Someone may have forgotten to turn off the TV at the other end of the universe.
Or maybe someone has sent us an emoji from a faraway mothership.
In other words, we don't have a clue what transmitted the single fast radio burst scientists picked up last week. But we do know where it came from: A galaxy far, far away.
In a study published this week, researchers at the California Institute of Technology claim to have traced a single radio burst back to its home nearly 8 billion light-years away.
Fast radio bursts, or FRBs — typically lasting anywhere from a fraction of a millisecond to a few milliseconds — have been enshrouded in mystery since they were first discovered in 2007. They're so powerful that they can make their way to our neck of the universe from impossibly far away, although it's rare that we receive them.
That's likely to change over the next few years as new pace-scanning equipment that specializes in FRBs comes online.
Back in January, a newly built Canadian telescope picked up no fewer than 13 fast radio bursts, all seeming to originate some 1.5 billion light-years away. But that's considerably easier to find than one solitary FRB.
What all fast radio bursts have in common is mathematical regularity. They beep-beep-beep at exactly the same intervals. But repeating FRBs are a lot easier to pick up and trace than a single radio burst.
"Finding the locations of the one-off FRBs is challenging because it requires a radio telescope that can both discover these extremely short events and locate them with the resolving power of a mile-wide radio dish," study author and Caltech professor Vikram Ravi explained a statement.
The signal appears to hail from a galaxy similar in size to our own, a region with such a low rate of star formation that scientists call it a "mellow" galaxy.
The report comes a week after scientists in Australia announced the signal's discovery, dubbing it FRB 190523. To find that tiniest of blips in the cosmos, the researchers sifted through vast amounts of data collected by the Australian Square Kilometre Array Pathfinder.
Keith Bannister, who led that study, called it "the big breakthrough that the field has been waiting for since astronomers discovered fast radio bursts."
And now that researchers have zeroed in on its source, we may soon learn what caused it.
In the meantime, that single, incredibly brief transmission can carry a universe of data. Its odyssey across staggering distances could reveal what lies between star systems.
"These bursts are altered by the matter they encounter in space," Jean-Pierre Macquart, the professor who authored last week's study, noted in a statement. "Now we can pinpoint where they come from, we can use them to measure the amount of matter in intergalactic space."