The curious case of ‘Oumuamua

On the night of 19 October 2017, Canadian astronomer Robert Weryk discovered something peculiar while reviewing image data from the Pan-STARRS 1 telescope in Hawaii. The telescope, which is sitting atop a high-rise volcano in Hawaii, specializes in scanning for near-Earth objects. Little did Weryk know that his discovery would baffle the world. This is the story of ‘Oumuamua.

The discovery

Finding something like an asteroid or a comet is surely exciting, but not an uncommon experience — we regularly spot these lingering masses of rock and ice around us, most of them never pose a threat to us.

Neither did this particular object that Weryk had found. Scientists plot out the object’s trajectory through space for any potential future interactions with our planet. However, what let from this investigation was baffling — it was moving fast and showed a very eccentric orbit, indicating that it may have come from beyond our Solar System. The object lingered around and zipped past our solar system, with a slight assist by our sun, never to return.

The object was named ‘Oumuamua, which is Hawaiian for a scout. The discovery was announced via the scientific journal Nature about a month after the observation. Naturally, the world was baffled, as it was our first “alien” encounter in many ways. Conspiracy theories flourished — from aliens to government projects and everything in between. The International Astronomical Union (IAU) had to create a whole new classification to catalogue this object, and hence ‘Oumuamua is the only object in the newly created I (interstellar) classification. People wanted to know more, and the Hubble and Spitzer space telescopes joined the party to answer the unknown.

Studying a space rock

A lot has been found out ever since the fly-by. ‘Oumuamua is about 100 to 1000 meters long, is more or less candy bar-shaped, is rocky and has a reddish hue similar to the asteroids found in the Solar System. ‘Oumuamua has a highly eccentric orbit, with an eccentricity of 1.2, which is the highest we have ever observed. This, along with its high velocity, indicates an interstellar origin. Scientists don’t rule out an Oort Cloud origin, which is a large spherical shell consisting of comets orbiting the far outskirts of our solar system.

This close encounter sparked public interest in a relatively obscure topic — rogue objects. When solar systems form, it is a very crowded situation with many planets and rocks bumping into each other. Often, through collisions, or because of passing too close to their parent star, such objects are slingshot out of their solar systems, becoming rogue. They then wander around in space for millions of years until they pass through neighboring solar systems like ours.

Upon further examination, we have found out that ‘Oumuamua might have been lingering around the milky way for billions of years before having an encounter with us. With millions of stars and countless permutations, it is difficult to understand its source without further data. ‘Oumuamua’s closest approach to Sun did change its orbit very slightly but did not cause any deceleration. It will hence continue to zip past our solar system into interstellar space, never to return.

I guess all we can say is — farewell, interstellar scout!

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Rishabh Tatiraju

Rishabh Tatiraju

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Grad student at University of Florida. Computer Science. Astrogeek.