‘Oumuamua: the first known visitor from outside our solar system behaved strangely because it … [+]
A team of astronomers investigating the first known visitor from another star system have concluded that its strange behaviour was down to a very normal activity for any comet—the release of gas.
‘Oumuamua, as it was later named, was noticed by astronomers in late 2017 when it was already exiting the solar system. Its trajectory suggested that it had come from another star system, but no-one could explain why it was accelerating.
A new study published in Nature by a chemist and an astronomer provides a compelling answer: it outgassed hydrogen as the comet warmed up in the sunshine.
“A comet traveling through the interstellar medium basically is getting cooked by cosmic radiation, forming hydrogen as a result,” said Jennifer Bergner, lead author and an assistant professor of chemistry at UC Berkeley, California. She wondered if it may have warmed-up and let out hydrogen in such a way that the force would be enough to accelerate it out of the solar system. After all, ‘Oumuamua is tiny, measuring about 115x111x19 meters. “Because ‘Oumuamua was so small, we think that it actually produced sufficient force to power this acceleration.”
That it was merely a regular interstellar comet will be disappointing news to those who thought ‘Oumuamua —which had no coma or tail—could be a light sail created by an alien civilization or a spaceship under its own power.
All other comets ever observed in the solar system come from either the Kuiper Belt—a ring of objects found beyond Neptune, and where Pluto and other dwarf planets reside—or the much more distant Oort cloud, a sphere of comets around the edge of the solar system.
“The comets and asteroids in the solar system have arguably taught us more about planet formation than what we’ve learned from the actual planets in the solar system,” said Darryl Seligman, a National Science Foundation postdoctoral fellow at Cornell University and a co-author on the paper. “I think that the interstellar comets could arguably tell us more about extrasolar planets than the extrasolar planets we are trying to get measurements of today.”
Wishing you clear skies and wide eyes.
