A mysterious source has been sending radio signals to Earth from space for decades

Unexplained emissions have been happening for 35 years

An unknown source has been sending radio blasts towards Earth since at least 1988, scientists say.

The researchers do not know what object is sending the radio waves towards Earth. The nature of the waves is such that they do not conform with any models that attempt to explain it.

For 35 years, the source has been sending out regular 20-minute blasts of energy that vary considerably in their brightness, researchers say.

The emissions appear something like the blasts that come out of pulsars or fast radio bursts, which last for milliseconds to several seconds. But the newly discovered source sends radio signals that pulsate on a period of 21 minutes – something previously thought impossible by expected explanations.

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.

Scientists believe that process can only work if the magnetic field of the pulsar is strong, and it is rotating quickly enough – if not, there would not be enough energy to see the pulsar from Earth. That has led to the development of the “pulsar death line”, which suggests that sources must be spinning fast and strong enough to be detected.

The newly discovered object named GPMJ1839-10, however, is way beyond that death line. If it is a pulsar, then it seems to be operating in ways that scientists thought impossible.

It could also be a highly magnetised white dwarf or magnetar, an extra kind of neutron star with incredibly strong magnetic fields. But they do not tend to send out emissions of this kind, researchers believe.

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.

Yet more discoveries may be made in this way in the future, said Victoria M Kaspi, a professor of physics at McGill University who did not work on the study. “Only time will tell what else lurks in these data, and what observations across many astronomical timescales will reveal,” she wrote in an accompanying article.

That might include some explanation of how unusual the newly discovered source is. By examining whether there are is a similar collection of other objects in the data, researchers might be able to understand the mechanisms behind the newly discovered emissions.

The findings are reported in a new paper, ‘A long-period radio transient active for three decades’, published in the journal Nature.