Astronomers say they have identified the source of mysterious radio signals from space that have puzzled scientists since 2022.
The signals, known as long-period transients, are bursts of radio waves that repeat every few minutes or hours, far slower than known pulsars.
In a study published in Nature Astronomy, researchers report that the longest known example, GPM J1839-10, is not a neutron star as initially suspected, but a white dwarf star in a binary system.
The object emits radio pulses every 21 minutes and follows a highly regular pattern that repeats every nine hours.
Long-period transients challenged existing physics because neutron stars are not expected to emit radio waves while rotating so slowly. White dwarfs, the dense remnants of dead stars roughly the size of Earth, offered an alternative explanation. While isolated white dwarfs do not emit radio pulses, scientists have previously observed fast spinning white dwarf pulsars in close binary systems.
GPM J1839-10, located about 15,000 light-years away, was studied using coordinated observations from radio telescopes in Australia, South Africa, and the United States.
Researchers found that its radio pulses arrive in structured groups, strongly indicating a two-star system orbiting every nine hours. Further analysis showed the system is likely a white dwarf paired with an M type dwarf star.
The findings suggest long-period transients may be slow-spinning cousins of white dwarf pulsars.
Scientists say the discovery is a key step toward understanding this new class of cosmic radio sources and may help explain others detected across the Milky Way.