Astronomers studying SN2014J, a Type Ia supernova discovered in January 2014, have found proof that this type of supernova is caused by a white dwarf star reigniting and exploding.
This finding was made by using ESA’s Integral observatory to detect gamma rays from the radioactive elements created during the explosion.
This sequence of artist's impressions shows some of the steps leading up to and following the explosion.
A white dwarf, a star that contain up to 1.4 times the mass of the Sun squeezed into a volume about the same size as the Earth, leeches matter from a companion star (image 1). The Integral measurements suggest that a belt of gas from the companion star builds up around the equator of the white dwarf (image 2). This belt detonates (image 3) and triggers the internal explosion that becomes the supernova (image 4). Material from the explosion expands (image 5) and eventually becomes transparent to gamma rays (image 6).