This Red Giant is Bringing a "Zombie Star" Back To Life
A rare spotting of cosmic necromancy.
Astronomers across the globe discover something new about the universe pretty much every day, and sometimes they don’t even do it on purpose. But what the European Space Agency discovered back in August 2017 is something out of a horror movie.
The space organization’s INTEGRAL space observatory — a radiation-detecting satellite — caught a burst of X-rays coming from an extremely rare stellar duo: a massive red giant breathing life into “zombie” neutron star, a process depicted below.
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Neutron stars are the hyper-dense cores stars 25 to 30 times more massive than the Sun leave behind after they erupt in a supernova. The one the ESA spotted released a flare of radiation after it fed on the winds emitted by a swollen red giant, a lot like how the undead feast on brains.
Artist impression depicting winds from a red giant star impacting a neutron star to create prolonged X-ray emission. Such a system is rare: no more than ten are currently known.
A paper published in the journal Astronomy & Astrophysics, categorizes this pair as a “symbiotic X-ray binary.” Only ten similar systems have been discovered.
“[INTEGRAL] caught a unique moment in the birth of a rare binary system,” the study’s lead author Enrico Bozzo of the University of Geneva says in a statement. “The red giant released a sufficiently dense slow wind to feed its neutron star companion, giving rise to high-energy emission from the dead stellar core for the first time.”
The age difference between the two stars makes this pair even more bizarre. Red giants are one of the final stages of sun-like stars, making them extremely old, while highly magnetized neutron stars are typically on the younger side of their lifespan.
Artist impression of some possible evolutionary pathways for stars of different initial masses.
This leads scientists to believe that the zombie star could have once been a white dwarf that absorbed so much matter from the red giant it transformed into a neutron star.
“These objects are puzzling,” Bozzo says in a press release. “It might be that either the neutron star magnetic field does not decay substantially with time after all, or the neutron star actually formed later in the history of the binary system. That would mean it collapsed from a white dwarf into a neutron star as a result of feeding off the red giant over a long time, rather than becoming a neutron star as a result of a more traditional supernova explosion of a short-lived massive star.”
The exact reason behind this stellar voodoo might not be clear just yet. But with another example of this system under their belt, astronomers are well on their way to understanding this cosmic necromancy.
