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The mysterious interstellar traveler we saw soar through our solar system two years ago — 'Oumuamua — could be alien technology, according to a recent paper published in The Astrophysical Journal Letters.
RELATED: NASA UNVEILS RESULTS OF STUDY ON INTERSTELLAR 'OUMUAMUA NOW 'GONE FOREVER'
Cosmic visitor 'Oumuamua could be alien technology, after all
The alternative explanation for the identity of the 'Oumuamua visitor — that it was some non-alien, naturally-formed body — could be inherently wrong, according to the new study.
However, most scientists think the idea of an alien origin is an unlikely hypothesis, reports Space.com.
In 2018, an interstellar object moved through our solar system. Dubbed 'Oumuamua, it had an unconventional shape — long and thin, like a colossal cigar in space, it tumbled like a football through our planetary neighborhood.
When scientists looked closer, they discovered it was accelerating — as if an external force were applied — baffling everyone.
'Oumuamua may have moved with alien technology
One hypothesis for the object's passage through our solar system suggests it was propelled via alien technology — like a lightsail, which is a wide yet millimeter-thin machine that accelerates from the force of solar radiation. Harvard University Astrophysicist Avi Loeb was the primary proponent of this idea.
However, most in the scientific community think 'Oumuamua accelerated because of natural forces. In June, a research team argued that hydrogen was blasting invisibly off of the interstellar object's surface, moving it faster and faster.
Non-alien hydrogen propellent theory not up to snuff
The recent paper from Loeb and Thiem Hoang — an astrophysicist from the Korea Astronomy and Space Science Institute — argue that the hydrogen propellent idea doesn't work in the real world. If they're right, this means the possibility of alien technology making its way through our solar system might be a reality, after all.
Not only that — but it could also mean we saw alien technology for the first time.
The issue with 'Oumuamua is that it traversed our solar system like a comet, but lacked the classic coma (or tail) we typically see on comets, said Darryl Seligman, an astrophysicist and author of the solid hydrogen hypothesis — at present starting a postdoctoral fellowship in astrophysics at the University of Chicago, to Space.com.
Lack of comet coma baffles scientists
The first interstellar object ever seen flying through our solar system, 'Oumuamua was different than most objects in our system — which typically orbit the sun, and never escape. The cigar-shaped object's accelerating path suggested 'Oumuamua — roughly 1,300 to 2,600 ft (400 to 800 m) long — was a comet.
However, "there was no coma or outgassing detected coming from the object," said Seligman, reports Space.com. Typically, comets come from a place farther away than asteroids, and surface ice evaporates directly to gas as soon as they near the sun — leaving a trail of gas that we usually associate with comet's tails, Seligman told Space.com.
This outgassing process in turn alters the trajectory of the comet, like a slow rocket engine, Seligman added. The sun warms the comet, and the hottest parts burst with gas. As it shoots away from the comet, the whole object is accelerated in the opposite direction.
Depending on which part of the object emits gas, this process can send the comet tumbling faster and faster, away from the sun.
Hydrogen propellant hypothesis for 'Oumuamua
The hydrogen hypothesis came to light in a June 9 paper from The Astrophysical Journal Letters, in which Seligman and Gregory Laughlin (Yale astrophysicist) proposed the comet consists either partly or entirely of molecular hydrogen, which are lightweight molecules containing two hydrogen atoms (H2).
The H2 gas freezes into a low-density solid at extremely low temperatures — minus 434.45ºF (minus 259.14ºC, only 14.01 degrees higher than absolute zero) under sea-level atmospheric pressure. As of publishing, researchers had already proposed the existence of "hydrogen icebergs" way out in the coldest fathoms of deep space, according to Seligman and Laughlin's study.
Outgassing hydrogen from such bodies wouldn't be visible to Earth-bound observers, which means we would see nothing, where something was, in fact, there.
'Oumuamua would not exist if hydrogen hypothesis is true
However, in the more recent paper from Hoang and Loeb, this idea was criticized on the grounds of a basic issue: comets form when icy grains of dust collide in space, amassing into larger clumps that again combine like multiple snowballs until the comet is complete. This goes on until the comet melts.
Hoang and Loeb argued that even ambient starlight in the coldest reaches of space could warm small chunks of solid hydrogen before they can clump together to form a comet the size of 'Oumuamua (which is big). Notably, the trek from the nearest "giant molecular cloud" — gassy and dust-ridden regions of space where hydrogen icebergs probably come to be — is way too far away.
Hydrogen icebergs moving hundreds of millions of years through interstellar space will be ripped apart, fried in ambient starlight.
As the 'Oumuamua mystery shifts hues once again from mundane to interesting, it seems the universe is never lacking in intrigue and suspense, as the scientific community studies the night sky for signs of intelligent life beyond Earth.