Astronomers have discovered a mysterious spinning object in the Milky Way that emits a radio wave beam every 18 minutes - and is unlike anything seen before.

The object has been observed to release a huge burst of radio energy for a whole minute every 18 minutes.

Researchers estimate that it is around 4,000 light years away and could be a new class of slowly rotating neutron star with an ultra-powerful magnetic field that can be detected by radio telescopes.

The observation is known as a radio transient, which refers to an object that periodically releases brief flashes of radio signals, as if it is switching on and off in space.

'Spooky' discovery

"It was kind of spooky for an astronomer because there's nothing known in the sky that does that," said Natasha Hurley-Walker, of the International Centre for Radio Astronomy Research at Curtin University, who led the team that made the discovery.

While the occurrences have been seen before - usually as very quick events that flash on and off within seconds or milliseconds or as longer pulses that last days - radio transients had not previously been detected appearing and disappearing over a few hours, Ms Hurley-Walker said.

The team is carrying out more research to figure out what is causing the bursts of energy, but the astronomers think it could be a so-called magnetar, which is a special type of "dead" star with an ultra-strong magnetic field.

Ms Hurley-Walker said the prospect of a repeating radio signal in space may cause some to think it could be a dispatch from aliens, but she said the observations spanned a wide range of frequencies - indicating that they have a natural origin.

First discovered by a student

Former undergraduate student at Curtin University, Tyrone O'Doherty, first discovered the object by looking at Milky Way observations from March 2018 and May 2018 and searching for any differences.

He said he hadn't expected to make such a fascinating discovery, telling a news briefing: "It really feels quite surreal to have found something like this."

To confirm the discovery, Ms Hurley-Walker sifted through extensive archives stretching back to 2013, to see whether the telescope had picked up any other activity from the object.

She found that it had switched on in the first part of 2018, emitting 71 flashes of radio signals from January until March, before switching off again. As she and her colleagues saw in their own observations, the pulses came at regular intervals.

"It's just every 18.18 minutes, like clockwork," she said.

Unleashing further details will require observing the object when it is active again or finding similar objects elsewhere in the Milky Way, Ms Hurley-Walker said.

The team also found that the newly detected object appears to be spinning much more slowly than other magnetars, suggesting it has outlived others that usually last only a few thousand years.

But Ms Hurley-Walker said it could also be an entirely new type of cosmic object that caused the flashes of energy.

"Because we didn't expect this kind of radio emission to be possible, the fact that it exists tells us that some kind of extreme physical processes must be happening," she said.

The researchers detailed the finding in a study published this week in the journal Nature.