Dead star emits perplexing shock wave for 1,000 years
A star spends its entire life influencing the cosmos for billions of miles in every direction. In some circumstances, surrounding plumes of gas and dust will even interact to generate powerful, observable shock waves. However, once its nuclear fuel is completely exhausted, a star is often reduced to a dense, inactive core that floats in space with little impact on its surroundings. So when astronomers detected shock waves emanating from a dead stellar object 730 light years from Earth, they were understandably perplexed.
âWe discovered something never seen before and, more importantly, completely unexpected,â explained Simone Scaringi, a researcher at the University of Durham in the United Kingdom.
As Scaringi and his team describe in a study published today in the journal Natural astronomyThey first noticed curious signals coming from the white dwarf RXJ0528+2838 while analyzing images taken by the Spanish Isaac Newton telescope. A white dwarf is what remains after the death of a low-mass star and sometimes exists in a binary system with another stellar object. In this case, RXJ0528+2838 is around a still-living star similar in size to our sun.
An unexpected shock wave
In such cases, material from the active star is usually siphoned into the white dwarf to form a debris disk around it. Part of this energy is then also projected into space in so-called outputs. But RXJ0528+2838 doesn’t have a disk, so the dead star shouldn’t create such a curved “arc shock” outflow or the resulting nebula â and yet it does. Additionally, the white dwarf’s outflow has been going on for at least 1,000 years.
âOur observations reveal a powerful outflow that, based on our current understanding, should not be there.â » added Krystian IĆkiewicz, co-author of the study at the Nicolaus Copernicus Astronomical Center in Poland.
To study the cosmic anomaly in more detail, the team used the Multi-Unit Spectroscopic Explorer (MUSE) inside the European Southern Observatory’s Very Large Telescope. MUSE helped the researchers construct a detailed map of the arc damper and its composition, which they traced back to RXJ0528+2838 instead of an unrelated dust cloud or nebula.
The team confirmed that RXJ0528+2838 also has a powerful magnetic field that allows it to collect material from its companion. Although further examination is needed, they believe it is this magnetic field that may help explain the dead star’s strange behavior.
âOur discovery shows that even without a disk, these systems can generate powerful outflows, revealing a mechanism that we do not yet understand,â IĆkiewicz said, adding that their new study ânow challenges the standard picture of how matter moves and interacts in these extreme binary systems.â
There are still many unanswered questions about this unprecedented cosmic relationship. Importantly, the magnetic field that Scaringi calls the white dwarf’s “mystery engine” does not appear strong enough to generate the observed arcing shock. Instead, the current field is expected to fuel an outflow that will last only a few hundred years. But with further research, astronomers hope to one day resolve this discovery that no one predicted.
“The surprise that a supposedly quiet, quiet system could drive such a spectacular nebula was one of those rare ‘wow’ moments,” Scaringi said.
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