To telescopes, ‘Oumuamua, the interstellar asteroid that made itself known to Earth in October, looks like a point of light in the dark, much like a star in the night sky—a perhaps underwhelming picture of a significant discovery.
But for astronomers, the tiny speck—the sunlight reflected by the asteroid—can reveal a trove of information. They can break down the light from an object into a spectrum of individual wavelengths, from which they can infer the object’s shape, chemical composition, and other properties. As astronomers like to say, if a picture is worth a thousand words, then a spectrum is worth a thousand pictures.
The astronomy community has spent weeks sorting through these pictures of ‘Oumuamua, captured by telescopes around the world as the asteroid sped away from the sun and faded from view. The earliest analysis of the light from ‘Oumuamua, conducted by its discoverers in Hawaii, revealed a strange, fast-spinning, cigar-like object unlike anything they’ve ever seen. The latest analyses continue to produce tantalizing results, further challenging long-standing predictions for the first visitor to our solar system.
‘Oumuamua has a thick crust of carbon-rich material, hardened by years of exposure to cosmic radiation in interstellar space, that could be protecting an icy interior, according to a new analysis in Nature Astronomy of the object in visible and near-infrared wavelengths. The coating could explain why ‘Oumuamua shows no signs of being a comet, the kind of object scientists long expected would coast into our solar system.