"`Oumuamua 1i 2017 U1" by Interpott.nrw Unser Kosmos / CC BY-SA 4.0

How the first visitor to our Solar System may have formed—no alien technology required

Apr 13, 2020

By Sid Perkins

When ‘Oumuamua swooped into our Solar System in 2017, the object stirred up excitement. The strange shape and trajectory of this first known visitor from interstellar space prompted even some serious scientists to suggest it might be an alien probe. But a new study arrives at a much more mundane explanation.

‘Oumuamua—“scout” or “messenger” in Hawaiian—is about 100 meters long, or slightly longer than a U.S. football field, and at least six times longer than it is wide. The object also didn’t follow a path shaped only by the Sun’s gravitational attraction, which suggests ‘Oumuamua was releasing gas as a comet might, even though observations hint that the object doesn’t have the icy surface expected of a comet.

In a new study, Yun Zhang, an astrophysicist at the Cote d’Azur Observatory, and a colleague used computer simulations to understand how ‘Oumuamua got its strange shape and trajectory by looking at what happens to various orbiting objects if they strayed, Icarus-like, too close to their own sun. For example, if an asteroid, a small rocky body that in our Solar System is often nothing more than a loosely packed pile of rubble, passed within 60 million kilometers of its parent star, it would be stretched and then pulled apart by strong tides, creating a large number of tumbling, elongated fragments. Some of these would be ejected from the solar system into interstellar space, the researchers report today in Nature Astronomy.

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