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Headline: RAW VIDEO: Astronomers left stunned by mysterious shockwave around dwarf star
Caption: Astronomers have captured images of a striking shock wave surrounding a dead star, a discovery that is challenging existing theories about how such objects interact with their environment. Using the European Southern Observatory’s Very Large Telescope (ESO’s VLT), researchers observed the unexpected structure around the white dwarf star RXJ0528+2838, located about 730 light-years from Earth. According to current understanding, the small, inactive star should not be capable of producing such a feature. Gas and dust flowing from stars can sometimes collide with surrounding material, creating shock waves under the right conditions. However, scientists say no known mechanism can fully explain what is being seen around RXJ0528+2838. “We found something never seen before and, more importantly, entirely unexpected,” said Simone Scaringi, associate professor at Durham University and co-lead author of the study, which is published in Nature Astronomy. “Our observations reveal a powerful outflow that, according to our current understanding, shouldn’t be there,” added Krystian Iłkiewicz, a postdoctoral researcher at the Nicolaus Copernicus Astronomical Center in Warsaw and co-lead of the research. RXJ0528+2838 moves through the Milky Way like other stars, interacting with the thin gas between stars as it travels. This motion can create a bow shock — a curved wave of material — similar to the wake that forms ahead of a ship moving through water. “A curved arc of material, similar to the wave that builds up in front of a ship,” explained Noel Castro Segura, a research fellow at the University of Warwick and collaborator on the study. Bow shocks are usually driven by material being expelled from a star. But in this case, scientists cannot identify any recognised process that would allow RXJ0528+2838 to generate such an outflow. The star is a white dwarf — the dense, left-over core of a low-mass star — and is part of a binary system with a Sun-like companion. In many such systems, material is pulled from the companion star to form a disc around the white dwarf, with some of the gas being expelled into space. That process can generate powerful outflows. RXJ0528+2838, however, shows no evidence of having such a disc, leaving astronomers uncertain about the origin of the outflow and the nebula surrounding it. “The surprise that a supposedly quiet, discless system could drive such a spectacular nebula was one of those rare ‘wow’ moments,” said Professor Scaringi. The unusual structure was first noticed in data from the Isaac Newton Telescope in Spain. Follow-up observations using the MUSE instrument on ESO’s VLT allowed the team to study it in greater detail. “Observations with the ESO MUSE instrument allowed us to map the bow shock in detail and analyse its composition. This was crucial to confirm that the structure really originates from the binary system and not from an unrelated nebula or interstellar cloud,” said Dr Iłkiewicz. Analysis suggests the white dwarf has been producing the outflow for at least 1,000 years. While the exact cause remains unclear, researchers believe the answer may lie in the star’s intense magnetic field, which was also confirmed by the observations. The magnetic field appears to funnel material directly from the companion star onto the white dwarf, bypassing the formation of a disc. “Our finding shows that even without a disc, these systems can drive powerful outflows, revealing a mechanism we do not yet understand. This discovery challenges the standard picture of how matter moves and interacts in these extreme binary systems,” Dr Iłkiewicz said. Even so, the magnetic field observed today seems strong enough to power the bow shock for only a few hundred years, meaning it does not fully explain the structure’s size and age. Researchers believe an as-yet-unidentified energy source may be at work. Further observations of similar systems will be needed to solve the puzzle. Astronomers say ESO’s Extremely Large Telescope, currently under construction, will play a key role. It will allow scientists “to map more of these systems as well as fainter ones and detect similar systems in detail, ultimately helping in understanding the mysterious energy source that remains unexplained,” Professor Scaringi said.
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