Survivor Star Hurtling Across the Milky Way
University of Warwick, UK | 2020 Jul 14
An exploding white dwarf star blasted itself out of its orbit with another star in a ‘partial supernova’ and is now hurtling across our galaxy ...The material ejected by the supernova will initially expand very rapidly, but
then gradually slow down, forming an intricate giant bubble of hot glowing gas.
Eventually, the charred remains of the white dwarf that exploded will overtake
these gaseous layers, and speed out onto its journey across the galaxy.
Credit: University of Warwick/Mark Garlick
It opens up the possibility of many more survivors of supernovae travelling undiscovered through the Milky Way, as well as other types of supernovae occurring in other galaxies that astronomers have never seen before.
... the research ... analysed a white dwarf that was previously found to have an unusual atmospheric composition. It reveals that the star was most likely a binary star that survived its supernova explosion, which sent it and its companion flying through the Milky Way in opposite directions. ...
This star, designated SDSS J1240+6710 and discovered in 2015, seemed to contain neither hydrogen nor helium, composed instead of an unusual mix of oxygen, neon, magnesium and silicon. Using the Hubble Space Telescope, the scientists also identified carbon, sodium, and aluminium in the star’s atmosphere, all of which are produced in the first thermonuclear reactions of a supernova.
However, there is a clear absence of what is known as the ‘iron group’ of elements, iron, nickel, chromium and manganese. These heavier elements are normally cooked up from the lighter ones, and make up the defining features of thermonuclear supernovae. The lack of iron group elements in SDSSJ1240+6710 suggests that the star only went through a partial supernova before the nuclear burning died out.
The scientists were able to measure the white dwarf’s velocity and found that it is travelling at 900,000 kilometres per hour. It also has a particularly low mass for a white dwarf – only 40% the mass of our Sun – which would be consistent with the loss of mass from a partial supernova. ...
SDSS J124043.01+671034.68: The Partially Burned Remnant of a Low-Mass
White Dwarf that Underwent Thermonuclear Ignition? ~ Boris T. Gaensicke et al