A new kind of starburst: here are the micronovae!

As Futura has already explained, especially in a File, it is at the end of the XVIand century that the astronomers Tycho Brahe and Johanna Kepler introduced the term nova stella, which means “new star” in Latin. In fact, this became necessary after the temporary appearance of new stars in the celestial vault, stars not mentioned in any of the star catalogs adopted by Greek science. But it was necessary to await the developments of astrophysics in the XXand century so that we can begin to understand what lies behind these strange phenomena and that we can distinguish between novae and novae supernovaethanks to the work of Walter Baade and Fritz Zwicky in the 1930s. NS I and SN II of the famous classification devised by the German-American astronomer Rudolph Minkowski and Fritz Zwicky, the famous and bubbly Swiss astronomer.

But let’s return to the initial dichotomy of ” novae stellae “.

Excerpt from the documentary From the big bang to the living (ECP Productions, 2010). Jean-Pierre Luminet talks about the evolution of sun-like stars, their transformation into a red giant and then into a white dwarf. © Jean Pierre Luminet

Classic novae, recurring explosions in a binary system

We now know, therefore, that novae, in contrast to supernovae, are explosions that do not (or rarely) lead to the destruction of the parent star or produce a neutron star or black hole. in case of an novaeverything starts with a white dwarf in one binary system that accumulateshydrogen from its companion star to Print and the surface temperature become sufficient to initiate a reaction merger explosive thermonuclear. Remember that a white dwarf is a stellar corpse, which is the ultimate fate of all stars less than 8 in size crowds Solar. Our sun will end up as a in this state star hyperdense, containing its mass in an Earth-sized volume, described by quantum and relativistic effects.

When a nova occurs, the brightness of the white dwarf is then multiplied by 10,000 for a few days. The process can be repeated: we know, for example, that RS Ophiuchi exploded six times in a century. So the novae are recurring because, as said, the explosion does not destroy the white dwarf.

Today the Novae bestiary has just been expanded following a publication in the newspaper Nature conducted by a team of astronomers using the Very large telescope the European Southern Observatory (VLT of’IT) observed a new type of stellar explosion that the researchers dubbed micronovae. They perform like their cousins white dwarves growing out matter of an asterisk in a binary system.

As Nathalie Degenaar, astronomer at the University of Amsterdam in the Netherlands, explains in an ESO press release, it is thanks to the Tess satellite (Transit exoplanet survey satellite) that it all began for her and her colleagues: ” By examining the astronomical data collected by Tess de la NASAwe discovered something unusual: a lightning bright from bright Optics that lasted a couple of hours. As we searched further, we found several similar signals. Tess revealed three more micronovae, two of which were clearly associated with white dwarfs, but the instrument had to be used X shooter at ESO’s VLT to determine the origin of the third explosion and confirm that a white dwarf was involved again.

Astronomers have discovered a new type of explosion occurring in white dwarfs in two-star systems. This video summarizes the discovery. For a fairly accurate French translation, click the white rectangle at the bottom right. Then the English subtitles should appear. Then click on the nut to the right of the rectangle, then on “Subtitles” and finally on “Translate automatically”. Choose French. ©ESO

Misunderstood thermonuclear explosions

Also in the ESO press release, we learn that researchers have found that the thermonuclear explosion that occurs on the surface of white dwarfs, while less powerful than that of a classic nova, is still up to a mass of 3.5 billion Great converts Giza Pyramids into energy and that in just a few hours. Remember that the mass of the Pyramid of Cheops on the Giza Plateau in Cairo is approximately 5,900,000,000 kg.

For Simone Scaringi, an astronomer at Durham University in the UK who led the team behind the discovery of micronovae: The phenomenon challenges our understanding of how thermonuclear explosions occur in stars. We thought we knew, but this discovery offers a whole new way to do it. » Co-author of the article by Nature, Nathalie Degenaar explains that in the case of micronovae, however, we already know: ” Such explosions cause the white dwarf’s entire surface to burn and glow for several weeks. However, his colleague Paul Groot, an astronomer at Radboud University in the Netherlands, adds: For the first time we have seen that hydrogen fusion can also be localized. Hydrogen can be contained at the base of magnetic poles of some white dwarfs, so that the fusion only takes place at these magnetic poles. This results in the explosion of microfusion bombs, which are about one-millionth the power of a nova explosion, hence the name micronova. »

We still have much to learn about micronovae, which are probably more widespread than we think, which should allow many more observations to be made about them. As Simone Scaringi finally explains: The quick reply from telescopes like the VLT or the New technology telescope ESO and the range of instruments available will allow us to discover more precisely what these mysterious micronovae are. »

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