On October 19, 2017, Canadian physicist and astronomer Robert Weryk spotted a mysterious object zipping through the solar system at an immense speed. The discovery was made using the Pan-STARRS 1 telescope at the Haleakala Observatory in Hawaii, hence the name “Oumuamua” which means ‘scout’ to ‘reach out first’, as Weryk said he saw the object as a messenger from the past that is reaching out to us.
Oumuamua was first thought to be a comet, though it was quickly reclassified due to its lack of cometary tail. The object was travelling at a high velocity that it had to come from interstellar space. It was soon reclassified again and thought to be possibly coming from the star Vega in the Lyra constellation. The object was behaving in an unusual manner that every time it is classified, it would exhibit a behaviour that defied its classification, leaving scientists confused and without explanation.
This interstellar object, being the first of its kind ever observed, was given a unique classification with the name 1I-2017 U1 a.k.a Oumuamua.
Oumuamua is several hundred feet in length, with a width and height about tenth of that. It has an odd cigar shape to it with a rocky surface of highly metallic content, and a dark red color reflecting only 4% of sunlight. The object was estimated to be travelling at around 196,000 mph and had a rotation rate similar to the average spin rate of regular asteroids seen around our solar system.
Despite its close approach to the Sun however, the object showed no sign of having a coma. Oumuamua’s light curve indicated its motion as “tumbling” rather than spinning as it made its way through our solar system. This tumbling was not characteristic of an asteroid, nor of a comet. Nonetheless, researchers still concluded that it was likely an asteroid.
Although, astronomers expected that when they looked more closely at it, they would find a dry space rock like most asteroids in our solar system. Based on measurements however, it was concluded that ice with organic elements similar to comets could exist beneath its rocky surface.
Further analysis showed that Oumuamua sped up as it left the solar system, a behaviour typically known for comets during a process called “outgassing”. Being mostly of ice, as comets pass close to the Sun, that ice starts to melt and pockets of gas are then extracted through holes in a pressurized stream, producing an atmosphere or coma, or sometimes also a tail. This process is also known for increasing the velocity of comets approaching the Sun as trapped materials are being extracted from them. This led Oumuamua to be redesignated and widely accepted as a comet, classified with the name C/2017 U1.
However, new data showed no sign of Oumuamua having a tail despite the fact that it had passed its closest point to the Sun, leaving scientists confused and wondering how the object could have possibly sped up when it left the solar system.
To further support the idea that Oumuamua was not a comet, an astrophysicist by the name of Roman Rafikov at the University of Cambridge stated that if outgassing was the reason for Oumuamua’s increased velocity, then not only it would have disrupted the object’s uniform tumble, but the acceleration and spin would have also caused the object to break into pieces.
This once again led Oumuamua to be finally classified as I-2017 U1, with ‘I’ standing for ‘interstellar’.
Although Oumuamua is still widely perceived as a natural occurrence, some researchers started looking at it from another perspective, speculating – based on its highly unusual shape and metallic content, that it was of extraterrestrial origin. Some even drew the eerie connection to the Arthur C. Clarke novel “Rendezvous with Rama” in which a cylindrical alien spaceship, initially thought to be an asteroid, entered our solar system.
This is where the Breakthrough Listen project got involved. Funded by Russian billionaire Yuri Milner in coordination with Stephen Hawking and the SETI program at UC Berkeley to search for intelligent extraterrestrial communications in the universe, they pointed the Green Bank telescope at Oumuamua for a period of 10 hours in an attempt to pick up any radio frequencies.
Even though scientists didn’t believe they had discovered any signals, some believed, however, that the scans could have triggered “an awakening” of the extraterrestrial entity from which it originated. This is according to Nick Pope, the former head of Ministry of Defense for the U.K, who said during an interview with TheSun: “While nothing has been found yet, there’s another intriguing possibility: If this ship is an alien probe, it’s possible that our scans will awake the intelligence inside.”
While readings from the Breakthrough Listen showed no sign of Oumuamua being an alien spacecraft, Mr. Pope suggested the possibility that scientists may have been looking for the wrong thing.
“Because there’s no air in space, an alien spaceship wouldn’t need to be designed in the same way that our aircraft have to be.” He said.
“Rather than building an interstellar spacecraft from scratch, it makes perfect sense to take an asteroid and then build your ship around it, or hollow it out and build inside it, for the protection you’d derive from being surrounded by so much rock.”
On October 26, 2018, scientists from Harvard University re-examined the mysterious interstellar object and released a paper suggesting the possibility that Oumuamua might be an artificial thin solar sail accelerated by solar radiation pressure, in an attempt to explain the non-gravitational acceleration that the object exhibited when exiting our solar system, and how it survived such immense speed.
“Known solar system objects, like asteroids and comets, have mass-to-area ratios orders of magnitude larger than our estimate for Oumuamua,” said Shmuel Bialy and Abraham Loeb of the Harvard Smithsonian Center for Astrophysics.
“If radiation pressure is the accelerating force, then Oumuamua represents a new class of thin, interstellar material, either produced naturally, or of an artificial origin.”
They even speculated about the possibility of Oumuamua as a type of artificial satellite known as a “lightsail”, which is a technology currently in development by the Breakthrough Initiative program.
“The lightsail technology might be abundantly used for transportation of cargos between planets or between stars. In the former case, dynamical ejection from a planetary system could result in space debris of equipment that is not operational anymore and is floating at the characteristic speed of stars relative to each other in the Solar neighborhood. This would account for the various anomalies of Oumuamua, such as the unusual geometry inferred from its lightcurve” The two scientists said.
Unfortunately, by the time this report reached its peak in popularity, Oumuamua was long gone. Unlike asteroids or comets which can always be studied again when their orbit brings them back, Oumuamua is an interstellar traveler, and our solar system was just a small stop. In all likelihood, we may never see it again.