Is interstellar object ‘Oumuamua an alien spacecraft?

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When ‘Oumuamua — a Hawaiian word meaning “a messenger from afar arriving first” — was discovered last year, it became the first object originating beyond our solar system to be observed in our environs.

The discovery caused speculation over whether it was a comet or an asteroid, as it did not develop a halo of gas as it got close to the Sun.


The interstellar object Oumuamua was traveling through space for millions of years before its chance encounter with our star system.M. Kornmesser/European Southern Observatory / NASA

The fact that ‘Oumuamua was too faint for Spitzer to detect sets a limit on the object’s total surface area. However, since the non-detection can’t be used to infer shape, the size limits are presented as what ‘Oumuamua’s diameter would be if it were spherical. Using three separate models that make slightly different assumptions about the object’s composition, Spitzer’s non-detection limited ‘Oumuamua’s “spherical diameter” to 1,440 feet (440 meters), 460 feet (140 meters) or perhaps as little as 320 feet (100 meters). The wide range of results stems from the assumptions about ‘Oumuamua’s composition, which influences how visible (or faint) it would appear to Spitzer were it a particular size.


PHOTO: ‘Oumuamua was first detected by the Pan-STARRS telescope in Hawaii. (Flickr: CharlyWKarl)

Little but Reflective

The new study also suggests that ‘Oumuamua may be up to 10 times more reflective than the comets that reside in our solar system — a surprising result, according to the paper’s authors. Because infrared light is largely heat radiation produced by “warm” objects, it can be used to determine the temperature of a comet or asteroid; in turn, this can be used to determine the reflectivity of the object’s surface — what scientists call albedo. Just as a dark T-shirt in sunlight heats up more quickly than a light one, an object with low reflectivity retains more heat than an object with high reflectivity. So a lower temperature means a higher albedo.

The interstellar object ‘Oumuamua could be a “light-sail” created by an alien civilization. That is the highly speculative conclusion of Shmuel Bialy and Avi Loeb of Harvard University, who say that the unexplained trajectory of the object as it travelled through the solar system could be the result of it being accelerated by sunlight.

Origin

Loeb said that if ası Oumuamua is an asteroid from another star randomly reaching here, then every star in the Milky Way must have about
1015 similar objects associated with him. This number is much higher than a theoretical asteroid calculation conducted by Loeb and his partners ten years ago, suggesting that a natural origin is very low.

Bialy and Loeb said, B He is not the first person to suggest that Oumuamua could be an alien spacecraft. In fact, researchers from the SETI Institute scanned the object for radio emissions, although none was found when they approached the Earth in 2017.

Unfortunately, Oumuamua is now far away from the Earth to work harder, so we can never know its exact nature and source. He says astronomers should scan the sky for other interstellar objects, including possible light sails.

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