The first interstellar object discovered to visit our solar system, the alien comet ‘Oumuamua, had an unusual acceleration as it hurtled away from the Sun. The quirky comet ‘Oumuamua (pronounced oh-MOO-uh-MOO-uh) has been a subject of fascination since it was spotted in 2017.
“Oumuamualacks tail of gas and dust characteristic of many comets. It was previously described as cigar-shaped, but is now thought to resemble a stone pancake. Smaller than originally estimated, it is now anchored at approximately 375 feet (115 meters) by 365 feet (111 meters), with a thickness of about 60 feet (19 meters).
Hypothesis
In light of its unexpected behavior, hypotheses have been raised, including fleeting speculation that it may actually have been an alien spacecraft. A new study offered a more sober explanation that ‘Oumuamu’s acceleration was caused by the release of hydrogen gas as the comet warmed in sunlight.
The researchers said that ‘Oumuamua appears to have been born like many other comets as what is called a planetesimal a small object formed in the early stages of planet formation and was essentially a large icy space rock.
After somehow being ejected from its original solar system, they said, the comet’s chemical composition changed as it was bombarded with high-energy radiation as it hurtled through interstellar space. This converted some of the comet’s ice frozen water into hydrogen gas, which was trapped in the rest of its ice.
‘Oumuamua then warmed up as it passed through our inner solar system, causing the comet’s ice structure to rearrange and release trapped hydrogen gas – giving ‘Oumuamua a bit of a kick as it headed away from the Sun. The release of this hydrogen in a process called outgassing would not cause a visible tail.
Key takeaways
“The key finding is that ‘Oumuamua may have started as an icy, water-rich planetesimal, essentially similar to Solar System comets. This model can explain ‘Oumuamua’s strange behavior without resorting to any exotic physics or chemistry,’ said University of California, Berkeley astrochemist Jenny Bergner, lead author of the research published this week in the journal Nature.
“The simplest explanation, and exactly what we would expect from an interstellar comet, fits all the data without fine-tuning,” said study co-author Darryl Seligman, a postdoctoral fellow in planetary science at Cornell University.
Oumuamua, whose name in the native Hawaiian language refers to a messenger arriving from a great distance, was first detected by the University of Hawaii’s Pan-STARRS1 telescope.
“We don’t know its place of origin, but it probably traveled through interstellar space for less than 100 million years. It had a reddish color consistent with the colors of many small bodies in the solar system. It is currently behind Neptune on its way out of the solar system,” Bergner said.
A second interstellar object, Comet 2I/Borisov, was discovered visiting our solar system in 2019. This one looked and behaved more like a typical comet.
These extraterrestrial invaders may be more common than previously known. Scientists say one to two interstellar objects could be discovered each year in our solar system once a new astronomical observatory now under construction in Chile starts operating as planned next year.
Written by: VAISHALI VERMA
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