A strange signal from deep space has been detected every 22 minutes for more than 30 years. Scientists have no idea what is causing it.

• A mysterious object spotted in the cosmos is beaming radio waves toward Earth every 22 minutes.
• Signals from this type of cosmic object usually slow down over time.

A cosmic object that has been pulsing radio waves toward Earth every 22 minutes for more than 30 years has left scientists baffled.

The object is thought to be a dying star that is emitting energy from its poles. But it's spinning too slowly to exist.

"Assuming it's a magnetar, it shouldn't be possible for this object to produce radio waves. But we're seeing them," said Natasha Hurley-Walker, a radio astronomer from Curtin University in Australia who led the research, in a statement.

A phenomenal cosmic lighthouse that shouldn't exist

This object, given the scientific name of GPM J1839−10, sets itself apart because it is remarkably slow and remarkably stable.

"Astronomers expect to see some repeating radio signals in space, but they usually blink on and off much more quickly," Hurley-Walker told The Conversation.

At the end of their life, stars can collapse into neutron stars, superdense objects that pack billions of tons of matter into tiny little spaces, per NASA.

Some neutron stars shoot brilliant beams of light and energy from their magnetic poles. We only pick up the signal as the beam washes over our planet, similar to the light from a lighthouse blinking to a boat offshore.

These create repeated blips on Earth that are so consistent that scientists that first detected them wrongly thought they could be communications from aliens in outer space. But since then, they have figured out they are the gasps of a dying star beaming through the universe.

This star is crossing the death line

Scientists expect pulsating neutron stars to slow down until they reach a "death line." This is a theoretical threshold that dictates that stars that are too slow are about to die. This threshold is usually thought to be crossed when the pulses slow to more than a few minutes apart.

But the pulses coming from GPM J1839−10, the team found, came every 22 minutes. And these could last up to five minutes each, defying all expectations.

"The object we've discovered is spinning way too slowly to produce radio waves," Dr Hurley-Walker said.

This wasn't the first time a super slow object like this one had been spotted.

The same team had previously spotted another slow object that pulsed every 18 minutes or so, lasting up to a minute each. The team postulated the beams were coming from a magnetar, a neutron star with intense magnetic fields.

But GPM J1839−10 had one more science-defying surprise in its pocket.

A dying star that refuses to die out

Looking through archives, Hurley-Walker said the team uncovered GPM J1839−10's "real surprise."

This object's pulses had been picked up, unnoticed, by observatories around the world for years, beaming "like clockwork, every 1,318.1957 seconds, give or take a tenth of a millisecond," per Hurley-Walker.

This goes against what we know about neutron stars. These are expected to die out in months. For instance, the 2018 object only blazed for a short while, between January and March 2018.

But the first record of GPM J1839−10's pulses dates back to 1988 — about 33 years ago.

This could mean the object is a new type of stellar system altogether.

"This remarkable object challenges our understanding of neutron stars and magnetars, which are some of the most exotic and extreme objects in the universe," said Hurley-Walker.

The team will now be trying to reconcile their observations with what we know about the physics of stars.

"Whatever mechanism is behind this is extraordinary," she said.