It has been several months since ‘Oumuamua’s discovery, but scientists are still puzzling over our first interstellar visitor. We’ve determined a few important facts, like it’s not an alien spaceship and it’s sort of cigar-shaped. Bigger questions like where it started out and how it got to our solar system are still up in the air. Researchers from NASA’s Goddard Space Flight Center have used ‘Oumuamua’s composition to speculate on how it left its home system.
It was Oct. 17 of last year when astronomers at the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS1) facility spotted what they believed to be a new comet. The object we would eventually come to know as ‘Oumuamua was already rocketing out of the solar system at more than 196,000 mph (315,400 km/h). It also had an orbital eccentricity of 1.20. It was unmistakably alien to our solar system, but it didn’t look like we expected.
Astronomers were wrong when they initially labeled ‘Oumuamua as a comet. Upon closer observation, there was no coma of evaporating ice and dust around the object. So, it was an interstellar asteroid. This unexpected revelation is what the Goddard team is considering in the new study.
Based on what we know about planetary formation, icy comets accumulate toward the outer edge of a system like our Oort Cloud. They won’t last long toward the inner solar system because they’d just evaporate. It’s much easier to eject an object far from a star than one orbiting closer, so scientists always believed our first confirmed interstellar visitors would be comets. However, ‘Oumuamua appears to be inner solar system material. So, what gives?
According to the Goddard team, there may be something wrong with our models of planetary formation if most interstellar objects are rocky like ‘Oumuamua. We only have a sample size of one so far, so it’s hard to know for certain.
In the case of ‘Oumuamua, the team suggests an encounter with a gas giant is the most plausible explanation for its arrival in our neck of the galaxy. A planet the size of Jupiter would be able to fling an object like ‘Oumuamua (between 30 and 180 meters in length) out of its home system with a gravity slingshot. Scientists around the world will be on the lookout for more objects from beyond the stars. If too many of them turn out to look like ‘Oumuamua, we may have to reevaluate theories on solar system formation.
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