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Outback Telescope Eavesdrops on Interstellar Visitor

A telescope in outback Western Australia has listened to a mysterious cigar-shaped object that entered our Solar System in October 2017.

When ‘Oumuamua was first discovered, astronomers thought it was a comet or an asteroid from within the Solar System. But after studying its orbit and discovering its long, cylindrical shape, they realised ‘Oumuamua was neither and had come from interstellar space.

There was even speculation ‘Oumuamua could be an alien spacecraft, so astronomers went back through observations from the Murchison Widefield Array (MWA) telescope to check for radio transmissions coming from the object between the frequencies of 72 and 102 MHz – similar to the frequency range in which FM radio is broadcast. While they did not find any signs of intelligent life, Prof Steven Tingay of the Curtin University node of the International Centre for Radio Astronomy Research said: “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”.

Tingay said the research team was able to look back through all of the MWA’s observations from November, December and early January, when ‘Oumuamua was between 95 million and 590 million km from 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 extraterrestrial intelligence from traditional targets such as stars and galaxies to objects that are much closer to Earth. 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.”

By combining observations from a host of telescopes, scientists have determined that ‘Oumuamua is most likely a cometary fragment that has lost much of its surface water because it was bombarded by cosmic rays on its long journey through interstellar space. Researchers have now suggested there could be more than 46 million similar interstellar objects crossing the Solar System every year.

While most of these objects are too far away to study with current technologies, future telescopes such as the Square Kilometre Array (SKA) will enable scientists to understand more about these interstellar interlopers. “So once the SKA is online, we’ll be able to look at large numbers of objects and partially balance out the low probability of a positive detection,” Tingay said.

The discovery was published in The Astrophysical Journal (https://goo.gl/bfiKpc).