Although the first known interstellar object to pass through our Solar System has long since passed beyond our reach, the Harvard astrophysicist that first proposed that ʻOumuamua might have been an artificial object built by an extraterrestrial civilization has expanded on the concept. In an interview with Salon magazine about his new book Extraterrestrial: The First Sign of Intelligent Life Beyond Earth, astrophysicist Avi Loeb outlined the various attributes exhibited by the strange visitor that point toward a manufactured origin, such as its odd motion that includes a similarity to that of known artificial objects, and the high possibility that ʻOumuamua might be disk-shaped, rather than cigar-shaped, as is commonly believed.
First spotted in October 2017, ʻOumuamua was 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 ʻOumuamua, a Hawaiian word meaning “first distant messenger”, our first confirmed interstellar visitor. Further study of the object also revealed that it appeared to be cigar-shaped, being at least ten times as long as it was wide, and deep red in color.
But instead of slowing down after hooking its way around the Sun after being drug back by our home star’s gravitational pull, ʻOumuamua actually sped up slightly, travelling 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 ʻOumuamua, and the object’s rotation didn’t change, something that would be expected from its surface being heated unevenly.
ʻOumuamua’s behavior simply didn’t match what would be expected from a natural object, prompting Loeb, then-chair of Harvard’s Astronomy Department, along with postdoctoral fellow Shmuel Bialy, to publish a paper that speculated on the possibility that ʻOumuamua might have been an artificial solar-powered artifact, such as a solar sail.
While the idea of a solar sail doesn’t fit the cigar-shaped visage commonly attributed to our interstellar visitor, one has to bear in mind that the pictures of ʻOumuamua widely circulated in media are just an artist’s depiction of what astronomers think the object looks like; in reality, direct observations of the strange messenger appeared solely as a single pixel captured by observatories—remember, ʻOumuamua is only somewhere between 100 to 1,000 meters (328 to 3,280 feet) long and only one-tenth as wide; even at its closest approach to Earth of 14.4 million km (8.9 million miles), that’s an extremely tiny object for even the most powerful of telescopes to spot.
Since a detailed direct observation was impossible, astronomers extrapolated ʻOumuamua’s elongated cigar shape from its marked change in brightness as it completed its 8-hour rotation, described as more of a tumble by the researchers. But a cigar-shaped scenario was only one of the possibilities, considered the most likely by ʻOumuamua’s observers, with the idea of the object instead being disk or pancake-shaped also being considered as a possibility.
According to Loeb, this pancake-shaped theory supports his idea of ʻOumuamua being the derelict product of an extraterrestrial civilization, since a solar sail would also be broad and thin in appearance.
“The most likely model that explains the reflective sunlight as a function of time—as it was doubling every eight hours—was that it has a flat, pancake-like geometry, not cigar-shaped the way it was depicted in some cartoons.”
Loeb also cites the recent observation of another object getting a similar boost from its exposure to sunlight, that of a Centaur rocket booster left over from 1966’s Surveyor 2 lunar lander mission. Initially labeled 2020-SO after its discovery in September of last year, the object was later identified as part of the discarded vehicle, its orbit having been traced back to Earth at the time of the mission’s launch.
According to Loeb, the derelict rocket “also showed an excessive push, because it’s a hollow rocket booster that is very thin and pushed by sunlight. We know that it’s artificially made. It had no cometary tail. We know that we made it. So that provides evidence that we can tell the difference between a rock and an object that is pushed by sunlight. To me, it demonstrated the case that perhaps ʻOumuamua was artificial, definitely not made by us.”
Another odd observation made regarding ʻOumuamua was that the frame of reference for its movement through space matched what is known as the Local Standard of Rest, meaning that the object’s motion through the galaxy matched the rotation of the galactic disk, rather than the motions of the stars in our immediate galactic neighborhood. If ʻOumuamua was a once-operational spacecraft, was it en route between the stars when it stopped functioning?
“Only one in 500 stars is so much addressed relative to that frame as ʻOumuamua was,” Loeb explains, and in the process offering odds that it would have been ejected from a star system naturally, as opposed to being piloted through the interstellar medium. “So it was just like a buoy sitting on the surface of the ocean and then the solar system is like a giant ship bumping into it.”
Loeb admits that there is simply not enough data to positively determine whether or not ʻOumuamua was artificial or natural in origin, due to the extremely limited time scientists had to collect data on the object as it whizzed by the Solar System. But he feels that the rejection of the idea that ʻOumuamua might have been produced by an extraterrestrial civilization signals a broader failure in regards to the scientific community’s attitudes toward cutting-edge concepts, especially in light of the theories attempting to explain ʻOumuamua as a natural phenomenon failing to fully account for the object’s strange behavior.
Loeb says that “the way to make progress is not to stick to your notions and maintain a prejudice. Of course that’s a self-fulfilling prophecy. If you say I don’t need to search, I know the answer, I don’t need to look through Galileo’s telescope, of course it’s a self-fulfilling prophecy. You will never find that you’re wrong because you bully people that will do this kind of search, and you don’t fund the research in that direction. It’s like stepping on the grass and saying look it doesn’t grow.
“Science is not about that, science is about finding the truth.
- This artist’s impression shows the first interstellar object discovered in the Solar System, `Oumuamua. Observations made with ESO’s Very Large Telescope, the NASA/ESA Hubble Space Telescope, and others show that the object is moving faster than predicted while leaving the Solar System. via Wikimedia Commons