A mysterious object unlike anything that astronomers have seen before has been discovered in our “galactic backyard”.

In research published Wednesday, scientists described the strange, spinning mass, which is said to release an enormous burst of energy every 20 minutes.

That radiation, which crosses the line of sight of telescopes on Earth for 60 seconds at a time, is one of the brightest radio sources in the sky.

It was detected by a team at the Australia-based International Centre for Radio Astronomy Research, who were mapping radio waves in the Universe.

They believe that the cosmic flasher could be a super-dense star or a white dwarf – collapsed cores of stars – with a powerful magnetic field.

“This object was appearing and disappearing over a few hours during our observations,” said Dr Natasha Hurley-Walker, an astronomer from Curtin University in Australia who led the team.

“That was completely unexpected. It was kind of spooky for an astronomer because there’s nothing known in the sky that does that.

“And it’s really quite close to us – about 4,000 lightyears away. It’s in our galactic backyard.”

The object was discovered using the Murchison Widefield Array (MWA) telescope in the Australian outback.

It’s what’s known to astronomers as a transient – an object in the night sky that turns on and off, such as a dying star.

So-called “slow transients” appear over the course of several days and vanish after a few months. One example is a stellar explosion called a supernova.

“Fast transients” – such as a type of neutron star called a pulsar – flash on and off within seconds or even milliseconds.

The newly discovered object is unusual because it fits neither category, beaming its radio waves across the galaxy in bouts lasting roughly a minute.

Study coauthor Dr Gemma Anderson said that the space thingamajig is smaller than the Sun but incredibly bright.

It’s firing out highly-polarised radio waves, suggesting that it has a powerful magnetic field.

Dr Hurley-Walker said the observations match the description of a hypothetical object called an “ultra-long period magnetar”.

“It’s a type of slowly spinning neutron star that has been predicted to exist theoretically,” she said.

“But nobody expected to directly detect one like this because we didn’t expect them to be so bright.

“Somehow it’s converting magnetic energy to radio waves much more effectively than anything we’ve seen before.”

The team are continuing to monitor the object with the MWA to get a better idea of what it might be.

“More detections will tell astronomers whether this was a rare one-off event or a vast new population we’d never noticed before,” Dr Hurley-Walker added.

The research was published in the journal Nature.