Artist's depiction of 'Oumuamua

Australian radio telescope tunes in to speedy space cigar

Image credit: ESO/M. Kornmesser

Astronomers used the Murchison Widefield Array (MWA) telescope in Western Australia to listen for signs of intelligent life from an asteroid that has fascinated astronomers and laypeople alike because of its unusual shape.

The asteroid, which is named ‘Oumuamua (“a messenger reaching out from the distant past”), was discovered in October 2017 as astronomers observed its passage across the Sun. Its extreme speed, nearly 100,000km/h, is so great that researchers believe it is likely to have originated from outside our solar system, although its precise origins are unknown. This makes ‘Oumuamua the first known interstellar object to have passed through our Solar System.

Due to its interstellar origin and unusual elongated shape, some have speculated that it could contain signs of intelligent life.

“Researchers working on long-distance space transportation have previously suggested that a cigar or needle shape is the most likely architecture for an interstellar spacecraft, since this would minimise friction and damage from interstellar gas and dust,” said Professor Avi Loeb last year. Loeb is a Harvard University astronomer and advisor to the Breakthrough Listen project, which searches for signs of intelligent extra-terrestrial life.

Investigations by the Allen Telescope Array and the Green Bank Telescope in December 2017 detected no signs of intelligent life or technology, although observations of ‘Oumuamua continued into January with a search for radio transmissions by the MWA.

“If advanced civilisations do exist elsewhere in our galaxy, we can speculate that they might develop the capability to launch spacecraft over interstellar distances and that these spacecraft may use radio waves to communicate,” said Professor Steven Tingay, who works for the International Centre for Radio Astronomy Research at Curtin University.

“Whilst the possibility of this is extremely low, possibly even zero, as scientists it’s important that we avoid complacency and examine observations and evidence without bias.”

Astronomers used the radio telescope – which is made up of thousands of antennas spaced across the remote landscape – to search for transmissions in the frequency band 72-102MHz while ‘Oumuamua was closer to the Earth. While there were no observed signals from the asteroid, this research has helped broaden the search for intelligent extra-terrestrial life to objects near the earth.

“We found nothing, but as the first object of its class to be discovered, ‘Oumuamua has given us an interesting opportunity to expand the search for extra-terrestrial intelligence from traditional targets such as stars and galaxies to objects that are much closer to Earth,” said Tingay.

“This also allows for searches for transmitters that are many orders of magnitude less powerful than those that would be detectable from a planet orbiting even the most nearby stars.”

Astronomers training their telescope on the unusual object believe it is probably a cometary fragment that lost much of its surface water while being struck by cosmic rays. Although ‘Oumuamua is the first such object confirmed, there may be nearly 50 million similar interstellar objects passing through the Solar System every year.

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