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5h ago

Millennia-Old Bow Shock Found Around Magnetic White Dwarf Defies Theory

The discless polar shows a millennia-long outflow unexplained by its current magnetic field, spurring a systematic hunt for similar binaries.

The central square image, taken with the MUSE instrument on ESO's Very Large Telescope, shows shock waves around the dead star RXJ0528+2838. When a star moves through space it can push away nearby material creating a so-called bow shock, which in this image is glowing in red, green and blue. The colours represent hydrogen, nitrogen and oxygen, respectively. These shocks are usually produced by a strong outflow expelled from the star. However, in the case of RXJ0528+2838 –– a white dwarf with a Sun-like companion –– astronomers discovered that the shock wave can’t be explained by any known mechanism. Some hidden energy source, perhaps magnetic fields, could be the answer to this mystery. European Southern Observatory (ESO)/K. Ilkiewicz and S. Scaringi et al./Handout via REUTERS
Image
The central square image, taken with the MUSE instrument on ESO's Very Large Telescope, shows shock waves around the dead star RXJ0528+2838. When a star moves through space it can push away nearby material creating a so-called bow shock, which in this image is glowing in red, green and blue. The colours represent hydrogen, nitrogen and oxygen, respectively. These shocks are usually produced by a strong outflow expelled from the star. However, in the case of RXJ0528+2838 –– a white dwarf with a Sun-like companion –– astronomers discovered that the shock wave can’t be explained by any known mechanism. Some hidden energy source, perhaps magnetic fields, could be the answer to this mystery. European Southern Observatory (ESO)/K. Ilkiewicz and S. Scaringi et al./Handout via REUTERS

Overview

  • Peer-reviewed results in Nature Astronomy on January 12, 2026 report the first confirmed bow shock around a polar white dwarf, RXJ0528+2838.
  • ESO’s VLT/MUSE mapped the structure to the binary and identified emission from hydrogen, nitrogen, and oxygen.
  • The bow shock spans roughly 3,800–4,000 times the Earth–Sun distance and indicates sustained outflow for at least 1,000 years.
  • The system lacks an accretion disc, and its measured magnetic field could only power such activity for a few hundred years, leaving the energy source unresolved.
  • Located about 730 light-years away, the object was first flagged by a student, and the international team now plans broader searches that future facilities like ESO’s ELT can advance.