A visitor from far beyond the solar system is getting better acquainted with the Sun this week. Tomorrow, it’ll make its closest approach to the Sun – just 126 million miles. After that, it’ll head back toward interstellar space.

The visitor is 3I/ATLAS. It was discovered on July 1st by an automated telescope that looks for comets and asteroids. Calculations of its orbit quickly showed that it came from outside the solar system. That makes it the third known visitor from interstellar space.

It originated in the galaxy’s “thick disk.” That’s a region that sandwiches our part of the disk. It contains stars that are far older than the Sun. Estimates say 3I/ATLAS could be three billion years older than the solar system, so it could preserve a chemical record of an earlier era in galactic history.

3I/ATLAS is a comet – a ball of rock and frozen gases a few miles in diameter. As it’s closed in on the Sun, some of its gas has vaporized, releasing bits of dust as well. Observations will reveal the composition of this material, telling astronomers about conditions in the region where it formed.

Unfortunately, astronomers can’t see 3I/ATLAS at all right now – it’s hidden in the Sun’s glare. It’ll return to view in December – but only when viewed through a telescope. It’ll pass closest to Earth on December 19th – almost 170 million miles away.

Script by Damond Benningfield