Mysterious Interstellar Object 'Oumuamua Was Likely Part Of A Pluto-Like Planet

Researchers from Arizona State University have been looking into the origins of the interstellar object called 'Oumuamua discovered in 2017. 'Oumuamua has become quite famous because it was the first interstellar object from beyond our solar system discovered using the Pan-STARRS astronomical Observatory in Hawaii. The word "'Oumuamua" means scout or messenger in Hawaiian.

Astrophysicists Steven Desch and Alan Jackson have been working to explain some of the strange features of 'Oumuamua and have concluded that it's likely a piece of a Pluto-like planet from another solar system. The researchers say in many ways 'Oumuamua resembled a comet, but it had peculiarities that made its exact nature and history a mystery. Using observations of the object, the researchers determined several characteristics that differed from what would be expected in a typical comet.

The differences included its velocity, which was a bit lower than would be expected and indicated that it had not been traveling in interstellar space for more than a billion years or so. It also had a pancake shape that was more flattened than any other known solar system object. While 'Oumuamua did receive a slight push moving away from the sun (rocket effect), which is common in comets when sunlight vaporizes ices the comet is made of, the push for 'Oumuamua was stronger than could be accounted for.

The object also lacked detectable escaping gas, which is typically discovered in the tale of a comet. The researchers hypothesized the object was made from different ices, and they calculated how quickly the ices would sublimate as the object passed the sun. They were able to calculate the rocket effect, the mass and shape of the object, and reflectivity of the ices.

The duo realized a chunk of ice would be more reflective than people assumed, which meant it could be smaller. The same rocket effect would give 'Oumuamua a bigger push than was expected. One particular ice discovered was solid nitrogen that gave an exact match to all the object's features at the same time.

Solid nitrogen can be seen on Pluto's surface, so it's possible that 'Oumuamua could be made of the same material as Pluto. They believe it's likely the object was knocked off the surface by an impact about half a billion years ago and thrown out of its parent system. Frozen nitrogen would also account for the strange shape of 'Oumuamua because as the layers of nitrogen ice evaporated, the shape of the body would become more progressively flattened.