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The First Interstellar Object Seen Buzzing by Earth Is Pretty Weird

Roughly the size of a football field, the object is roughly 10 times longer than it is wide

Artist's rendering of 'Oumuamua (ESO/M. Kornmesser)
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In October, astronomers announced the first sighting of an object from interstellar space in our solar system. Now, after getting a good look at it astronomers, are proclaiming it a true “oddball.”

First observed by the Pan-STARRS1 telescope on the island of Maui, researchers dubbed the space rock 'Oumuamua, which means “a messenger from afar arriving first” in Hawaiian. They initially classified the space rock as a comet, Michael Greshko at National Geographic reported in October. But they soon realized that unlike comets, the object had no tail or halo of gas and dust. Zipping along at 58,000 miles per hour, it was moving much too fast to be orbiting our sun and likely originated from interstellar space.

Now a new study, published in the journal Nature, shows just how weird the object truly is.

When it was first spotted, the asteroid had already passed the sun and was heading back into interstellar space, so astronomers had to hustle to learn more about the space rock, according to a press release from the European Southern ObservatoryThe ESO’s Very Large Telescope in Chile was able to pinpoint 'Oumuamua as well as the Gemini North and South telescopes, which are located in Hawaii and Chile. The trio tracked 'Oumuamua for three days. 

What they saw is an asteroid unlike our local space rocks. “What we found was a rapidly rotating object, at least the size of a football field, that changed in brightness quite dramatically,” Karen Meech of the University of Hawaii's Institute for Astronomy, who is leading the investigation of the asteroid, says in the Gemini Observatory press release. “This change in brightness hints that 'Oumuamua could be more than 10 times longer than it is wide—something which has never been seen in our own Solar System."

According to the ESO, the asteroid has a dark red color—which likely comes from millions of years of absorbing cosmic radiation—and it has no dust around it. Any ice or liquid water has already dissipated.

Finding out where it came from is harder to pinpoint. Tracking its path backwards, it appears to have originated in the constellation Lyra near the star Vega. But that’s misleading since the stars have shifted their position above the Earth in the 300,000 years it would have taken 'Oumuamua to travel from Vega to our solar system. So researchers still can't be certain where the strange body originated.

Where ever it came from, it will likely help researchers understand the formation of planets and solar systems outside our own, according to the Gemini Observatory. Our own star system tends to eject comets and asteroids that interact with gas giants like Jupiter and Saturn, sending them into interstellar space. Astronomers surmise that other solar systems do the same, sending a shower of rocks like 'Oumuamua into space.

“These observations allow us to reach into another planetary system to learn about one of its rocky bodies, and compare this object with the asteroids we know throughout our own Solar System,” Faith Vilas, solar and planetary research program director at the National Science Foundation says in the Gemini press release.

For astronomers, observing 'Oumuamua is a big deal. “This has been crazy-cool—for the asteroid community, this is as big as the gravitational-wave announcement,” NASA astronomer Joseph Masiero told Greshko in October. “This the first piece of evidence we’ve seen of how planets are built around other stars.”

Hopefully 'Oumuamua is not the last long-distance traveler that wanders through our solar system. The ESO estimates that an interstellar object likely passes through the inner solar system at least once a year. But it’s only since the advent of powerful survey telescopes like Pan-STARRS that we’ve had the ability to pick up the dim, fast-moving specks.

About Jason Daley

Jason Daley is a Madison, Wisconsin-based writer specializing in natural history, science, travel, and the environment. His work has appeared in Discover, Popular Science, Outside, Men’s Journal, and other magazines.

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