Interstellar Interloper ‘Oumuamua may have been an Extraterrestrial Spacecraft, according to Harvard Astronomers
A controversial paper has been published by astronomers at Harvard University that suggests that that the odd behavior being exhibited by the interstellar object known as ‘Oumuamua might actually be an artificial object that was built by an extraterrestrial civilization in the form of a solar-powered "lightsail".
First spotted in October 2017, ‘Oumuamuawas at first thought to be a comet, due to its highly-elongated orbit, but it was soon reclassified as an asteroid after it was found to lack a coma and tail that would distinguish it as a comet. As astronomers refined their understanding of the object’s orbital path, they soon realized that it couldn’t have originated from our solar system, making ‘Oumuamua, a Hawaiian word meaning "first distant messenger", our first confirmed interstellar visitor. Further study of the object also revealed that it was cigar-shaped, being at least ten times as long as it was wide, and deep red in color.
But ‘Oumuamua’s litany of surprises didn’t end there: after it made its close pass to the Sun, the strange object didn’t slow down as astronomers expected, pulled back by the Sun’s gravity as most objects would be: instead, it actually sped up slightly, travelling at about a tenth of a percent faster than what was expected. Astronomers initially speculated that this was due to an outgasing event, something seen in comets as they are heated by the Sun, turning the object’s surface into an ad-hoc rocket that provides a gentle push on its sunward side. But no tail of gases was seen emanating from ‘Oumuamua, and the object’s rotation didn’t change, something that would be expected from its surface being heated unevenly.
‘Oumuamua’s behavior simply didn’t match what would be expected from a natural object.
Intrigued by the mystery, Avi Loeb, chair of Harvard’s Astronomy Department, sought to find an explanation for what was behind ‘Oumuamua’s odd behavior. Along with postdoctoral fellow Shmuel Bialy, Loeb began investigating the possibility that the enigmatic object might very well be solar powered — an explanation that would fit the evidence we have so far — such as a solar sail, something that would have to have been constructed by an extraterrestrial civilization.
"When I first heard about ‘Oumuamua, this idea was in the back of my mind," Loeb explains. "So I approached Shmuel and said, ‘Let’s see whether sunlight can push this’… because there was nothing else I could think of which could account for our observations, because this object is weird. So, my approach was to follow the maxim of Sherlock Homes — ‘When you have excluded the impossible, whatever remains, however improbable, must be the truth.’"
In their paper published in Astrophysical Journal, Loeb and Bialy calculated what characteristics ‘Oumuamua would have to have to have to been accelerated in the manner that was observed. But their numbers revealed that the object would have to have be much smaller than the 500 meters long by 40 meters wide (1,640 by 131 feet) that it is estimated to be: instead, they found it would have to be reduced down to dimensions less than 20 meters (67 feet) in diameter, and less than a millimeter (0.04 inches) thick.
Loeb and Bialy posit instead that, instead of being a naturally-occurring object, ‘Oumuamua might be either debris from a defunct spacecraft, adrift through the cosmos, or a reconnaissance probe deliberately sent to our star by an extraterrestrial civilization.
"It’s possible that, once a civilization reaches a certain maturity technologically, that this is a very common technological solution," according to Loeb. "A rocket is limited to a certain speed… because you are carrying the fuel with you. But if you are using light to push yourself, you’re not limited in the same way."
‘Oumuamua’s fast pace took it out of the range of our telescopes earlier this year, and with an interstellar speed of 87.71 kilometers per second (54.5 miles per second) it will sail past past Neptune’s orbit in 2022. But Loeb expects that we may one day see more interstellar visitors like ‘Oumuamua, and hopefully those new interlopers will offer new insights into the mystery our distant messenger provided us with.
"It may well be that it’s a natural object, and if it is, I would argue that it has so many peculiar features that we should understand where it comes from, and we will learn something new from it," Loeb said. "But until then, all possibilities should be on the table."
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