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Our First Interstellar Visitor — Alien Tech?

Claims by Harvard scientists have led to speculation

An artist’s impression of how Oumuamua might look. When scientists describe the object as being reddish, they don’t necessarily mean that it’s notably red in color, only that Oumuamua better reflects red light waves over blue ones. Image: ESO / M. Kornmesser

A little over a year ago, our solar system was visited by a mysterious object tumbling in from interstellar space. It approached above the plane of our unsuspecting planets and came down inside Mercury’s orbit, swinging past our enormous sun before shooting out and disappearing from view of our telescopes, starting its long path out of our solar system once more. The object caused a rush while it was here; scientists fought competitively for telescope time in the few weeks the object remained visible to us. A process that normally took months was shaved down to just days. It was a moment that made history for many reasons. Not only was this our first ever encounter with any object outside of our solar system, the object itself was so elusive as to spur an all new category of space objects.

While it was first named Rama after Arthur C. Clarke’s science fiction story, scientists later consulted with cultural experts to decide on a Hawaiian name in honor of the Pan-STARRS 1 telescope that first spotted the object flying across our skies. The name they settled on turned out to have a very poetic meaning: “Oumuamua”, or a messenger sent from the past to reach out to us here on Earth.

Unfortunately, during the time of its visit, a hurricane was raiding across parts of Puerto Rico where the Arecibo Observatory is located — one of the largest single-aperture telescopes in the world. The storm managed to briefly put Arecibo out of commission. What our telescopes did manage to pick up was little more than a twinkling dot traveling overhead, at times bright and at times hardly visible as it made dramatic changes in brightness about every 7 hours. Researchers were confused as contradicting results from global observations started to pour in. The drastic changes in brightness led to the conclusion that Oumuamua was spinning and tumbling in every direction, reflecting more or less light depending on what position it was in.

These graphics from NASA show the movement Oumuamua is thought to have exhibited.

It also brought up discussions about its shape. Speculations ranged from something flat and oval-like to the shape most commonly agreed on now — a long, cylindrical body with extreme proportions. The rocky object is thought to be half a mile in length, 10 times longer than it is wide. According to NASA, “Astronomers had never seen a natural object with such extreme proportions in the solar system before.” Because of this, we aren’t sure how an object like Oumuamua would form. It might be something unique to our visitor’s home solar system.

When it first came rapidly hurtling into our field of view, it was moving at 196,000 miles per hour or 55 miles per second, a speed that it couldn’t have achieved from the sun’s gravity alone. When objects originate from within our solar system, their momentum takes them back to their point of origin. The only way an object from our own system could have reached such speeds is if a planetary body (Planet Nine, perhaps?) would have given Oumuamua some additional momentum, though researchers concluded that this was exceptionally unlikely.

So, then, Oumuamua must have come from some other distant star. Even if it came from our closest neighboring system — Alpha Centauri at 4.4 light years away — that means it would have been traveling for at least 50,000 years just to reach us. At its nearest to Earth, it was a cozy 15 million miles away (considered quite close in astronomical terms) and it’ll take another 20,000 years to leave our solar system altogether.

Traveling so long through interstellar space, it’s a wonder what kind of stories Oumuamua could tell if we were able to further observe it or have a sample of it in our labs. Even the reddish hue isn’t much help in figuring out its composition since any number of organic compounds could have given Oumuamua its color. We do know, however, that it must have withstood constant exposure to cosmic rays during its journey.

When scientists first noticed Oumuamua through the telescopes, they thought it was a comet (it took them over 30 days to realize it was an interstellar object) and then later an asteroid. But Oumuamua defies categorization. It has properties of both, and some properties that don’t belong to either.

While comets are more common and easier to eject from a nearby star system into our own, they also have a gauzy haze around their bodies that forms due to their icy surfaces evaporating as they come close to the sun. This haze then becomes the familiar tails we associate with comets (or, as they’re more dreamily named, “shooting stars”). But there was no such haze noticed around Oumuamua. It also is expected to have shredded under the pressure and speed of its travel but Oumuamua instead remained quite solid, exhibiting a more stable structure like that of an asteroid.

Artist’s impression of Oumuamua if it experienced a comet-like haze. Image: NASA/ESA

But the strangest thing about Oumuamua is its unexpected acceleration as it left our field of view. It’s not a boost in speed that could have come from the sun’s gravity, though scientists figure the sun heating Oumuamua could have caused outgassing (venting material from its surface) and thus given it the boost we observed. This would be in line with how a typical comet behaves though research on outgassing says the process would have changed Oumuamua’s spin, which it didn’t.

Some scientists have since suggested very different theories as to what our special visitor might actually be.

A paper released last week by Shmuel Bialy and Abraham Loeb of the Harvard Smithsonian Center for Astrophysics claims that pressure from solar radiation could explain Oumuamua’s acceleration and that the object might be “a lightsail of artificial origin.” In other words, alien technology.

Lightsails are propelled by pressure from radiation and are a technology we have here on Earth. The Starshot projects aims to develop and launch a lightsail that will travel across the universe in search of signs of life. This, says Loeb, might be just what Oumuamua is. A lightsail capable of surviving interstellar travel would only need to be a fraction of a millimeter thick, depending on the object’s mass density. This would be enough to withstand tidal forces, dust, gas, and the centrifugal forces found in the interstellar medium. It would also explain the object’s strange shape since some manmade lightsails have similar dimensions.

But if this is alien technology, how does it explain Oumuamua’s silence? SETI (Search for Extraterrestrial Intelligence) scanned the object while it was still near to Earth and found no signs of radio signals. Bialy and Loeb explain that this lightsail may actually be a defunct model, moving along through space thanks to gravity and photon emissions like driftwood bobbing up and down on ocean waves.

Oumuamua’s path was also a clever one since coming so close to Earth could have been a maneuver for a flyby and its .25 AU from the sun would have allowed it to observe Earth without being damaged due to solar radiation.

Needless to say, not everyone is ready to accept the claims of alien technology. But there’s not enough evidence to disprove it, either. A month after it was discovered, Stephen Hawking along with researchers at Breakthrough Listen were open to the idea of Oumuamua being an alien ship, mentioning that the object’s elongated shape would be the most efficient for use in interstellar travel in order to reduce friction from dust and gas.

This is the path the object took as it first approached from the Lyra constellation. The trajectory seems to be a natural one, leaving scientists even more skeptical of any claims that it could be of artificial origin. Image: NASA

Most scientists believe Oumuamua is an artifact from the birth of another solar system or from a powerful event like a supernova. In these spectacular moments there is violence — shredding of cosmic bodies, light, heat, giant planets moving among rocky disks looking to find their place in the forming solar system, material ejected out into some other part of the universe to pass by another star. Or Oumuamua could simply be part of a cloud of debris permeating the galaxy.

By 2021 a new telescope will be set to start scanning the sky in the hopes that it’ll be able to find a lot more of these interstellar objects. It’s predicted 2–12 of these should pass by Earth’s orbit every year, though we don’t have the technology to detect them unless they come as close as Oumuamua did.

No matter how many new interstellar objects we come to find, Oumuamua will remain the first. It marks our meeting with the rest of the universe far outside the comforts of our solar system. Whether natural or alien made, the object is a special one, leaving us all too soon but not without making a profound impression.

This is how Oumuamua appeared in our telescopes on October of 2017. A faint, exciting little dot marking the sky. Image: Queen’s University Belfast/William Herschel Telescope