July 2, 2019
Ryan Whitwam

Scientists: Sorry, ‘Oumuamua Still Isn’t an Alien Spaceship

Astronomers have been pondering the nature of our first interstellar visitor ever since its discovery. ‘Oumuamua is bizarre — not only is it from beyond the stars, but it’s also long and cigar-shaped. That led some to wonder if it wasn’t really an alien spacecraft, but past studies of ‘Oumuamua have suggested that it’s just a space rock. Now, a comprehensive analysis from scientists at the University of Maryland and other institutions has ruined our fun once and for all. ‘Oumuamua isn’t an alien spaceship. 

While there have no doubt been alien objects in our solar system before, ‘Oumuamua was the first one we ever spotted. Astronomers at the Pan-STARRS observatory identified ‘Oumuamua in October 2017, but it was already on its way out of the solar system at that point. Its incredible speed and orbital eccentricity meant it could not have come from inside the solar system, but it was moving too fast for anything to catch up and take a closer look. 

It didn’t take long after the discovery for people to start half-jokingly wondering if ‘Oumuamua was an alien ship. Even if we ignore that, it took scientists a few tries to properly identify the object. The initial assumption was that ‘Oumuamua had to be a comet because comets would be easier to eject from the edges of a solar system. However, scientists couldn’t see a cometary tail (or coma) on ‘Oumuamua. After labeling it an asteroid, further analysis of its trajectory found evidence of slight out-gassing. Astronomers finally decided ‘Oumuamua was likely a very old comet. 

‘Oumuamua’s path through the solar system in 2017.

So, why is it definitely not an alien spaceship with a fuel leak or something? The team behind the new study included experts from a variety of fields to create a “big-picture summary” of ‘Oumuamua. They began with its origins, showing that there are several possible mechanisms by which an object like ‘Oumuamua could end up in interstellar space. Its behavior in our solar system, while strange, is also explainable with natural origins. In fact, its path around the sun matches a prediction published by one of the study authors six months before ‘Oumuamua’s discovery. 

‘Oumuamua is strange, but the study concludes there’s nothing unexplainable going on here. Jumping to the conclusion that it’s an alien spacecraft is fun, but the evidence does not support that. Astronomers hope to get a look at more alien visitors in the future. Upcoming instruments like the Large Synoptic Survey Telescope (LSST) will make it easier to spot small objects passing through the solar system. If we can find a few dozen alien space rocks, we might find that ‘Oumuamua is very typical of visitors from beyond the stars.

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