Astronomers have observed a rainbow-shaped bow shock around a nearby dead star, RXJ0528+2838. It is located 731 light-years away. The astronomers were puzzled after this surprising discovery, as it doesn't fit with the current understanding of how dead stars interact with their surroundings.
The bow shock, observed using the European Southern Observatory's Very Large Telescope (VLT), is a massive, glowing structure composed of hydrogen, oxygen and nitrogen. Because of its glow, it looks like a rainbow.
As per the findings, which were published in Nature Astronomy, the star rotates around the centre of our galaxy. It also interacts with the gas that permeates the space between stars as it moves. The process creates a type of shock wave called a bow shock, which, according to the astronomers, is a curved arc of material, similar to the wave that builds up in front of a ship.
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The astronomers further noted that these bow shocks are usually formed by material ejecting from the central star. However, in this case, none of the known mechanisms can fully explain the observations. The shape and size suggest the outflow has been ongoing for at least 1,000 years, which is unexpected for a diskless white dwarf like RXJ0528+2838.
"We found something never seen before and, more importantly, entirely unexpected," astronomer Simone Scaringi of Durham University in the UK, said in the official statement. "The surprise that a supposedly quiet, diskless system could drive such a spectacular nebula was one of those rare 'wow' moments."
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The white dwarf's magnetic field is thought to be channelling material from its companion star directly onto the dead star, creating the outflow. However, the magnetic field's strength doesn't fully explain the shockwave's longevity, leaving scientists searching for an additional energy source.
"Our observations reveal a powerful outflow that, according to our current understanding, shouldn't be there," said astronomer Krystian Ilkiewicz of the Nicolaus Copernicus Astronomical Center in Poland.
"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."
