Our First Interstellar Visitor May Have a Violent Past

Scientists are still puzzling over a mysterious object dubbed ‘Oumuamua detected by the Pan-STARRS (Panoramic Survey Telescope and Rapid Response System) observatory last year. Researchers confirmed that ‘Oumuamua was the first interstellar visitor ever discovered, but it was moving too fast for anyone to get a close look at it. Still, scores of instruments were turned toward the alien asteroid to gather study its size, trajectory, and even check to make sure it wasn’t actually an alien spacecraft (it’s not). Now, a new analysis suggests that ‘Oumuamua may have extremely violent origins.

When it was first discovered, astronomers thought 1I/2017 U1 ‘Oumuamua (as it’s now officially known) would turn out to be a comet. We’d always assumed the first interstellar object would be a comet ejected from the Oort cloud at the very edge of another solar system. ‘Oumuamua turned out to be a rock of truly bizarre measurements. It’s roughly cigar-shaped with a width of about 30 meters and a length of 200 meters. Most asteroids in our solar system are lumpy and potato-shaped.

One of the many observations of ‘Oumuamua occurred at Queen’s University Belfast in Northern Ireland. There, researchers charted the changes in ‘Oumuamua’s brightness over time. In a newly published paper, the team says the data shows ‘Oumuamua isn’t just tumbling but tumbling “chaotically.” That’s another marked difference compared with asteroids native to our solar system, which tend to rotate in an orderly fashion — they have a principal axis of rotation.

The researchers can’t know the cause of ‘Oumuamua’s tumbling, but they speculate it’s the result of the impact that ejected it from its home solar system. It may have been part of a larger object that was splintered, accounting for its unusual shape. A model of ‘Oumuamua based on the Queen’s University data indicates that ‘Oumuamua will continue its chaotic tumbling for billions of years.

The team’s observations also suggest that ‘Oumuamua has a very complex composition. Most of the surface appears to be the color of dirty snow, and there’s a large red spot on one side. This could point to very different conditions in its home solar system, wherever that is.

Research on ‘Oumuamua will continue appearing over the coming months and years, but there won’t be any new data. Our interstellar visitor is already nearing the orbit of Jupiter on its way out of the solar system at 38.3 kilometers per second (23.8 miles per second).