A mysterious source has been sending 20 minute radio signals to Earth for 35 years

A mysterious source has been sending radio waves towards Earth since at least 1988, scientists say. 

For the past 35 years, the unknown source has been sending out regular 20-minute blasts of energy that vary in their brightness, however, researchers do not know what object us sending the radio blasts towards Earth. 

The wave's nature does not conform to any models that attempt to explain it.

The emissions appear something like the blasts emitted from pulsars or fast radio bursts, which last for milliseconds to several seconds. 

Pulsars are neutron stars that spin around quickly, throwing out radio blasts as they do. When one crosses Earth, the emissions can be picked up very briefly and brightly, like being in the path of the light from a rotating lighthouse.

But the newly discovered source sends radio signals that pulsate on a period of 21 minutes – something previously thought impossible by expected explanations.

However, this new object, called GPMJ1839-10, is beyond the "pulsar death line" - if the magnetic field of the pulsar is strong, and it is rotating quickly enough it can be picked up– if not, there would not be enough energy to see the pulsar from Earth. 

This means the source must be spinning fast and strong enough to be detected. But if it is a pulsar, then it is operating in ways that were thought to be impossible. 

It is also thought that the object could be a highly magnetised white dwarf or magnetar, an extra kind of neutron star with incredibly strong magnetic fields - but these do not sound out emissions. 

The signals have been detected on Earth since at least 1988, scientists found by going through old records, but they had gone unnoticed by those collecting that data. After the source was detected, researchers checked radio archives and found that the source has been repeating for at least 35 years.

The details of this discovery are published in the journal Nature in a paper titled “A long-period radio transient active for three decades.”

Despite having been detected on Earth for over 30 years, they have gone unnoticed by those compiling the data. 

Victoria M Kaspi, a professor of physics at McGill University who was not involved with the study, wrote in an accompanying article: “Only time will tell what else lurks in these data, and what observations across many astronomical timescales will reveal.”