This 4-star system could trigger a rare supernova!

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[EN VIDÉO] Binary systems of stars and black holes
Collection made by NASA of 22 binary systems consisting of a star and a black hole with star mass. Their dances are accelerated 22,000 times and shown from Earth. The colors of stars and growth disks surrounding black holes reflect their temperatures. © Nasa

In 2017, researchers from the University of Canterbury in New Zealand discovered a quadruple system ofstars, since christened HD74438. More precisely, it is a double star system binaries : a first with a orbit close and fast, and the other much more distant and slow. In a new journal issue Nature astronomyfrom astrophysicists study the possible developments of this system, based on modeling of the orbit for each star it contains.

The youngest quadruple system ever found

Located in constellation of Vela only visible insouthern hemisphereHD74438 was discovered during an observation campaign by ESA Gaia satellitewhich has already identified more than 100,000 stars in our Galaxy. Then everything was done thanks to spectrographs on high solution located at the University of Canterbury in New Zealand and Southern African Large Telescope in South Africa. They make it possible to characterize the star’s light spectrumi.e. to decompose light it emits and analyzes the intensity of each wavelength. Thanks to this method, they can derive not only the temperature of the star, but also the composition of its atmosphere.

This star system 43 million years old is still young, because if it seems far, let’s remember that ours Sun It is already 4.6 billion years old! This makes it the youngest quadruple system ever found to date. These four-star systems are rare, on the order of a few percent of several systems which are already quite rare and have complex developments. In this specific case is binary system external exerts a gravitational attraction on the internal system and tends to deform its two-star orbit.

A future thermonuclear supernova?

To model the possible developments of the HD74438, the team of scientists modeled the gravitational effects that control the quadruple system. They thus showed thateccentricity of the internal system tended to increase. In practice, this means that the track will evolve to become less and less circular: a collision could be triggered after this deviation between a star in each system.

And from this collision it would result … first and foremost one white dwarf ! It’s not there yet thermonuclear supernova long-awaited. “ A star like our sun will end its life as a small, densely dead star known as a white dwarf, and lot white dwarfs can not exceed the so-called Chandrasekhar limit (about 1.4 times the mass of the Sun) “explains Professor Karen Pollard, lead author of the study and astrophysicist at the University of Canterbury. “If so, due to mass transfer events or fusion, it can collapse and produce a thermonuclear supernova. » And that’s exactly what would happen to the HD74438!

“The evolution of stellar quads such as HD 744384 therefore represents a promising new path for the formation of thermonuclear supernova explosions inUniverse, she concludes. FInterestingly, 70% to 85% of all supernova thermonuclear cells are now suspected to be the result of the explosion of white dwarfs with sub-Chandrasekhar masses. As a result of mass transfer or mergers, these will dwarf stars white can explode in a thermonuclear supernova. » What question are the current models of thermonuclear supernovae.

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