They discover the micronova, the “little sister” of the nova and the supernova

An international team of scientists has discovered a new type of star burst: the micronova. As the name suggests, it’s basically a small nova. Novas are the result of stars white dwarfs in which an explosive nuclear fusion process has occurred which ignites its entire surface during weeks. If the process is particularly bright, it is known as supernova. And on the other side now are the micronovae.

In his case, such a luminous explosion does not occur over the entire surface, but only in the magnetic poles of the star. Moreover, it does not last for weeks, but only a few hours. For this reason, it is believed that there must be many micronovae in the universe, but until now they have not been observed due to their short duration.

In fact, an example of its abundance is that the authors of the study just published in Nature They found neither more nor less than three. This would not have been possible without the collaboration of two great instruments: NASA’s Transiting Exoplanet Survey Satellite (TESS) and the European Southern Observatory’s (ESO) Very Large Telescope (VLT) x-shooter. The combination of the two made it possible to find these three and it is not excluded that they will soon find many others. But let’s see what we know so far about micronovae.

The different sizes of the nova

In November 1572, the Danish astronomer Tycho Brahe he first coined the term “nova” by observing something in the sky which for him was a new star newly installed in the firmament.

That was all we could know with the technologies available at the time. However, over time other astronomers have verified that in reality it is not a new star. Novas form in binary systems composed of at least one white dwarf; that is, a very dense dead star, with a mass close to that of our Sun, but as small as the Earth. In this system, the white dwarf tends to steal material from its companion star, usually hydrogen. When it falls on the hot surface of the white dwarf, a process of fusion between hydrogen atomsto give rise to atoms of helium. It is a very explosive phenomenon, which ignites the entire surface of the star during weeks.

When Tycho Brahe first observed a nova, he thought it was a new star, hence its name.

This ignition was what Tycho Brahe saw. For him, a new light in the sky meant a new star, but in reality it had been there for a very long time. Despite everything, the name of nova was kept and the name of supernova for the brightest explosions. In fact, what the Danish astronomer saw was what is now called a supernova.

As for micronovae, their discovery was similar to that of Tycho Brahe, but with a few much more advanced technology. Its officials were observing astronomical data collected by TESS when they detected an unusual flash of optical light that lasted for a few hours. They decided to keep digging and found at least two more. The first two came from known white dwarfs, and further investigation, this time with the VLT’s x-shooter instrument, showed the third to be the same. They could be novae, but they had certain peculiarities unrelated to this type of explosion. And that’s what made them realize that they were facing something new: the micronova.