Researchers have been stumped for two years as to what 'Oumuamua, the structure that was seen passing through the solar system really is.
Astronomers and physicists think it could be an asteroid, but it's too agile and doesn't move like a rigid rock. It doesn't fall under the comet category because its too dry a structure.
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Could sunbeams move 'oumuamua?
Some think its made of a porous material that makes it light enough to be moved by sunbeams but sturdy enough not to break apart as it travels through the solar system. Research out of the University of Oslo supports that theory.
The work, led by Eirik Flekkøy, a physicist at the University of Oslo was inspired by Amay Moro-Martin's theory that the sun was indeed pushing 'Oumuamua because it was lightweight enough, according to Popular Science. Moro-Martin is a Spec Telecor Science Institute Astronomer.
Flekkøy and his team wanted to see if that theory was true and after studying 'Omuamua's rotation they noticed the slowing of the rotation fit with the theory that light can provide more force on certain surfaces. When the surfaces cool down it two can force movement. So if the sun can cause 'Oumuamua to turn it could also make it go faster, validating the theory.
Light but sturdy enough not to break apart
To test the theory further, after all, it has to be porous enough to push the sunbeams through, the researcher calculated how a dust ball would hold up if it was spinning with the sun gravitational pull hard on one side. The structure is strong enough to not break apart on its journey.
"The first known interstellar object 'Oumuamua exhibited a nongravitational acceleration that appeared inconsistent with cometary outgassing, leaving radiation pressure as the most likely force," wrote the researchers in a paper published in the journal Astrophysical. "Barring the alien lightsail hypothesis, an ultra-low density due to a fractal structure might also explain the acceleration of 'Oumuamua by radiation pressure."
In the fall the second interstellar comet sighting was made, with astronomers saying they detected another space rock that formed in a distant system before passing through our solar system. Scientists are able to tell its coming from outside our solar system because of speed and trajectory.