The debate continues
Karen Meech, an astronomer at the University of Hawai‘i who has studied ‘Oumuamua but wasn’t involved in this research, says she still believes the space rock has to be a comet. Part of why she thinks that is because one piece of evidence hinting that the space rock is an asteroid could simply be a dearth of observations.
She points out that ‘Oumuamua’s high-speed trip through the solar system was too quick for astronomers to get a detailed look at the object.
“Most of the observations of ‘Oumuamua had to occur within a one-week period, and we simply did not have the ability to detect water,” she says. “That isn’t a lack of water. We just didn't have the sensitivity to see it.”
And there’s another outstanding property these researchers haven’t explained yet, she says. ‘Oumuamua’s movement through our solar system implied it was being driven by more than just gravity — like a comet whose direction is slightly changed by the force of gases streaming off of it.
“I think it absolutely is a comet,” Meech says. “The nongravitational motion that our group detected was super strong, and there’s no other way to maintain it except for outgassing. There’s no other explanation.”
Because of ‘Oumuamua’s incredible speed, even the fastest spaceship humanity has ever built, NASA’s Parker Solar Probe, couldn’t catch it. As quickly as it came, the alien interloper was gone, never to be seen again.
“We will never know for sure where ‘Oumuamua came from or where it was created, and I’ve been very impressed with the models and the way people have tried to explain it,” Meech says. “I don’t think it proves anything.”
However, future observations still could help resolve the argument. If Zhang and Lin are right, interstellar asteroids may be even more common than interstellar comets, the authors say. These alien asteroids would be relatively small and lack the comas of comets, which would make them much harder to detect while they’re passing through our solar system. However, new cutting-edge telescopes, like the Vera C. Rubin Observatory being built in Chile, could spot them.
“‘Oumuamua is just the tip of the iceberg,” Lin said in a media release. “We anticipate many more interstellar visitors with similar traits will be discovered by future observation.”