Is ‘Oumuamua an Alien Probe or a Strange Comet? This space mystery will never end
In September 2017, a very strange object grazed fast through the solar system and passed close to the sun before setting off. Shiny, elongated, and possibly hundreds of feet long, the object was unlike anything scientists had ever seen. Not exactly an asteroid. Not exactly a comet.
Five years later, scientists are still arguing about the object, which they dubbed Oumuamua. It’s Hawaiian for “spy”. A debate that could shake up entire scientific fields.
On one side is a camp led by iconoclastic Harvard physicist and noted alien hunter Avi Loeb who argues that we should at least consider the possibility that ‘Oumuamua is an alien spacecraft. On the other hand, there is a loose confederation of scholars who advocate more prosaic explanations for the mysteries of ‘Oumuamua.
“What’s at stake in the debate about ‘Oumuamua is whether the scientific community can keep open any plausible hypothesis about the object’s origins without fear or prejudice until more evidence becomes available — or until we can think of better questions about the object.” Wade Roush, professor of popular science and author of the non-fiction book alienssaid The Daily Beast.
Loeb has slammed the skeptics for what he describes as essentially scientific laziness and a failure to honor the stakes of the ‘Oumuamua debate. “Finding a partner in interstellar space will make sense of our cosmic existence,” Loeb told The Daily Beast.
Meanwhile, at least one of the skeptics has defended the opposite position, citing an age-old principle of logic: Ockham’s Razor, named after the 14th-century English philosopher William of Ockham. The simplest explanation is usually the best. Even if the more complex answer is more cosmically satisfying.
“Finding a partner in interstellar space will give meaning to our cosmic existence.”
— Avi Loeb, Harvard University
The debate about ‘Oumuamua currently focuses on the object’s speed – more specifically, the nature of its speed acceleration as it zoomed through the solar system, accelerating until it was traveling at almost 200,000 miles per second. Even for an asteroid or comet fast. NASA described it as “bubble formation.”
It’s conceivable that an asteroid could travel that fast if it started its journey really, really far away — say, several star systems away — and had enough time to gain speed from the gravity of nearby stars before colliding with ours solar system arrived where our own sun pinned it down for another rate-limiting gravitational train.
What doesn’t make sense is that when astronomers tracked ‘Oumuamua through various telescopes, they discovered what NASA called “non-gravitational acceleration in ‘Oumuamua’s motion.” In other words, an acceleration that scientists cannot attribute to gravity alone.
Something in ‘Oumuamua added speed to the object. For Loeb, that’s another hint that maybe, just maybe, Oumuamua is an alien ship — one with some sort of propulsion system.
But in a newspaper that appeared in Nature On March 22, Cornell University astrophysicist Darryl Seligman and Jennifer Bergner, an astrochemist at the University of California Berkeley, challenged that assumption.
Seligman and Bergner reminded readers that comets can generate their own acceleration as their ice sublimates into gas and shoots into space like a jet engine. “We report that the acceleration of ‘Oumuamua is due to the release of trapped molecular hydrogen,” Seligman and Bergner wrote.
That said, Oumuamua is not a spaceship. It’s just a very strange comet.
That explanation is consistent with Ockham’s Razor, Seth Shostak, an astronomer at the California-based SETI Institute, told The Daily Beast. “One should choose the simplest among the possible understandings,” said Schostak. “And while it’s entirely possible that ‘Oumuamua is actually an extraterrestrial artifact, the simpler explanation is that it’s an asteroid or a comet — possibly a fragment of one or the other.”
Shostaks is right. Scientists have observed many asteroids and comets – some of them quite strange – in our centuries of peering at the night sky. But we’ve never seen anything that we know for sure is an alien vehicle. “Comet” is the simpler explanation for the strange object that visited our corner of the galaxy five years ago.
“While it’s certainly possible that ‘Oumuamua is actually an alien artifact, the simpler explanation is that it’s an asteroid or comet – possibly a fragment of one or the other.”
— Seth Shostak, SETI Institute
Soon after Nature When the study was published, Loeb fired back: Seligman and Bergner’s explanation may be simple — but it’s wrong. For their theory to work, he argued, Oumuamua would need to be hot enough to break up the frozen water on its surface and shoot the leftover hydrogen into space.
But when calculating ‘Oumuamua’s temperature, the Berkeley and Cornell scientists failed to account for the cooling effect of hydrogen evaporating from the object’s surface as it passed the Sun, Loeb said. “As a result of the decrease in surface temperature, the thermal rate of hydrogen outgassing is reduced by a factor of three,” the Harvard physicist wrote in a blog published on Medium March 23.
With the jet-like effect of sublimating ice reduced by a third, it’s no longer believable that ‘Oumuamua was accelerated due to natural phenomena, Loeb argued. “If the Emperor has no clothes, we better admit it,” he wrote. What he meant was that the scientific community should remain open to the possibility that ‘Oumuamua could be something new – an alien spacecraft – and not just another asteroid or comet.
Bergen said Loeb’s counterpoint doesn’t change her team’s results. “We identified several reasons why including effects such as [hydrogen] Evaporative cooling … probably won’t change our conclusions,” she told The Daily Beast. However, she declined to give those reasons, saying she prefers to let the scientific peer review process unfold for any further formal studies Loeb might publish on the subject of ‘Oumuamua.
In a discussion streamed online Tuesday and sponsored by news website Lexington Observer, Loeb tried to explain why skeptics are so reluctant to consider the idea that ‘Oumuamua could be a ship. Some scientists don’t seem able to think beyond their own experience, he said. “People who have studied rocks for decades say if they see something in the sky, it’s a rock.”
It’s a failure of the imagination, Loeb said. An inability to see a new discovery for what it is. “Nature has a better imagination than my peers,” he joked.
“Nature has a better imagination than my peers.”
— Avi Loeb, Harvard University
Bergner disagreed with this characterization. She told The Daily Beast that scientists from many different fields are doing their best to understand ‘Oumuamua. “A lot of very novel and creative ideas have been proposed to try to explain its behavior.”
Roush acknowledged that the scientific establishment has a “phobia about talking about extraterrestrials.” This phobia could work for Skeptics like Seligman and Bergner and against Freethinkers like Loeb. The former are more likely to be taken seriously, even if their studies have fundamental flaws, as Loeb claimed.
“Personally, I think Avi is more wrong than right about ‘Oumuamua,” Roush said. “But I will defend to the death the right of every scientist to have their ideas heard with respect and judged on their merits, even when they carry a perceived cultural stigma.”
Brian Keating, a cosmologist at the University of California, San Diego, attempted to chart a middle ground between Loeb and the skeptics. You’re both doing important work, and you’re doing it in good faith.
Whichever side ultimately proves right — Loeb with his extraterrestrial hypothesis, the skeptics postulating their strange comet — mankind will learn something new, Keating emphasized. “If the object is a comet, it’s not that interesting,” he said, “but it would still be important to astronomers because it’s not something we’ve ever seen before.”
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