During its brief trip through our solar system, the interstellar space object named ’Oumuamua was at one time or another speculated to be an asteroid, a comet or a spaceship that may or may not be occupied by living beings. It has since left the solar system for destinations unknown, but the arguments about what it is continue. The latest theory replaces “none of the above” with “an ejected protoplanetary disk object.” A what?
Its rare cigar shape made ’Oumuamua a puzzle from the start, as did its rotation, which American football-loving astronomers described as not a tight quarterback spiral but a botched end-over-end field goal kick. (Female astronomers assumed their best Captain Picard facepalm poses.) This caused speculation that the object may have been involved in a violent interstellar collision. While its seemingly dry surface said ‘asteroid’, the erratic spin said ‘comet’. This theory was strengthened with other observations that the object seemed to accelerate on its way out, implying it was getting some sort of boost from gases released when the icy surface melted on its close turn around the Sun.
That was accepted for a while, until it was pointed out that comets have tails and ’Oumuamua didn’t even have a Doberman’s nub, let alone a gaseous trail or fuzzy aura about it. Also, that acceleration combined with the tumbling rotation should have broken a cigar of ice and dirt apart. Then there’s the fact that this was the first interstellar object ever discovered. What kind of force could have propelled it across light years from one sun to another?
“Basically, it’s a messenger from a dead star.”
In a new study, Roman Rafikov, an astrophysicist at the University of Cambridge, proposes that ’Oumuamua is actually a sliver of a planet that was blown to pieces as its sun collapsed and died and transformed into a white dwarf. In an interview with Quanta magazine and in the study’s abstract, Rafikov builds his case by process of process of elimination of other causes combined with a comparison to the behavior of other tidal disruption events like the death of a star and destruction of its planets.
“Based on these arguments, as well as the lack of direct signs of outgassing, we conclude that the classification of 'Oumuamua as a comet (invoked to explain its claimed anomalous acceleration) is questionable.”
Well … that settles it -- 'Oumuamua is a messenger from a dead star. Or is it? There’s little chance of tracing it back to its white dwarf because the event occurred millions of years ago. The data on it is limited because it showed up unexpectedly, was not detected until it was leaving and passed through in a hurry. At best, astronomers are hoping to spot another one in the future with a better telescope.
In the meantime, Outgassing would make a great name for a band whose first prog-rock album is "Messenger From A Dead Star."