When a cigar-shaped interstellar object, `Oumuamua, entered our skies in October 2017, it caused quite a stir. There were even suggestions(however spurious) it could be an alien spaceship. Well, sorry to put a dampener on any ET-type fantasies you may be harboring, but scientists have been listening out for radio signals emanating from the space rock – and heard nothing (results published in The Astrophysical Journal). So unless there are some very sneaky aliens on board keeping suspiciously quiet, we can safely assume it is definitely not an alien spacecraft. At least it means we won't have to worry about any "Independence Day" -style alien invasion just yet. (Especially as there are plenty of other things closer to home to worry about.)
`Oumuamua is our first known interstellar visitor, and while its origins remain a bit of a mystery, we do know that it is roughly 10 times as long as it is wide, it measures 400 meters (1,300 feet) or more tip-to-toe, and it is a dark, reddish color. This tint is due to the cosmic rays hitting it as it travels through different star systems.
The general consensus is that `Oumuamua is an asteroid visiting our star system from a different part of space. But to thoroughly rule out the possibility we have a spacecraft manned by little green men on our hands, astronomers from Western Australia re-examined data from the Murchison Widefield Array telescope made between December and early January. At this point, `Oumuamua would have been between 95 million and 590 million kilometers (59 million and 366 million miles) away from Earth.
“If advanced civilizations 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,” Steven Tingay, a professor at the Curtin University node of the International Centre for Radio Astronomy Research (ICRAR), said in a statement.
“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.”
The telescope sits in a remote part of Australia in a region called Murchison, where there is little human activity or radio interference that can affect the data.
The researchers were particularly interested in radio transmissions emitted at frequencies around the 72 to 102 megahertz mark. Disappointingly (or reassuringly, depending on where you stand), they heard diddly squat.
Instead, they reckon the most likely scenario is that it is a cometary fragment – a bit like a slab of extraterrestrial driftwood. What's more, there may be more than 46 million such interstellar objects visiting our Solar System every single year.
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