Scientists have studied plenty of asteroids and comets — the ESA even landed a spacecraft on one. However, the mysterious object known as ‘Oumuamua is something new. It’s from someplace outside of our solar system, the first such object ever detected. It’s moving too fast to be studied closely, but scientists from the Breakthrough Listen project announced a plan to make sure it wasn’t a spaceship. Having checked, you can probably guess at the outcome. ‘Oumuamua isn’t an alien craft, but it is a really strange asteroid.
Astronomers working at the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) facility in Hawaii discovered ‘Oumuamua about two months ago. It has an orbital eccentricity of 1.20, so it’s 20 percent past the sun’s escape velocity. No object that originated in our solar system could reach such a high rate of speed, even gravity slingshots from large planets like Jupiter.
It’s certainly a distinctive object thanks to its extra-solar origins, but the rock itself seems to be quite unusual as well. It’s cigar-shaped with a length of 180-400 meters and a width of just 30 meters. Astronomers first thought ‘Oumuamua was a comet, based on what we know of solar system formation. However, it doesn’t have a coma of dust and gas. So, it’s an asteroid, but a weird one — all the asteroids in our solar system are lumpy and potato-shaped. That led Breakthrough Listen to announce its plan to observe ‘Oumuamua for 10 hours across four radio bands.
The Green Bank Telescope used by Breakthrough Listen.
Breakthrough Listen has announced that ‘Oumuamua is completely quiet based on last week’s observations. The team is still analyzing the data, but there’s little reason to hold out hope this object is a messenger from a distant civilization. In addition to dashing our science-fiction hopes, Breakthrough Listen reports it also scanned portions of the radio spectrum that could indicate the presence of a coma, just to make sure. According to Andrew Siemion from Breakthrough Listen’s UC Berkeley laboratory, “Oumuamua is most likely an asteroid, ejected from its host star in some chaotic event billions of years ago, and finding its way to our solar system by chance.”
‘Oumuamua is currently swinging through the solar system at 38.3 kilometers per second (23.8 miles per second). It’ll pass the orbit of Jupiter next year, and by the mid-2020s it will pass into the Kuiper Belt. That’ll be the last we ever see of our first known interstellar visitor — an asteroid, not a spaceship — as it speeds out into deep space.
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