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Why some scientists saw asteroid Oumuamua as ET

Could 'Oumuamua be an extra-terrestrial solar sail?
Artist’s impression of interstellar asteroid/comet, Oumuamua /ESO, M. Kornmesser

We are always looking for evidence that we are not alone. Remember when Oumuamua was characterized as an extraterrestrial light sail? It is now in Saturn’s orbit and public attention is fading but an astrophysicist reflects on why some thought Oumuamua was ET:

Telescopes like Pan-STARRS on Haleakalā in Hawaii, with the ability to detect objects like ‘Oumuamua, have been operational only in the past decade. Some calculations suggest that the natural ejection of asteroids from other solar systems should be too rare for us to happen to spot even one interstellar asteroid in the few years since we’ve gained the ability to see them. The velocity of ‘Oumuamua when it entered the solar system is also unusual and in some sense too slow to easily reconcile with ejection from another stellar system. ‘Oumuamua’s shape is more elongated than any solar system object, a challenge to explain. ‘Oumuamua put off no detectable infrared radiation, implying it is very small; some calculations suggest it would have to be unusually reflective to be seen at all. Strangest of all is the fact that ‘Oumuamua is not simply orbiting the sun on a ballistic trajectory—it is receiving small but definite thrusts. Comets receive thrusts, too, as ice sublimates on their surfaces and shoots off as gas, like a rocket. But no gases or dust were detected around ‘Oumuamua. Loeb and colleagues suggest it is responding to sunlight in the same way as an advanced spacecraft design called a solar sail, using the sun’s radiation like a sailboat uses the wind. Steve Desch, “The Anthropomorphization of the Universe” at Slate

Then it all fell apart. Never mind, SETI. ET will always be Out There.

See also: Astronomers: Solar System Object In Transit, Oumuamua, Might Be A “Light Sail Of Extra-Terrestrial Origin”

Astrophysicist: Climate Change Killed The ET Civilizations

SETI finds more creative ways to keep looking. As long as there’s an Out There, They’ll always be Out There, of course.

SETI reacts to the study that says not to wait up for the extraterrestrials

Researchers: We have dissolved the Fermi Paradox!

Extraterrestrial civilizations: When all else fails, try Bayesianism. The good news is, no one can ever prove They’re Not Out There.


How do we grapple with the idea that ET might not be out there?

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