversed vast distances through empty space before approaching us.”