Astronomers have completed their first round of telescope observations of ‘Oumuamua, the first known interstellar object to enter our solar system, to check the asteroid for signs of alien technology.
So far, they have found no evidence of artificial signals coming from the asteroid, they said Thursday—but the search isn’t over yet.
“Indeed, nothing has popped up, but we’re busy churning through the data we’ve collected so far,” said Andrew Siemion, the director of the Berkeley SETI Research Center who leads its Breakthrough Listen Initiative, a $100 million effort in the search for intelligent extraterrestrial life.
The decision to check ‘Oumuamua for artificial signals came from Yuri Milner, the Russian billionaire and tech investor who is spending $100 million over 10 years to fund SETI efforts.
‘Oumuamua was first detected by Hawaiian astronomers in October. The asteroid, named for a Hawaiian word meaning “messenger,” puzzled the astronomy community. The properties of the mysterious space rock were unusual, particularly its extremely elongated, cigar-like form, a shape difficult to create through the natural, known processes of the universe. Somewhere along the way, some astronomers began to wonder whether this space rock could be a probe of some kind, dispatched by an advanced civilization.
Aliens are, of course, at the very bottom of the list of explanations for new and confounding astronomical discoveries. But for Milner, it was worth checking when astronomers had the chance, before ‘Oumuamua zoomed out of reach of even the most powerful telescopes.
The observations began Wednesday at 3:45 p.m. Eastern Time. For six hours, a Breakthrough Listen instrument on the Green Bank Telescope in West Virginia scanned ‘Oumuamua across four radio bands. The instrument is capable of scanning billions of individual channels at once, listening for pings between one and 12 gigahertz—a range of frequency that on Earth includes signals from technology like cellphones and microwave ovens.
Astronomers have so far only analyzed the data from one of the bands. “I’m certainly anxious to see if anything pops up from searches of the other bands,” Siemion said. When astronomers analyze data in the range of one to two gigahertz, they can look for evidence of the molecule hydroxyl, which would suggest the presence of water on ‘Oumuamua.
Software developed for the Breakthrough Listen project will search for narrow-bandwidth signals drifting in the frequencies detected by Green Bank. “By matching the rate at which these signals drift to the expected drift due to the motion of ‘Oumuamua ... the software attempts to identify any signals that might be coming from ‘Oumuamua itself,” the team said Thursday. The software will also weed out signals coming from human technology on or around Earth.
Siemion said the analysis will take some time. “We’re looking for signals from weakly transmitting or very distant technologies, bathed in a sea of signals from our own technology,” he said. “SETI is not an especially good field for the easily discouraged.”
‘Oumuamua is currently about twice the distance between the Earth and the sun from our planet, and barreling through the solar system at a rate of 38.3 kilometers per second. At this distance, Green Bank can still detect signals as faint as the radio waves from a cellphone. The next round of observations at Green Bank will likely begin Friday.
Astronomers predict many more interstellar objects will be detected in the solar system in the years to come. For Milner and SETI astronomers, it’s worth checking each one for signs of artificial technology.
“More and more SETI is going to be done on those types of objects over time, because I think this is not the only one that we will detect,” Milner said. “We need to start doing this, to practice.”