Thermonuclear Blast Sends Supernova Survivor Star Hurtling Through Galaxy

The material ejected by a supernova initially expands very rapidly, but then gradually slows down, forming an intricate giant bubble of hot glowing gas. Eventually, the charred remains of the white dwarf that explosed, known to astronomers as “Dox,” will overtake these gaseous layers, and speed out onto its journey across the galaxy. (University of Warwick / Mark Garlick)

(CN) — Nothing is certain in space, especially the evolution of a dying star sent careening across the cosmos.

The habits of dying stars have been recorded by astronomers for centuries, but researchers from the University of Warwick say a white dwarf making its way across the galaxy has a unique origin story. They detail their findings Tuesday in the journal Monthly Notices of the Royal Astronomical Society.

Long before the white dwarf arrives on the scene there is a red giant.

Typically, a red giant is one of the last stages of the stellar evolution for a star. Eventually our own sun will undergo the same process and burn away its helium, shedding its outer layer in a brilliant nebula with ejected ionized gas escaping into space like glowing wisps from a fairy tale.

After this light show remains the white dwarf, the core of a red giant and one of the most common stars in the Milky Way galaxy.

Researchers say the white dwarf at the heart of Tuesday’s study — with the memorable designation SDSS J1240+6710, or Dox as it was named by team who discovered it in 2016 — has an atmosphere of almost pure oxygen with detections of neon, silicon and magnesium. This makes Dox peculiar because most white dwarfs are made up of hydrogen or helium.

Study authors say this white dwarf was most likely part of a pair of stars that survived its own supernova explosion. The thermonuclear blast sent the two stars were sent in opposite directions.

Using the Hubble Space Telescope, researchers noted carbon, sodium and aluminum in the star’s atmosphere. All are byproducts of the early stages of a supernova’s thermonuclear reaction.

Missing from the equation are iron, nickel and other iron elements that are normally found after a supernova. This proves a partial supernova explosion occurred before the nuclear process ended, according to the researchers.

Dox is hurtling through space at 559,234 miles per hour and has a mass of about 40% of our sun’s mass.

Physics professor and lead study author Boris Gaensicke of the University of Warwick said in a statement this white dwarf underwent a supernova that has not been recorded before and must have interrupted the two stars’ orbit.

“We are now discovering that there are different types of white dwarf that survive supernova under different conditions and using the compositions, masses and velocities that they have, we can figure out what type of supernova they have undergone,” said Gaensicke. “There is clearly a whole zoo out there. Studying the survivors of supernova in our Milky Way will help us to understand the myriads of supernova that we see going off in other galaxies.”

Without the radioactive nickel to power a long-lasting glow, researchers say the explosion that sent Dox on its trajectory would have been a quick pulse of light that would have gone unnoticed.

The University of Warwick did not immediately respond to requests for comment on the study.

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