When the celestial body Oumuamua traveled through our solar system in 2017, it made headlines around the world. Because the cigar-shaped lump impressed experts and laypeople alike – the latter mainly because of its strange appearance. In addition, the astronomers who had spotted the chunk through the Pan-Starrs telescope in Hawaii could not provide any reasonable explanations as to what kind of object it was. After all, they had a name ready: Oumuamua in Hawaiian means something like leader or, in a slightly different context, scout.
Maybe it was a comet or an asteroid, definitely something interstellar. Perhaps, so believed the Harvard astronomer Avi Loeb, but also something that extraterrestrial life forms had a hand in – if they have any.
Two researchers from Arizona State University in the USA are now delivering a new attempt. According to Alan Jackson and Steven Desch, the most likely explanation for Oumuamua is that it is a fragment from an exoplanet. This planet, which orbits another star somewhere in space, may have lost a piece in a collision with an asteroid, the researchers report in two studies in the journal “Journal of Geophysical Research: Planets”.
Jackson and Desch even have a very specific celestial body from our solar system in mind, whose properties roughly correspond to those of the one described: Pluto. The small celestial body between Uranus and Neptune, far out in our solar system, was once traded as an independent planet, but then a few years ago astronomers degraded it to a dwarf planet.
According to the researchers, Oumuamua comes from an exo-Pluto that is as far from its star as our Pluto is from the sun. However, a powerful collision estimated half a billion years ago detached the splinter from the gravity of its star and sent it on its journey through space.
Astronomers believe that Oumuamua can be formed from frozen nitrogen (N.2) consists. But the outer layers of the nitrogen ice have melted. As a result of the movement in space, it lost most of its mass and gradually assumed a flat shape. Nitrogen is also found on the surface of Pluto, where the temperature is more than minus 200 degrees Celsius. A special form of nitrogen ice could basically explain all of Oumuamua’s properties, the researchers argue.
Recoil effect from melted ice
Earlier analyzes showed that Oumuamua has some strange properties. As it moved away from the sun, it flew faster. But it didn’t emit gas or dust, as you’d expect from asteroids that hit the evaporated ice experience a kind of recoil effect. In any case, nothing of the kind could be observed through the telescopes. However, nitrogen provides a conclusive explanation, because evaporating nitrogen ice could have caused the acceleration without leaving any visible residues, the researchers argue.
Astronomers had already developed similar hypotheses in previous studies. In one study, scientists speculated that a mighty gas planet the size of Jupiter had catapulted Oumuamua out of its traditional orbit.
If the conclusions are correct, it would be an important milestone in astronomy. Then the researchers would have seen a fragment of an exoplanet for the first time in October 2017, when Oumuamua flew past Earth at a distance of 24 million kilometers and a speed of a good 87 kilometers per second.