ʻOumuamua: A Messenger From Afar
ʻOumuamua was discovered by Robert Weryk using the Pan-STARRS1 telescope at Haleakalā Observatory, Hawaii, on 19 October 2017. After a couple name changes, from A/2017 U1 for Asteroid, then C/2017 U1 for Comet, it was formally designated 1I/2017 U1 for Interstellar, with the "1" identifying it as the first. At the time of its discovery, it was about 33 million km (21 million miles) from Earth, and already on its way out.
We literally never saw it coming, and it was moving so fast that we almost never saw it at all. The fastest human object is the Voyager1 spacecraft, traveling at 17km/second. So fast it makes a bullet look like it’s moving in slow motion. ‘Oumuamua entered our solar system traveling at 26km/second. As it traveled, the light it reflected grew and dimmed by a factor of 10, which meant it was spinning. From there, we were able to estimate its size, which is where its reputation of being unusual began. It was estimated to be between 100-400 meters long, with a length of up to 10x its width. Up to this point, the most extreme aspect ratio ever recorded was 3:1. Even ignoring its unusual behavior and origin, its shape alone was unlike anything we had ever seen. And due to its hyperbolic order, it's one we'll never see again.
The Plot Thickens
2I/Borisov, named after its founder, became the second confirmed interstellar object ever detected. A rogue comet that came streaking through our solar system with a large visible tail of dust, before fragmenting in early 2020. This was both eventful and uneventful at the same time. Uneventful because it behaved exactly how we expected an interstellar object to behave, and eventful because it furthered just how bizarre 'Oumuamua was.
When 'Oumuamua was first designated A/2017 U1 for Asteroid, it was simply because that's all it was, a giant rock drifting through space. When it was changed to C/2017 U1 for Comet, it's because it behaved like a comet, speeding up as it moved away from the sun. The is common for comets due to a process known as outgassing: ice on or near their surface turns to gas from the sun's heat and shoots off into space acting as a propellent. This fast-escaping gas and dust is what gives comets their distinctive bright tail. But 'Oumuamua didn't have a tail. With countless theories being proposed and debunked, no one could figure how or why it was speeding up.
In September 2020, and asteroid was discovered, designated 2020 SO, that seemed to be very similar to 'Oumuamua, accelerating as it moved away from the sun without any outgassing or comet tail. This, however, turned out to be nothing, as 2020 SO appeared to have originated within our solar system. Astronomers retraced its orbit and discovered it was a long-lost rocket booster from NASA's 1966 Surveyer-2 Mission. However, this discovery added a lot of fuel to an already burning conspiracy theory fire.
Could a lack of outgassing be a trait of something artificial?
Rendezvous With Rama
Getting into the conspiracy theories, of which there are far too many to go into here, but obviously the most popular are those that believe 'Oumuamua was our first encounter with alien technology. Some of the most prominent are those that claim it was in fact an alien spacecraft, or at least part of one. Similar to 2020 SO, some speculate that 'Oumuamua is the alien equivalent to NASA space junk and is just a small part of a larger object that got broken off. Some also claim this is corroborated by how it tumbled on multiple axis, indicating a lack of control. Due to its unique shape, the most common comparison is to that of Rama. The ship from the classic science fiction novel Rendezvous With Rama by Arthur C. Clarke, featuring an alien world contained inside a spinning cylinder.
Alien or not, as technology advances and our database of interstellar objects grows, one of two things will be confirmed. We discover that 'Oumuamua is just one of those things we don't yet understand about our universe; a common object we've simply never seen before. Or we never find another elongated spinning shard, in which case, 'Oumuamua will have truly been a unique event.
