Could this finally be our first close encounter, the visit from ET we have waited our whole lives for?
Scientists led by Stephen Hawking are today using high-tech scanners to discover if a huge, cigar-shaped space object hurtling through our solar system was sent by an alien civilisation.
The object in question, christened "Oumuamua", is about 400m long, 80m wide and travelling at 315,000km/h. And although it could just be an asteroid, barmy as it may seem, researchers are taking seriously the possibility that it could be a spaceship, according to the Daily Mail.
The team of scientists, called Breakthrough Listen, will use the world's largest directable radio telescope, at Green Bank in West Virginia, to follow it for 10 hours.
They are listening for electromagnetic signals, no stronger than those emitted by a mobile phone, that cannot be produced by natural celestial bodies. If they find them, it would be proof that extraterrestrial forces really could be at play.
For the moment, they are trying to contain their excitement. But the name they have given this bizarre object betrays their optimism. Oumuamua is a Hawaiian term meaning "a messenger from afar arriving first". (The far less sexy official name is A/207 U).
Most intriguingly, it is the wrong shape for an asteroid — they are typically round.
Hawking and his colleagues at Breakthrough Listen report: "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."
Another oddity is that Oumuamua is flying very "cleanly", without emitting the usual cloud of space dust that astronomers observe around asteroids.
Experts say this suggests it is made of something dense: probably rock, but possibly metal.
It was first detected on October 19 by a long-running research programme called Pan-Starrs, which uses powerful telescopes to photograph and monitor the night sky at the University of Hawaii. Its amazing speed has led some experts to conclude it is the first such object to have come towards us from outside our solar system. Analysts also say its faintly red colour indicates it has been subjected to interstellar cosmic radiation which is harsher than we experience in our solar system.
The fact that it doesn't seem to have engines or show signs of propulsion may wreck the interplanetary-spacecraft theory. But Professor Avi Loeb, an astrophysicist from Harvard University, suggests it might just be coasting.
"Perhaps the aliens have a mothership that travels fast and releases baby spacecraft that freely fall into planetary systems on a reconnaissance mission," Professor Loeb posited to the journal Scientific American.
"In such a case, we might be able to intercept a communication signal between the different spacecraft."
While he acknowledges that the chances of detecting alien activity are "very small'", Prof Loeb adds that it's "prudent" to check. After all, it could even turn out to be some sort of intergalactic Marie Celeste, the infamous ghost ship found drifting with no crew.
"Even if we find an artefact that was left over — some space device or junk from an alien civilisation — and there are no signs of life on it, that would be the greatest thrill I can imagine having in my lifetime," he says.
"It's really one of the fundamental questions in science, perhaps the most fundamental: are we alone?"
Today, we may finally find out, even if it is a bit late.
When Oumuamua was first spotted, it was already heading away from Earth, having passed within 24 million kilometres of us on October 15. (That's about 85 times the distance from Earth to the moon, which may sound an awfully long way, but considering the speed it travels, it's really a squeak away.)
At that point, no alien passenger seems to have waved from the window. Perhaps they scanned Earth for signs of intelligent life and chose to keep whizzing along.
Nevertheless, we can still get a good enough look at Oumuamua's rear end to detect any extraterrestrial technology on board, says Andrew Siemion, the research centre director at the Search for ExtraTerrestrial Intelligence (Seti) in California, which works with the scientists at Breakthrough Listen. The Green Bank telescope's 10-hour scan will check for any transmissions across the full spectrum of electromagnetic wavelengths, Dr Siemion says.
"It's like a radio station you tune into with your car stereo," he explains.
"Nature doesn't broadcast on a very specific frequency — it smears it out. Technology behaves differently. It can compress electromagnetic energy. So we look for those specific signs and for repeating patterns which nature doesn't tend to do. We look for structure."
Presumably they are also looking for Nobel Prizes, along with a place in the roll-call of humankind's greatest discoveries.
On the other hand, if Green Bank draws a blank, there is always the possibility that the aliens are using technologies that even our best kit can't detect. That, of course, is one of the challenges of hunting for aliens.
Meanwhile, Oumuamua will still present us with a host of other problematic questions.
For example, where did this weird object come from?
Scientists' initial calculations suggested Oumuamua came from Vega, a star some 25 light years away in the Lyra constellation. This might be plausible, were it not for the fact that, even travelling at its amazing speed, it would have taken around 300,000 years to get here.
But space doesn't stand still, and Lyra wasn't in that position 300,000 years ago. Instead, it's likely Oumuamua has been travelling through space for hundreds of millions of years.
Furthermore, how many other Oumuamuas are there pinging about, and could they pose a lethal danger to us if they were to come rather closer than this one
The answers to those questions seem to be "a lot", and "yes".
That astronomers have finally confirmed the existence of such an "interstellar interloper" (as they call it) may prove earlier theories true — that there are multitudes of these things flying through our cosmic neighbourhood.
A new report in the Astrophysical Journal, by astronomers at the University of California, makes the bold projection that there could be as many as 1000 interstellar visitors arriving and leaving our solar system every year.
Oumuamua is now due to pass Jupiter in May 2018, and Saturn in January 2019. After that, it will fade from view and leave us for ever. But what about the others? The odds suggest that our planet has survived countless near-misses by these intergalactic speedsters. And each time one shoots past, the odds against a collision can only get smaller.
It is not clear what would happen if one were to hit us. But a report in the respected journal Nature warns that the sheer speed of an intergalactic object such as Oumuamua would make its impact on Earth more catastrophic than any wrought by a comet or asteroid from within our home solar system. Depending on its size, it is possible it could wipe out life on the planet.
The most likely lesson Oumuamua brings is that we may be a cosmic hair's width away from being smashed out of existence, just like our dinosaur forebears. With that in mind, perhaps it would be reassuring if this interstellar visitor turned out to be a tin can full of aliens.