A Team of astronomers have made a fascinating discovery that forces us to rethink our understanding of how dead stars behave. Using the powerful Low Frequency Array (LOFAR) radio telescope in the Netherlands, the team have found a white dwarf star that’s doing something completely unexpected, sending out bright radio pulses in a strange, rhythmic pattern.
The star system, officially called ILT J163430+445010 (or J1634+44 for short), is located over 3,500 light years from Earth. What makes it extraordinary isn’t just that it’s sending radio signals, it’s how those signals behave. Every 14 minutes, this dead star emits radio pulses that have a bizarre twist, some waves spin in circles while others vibrate in straight lines. This rapid switching between different types of polarisation has never been seen before in any white dwarf.
“J1634+44 is unique, even among the small population of long period transients that have been found so far. Its rapid polarisation switching, from circular to linear, has never been observed before on any type of object” – Sanne Bloot, lead researcher from the Netherlands Institute for Radio Astronomy.
To appreciate why this discovery is so remarkable, it helps to understand what a white dwarf is. When a star like our Sun reaches the end of its life, it sheds its outer layers and leaves behind a hot, incredibly dense core, a white dwarf. These stellar remnants are typically about the size of Earth but contain as much mass as our Sun. They’re usually quiet objects that simply cool down over billions of years.
Image of the Sirius system taken by the Hubble Space Telescope. Sirius B, which is the closest white dwarf to Earth, can be seen as a faint point of light to the lower left of the much brighter Sirius A. (Credit : NASA/ESA)
This particular white dwarf is exceptionally hot, with surface temperatures between 15,000 and 33,000 degrees Celsius, much hotter than our Sun’s 5,500 degree photospheric temperature. But temperature isn’t what makes it special, it’s the fact that it’s actively producing powerful radio emissions.
The radio pulses don’t arrive randomly. Instead, the pulses come in pairs, but only after the dead star has spun around several times without producing any detectable signals. The team believe this rhythmic behaviour indicates the white dwarf has a companion, possibly another dead star or a brown dwarf (a “failed star” that never ignited nuclear fusion).
This white dwarf belongs to an extremely rare class of objects called long period transients (LPTs). Only ten of these slow pulsing radio sources have been discovered so far, making each new find precious for understanding how they work. Unlike typical pulsars that spin rapidly and emit regular signals, these objects pulse much more slowly and sporadically.
The LOFAR ‘superterp’. This is part of the core of the extended telescope located near Exloo, Netherlands (Credit : LOFAR / ASTRON)
The discovery was made possible by LOFAR’s systematic survey of the northern sky. Over nearly four years, astronomers tracked the source and recorded 19 separate radio bursts, with the brightest being hundreds of times stronger than the faintest detectable signal.
As radio telescopes continue surveying the sky, the team hope to find more of these mysterious objects, potentially revealing an entirely new population of cosmic radio sources and helping solve the puzzle of how dead stars can spring back to life as powerful radio beacons.
Source : Astronomers Uncover White Dwarf System Emitting Bright Radio Pulses With Strange Rhythm