White dwarfs can only partially explode. Since this type of star explosion may be huge for earthly standards, but is more likely to take place in miniature format for cosmic standards, the scientists describe this newly discovered phenomenon as micronova. They describe their observations in the specialist magazine »Nature«.
White dwarfs are good for several types of Novae as the remnants of stars. But this always needs an accompanying star from which a white dwarf can suck out material. So he can even explode as a thermonuclear supernova, which shines as brightly as an entire galaxy for a short time. The white dwarf then probably has little or nothing. In the case of 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 merged 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 stellar explosion to offer on a smaller scale. The initial scenario is supposed to be a white dwarf in a binary system with a companion star. If the white dwarf has a strong magnetic field, the material of the companion star could be thrown in the direction of the magnetic poles. The result: a thermonuclear explosion localized at the magnetic poles. The nuclear fusion processes are not ignited on the entire surface of the white dwarf, as in the case of a nova. Since a nova explosion is about one million times stronger, the researchers refer to this newly discovered phenomenon as a "micronova".
On the trail of the micronovae, the researchers were initially based on data from the NASA telescope Tess and the Very Large Telescope of the European South Sternhewarte: They had shown some bright optical flashes of light that stopped several hours. Scaringi and his colleagues found three white dwarfs, who worked as micronovae. Since there are references to short -term outbursts of other white dwarfs in the specialist literature, the researchers suspect that the newly discovered type of star explosion could take place more often than expected.
