For more than three decades, a mysterious source has been broadcasting 21-minute-long radio pulses at various levels of brightness, or so says an article in Nature. The unknown source has been continuously sending radio signals back to Earth since at least 1988.

The newly discovered source follows a 21-minute pulse pattern, a phenomenon previously considered impossible by scientific explanations. Scientists point out that when this phenomenon crosses the Earth, the emission can be captured very briefly and brightly, as if in the light path of a rotating beacon, uniform bursts of energy alternate with brightness like a rotating disco mirror ball.

Emissions from the bursts are approaching from pulsars—fast-spinning neutron stars that emit beams of radio energy—or fast bursts of radio, lasting from milliseconds to several seconds.

Details of the discovery were published in Nature in a paper titled “Long Period of Transient Radio Active for Three Decades.” The object called GPMJ1839-10 crosses the “pulsar death line” — if the pulsar’s magnetic field is strong and rotates fast enough, it might be captured — otherwise, there won’t be enough energy to see the pulsar from Earth.

Another theory is that the object could be a highly magnetized white dwarf or magnetar, which is an extra type of neutron star with incredibly strong magnetic fields – but these are not detecting emissions.

Scientists believe that these radio signals have been emitted to Earth since 1988, through ancient recordings, but have gone unnoticed by those who collected this data. After discovering the source, the researchers examined the radio archives and found that the source had been repeating for at least 35 years. The nature of this phenomenon remains uncertain.

According to the researchers, it is not known which object is sending these radio waves to the planet. Studies in this field may include some explanations for how strange this mysterious source is.

“Only time will tell what lies in this data and what observations will reveal at many astronomical time scales,” Victoria M. Caspi, a professor of physics at McGill University who was not involved in the study, wrote in an accompanying paper.

* Trained under Thays Martins