When you buy through links on our articles, Future and its syndicate partners may earn a commission.
Credit: ESO/K. Iłkiewicz and S. Scaringi et al. Background: PanSTARRS
Using the Very Large Telescope (VLT), astronomers have discovered an unexpected shock wave around a dead star. The team behind the shock discovery (in more ways than one) is stunned by this beautiful arc of material, which defies current expectations and theories surrounding such stellar remnants. Thus, it could redefine our understanding of how dead stars interact with their environment.
This stellar remnant is a white dwarf, the depleted stellar core left when a star orbiting the same mass as the sun runs out of fuel for nuclear fusion and loses its outer layers. This white dwarf is designated RXJ0528+2838 and is located 730 light-years away from Earth. It has a companion star in orbit around it, from which the dead star pulls material away with its gravity. Under normal circumstances, this matter would typically form a disk around the white dwarf that gradually escapes material to its surface, leaving other stellar matter to be lost to space by strong outflows that hurl it into space. However, in the case of RXJ0528+2838, there is no sign of such a disc, making the presence of the shock wave completely unexpected.
“We found something never seen before and, more importantly, completely unexpected,” team leader Simone Scaringi of Durham University in the UK said in a statement. “The surprise that a supposedly quiet, diskless system could drive such a spectacular nebula was one of those rare ‘wow’ moments.”
An image taken by the MUSE instrument on ESO’s Very Large Telescope shows shock waves around the dead star RXJ0528+2838. | Credit: ESO/K. Iłkiewicz and S. Scaringi et al
The shock wave, observed by the VLT’s Multi Unit Spectroscopic Explorer (MUSE), is created as the white dwarf moves through space, rotating around the center of the Milky Way, just like the sun and the other stars of our galaxy. The dead star pushes the interstellar gas in front of it as it travels, creating a type of shock wave called a bow shock, similar to how a wave forms in front of the bow of a ship.
“Our observations reveal a strong flow that, according to our current understanding, should not exist,” said Krystian Iłkiewicz, a postdoctoral researcher at the Nicolaus Copernicus Astronomical Center in Warsaw, Poland.
The team first saw hints of this unexpected structure when they examined images of RXJ0528+2838 captured by the Isaac Newton Telescope in Spain. Noting the unusual shape of this formation, they followed up these initial observations with the VLT’s MUSE instrument.
“Observations with the MUSE instrument allowed us to map the arc shock in detail and analyze its composition,” added Iłkiewicz. “This was crucial to confirm that the structure really came from the binary system and not from an unrelated nebula or interstellar cloud.”
This image from the Digitized Sky Survey (DSS) shows the region of the sky around the dead star RXJ0528+2838, which is right in the center of the image. | Credit: ESO/Digitized Sky Survey 2. Acknowledgments: D. De Martin
Both the size and the shape of the arc shock around RXJ0528+2838 suggest to the team that material has been removed from this white dwarf for at least 1,000 years. This is a mystery in itself, as scientists cannot explain how a white dwarf without a surrounding disk of matter can maintain an outflow for such an extended period.
The team isn’t completely in the dark about this, though. They suspect that RXJ0528+2838’s strong magnetic field funnels stolen stellar matter from the companion star directly to the white dwarf, without giving a disk a chance to form.
“Our finding shows that even without a disk, these systems can generate strong flows, revealing a mechanism we still don’t understand,” Iłkiewicz said. “This discovery challenges the standard picture of how matter moves and interacts in these extreme binary systems.”
However, even with this magnetic field, the team believes that the shock wave should only have been maintained for about 100 years. That means there must be another energy source or “mystery engine” in this system that has fueled this flow and the shock wave it creates for ten times longer than that.
An illustration of the ELT that could be integral to solving the mystery of this unexpected white dwarf shock wave | Credit: ESO/L. the pavement
Solving this mystery may depend on studying such binary systems using the future Extremely Large Telescope (ELT), currently under construction at the same location where the VLT operates, the Atacama Desert region of northern Chile.
Scaringi predicts that the ELT will help astronomers “map more of these systems, as well as fainter ones, and detect similar systems in detail, ultimately helping to understand the mysterious energy source that remains unexplained.”
The team’s research was published Monday (January 12) in the journal Astronomy of nature.