‘Oumuamua: Interstellar rock, or alien spaceship?

‘Oumuamua, a Hawaiian word loosely translating to “a messenger that reaches out from afar”, and the name of a tricky asteroid that has been stumping astronomers for over a year. It first made headlines last December, but now it’s back.

Well, figuratively speaking, that is. It’s already passed by earth and doesn’t seem to be circling back around any time soon. Unless the most recent theories have any merit, that is.

Let’s backup, though. Last year, astronomers in Hawaii noticed what appeared to be a weirdly shaped asteroid tumbling through the solar system. In fact, its cigar shape was so unnatural for an asteroid that they originally thought it was a comet, but a quick look at its behaviour shot that theory down pretty quickly.

But ‘Oumuamua also doesn’t behave like a typical asteroid. Aside from its cigar-shape, its surface also appears to be made of a carbon-based material, not the typical rock found on other asteroids. To make matters weirder, it also seemed to speed up as it passed by the sun. This unusual behaviour lead to a very bizarre theory, published in a new paper by Harvard professors Shmuel Bialy and Abraham Loeb: ‘Oumuamua might be an alien spacecraft.

Now, don’t get too excited. This “conclusion” is based largely off the fact that we can’t definitively prove that ‘Oumuamua wasn’t made by aliens, something that can be said about practically everything. But, just because I can’t 100% prove that an alien didn’t break into my room last night and eat my leftover Halloween sweets, doesn’t mean that’s why some of my Maltesers appear to have gone missing.

Astronomers did investigate the alien theory, of course, because how could they not? And what they found was: Nothing. There are absolutely no signs of life on the asteroid, and no transmissions have been detected from it. So, if it is alien-made (and that’s a big “if,”) it would have to be a chunk of some sort of debris, and not a probe specifically sent to us.

And as for why it started moving faster, there are a few theories. The fanciful explanation, the one that supports the alien theory, is that the object is solar-powered and its proximity to the Sun gave it a bit of a push. The more likely explanation is something called outgassing, which is when objects such as comets release gas when passing in front of stars, causing them to speed up. No gas was detected from ‘Oumuamua at the time of its speed increase, but that doesn’t mean there wasn’t any. It just means we didn’t see it.

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The outgassing theory is supported by a new study in the Astronomical Journal, which used the NASA Spitzer Space Telescope to determine the object’s size. And what they found was that ‘Oumuamua is pretty small- too small for Spitzer to detect after it had passed by the Earth. This is good news for the alien nonbelievers, since the outgassing theory was dependent on ‘Oumuamua being smaller than your average comet. 

Further studies of ‘Oumuamua’s reflective properties suggested that the object is probably no more than 800 metres at its longest point. (If that doesn’t sound small, know that some comets can be tens of kilometres long.) But the reflection tests also showed us another one of ‘Oumuamua’s little quirks: It’s very shiny, maybe 10 times more reflective than any known comet in our solar system. Why? The researchers, once again, suggested outgassing.

When an ice-covered object passes in front of a star, its frozen surface melts and turns directly to gas, revealing a fresh layer of reflective ice and snow underneath. And since ‘Oumuamua has been travelling for millions of years, far away from any galactic heat source, there was plenty of ice to refresh.

With all of this evidence, I, personally, am going to have to side with astrophysicist Paul M. Sutter’s theory: that ‘Oumuamua is just a “big dumb rock.”

You go, you big, dumb rock.

But even without the possibility of aliens, ‘Oumuamua is still fascinating. It’s fast, it’s old, and it’s wildly mysterious. Its incredible speed means that it clearly has interstellar origins, which makes it the first object detected in our solar system to come from another part of the galaxy. It didn’t appear to be gravitationally attracted to our sun, sailing past it at over 96,000 km/h. So, even if we do officially toss aside the alien theory, there’s a lot to ‘Oumuamua that still needs to be answered, making this a landmark discovery.

Alien or not, you gotta admit: ‘Oumuamua is pretty cool. But unfortunately for us, we’ve seen all of it that we can. This strange object is long gone, heading out of our solar system forever. Whatever secrets this big, dumb rock may have held for us are quickly rocketing away from our prying eyes. Bon voyage, ‘Oumuamua. It’s been fun.