Oumuamua: Neither comet nor asteroid, but a cosmic iceberg
By Dennis Overbye
It has been 2 1/2 years since astronomers in Hawaii discovered a strange, cigar-shaped object speeding through the solar system on a trajectory from far away and toward even farther away. Today Oumuamua, the Hawaiian term for “scout,” as the object was named, is now long gone, somewhere between the orbits of Saturn and Neptune and on its way to the Great Out There, but astronomers are still wondering and debating what it was.
The cosmic interloper was first thought to be an interstellar asteroid, a chunk of rock shed by another star system. Then astronomers decided it must be a comet, likewise flung loose from some faraway star and planetary system. Briefly they speculated that it could be an alien artifact, a derelict probe like the giant spaceship in Arthur C. Clarke’s novel “Rendezvous With Rama,” or a fragment from a planetesimal that was ripped apart by a gravitational interaction or collision.
Now a pair of Yale astronomers have suggested that Oumuamua was neither an asteroid nor a comet. Rather, it was a cosmic iceberg: a chunk of frozen hydrogen.