NASA’s Hubble Space Telescopes finds a unique kind of supernova blasting a strange white dwarf star across the Milky Way.
An exploding white dwarf star managed to survive a “partial supernova” blasting itself out of its orbit with another star.
The star designated SDSS J1240+6710 lies about 1,430 light-years from Earth in the constellation of Draco. Scientists discovered it in 2015.
When a star dies it ejects its mass in a supernova and it expands quickly. Eventually, it slows down, forming a bubble of glowing gas, and a white dwarf emerges at the center.
Our sun will one day become a white dwarf. As will more than 90% of the stars in the Milky Way.
Astronomers previously thought the white dwarf had an unusual atmospheric composition. The new study found that the star was probably part of a binary star system that survived its supernova explosion. The blast sent it and its companion star flying through the Milky Way in opposite directions.
The majority of white dwarfs have atmospheres composed almost entirely of hydrogen or helium. They are sometimes dotted with carbon or oxygen that was once in the core of the star.
However, the flying white dwarf seemed to contain neither hydrogen nor helium. It was instead composed of an unusual mix of oxygen, neon, magnesium, and silicon. Hubble also identified carbon, sodium, and aluminum in the star’s atmosphere, all of which are produced in the first thermonuclear reactions of a supernova.
There is also a clear absence of the iron group of elements — iron, nickel, chromium, and manganese.
The lack of the heavier elements suggests the star only went through a partial supernova before the nuclear burning died out.
The researchers also found that the white dwarf was traveling about 560,000 miles per hour (900,000 km/h) in the opposite direction that the galaxy is rotating. Moreover, it had an especially low mass for a white dwarf — only about 40% of the mass of our sun.
It appears the binary star lost a lot of its mass during the partial supernova. It also sent the two stars flying in opposite directions across our galaxy. The researchers compared the movement to that of a slingshot.
The white dwarf’s chemical composition, low mass, and high velocity suggest both that it was closely orbiting another star and experienced the hallmarks of “thermonuclear ignition.”
Whatever type of supernova happened here is one we haven’t observed before.
The researchers reported their study in Monthly Notices of the Royal Astronomical Society.