After the kilonovae, here are the micronoves, a new type of stellar explosion

As Futura has already explained, especially in a file is at the end of the XVIi century that the astronomers Tycho Brahe i Johaness Kepler introduced the term new star, which in Latin means “new star”. In fact, this became necessary due to the transient appearance of new stars in the celestial vault, stars that were not mentioned by any of the stellar catalogs inherited from Greek science. But it was not until the developments of theastrophysics to the XXi century because we are beginning to understand what was hidden behind these curious phenomena and that we distinguish between new and supernovaethanks to the work of Walter Baade and Fritz Zwicky during the 1930s. NS I and SN II of the famous classification designed by the German-American astronomer Rudolph Minkowski and Fritz Zwicky, the famous and bustling Swiss astronomer.

But back 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 solar-type stars, their transformation into a red giant and then a white dwarf. © Jean-Pierre Luminet

Classic news, recurring explosions in a binary system

So today we know that, unlike supernovae, new ones are explosions that do not lead (or rarely) to the destruction of the parent star or that do not produce a neutron star or a star. black hole. In the case of a newit all starts with a white dwarf in a binary system which increaseshydrogen from its accompanying star to the pressure and the surface temperature becomes sufficient to trigger a reaction of fusion thermonuclear explosive. Remember that a white dwarf is a stellar corpse that is the final destination of all stars that contain less than 8 stars. masses solar. Our Ground will end up in this state as star hyperdense containing its mass in a volume the size of the Earth, described by quantum and relativistic effects.

When a new one occurs, the brightness of the white dwarf multiplies 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. Therefore, the new ones are recurring because, as we said, the explosion does not destroy the white dwarf.

Today the novae bestiary has just been expanded following a publication in the newspaper Nature carried out by a team of astronomers who, with the help of the Very large telescope of the Southern European Observatory (VLT from’ESO), observed a new type of stellar explosion that researchers called micronoves. They act like their cousins ​​with white dwarfs increased by subject matter of a star in a binary system.

As explained by Nathalie Degenaar, an astronomer at the University of Amsterdam in the Netherlands, in an ESO press release, it is thanks to the satellite Tess (Exoplanet exploration satellite in transit) that it all started for her and her classmates: ” Examining the astronomical data collected by Tess of the Nasawe discovered something unusual: a flash brilliant from light optics that lasted a few hours. Looking further, we found several similar signs. Tess revealed three other micronoves, two of which were clearly associated with white dwarfs, but the instrument had to be used. X shooter in the ESO VLT to determine the origin of the third explosion and confirm that, again, a white dwarf was involved.

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

Misunderstood thermonuclear explosions

Also in the ESO press release, we learned that researchers have determined that the thermonuclear explosion that occurs on the surface of white dwarfs, although less powerful than that of a new classic, becomes, however, in the equivalent of the mass of 3.5 billion grains. Pyramids of Giza a energy and in a few hours. Recall that the mass of the Great Pyramid of Cheops on the Giza Plateau in Cairo is approximately 5.9 billion kg.

For Simone Scaringi, an astronomer at the University of Durham in the United Kingdom, who led the team behind the discovery of micronoves: 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 we already know, however, that in the case of micronovies: ” These explosions cause the entire surface of the white dwarf to burn and glow for several weeks. His colleague Paul Groot, an astronomer at Radboud University in the Netherlands, adds, however: For the first time, we have seen that hydrogen fusion can also occur locally. Hydrogen may be contained in the base magnetic pulses of some white dwarfs, so fusion only occurs on these magnetic poles. This leads to the explosion of micro-fusion bombs, which are about one millionth of the force of a new explosion, hence the name micronova. »

We still have a lot to learn about micronovies that are probably more widespread than we think, which should allow for many other observations in this regard. As Simone Scaringi finally explains: The quick response from telescopes such as the VLT or the New technology telescope ESO and the set of instruments available will allow us to discover in more detail what these mysterious micronoves are. »

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