The interstellar object Oumuamua, that strange cigar-shaped rock found somewhere a great distance beyond the solar system, is not an alien spacecraft, according to new research published in the journal Nature Astronomy .
When the first known interstellar visitor to the solar system was spotted on October 19, 2017, scientists were quick to observe the strange object. The traveler had been kicked out of his system and perhaps it was a comet or asteroid, or even a part of a shredded planet. A couple of scientists even suggested that it could be an alien spacecraft.
“We have never seen anything like ‘Oumuamua in our solar system,” said Matthew Knight, an astronomer at the University of Maryland and first author of a new paper on the mysterious object, in a statement. “It’s really still an enigma.”
Knight was part of the Oumuamua International Space Science Institute (ISSI) team. The scientists concluded that Oumuamua is not of extraterrestrial origin, as a natural explanation satisfies the observations.
“Our preference is to stick with the analogs we know about, unless or until we find something unique. The alien ship hypothesis is a fun idea, but our analysis suggests that there are a whole host of natural phenomena that could explain it,” Knight said. .
An unusual object
Oumuamua’s rapid speed gave astronomers just a few weeks to collect as much data as possible. Their observations revealed that the object was small and red in color and appeared to have a cigar-shaped shape and unusual twist, as well as a strange change in direction that has been challenging to explain.
“The motion of ‘Oumuamua was not limited to following gravity along a parabolic orbit as you would expect from an asteroid,” Knight clarified.
The jets of gas could gently nudge the traveler, providing a possible explanation for their change in turn and direction. But the astronomers did not detect any signs of material fired outside the elongated object that matched current models.
Scientists who suggested that the object could be an alien craft also argued that the lack of similar natural objects in space suggests that Oumuamua should never have been discovered and therefore deliberately pointed at Earth. Similarly, its unlikely orbit sent it closer to Earth than any other planet, the so-called special orbit that suggests it may have searched for us.
Knight and his colleagues argued that while the simulations suggest how much material, roughly a mass of Earth, is expelled during the planet’s formation, the actual amount of debris expelled during these events remains unknown: it could be a few large objects or many. More smalls.
What about the strange elongated shape of the visitor?
” The point is, we don’t know the actual form of Oumuamua,” Raymond wrote. The researchers only had a limited time to observe the faint fleeing object. While it might look like a cigar, it could also bear a strong resemblance to a pancake.
Even the cigar shape could have a natural explanation . ‘Oumuamua could be a fragment of a larger object crushed before being ejected, a process that stretched it. Slow collisions with objects in your home system could have produced its strange shape. Or the fast-traveling dust between the stars could have crashed into the visitor, forging an elongated cigar. Or it could be something else entirely.
If Oumuamua is not an alien ship, what could it be?
“There is no universally accepted answer, but the signs are that ‘Oumuamua is similar to comets in the solar system ,” says Sean Raymond, also a member of the ISSI team.
Comet-like objects are constantly being pushed out of their systems by large planets and stars. A full-size comet or a fragment of a comet would fit the appearance and acceleration of ‘Oumuamua, according to the researchers.
“It is possible that some of ‘Oumuamua’s oddities are simply due to its small size, ” clarifies Raymond. He added that the properties of very few similar-sized objects in the solar system are known due to their small size, which makes them challenging to observe.
“The signs suggest that ‘Oumuamua is a natural object. Perhaps something similar to a comet,” he wrote. “But there are no aliens.”
Reference: The natural history of ‘Oumuamua, Nature Astronomy (2019). DOI: 10.1038 / s41550-019-0816-x, https://nature.com/articles/s41550-019-0816-x
Image credit: ESO / M. Kornmesser
