Published: Fri, November 09, 2018
Sci-tech | By Patricia Wade

A new "alien spacecraft" paper poses a challenge for astrophysicists

A new

If Oumuamua is a lightsail, he added, one possibility is that it was floating in interstellar space when our solar system ran into it, "like a ship bumping into a buoy on the surface of the ocean".

Scientists have been trying to figure out what the 1,312ft (400m) object named Oumuamua might be after it was first spotted by a telescope in Hawaii in October 2017 . 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.

Earlier this week, researchers from Harvard suggested it "may be a fully operational probe sent intentionally to Earth vicinity by an alien civilisation".

In June 2018, Marco Micheli of the European Space Agency and colleagues showed that the trajectory of the object through the solar system can not be explained exclusively by the gravitational attraction of the Sun, planets and large asteroids. "It's already a known phenomenon that when radiation hits an object, it can cause acceleration", says Bialy. But 'Oumuamua didn't have a "coma", the atmosphere and dust that surrounds comets as they melt. Loeb says that astronomers should be scanning the sky for other interstellar objects, including possible light-sails.

Since its discovery, scientists have been at odds to explain its unusual features and precise origins, with researchers first calling it a comet and then an asteroid before finally deeming it the first of its kind: a new class of "interstellar objects".

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"Like most scientists, I would love there to be convincing evidence of alien life, but this isn't it", said Dr Alan Fitzsimmons of Queens University Belfast. "Some of the arguments in their study are based on numbers that contain a lot of uncertainty".

The Harvard researchers say that Oumuamua could be a solar light sail, created to be carried along by the solar wind.

Katie Mack, a well-known astrophysicist at North Carolina State, also took issue with the alien hype.

"The thing you have to understand is: scientists are perfectly happy to publish an outlandish idea if it has even the tiniest *sliver* of a chance of not being wrong".

"It is impossible to guess the goal behind Oumuamua without more data", Loeb was quoted as saying.

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