ESO ‘Oumuamua
This artist rendering shows the highly unusual ‘Oumuamua interstellar asteroid. ESO

Our solar system has a visitor, researchers announced new details Monday about the first interstellar asteroid that was discovered back in October. The asteroid, named 1I/2017 U1 or 'Oumuamua, was first detected by the Pan-STARRS 1 telescope in Hawaii, according to a release from the European Southern Observatory. The telescope detected a faint light traveling across the sky and additional observations showed that the asteroid was different from others in our system, it was from interstellar space.

When it was detected it had already passed the sun and was heading back away from it out to interstellar space, so the researchers had to work within constrained time. To conduct the further investigation on the asteroid, the researchers involved use the Very Large Telescope in Chile, the highly advanced visible light observatory.

The observations made by the VLT proved to researchers that 'Oumuamua was unique for reasons other than the fact that it originated in interstellar space. The asteroid has a number of other qualities that set it apart from usual asteroids. For instance, it varies in brightness “dramatically,” according to ESO, by a factor of ten to be exact. It also spins on its own axis every 7.3 hours.

That variation in brightness means that the object is very elongated, Karen Meech, the lead astronomer on the team that studied the asteroid told ESO. It’s likely about 10 times as long as it is wide, and at most, it’s about a quarter of a mile long. The longest known objects in the solar system currently are no more than three times as long as they are wide.

The anomalies don’t stop there, the asteroid also has a dark red color and lacks any dust around it like many asteroid have. All of these features indicate that the asteroid is fairly dense and rocky or has a high metal content and has very little water or ice if any, according to ESO.

Where the asteroid originated from is unclear, it’s traveled so far that it could have been unattached to any specific star system for thousands of years. 'Oumuamua appears to have come from the general current direction of the star Vega, but when the asteroid was in that part of space, about 300,000 years ago, Vega wasn’t there yet.

While asteroids from interstellar space are rare, astronomers estimate that one passes through the inner solar system every year or so, according to the ESO. But they’re hard to detect and until recently telescopes weren’t strong enough to detect them.