The previously unreconciled acceleration of 1I/2017 U1 ‘Oumuamua, a strange object of extrasolar origin discovered on October 19, 2017 by the Pan-STARRS 1 telescope, was due to the production of hydrogen gas from ice reserves, according to new research.
This artist’s impression shows ‘Oumuamua, the first interstellar object discovered in our Solar System. Image credit: NASA / ESA / Hubble / ESO / M. Kornmesser.
In 2017, a mysterious object dubbed ‘Oumuamua fired the imaginations of scientists and the public alike.
It was the first known visitor from outside our Solar System, it had no bright coma or dust tail, like most comets, and a peculiar shape — something between a cigar and a pancake — and its small size more befitted an asteroid than a comet.
But the fact that it was accelerating away from the Sun in a way that astronomers could not explain perplexed scientists, leading some astronomers to suggest that it was an alien spaceship.
In a new model developed by University of California, Berkeley astrochemist Jennifer Bergner and Cornell University astronomer Darryl Seligman, the acceleration of ‘Oumuamua is attributed to the release of trapped molecular hydrogen from within the object.
This hydrogen has been formed through energetic processing of water-rich ice as the body passed close to the Sun, and is subsequently released from the object, slightly bending its path through our Solar System.
Such reactions have been demonstrated in existing experimental work, showing that molecular hydrogen is known to be produced and subsequently expelled under such conditions.
Importantly, this model helps the astronomers understand ‘Oumuamua’s unusual properties without requiring further fine-tuning.
“For a comet several kilometers across, the outgassing would be from a really thin 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,” Dr. Bergner said.
“But because ‘Oumuamua was so small, we think that it actually produced sufficient force to power this acceleration.”
The findings support previous theories that ‘Oumuamua may have originated as an icy planetesimal — a small object formed during the early stages of planet formation — similar to solar system comets.
“The main takeaway is that ‘Oumuamua is consistent with being a standard interstellar comet that just experienced heavy processing,” Dr. Bergner said.
“The models we ran are consistent with what we see in the Solar System from comets and asteroids.”
“So, you could essentially start with something that looks like a comet and have this scenario work.”
“The idea also explains the lack of a dust coma,” Dr. Seligman added.
“Even if there was dust in the ice matrix, you’re not sublimating the ice, you’re just rearranging the ice and then letting hydrogen get released.”
“So, the dust isn’t even going to come out.”
The findings appear in the journal Nature.
J.B. Bergner & D.Z. Seligman. 2023. Acceleration of 1I/‘Oumuamua from radiolytically produced H2 in H2O ice. Nature 615, 610-613; doi: 10.1038/s41586-022-05687-w
Source : Breaking Science News