The material ejected by the supernova will initially expand very quickly, but then gradually slow down, forming an intricate giant bubble of hot, glowing gas. Eventually, the charred remnants of the exploding white dwarf will overcome these gaseous layers and speed up their journey through the Galaxy. Credit: University of Warwick / Mark Garlick
An explosion white dwarf The star shot out of its orbit with another star in a ‘partial supernova’ and is now hurtling through our galaxy, according to a new study by the Warwick university.
It opens up the possibility for many more supernova survivors to travel undiscovered through the Milky Wayas well as other types of supernovae that occur in other galaxies that astronomers have never seen before.
Informed today (July 15, 2020) in Monthly notices from the Royal Astronomical Society The research, funded by the Leverhulme Trust and the Science and Technology Facilities Council (STFC), looked at a white dwarf that previously had an unusual atmospheric composition. It reveals that the star was likely a binary star that survived its supernova explosion, sending it and its companion flying through the Milky Way in opposite directions.
White dwarfs are the remaining cores of red giants after these huge stars have died and shed their outer layers, cooling down over the course of billions of years. Most white dwarfs have atmospheres made up almost entirely of hydrogen or helium, with occasional evidence of carbon or oxygen extracted from the star’s core.
Designated SDSS J1240 + 6710 and discovered in 2015, this star appeared to contain no hydrogen or helium, rather than an unusual mixture of oxygen, neon, magnesium, and silicon. Using the Hubble space telescopeScientists also identified carbon, sodium, and aluminum in the star’s atmosphere, all of which occurs 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 from the lighter ones and constitute the defining characteristics of thermonuclear supernovae. The lack of elements of the iron group in SDSSJ1240 + 6710 suggests that the star only went through a partial supernova before the nuclear burn was extinguished.
Scientists were able to measure the speed of the white dwarf and discovered that it travels at 900,000 kilometers per hour. It also has a particularly low mass for a white dwarf, only 40% of the mass of our Sun, which would be consistent with the loss of mass of a partial supernova.
Lead author Professor Boris Gaensicke from the Physics Department at the University of Warwick said: “This star is unique because it has all the key characteristics of a white dwarf, but it has this very high speed and unusual abundances that make no sense. when combined with It is low mass.
“It has a chemical composition that is the fingerprint of nuclear combustion, a low mass and a very high speed: all these facts imply that it must come from some type of nearby binary system and that it must have undergone thermonuclear ignition. It would have been a type of supernova, but a type we haven’t seen before. “
Scientists theorize that the supernova disrupted the white dwarf’s orbit with its companion star when it abruptly ejected a large proportion of its mass. Both stars would have been driven in opposite directions to their orbital speeds in a sort of slingshot maneuver. That would explain the high speed of the star.
Professor Gaensicke adds: “If it was a narrow binary and it underwent thermonuclear ignition, expelling a large amount of its mass, you have the conditions to produce a low-mass white dwarf and make it fly at orbital speed.”
The best studied thermonuclear supernovae are “Type Ia”, which led to the discovery of dark energy, and are now routinely used to map the structure of the Universe. But there is increasing evidence that thermonuclear supernovae can occur under very different conditions.
SDSSJ1240 + 6710 may be the survivor of a type of supernova that has not yet been “caught in the act.” Without the radioactive nickel that powers the long-lasting glow of Type Ia supernovae, the blast that sent SDSS1240 + 6710 at full speed over our galaxy would have been a brief flash of light that would have been difficult to detect.
Professor Gaensicke adds: “The study of thermonuclear supernovae is a huge field and there is a great deal of observational effort to find supernovae in other galaxies. The difficulty is that you see the star when it explodes, but it is very difficult to know the properties of the star before it explodes.
“Now we are discovering that there are different types of white dwarfs that survive supernovae under different conditions and, using the compositions, masses and speeds they have, we can determine what type of supernova they have suffered. Clearly there is a complete zoo out there. Studying supernova survivors in our Milky Way Galaxy will help us understand the myriad supernovae we see in other galaxies. “
Professor SO Kepler of the Universidade Federal do Rio Grande do Sul, Brazil, and who originally discovered this star, said: “The fact that such a low-mass white dwarf was burned with carbon is a testament to the effects of evolution interactive binary and its effect on the chemical evolution of the universe “.
Dr. Roberto Raddi of the Universitat Politècnica de Catalunya, Spain, who performed the kinematic analysis, said: “Once again, the synergy between very accurate Gaia astrometry and spectroscopic analysis has helped limit the surprising properties of a unique white dwarf, which probably formed in a thermonuclear supernova and was ejected at high speed as a result of the explosion. “
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Reference: “SDSS J124043.01 + 671034.68: The partially burned remnant of a low-mass white dwarf that underwent thermonuclear ignition” by Boris T Gänsicke, Detlev Koester, Roberto Raddi, Odette Toloza, and SO Kepler, June 20, 2020 , Monthly notices from the Royal Astronomical Society.
DOI: 10.1093 / mnras / staa1761
The research received funding and support from the Science and Technology Facilities Council (STFC), part of the UK Research and Innovation.
