Research into the interstellar object says the object might be a frozen chunk of hydrogen that broke off a planet. It is not a starship piloted by aliens.
'Oumuamua baffled scientists as it sped through the solar system in 2017.
Studies by Arizona State University astronomers Alan Jackson and Steven Desch say 'Oumuamua appears to be made of frozen nitrogen - just like the surface of Pluto. The 45-meterwide object was torn from its home planet, likely by an asteroid, some 500 million years ago.
The reddish hue of 'Oumuamua is caused by the rock's outer layers being evaporated by cosmic radiation and our sun.
Jackson and Desch contend it is cookie-shaped and not cigar-shaped - which led to the alien spacecraft talk.
"In many ways 'Oumuamua resembled a comet, but it was peculiar enough in several ways that mystery surrounded its nature, and speculation ran rampant about what it was," said Desch.
'Oumuamua differs from comets in several ways. It had a lower velocity as it entered our solar system. Desch said 'Oumuamua would have had a higher velocity had it been traveling across interstellar space for over a billion years as a comet."
'Oumuamua was made of ices with different compositions allowing the scientists to calculate how quickly the ices would turn to gas as the object sped past our sun.
"We realized that a chunk of ice would be much more reflective than people were assuming, which meant it could be smaller. The same rocket effect would then give 'Oumuamua a bigger push, bigger than comets usually experience," said Desch.
