How a star plays with particle accelerators

It’s a dance between the stars that makes a boom! The action takes place in the constellation Ophiuchus. A white dwarf and a red giant revolve around each other. But this is a deadly dance. The white dwarf, compact and dense, sucks in the atmosphere of the red giant by gravity. And every 15 to 20 years, a white dwarf suddenly becomes much brighter, forming a new star that makes it visible to the naked eye from Earth. A team of astrophysicists gathered in the framework of the international collaboration HESS (High Energy Stereoscopic System) has just published in the journal The science the most complete study of the phenomenon. They recorded the explosion and ejection of matter for more than a month and found that these new stars are powerful particle accelerators…

White dwarf eats red giant

A white dwarf is the remnant of an average star with a mass of 3 to 4 solar masses, which, after the merger of all its gas, collapsed on itself. It only glows faintly. However, in the case of the Ophiuchus pair, the shriveled star has its closest pantry: a red giant. The white dwarf pierces the gas of its neighbor and is thus covered again with a layer of hydrogen and helium. “When the amount of accreted gas is sufficient, the nuclei fuse, just as when the star was active.described for Science and the future Mathieu Jacobet de Narois, CNRS (IN2P3) researcher and co-author of the publication. The fusion then produces the equivalent of a thermonuclear bomb.” Warned at the very beginning of the phenomenon by an amateur astronomer, the researchers were able to fully track it in the gamma-ray region thanks to the five telescopes of the HESS network installed in Namibia.

Particles as if hit with a tennis racket.

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