A NASA satellite, inactive since the 1960s, emits an unexpectedly powerful radio pulse, leaving astronomers perplexed.

NASA 's Relay 2 satellite was one of the first operational satellites, launched in 1964 as an experimental communications device. However, NASA discontinued its use the following year, and its onboard electronics ceased to function entirely in 1967 , leaving the inert metal hull orbiting Earth indefinitely.

But now astronomers have been puzzled to discover that this satellite suddenly emitted a powerful radio pulse that briefly eclipsed all other signals emitted by visible objects in space.

As reported by New Scientist , astronomers believe the sudden flash could have been caused by a micrometeorite impact or a random spark.

Clancy James, an astronomer at Curtin University in Australia, and his colleagues were puzzled when, nearly 60 years later , they detected a brief, powerful burst of radio waves coming from the location of the aging Relay-2 satellite.

James and his team were scanning the sky with the Australian Square Kilometre Array Pathfinder (ASKAP) , an array of 36 radio telescopes in Western Australia, looking for signals from fast radio bursts, pulses of radiation coming from other galaxies.

On June 13 of last year, they detected a signal that appeared to be coming from within our galaxy. "If it's nearby, we can easily study it with optical telescopes, so we were incredibly excited, thinking we might have discovered a new pulsar or other object," says Clancy.

But upon closer inspection, the signal appeared to be so close to Earth that ASKAP couldn't focus all of its telescopes at once. This meant it must have come from within 20,000 kilometers of Earth , Clancy says.

The researchers also discovered that the signal was very short-lived, lasting less than 30 nanoseconds. "It was an incredibly powerful radio pulse that far outshone everything else in the sky for a very short time," Clancy told New Scientist .

When they traced the signal back to its source and compared it to the known positions of satellites in the sky, they found only one plausible explanation: the Relay 2 satellite.

Since the satellite is no longer operational, Clancy and his team believe it must have come from an external event, such as an electrostatic discharge (a buildup of electricity that produces a spark-like flash) or a micrometeorite that hit the satellite and produced a cloud of charged plasma.

It would be very difficult to differentiate between these two scenarios, Karen Aplin, a scientist at the University of Bristol in the United Kingdom, adds to New Scientist , since the radio signal produced by both would be similar.

However, it could be useful for monitoring future electrostatic discharges from satellites, he says. "In a world with a lot of space debris and more small, inexpensive satellites with limited ESD protection, this radio detection could ultimately offer a new technique for assessing ESD in space," he concludes.