'Oumuamua is the interstellar space object that defies classification. It has at various times been thought to be a comet, an asteroid, an alien spaceship, a hydrogen iceberg, a light sail, a piece of a planet and probably a few more things. At some point, if a concrete identification is not determined, some proposal will finally jump the shark into absurd irrelevance. That day may have arrived.
“We propose that 'Oumuamua's properties could be explained as those of a fractal dust aggregate (a "dust bunny") formed in the inner coma of a fragmenting exo-Oort cloud comet. Such fragments could serve as accretion sites by accumulating dust particles, resulting in the formation of a fractal aggregate. The fractal aggregate eventually breaks off from the fragment due to hydrodynamic stress. With their low density and tenuously bound orbits, most of these cometary fractal aggregates are then ejected into interstellar space by radiation pressure.”
You read that right … 'Oumuamua may be a dust bunny. This was proposed by an esteemed astronomer -- Dr. Jane X. Luu, co-winner of the 2012 Kavli Prize "for discovering and characterizing the Kuiper Belt and its largest members, work that led to a major advance in the understanding of the history of our planetary system." As befitting of her experience, the intro to her new paper published in the Astrophysical Journal Letters and reviewed in Universe Today uses plenty of impressive terms like “fractal aggregate,” exo-Oort cloud” and “hydrodynamic stress,” but all of them disappear under the massive shadow of “dust bunny.”
a loose, tangled ball of dust, lint, hair, etc., especially as found under a low piece of furniture.
How does one go from something fluffy found under a bed that is held together by static electricity and moves away with the slightest of breezes to avoid capture by a mop to an interstellar object? Dr. Luu and her colleagues at the University of Oslo are using the simple dust bunny to explain their new concept – the cometary fractal. They propose that 'Oumuamua was once part of a larger long-period comet (one with a long orbit, like those in the Oort cloud of our own solar system) that broke off and began accumulating particles of itself, the bigger comet and other cosmic dust. They stick around to form a fractal body that would be flung away from the exo-Oort cloud and towards another solar system. Lacking much density, it would be easily blown around by solar radiation.
Believe it or not, Luu’s dust bunny theory is backed up by the other recent interstellar comet – Borisov – which arrived after ‘Oumuamua and showed definite signs of fragmenting. One other thing that supports the dust bunny theory is that the true shape of ‘Oumuamua is still not known. While telescope images show it as a cigar, it’s possible that it’s actually a disc whose round, flat surface could not be seen at the angle it passed by at. (That whooping sound you hear in the background is Flat Earthers celebrating the shape of ‘Oumuamua – we’ll deal with them at another time.) A disc-shaped fractal body apparently better fits the dust bunny model.
Will this “dust bunny” explanation for ‘Oumuamua be accepted by the astronomy community and the general public or will it be relegated to the snicker-inducing realm of the mispronunciations of Uranus? Only time will tell.