This kind of explosion would be able to destroy all traces of life on Earth in less than a day.
When a star dies, there are several possible scenarios. In the event that the latter would not have exploded in a supernova, it will collapse on itself after having fused its hydrogen into helium.
With the rise in pressure and temperature caused by the collapse, the star will begin to fuse its helium into (mostly) carbon, which will cause the star to puff up and become a red giant. Once the helium is consumed, the giant collapses again, but the resulting energy is not enough to start the carbon fusion.
At this point, the outer layers are expelled into space as a planetary nebula and only the very dense core remains (the mass of the Sun condensed into the size of the Earth) known as a white dwarf.
Ultraviolent surface explosions
White dwarfs are therefore extremely dense masses and in a binary system, it happens that they attract the lightest elements, such as hydrogen, of their binomial. It is in such systems that scientists have discovered a phenomenon that was not known until now.
Using the TESS, a space telescope launched in 2018, astronomers noted abnormal light “flashes”. The TESS is an instrument specially designed to track the luminous variations of stars and thus detect the drop in luminosity when a planet passes in front of its star at regular intervals.
These mysterious bursts of about ten hours would ultimately be thermonuclear explosions similar to novas (when the entire layer of hydrogen on the surface explodes at once, leaving the white dwarf), but in a less powerful and more localized way hence the term “micronova”.
A mechanism similar to the aurora borealis
These phenomena, which remained unexplained for a long time, took part in white dwarfs whose magnetic field is particularly high. According to the scientists, the hydrogen stolen by the white dwarf ends up accumulating at the poles. On Earth, we find an equivalent phenomenon with the charged particles of the Sun deflected by our magnetosphere and which form the aurora borealis.
In the case of hydrogen, the reaction is much more spectacular since it leads to a thermonuclear explosion. Even if it remains 1 million times fainter than a classic nova, this explosion consumes an enormous quantity of matter (more than 100,000 times the mass of Everest).
The energy released could destroy everything we know in less than a day. Of course, since this is a new discovery, there are still many unknowns such as the exact trigger mechanism or the frequency at which the phenomenon repeats itself.