Was Interstellar Visitor ‘Oumuamua Torn Apart by a Star?
You might remember ‘Oumuamua, the very first interstellar visitor astronomers ever detected in our solar system. This object is almost certainly not an alien spaceship, but it does have an extremely bizarre elongated shape. Now, researchers from the Chinese Academy of Sciences and the University of California, Santa Cruz have put forth a hypothesis that could explain how ‘Oumuamua got to be so weird.
Astronomers spotted ‘Oumuamua in October 2017 when it was already on its way out of the solar system. Its orbit and high speed confirmed it could not have come from any source inside our solar system, but it was impossible for any spacecraft to catch up to the mysterious space rock. Long-distance observations confirmed ‘Oumuamua was about 1,300 feet (400 meters) in length and just a few hundred feet wide. The scientific community went back and forth on whether ‘Oumuamua was an asteroid or a comet, eventually settling on a very, very old comet that doesn’t produce a visible coma of vaporized material.
That didn’t explain how this icy hulk from beyond the stars acquired its spindly shape. The new analysis suggests that ‘Oumuamua could be a result of “extensive tidal fragmentation” in its home solar system. Tidal interactions are the result of high gravity on comparatively small objects. For example, the high gravity of Jupiter causes tidal heating in some of its moons. Tidal interactions also famously ripped comet Shoemaker-Levy 9 into pieces before it collided with the planet in 1992.
The simulations developed for the new study show that tidal stresses from a star’s gravity could fracture an object like a comet or asteroid, imparting enough energy to eject the fragments from the system. The melted chunks would stretch into an elongated shape as they swing around the star. Moving away from the star would allow the fragments to cool and retain that stretched-out shape as they floated into interstellar space.
This is just a hypothetical simulation, but it would explain more than ‘Oumuamua’s unusual shape. The researchers note that heat diffusion during the tidal interaction would consume large amounts of volatile materials. That could explain ‘Oumuamua’s surface coloration and the lack of a coma.
It didn’t take long after the discovery of ‘Oumuamua for scientists to spot a second interstellar traveler — 2I/Borisov appeared in the sky in fall 2019, looking like a very typical comet. This is probably just the beginning. With better technology, we’ll find more of these objects, allowing us to better understand their origins.