Last year, astronomers spotted an object from beyond the stars. There have surely been many interstellar visitors to our humble solar system over the eons, but this is the first one we’ve been able to study as it passed through. ‘Oumuamua is a slender, cigar-shaped comet that could have come from almost any nearby star. However, scientists have pinned down the four most likely origins for ‘Oumuamua.
The scientific community announced the discovery of ‘Oumuamua in late 2017. By that point, it was already on its way out of the solar system after slingshotting around the sun. It entered the solar system going 15.8 miles per second (25.5km/s), and it’s going even faster now. Combined with an orbital eccentricity of 1.20, there’s no doubt it came from another solar system.
The high speed makes it impossible to catch up to ‘Oumuamua, so it’s been difficult to characterize it. Scientists first labeled it a comet, but the lack of a visible coma made everyone think it wasn’t one. Earlier this year, analysis of its path through space confirmed it was outgassing like a comet. It’s just a “mildly active comet.” We also know it’s probably not a spaceship.
Researchers from the Max Planck Institute have used data from the ESA’s Gaia satellite to calculate possible paths for ‘Oumuamua all the way back to nearby stars. The Gaia satellite is a star-mapper with data on some seven million stars. Since stars drift through the cosmos over time, you can’t draw a straight line from ‘Oumuamua to its origin point. However, the team did identify four stars which would have been very close to its path in the last several million years.
All four possible origins are dwarf stars. The one with the closest location and velocity correlation to ‘Oumuamua is HIP 3757. It’s a red dwarf about 81 light years distant. A million years ago, it would have been within two light years of ‘Oumuamua’s path. Next up is HD 292249. It’s a yellow dwarf like the sun and currently sits about 135 light years away. It was within a few light years of ‘Oumuamua’s projected path 3.8 million years ago. The other two stars had potential encounters with ‘Oumuamua 1.1 and 6.3 million years ago, but they didn’t match as closely as the first two.
This analysis is based on the second data set from the Gaia spacecraft. Another release in 2021 should provide velocity data on many more stars, which could lead to a more precise identification of ‘Oumuamua’s origin.