A new hypothesis provides a simple solution for 'Oumuamua mystery

Was it aliens? We may never know, though a new hypothesis suggests a new explanation for the mysterious 'Oumuamua comet.
Chris Young
An artist's impression of 'Oumuamua.
An artist's impression of 'Oumuamua.

NASA, ESA and Joseph Olmsted and Frank Summers of STScI 

Back in 2017, astronomers spotted a mysterious comet that was later called 'Oumuamua.

Due to the space rock's bizarre shape and its speed and trajectory, Harvard physicist Professor Avi Loeb and others famously suggested it could be an alien machine built by extraterrestrial intelligence.

Now, Jennifer Bergner, a Berkeley assistant professor of chemistry, has suggested there might be a more straightforward explanation related to the chemistry of the space rock.

A new hypothesis provides a simple solution for 'The Oumuamua mystery

Bergner teamed up with a UC Berkeley colleague, Darryl Seligman, now a National Science Foundation postdoctoral fellow at Cornell University, to test her hypothesis regarding 'Oumuamua.

"A comet traveling through the interstellar medium is getting cooked by cosmic radiation, forming hydrogen as a result. Our thought was: If this was happening, could you trap it in the body so that when it entered the solar system, and it was warmed up, it would outgas that hydrogen?" Bergner said in a press statement. "Could that quantitatively produce the force you need to explain the non-gravitational acceleration?"

During her research, Bergner was surprised that experimental studies from the 70s, 80s, and 90s showed that ice produces abundant amounts of molecular hydrogen (H2) when it's hit by high-energy particles similar to cosmic rays. This showed that cosmic rays could penetrate tens of meters into the ice, converting roughly a quarter of it into hydrogen gas.

"For a comet several kilometers across, the outgassing would be from a fragile shell relative to the bulk of the object, so both compositionally and in terms of any acceleration, you wouldn't necessarily expect that to be a detectable effect," Bergner explained. "But because 'Oumuamua was so small, we think that it produced sufficient force to power this acceleration."

Investigating 'Oumuamua

'Oumumua has been a great source of speculation, debate, and controversy since it was first discovered in 2017. Bergner and Seligman's new hypothesis adds a compelling new angle, and it will be interesting to see how the scientific community reacts.

Unfortunately, we can't know what 'Oumuamua is, as it has traveled far beyond our Solar System and into interstellar space.

Interestingly, the space rock has drawn so much speculation that scientists have proposed sending a swarm of space probes to catch up with it using light sails and lasers. Suppose the scientific community is still unsatisfied after reading Bergner and Seligman's new paper, published in Nature. In that case, it might spur that team to launch its mission toward interstellar space.

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