What We Know About our First Interstellar Visitor.


‘Oumuamua’s two proposed shapes.

Luke Jones

Back in October of 2017, Robert Weryk, using the Haleakalā Observatory in Hawaii, discovered the first ever known interstellar object to pass through our solar system. The object was dubbed “‘Oumuamua”, a Hawaiian term roughly translating to “first distant messenger.” When it was discovered, ‘Oumuamua was already on its way out of the system, so scientists had to rush to study it before it was lost to the stars.

‘Oumuamua was observed to be between 100 and 1000 meters long, and between 35 and 167 meters in width and thickness. When it was originally discovered, it was thought to be the shape of a cigar, but more recent evaluations suggested the shape of a disk. But without actually seeing it, we won’t be able to tell what exactly it’s shape is.

Another curious aspect of “Oumuamua is its speed. While everything speeds up when it gets to a large source of gravity, the object was moving very fast even before then. Astronomers calculated the speed of ‘Oumuamua as it was 100 years ago to be around 26.33 km (16.36 mi) per second. This speed is actually rather close to the average speed of materials orbiting the Milky Way within our general area, or neighborhood. This speed actually hints that ‘Oumuamua may be even older than we think and may have already orbited the galaxy several times. (One orbit around the galaxy takes ~230 million years from where we are)

‘Oumuamua pictured through the William Herschel Telescope, this is the clearest image we’ve gotten of the object.

How ‘Oumuamua formed is anyone’s guess, but there are several theories that have gained traction. The most prominent theory is that ‘Oumuamua was once part of a small, Pluto like dwarf planet that was shattered by tidal forces by, let’s say, getting too close to a larger planetary body. If correct, that would make our visitor a very rare object, as it’s theorized that most fragments like this would either collide with the planet that tore it apart, or begin to orbit it’s home star.

Another theory is very similar. The only main difference is that ‘Oumuamua was a piece of a super-Earth, a planet similar to Earth in composition but much larger. This theory has started to fall apart since ‘Oumuamua seems to be composed mainly of frozen hydrogen, which can be found on celestial bodies like Pluto. The final theory is that ‘Oumuamua is an artificial solar sail that would’ve had to have been built by some alien species. A solar sail is a type of propulsion for spacecraft that uses large sails to use light and solar radiation to propel it at high speeds. But this theory was disproved on account of the object’s apparent tumbling motion, which would not allow a solar sail to work.

Where it came from is also up to serious debate. At first it was theorized that it came from the direction of the star Vega, but since Vega is relatively close to us, it wouldn’t have been in the same place in the sky at the time. But if it was to have come from Vega, it would’ve taken around 600,000 years to reach our sun.

Further calculations have pointed in the direction of two groups of small red dwarf stars, these groups are known as Carina and Columba respectively. But as of now we cannot accurately predict where exactly where our strange and mysterious visitor came from. And as ‘Oumuamua moves away from the sun at insane speeds, it will be even harder to predict it’s origin in the future.