In a scenario that sounds like the opening for a “Zombies From Outer Space” movie, the European Space Agency released a photo of a never-before-seen star that was formed when two dead white dwarf stars collided – but instead of destroying each other, the white dwarfs merged into a new kind of zombie star that’s not really alive but still emitting a very bright X-ray light that’s expected to last a brief (in star time) 10,000 years before a ship can arrive and blow the zombie star’s brains out and chase down any zombie space ships it had launched.
Just kidding … it will last until the zombie star collapses into itself, forming a neutron star. Throw those zombie spaceships and the brain-blowing mission back in – is it plot-worthy?
“Recently, a WD merger product, IRAS 00500+6713, was identified. IRAS 00500+6713 consists of a central star embedded in a circular nebula. The analysis of the optical spectrum of the central star revealed that it is hot, hydrogen, and helium free, and it drives an extremely fast wind with a record breaking speed.”
From the journal Astronomy & Astrophysics comes that astronomer-speak analysis of an event that was first discovered in the constellation Cassiopeia (if you think that would be a good name for a band, it’s already taken (minus one 's')) by researchers at the University of Bonn in Germany and the Russian Academy of Sciences using NASA's Wide-field Infrared Survey Explorer (WISE) space telescope. Lacking both hydrogen and helium, two elements found in white dwarfs, the astronomers speculated that J005311 was something never seen before – the product of a white dwarf collision that became reanimated and started burning again. But how?
“Low-resolution X-ray spectra reveal large neon, magnesium, silicon, and sulfur enrichment of the central star and the nebula. We conclude that IRAS 00500+6713 resulted from a merger of an ONe and a CO WD, which supports earlier suggestion for a super-Chandrasekhar mass of this object. X-ray analysis indicates that the merger was associated with an episode of carbon burning and possibly accompanied by an SN Iax.”
Unfortunately, Google Translate doesn’t work on astronomer-speak. The study reveals that astrophysicist Lidia Oskinova of the University of Potsdam led a team using the ESA's XMM-Newton X-ray telescope to look at both J005311 and the nebula surrounding it -- IRAS 00500+6713. What they determined was that the colliding white dwarfs (that band name isn’t used yet) were distinct – one was primarily oxygen and neon (ONe) while the other was carbon monoxide (CO). The neon explains why the zombie star (photo here) glows green.
"Such an event is extremely rare. There are probably not even half a dozen such objects in the Milky Way, and we have discovered one of them."
Dr. Götz Gräfener from the Argelander Institute for Astronomy (AIfA) at the University of Bonn explains in the press release what a big deal this zombie star is. Unfortunately, its zombie lifespan is brief. J005311 will turn its elements into iron in just a few thousand years, fading away its glow. It will then collapse under its own gravity while its former electrons and protons fuse into neutrons. The end result will be an incredibly dense neutron star measuring only few kilometers in diameter. However, like all zombies, it will go out with a bang – in this case, a supernova explosion.
A movie-worthy ending for a unique zombie star. Throw in a parting shot of a small object emerging from the explosion and we’ve got the potential for a sequel.