The SETI initiative Breakthrough Listen has announced that preliminary observations of the first known interstellar asteroid show no sign that the 400 m (1,300 ft)-long object is anything other than natural. No directed or broadcast radio transmissions have been detected from `Oumuamua (A/2017 U1), but observations and analysis continue.

It was a long shot, but scientists at Breakthrough Listen couldn't pass up on the chance that the first detected interstellar visitor to the Solar System might be more than it seemed. Earth-based telescopic observations of `Oumuamua after it was discovered on October 19, 2017 by the University of Hawaii's Pan-STARRS 1 telescope on Haleakala indicated that the object was on an open-ended hyperbolic course that had already brought it to within 0.25 AU (23 million mi, 37 million km) of the Sun in September, and that it was speeding back into deep space at 95,000 km/h (59,000 mph).

But what intrigued Breakthrough Listen was that the object is a rocky or metallic spindle and that this shape could mean that `Oumuamua is artificial. Not wanting to miss the chance that it was an alien spacecraft similar to Sir Arthur C Clarke's fictional Rama, the scientists turned the Breakthrough Listen backend instrument on the Robert C. Byrd Green Bank Telescope in West Virginia on `Oumuamua.

The first of four planned observation blocks was conducted on December 13 from 3:45 pm to 9:45 pm EST. The scan was of the L, S, X, and C radio bands that consist of several billion radio bands between 1 and 12 GHz. After calibration, 90 TB of raw data was recorded over a two-hour period. This was then sent through the Breakthrough Listen "turboSETI" pipeline software to seek out signals that are drifting in their frequency. This allows the scientists to pick out intelligent signals while eliminating those caused by the asteroid's motion distorting background radio signals and human interference.

Though there are more observations to be made and more analysis to be carried out, Breakthrough Listen says that no intelligent signals have been found so far. However, the study is ongoing and the organization invites the public to inspect a subset of the S-band data for themselves with the help of an online tutorial.

"It is great to see data pouring in from observations of this novel and interesting source," says Andrew Siemion, Director of Berkeley SETI Research Center. "Our team is excited to see what additional observations and analyses will reveal."