White dwarfs can also partially explode. Since this type of stellar explosion may be huge by earthly standards, but takes place in miniature by cosmic standards, the scientists call this newly discovered phenomenon a micronova. They describe their observations in the journal »Nature«.
Actually the burnt-out remains of stars, white dwarfs are good for several types of novae. However, this always requires a companion star from which a white dwarf can suck material. It can even explode as a thermonuclear supernova that briefly shines as brightly as an entire galaxy. Little or nothing of the white dwarf will then remain. In a “normal” nova, on the other hand, the white dwarf also sucks material from its companion, mainly hydrogen. Then explosive nuclear fusion processes can be ignited on its entire surface, in which the hydrogen is fused into helium. This thermonuclear explosion makes the white dwarf shine much brighter than usual for weeks.
A team led by Simone Scaringi from Durham University has now discovered that the cosmos also has this type of star explosion to offer on a smaller scale. The initial scenario should be a white dwarf in a binary system with a companion star. If the white dwarf has a strong magnetic field, the material from the companion star could be thrown towards the magnetic poles. The result: a thermonuclear explosion localized at the magnetic poles. The nuclear fusion processes are not ignited over the entire surface of the white dwarf like in a nova. Since a nova explosion is around a million times stronger, the researchers call this newly discovered phenomenon a “micronova”.