In a landmark development, astronomers have successfully traced a repeating radio signal from space back to its origin – a red dwarf star in a binary system with a white dwarf.
Astronomers have been intrigued by periodic radio pulsations since their discovery in 2022. These signals, repeating every 18 minutes, stood out for their intensity and unexpected behavior. A team from Curtin University, including researcher Natasha Hurley-Walker, has advanced our understanding by identifying the source as a common red dwarf star, possibly partnered with a white dwarf in a binary orbit.
The nature of these radio bursts has puzzled scientists, primarily because traditional models suggest such slow pulsars should not emit radio waves. Pulsars, usually rapidly spinning neutron stars, emit beams of radio waves, much like a lighthouse. This new discovery, however, challenges existing theories, hinting at unexplored physics in pulsar emission or potentially offering new insights into pulsar mechanics.
While more slowly repeating radio sources have been found, totaling around ten known ‘long-period radio transients,’ their locations within the densely populated regions of the Milky Way make it difficult to pinpoint the exact star responsible. This challenge led to a concerted effort to scan less crowded areas of the galaxy using the Murchison Widefield Array radio telescope in Western Australia. Undergraduate Csanád Horváth’s analysis led to the discovery of a new source, GLEAM-X J0704-37, which distinguishes itself with pulses every 2.9 hours, marking it as the slowest yet discovered.
Further investigations conducted with the MeerKAT telescope, a highly sensitive instrument in South Africa, allowed researchers to precisely locate the radio waves emanating from a red dwarf star. These stars, making up 70% of the Milky Way’s population, are typically too faint for the naked eye, highlighting the significance of this technological breakthrough.
The interaction between the red and white dwarfs is seen as the probable cause of these radio signals. The red dwarf generates a stellar wind of charged particles, which, upon interacting with the white dwarf’s magnetic field, accelerates to produce radio emissions. This interaction draws parallels to how the Sun’s wind interacts with Earth’s magnetic field to create auroras and low-frequency radio waves.
Current analogous systems, such as AR Scorpii, have been observed, where a white dwarf intensely affects its red dwarf companion. However, these known systems do not match the brightness or slow pulse rate of the recently discovered sources, suggesting that more complex or varied systems may exist.
The discovery of the radio wave source is a testament to the unpredictable nature of space phenomena and the ongoing commitment of astronomers to unravel these mysteries. As they continue to scan the skies, new discoveries may provide further insights into these fascinating cosmic events.
