Free Astronomy Magazine May-June 2026

25 MAY-JUNE 2026 ASTRO PUBLISHING a strange nebulosity around RX- J0528+2838 on images from the Isaac Newton Telescope in Spain. Noticing its unusual shape, they ob- served it in more detail with the MUSE instrument on ESO’s VLT. “Ob- servations with the ESO MUSE in- strument allowed us to map the bow shock in detail and analyse its composition. This was crucial to con- firm that the structure really origi- nates from the binary system and not from an unrelated nebula or in- terstellar cloud,” Iłkiewicz explains. The shape and size of the bow shock author of the study published in Na- ture Astronomy . “Our observations reveal a powerful outflow that, ac- cording to our current understand- ing, shouldn’t be there,” says Krystian Iłkiewicz, a postdoctoral re- searcher at the Nicolaus Copernicus Astronomical Center in Warsaw, Poland and study co-lead. ‘Outflow’ is the term used by astronomers to describe the material that is ejected from celestial objects. The star RXJ0528+2838 is located 730 light-years away and, like the Sun and other stars, it rotates around our galaxy’s centre. As it moves, it interacts with the gas that permeates the space between stars, creating a type of shock wave called a bow shock, “a curved arc of mate- rial, similar to the wave that builds up in front of a ship,” explains Noel Castro Segura, research fellow at the University of Warwick in the UK and collaborator in this study. These bow shocks are usually cre- ated by material outflowing from the central star, but in the case of RXJ0528+2838, none of the known mechanisms can fully explain the observations. RXJ0528+2838 is a white dwarf — the left-over core of a dying low-mass star — and has a Sun-like companion orbiting it. In such binary systems, the material from the companion star is trans- ferred to the white dwarf, often form- ing a disc around it. While the disc fuels the dead star, some of the mate- rial also gets eject- ed into space, cre- ating powerful out- flows. But RXJ0528 +2838 shows no signs of a disc, mak- ing the origin of the outflow and resulting nebula around the star a mystery. “The sur- prise that a sup- posedly quiet, disc- less system could drive such a spec- tacular nebula was one of those rare ‘wow’ moments,” says Scaringi. The team first spotted T he 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 dis- covered 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 mys- tery. [ESO/K. Iłkiewicz and S. Scaringi et al. Background: PanSTARRS] T his image from the PanSTARRS survey shows the region of the sky around the dead star RXJ0528+2838, which is located at the very centre of the image. [PanSTARRS]