spaceSpace and Physics

The Interstellar Object 'Oumuamua Might Be The Remains Of A Planet That Was Destroyed


Jonathan O'Callaghan

Senior Staff Writer

Artist's impression of 'Oumuamua. ESO/M. Kornmesser

Astronomers have suggested that the interstellar object ‘Oumuamua, the first ever observed in our Solar System, might be the shard of a destroyed planet.

That’s according to a paper on arXiv, picked up by New Scientist. Matija Cuk from the SETI Institute in California suggests that the unusual size and shape of the object may be a result of a violent origin.


“‘Oumuamua’s physical characteristics were unexpected, starting with a complete lack of cometary activity,” Cuk writes in the paper. “The most puzzling feature of ‘Oumuamua is its very elongated shape.”

That shape is similar to a cigar, with the object (thought to be an asteroid) being 10 times longer than it is wide. It’s 400 meters (1,300 feet) long, and spins on its axis once every 7.3 hours. We’ve never seen an object like this in our Solar System. It was first spotted in October 2017, and is now making its way away from our Sun, never to return.

To explain its unusual origin, Cuk says it could have been born from a planet 10 times the size of Earth getting too close to its star, probably a red dwarf. As a result, it would have been ripped apart and the debris could have been flung to a possible companion star before heading our way (Cuk suggests its origin system is a binary star system).

This helps to explain one puzzle. Namely, if this was born out of a regular collision between two asteroids in a young planetary system, you would not expect its elongated shape to have survived. This explanation provides a possible solution.


“The present hypothesis is based on the assumption that ‘Oumuamua is not a fluke but a typical representative of interstellar asteroids,” Cuk writes.

He adds that if future discoveries are similar “monolithic fragments”, then his idea “may warrant a closer look, with in-depth modeling of binary system dynamics and tidal disruptions being needed before we can determine if this hypothesis is tenable.”

‘Oumuamua is the subject of countless pieces of research and papers at the moment, with plenty of people having a stab at its origin and characteristics. We’ve heard everything from it being an alien spaceship to a chunk of dark matter to just a plain old asteroid.

Whether it was formed in a dramatic collision in another planetary system, well, we’ll have to wait and see. Astronomers are hoping to find more interstellar objects like this in the future, and if they have a similar appearance then we might be able to paint a better picture.


(H/T: New Scientist)


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