A new article published in the scientific journal Nature offers an explanation for ‘Oumuamua, the first known interstellar object to visit our solar system.
‘Oumuamua was discovered by astronomers on Haleakala in 2017 using the University of Hawaii’s Panoramic Survey Telescope and Rapid Response System, or Pan-STARRS1.
The object, estimated to be between 100 and 1,000 meters long, led to several theories: a comet without a visible tail, or an asteroid despite its propulsive push.
The new article claims ‘Oumuamua was a water-rich comet traveling through space that was hit by radiation. Over time, that radiation formed hydrogen underneath the comet’s surface, causing it to accelerate without producing a comet tail.
But Karen Meech, the astronomer at the University of Hawaii’s Institute of Astronomy who led the team that first characterized the object, says the theory doesn’t quite explain ‘Oumuamua’s elongated shape.
“I don’t disbelieve it, but I don’t think it is necessary to explain ‘Oumuamua,” Meech said. “This new paper was trying to fit all the data together into a single, coherent model, and it was a creative solution, but we can’t prove it one way or another because we can never get any more data.”
Meech also doesn’t believe far-fetched theories about the object being a spaceship or “listening device” sent by extraterrestrials.
“I think ‘Oumuamua is just a piece that was left over from the process of building planets,” she said. “When you build up a young solar system, you have gas and dust that eventually coagulates into bigger and bigger pieces, and once they get to about kilometer scale, they either coalesce into a planet, get gravitationally tossed into the inner solar system, to the outer solar system, or they get ejected altogether.”
She finds this explanation just as exciting.
“What was really exciting about ‘Oumuamua was that it was very likely one of those planetary building blocks that got tossed out of its home solar system,” she said. “We don’t have powerful enough telescopes or the resolution to watch the birth process of a young solar system elsewhere, so this gave us a chance to study up close a leftover piece.”
Meech thinks the reason for the wide-ranging theories about ‘Oumuamua is, in-part, due to the short window scientists had to observe it.
“We had just over a week or so where you could do observations relatively easily,” she said. “When people are trying to figure out exactly what it was, piece all the data together and get a nice, consistent model, you can’t quite do that because you just don’t have enough information.”
She cautioned against jumping to conclusions, though, like one by Harvard scientist Avi Loeb suggesting the object is a “solar sail” or “space trash” discarded by an alien civilization.
“There were some mysteries with this first object that we couldn’t quite explain, but that doesn’t mean you have to go to an exotic hypothesis that has no evidence,” she said. “To go out on a limb and say, ‘this is the solution,’ is not scientifically responsible.”
Loeb’s theory has been criticized by others in the scientific community, including astrophysicist Neil deGrasse Tyson.
“The reason it’s probably not aliens, is that its trajectory around the sun was determined by gravitational forces,” he told Stephen Colbert on his show in 2018, later cautioning the media against citing articles that haven’t been peer-reviewed.
“I would’ve been totally happy with him (Loeb) saying, intriguing, could it be alien? Maybe, maybe not, but what sort of evidence would it take to confirm that aspect?” Meech added. “Carl Sagan said ‘extraordinary claims require extraordinary evidence,’ and (Loeb) has no evidence whatsoever that it’s alien.”
While ‘Oumuamua was the first interstellar object observed, Meech thinks it won’t be the last.
“I think when the Rubin telescope comes online in Chile in 2024, it will find one of these a year,” she said. “Even now, every couple months, there’s something interesting that we need to follow up with.”
‘Oumuamua’s name was chosen in consultation with UH-Hilo Hawaiian language experts Ka‘iu Kimura and Larry Kimura.
‘Ou means “reach out for,” and mua, with the second mua placing emphasis, means “first, in advance of,” with ‘Oumuamua meaning a scout or messenger sent from the distant past to reach out to us here.
“Something coming from outside the solar system does capture the imagination of people. What could it be?” Meech said. “It’s refreshing how many disciplines and how many people are still trying to explain this several years later.”
To learn more about ‘Oumuamua and astronomy in Hawaii, the Institute of Astronomy is hosting a free open house from 11 a.m. to 4 p.m. on April 23, with hands-on activities, family-friendly lectures and chances to meet and talk with local astronomers.
Email Grant Phillips at gphillips@hawaiitribune-herald.com.
