Researchers have used a high powered radio telescope to study the insterstellar comet ‘Oumuamua in a bid to find out if it is an alien craft. 

Scientists at the SETI Institute attempted to answer the controversial claim by Harvard researchers using the Allen Telescope Array (ATA) to observe ‘Oumuamua when it was about 170 million miles away, or slightly less than the diameter of Earth’s orbit. 

If artificial radio transmissions were found, researchers say it would have been ‘strong evidence’ the mysterious object is not simply a rock tossed into space by a random gravitational slingshot interaction that occurred in its home star system.

‘We were looking for a signal that would prove that this object incorporates some technology – that it was of artificial origin,’ says Gerry Harp, lead author of a paper to be published in the February 2019 issue of Acta Astronautica. 

‘We didn’t find any such emissions, despite a quite sensitive search. 

‘While our observations don’t conclusively rule out a non-natural origin for ‘Oumuamua, they constitute important data in accessing its likely makeup.’

Following its discovery in October 2017, Oumuamua was the subject of popular speculation about a possible non-natural origin largely because it brought to mind the interstellar spaceship in Arthur C. Clarke’s novel Rendezvous with Rama. 

Its highly elongated shape and the fact that no coma was observed strengthened this hypothesis for some, as these are uncharacteristic of asteroids and comets. 

Observations were made between November 23 and December 5, 2017, using the wide-band correlator of the ATA at frequencies between 1 and 10 GHz and with a frequency resolution of 100 kHz. 

No signals were found at a level that would be produced by an omnidirectional transmitter on-board the object of power 30 – 300 milliwatts. 

In portions of the radio spectrum that are routinely cluttered by artificial satellite telemetry, the threshold for detection was as high as 10 watts. 

In all cases, these limits to the powers that could be detected are quite modest – comparable to that of cell phones or citizen band radios.

While no signals were found coming from Oumuamua, the types of observations reported by SETI Institute scientists may have utility in constraining the nature of any interstellar objects detected in the future, or even the small, well-known objects in our own Solar System. 

It has been long-hypothesized that some of the latter could be interstellar probes, and radio observations offer a way to address this imaginative, but by no means impossible, idea. 

A new NASA study uses the fact the object was too small for the infrared Spitzer telescope to spot to estimate its size.

Researchers now say cigar shaped ‘Oumuamua is probably less than half a mile (2,600 feet, or 800 meters) in its longest dimension.

”Oumuamua has been full of surprises from day one, so we were eager to see what Spitzer might show,’ said David Trilling, lead author on the new study and a professor of astronomy at Northern Arizona University. 

‘The fact that ‘Oumuamua was too small for Spitzer to detect is actually a very valuable result.’ 

The new study also suggests that ‘Oumuamua may be up to 10 times more reflective than the comets that reside in our solar system — a surprising result, according to the paper’s authors.    

But it may have had its surface refreshed through ‘outgassing’ when it made an extremely close approach to our Sun, a little more than five weeks before it was discovered.  

Earlier this week the researcher who discovered  a cigar-shaped interstellar rock zooming through our solar system has dismissed claims from Harvard University it could be an alien spacecraft.

The Harvard researchers noted in a pre-print of their article that it was an ‘exotic scenario,’ but that ‘Oumuamua may be a fully operational probe sent intentionally to Earth vicinity by an alien civilization.’

However, Robert Weryk, who discovered the strange interstellar object in 2017 at the University of Hawaii’s Institute for Astronomy, told CBC’s Afternoon Drive their theory is ‘a bit of wild speculation’. 

‘I think it’s a remnant from another solar system. It’s just something that happened to run into us, and we were very lucky to have been operating the telescope that night and looking in that direction,’ Weryk said.

Oumuamua, the first interstellar object known to enter our solar system, accelerated faster away from the Sun than expected, hence the notion that some kind of artificial sail that runs on sunlight – known as a light sail – may have helped push it through space.

‘Currently there is an unexplained phenomena, namely, the excess acceleration of Oumuamua, which we show may be explained by the force of radiation pressure from the sun,’ co-author and Harvard astrophysicist Shmuel Bialy said.

‘However this requires the body to have a very large surface and be very thin, which is not encountered in nature.’

Their suggestion of an alien force at work went viral.

‘Honestly, that’s a bit of wild speculation,’ Weryk said when asked about the paper by Harvard scientists Abraham Leob and Shmuel Bialy. 

‘(The Harvard researchers) decided to focus on another aspect of that, that it’s an alien space craft and that it has a solar sail type material that’s causing the non-gravitational trajectory. But we actually believe that’s not true based on the data we obtained.’