James Webb unravels the mystery of a nebula around a dying star

In the center, there remains the heart of this star, called a white dwarf: a very hot and very small star, difficult to see directly, but whose presence can be guessed thanks to the orange rings all around, traces of the matter it ejected . In a few billion years, our Sun should know about the same fate, as the vast majority of stars.

Except that unlike the Sun, which will die alone, the white dwarf at the heart of the Southern Ring Nebula is accompanied. We knew so far a “companion” star, easier to observe than the white dwarf because it is still in the prime of life. It is this companion star that appears brightest in the center of the dusty disk, in the photos taken by the James Webb telescope, which has been operating since this summer 1.5 million kilometers from Earth.

But this duo operation, fairly classic in the Milky Way, did not explain the “atypical” structure of the nebula, explains to AFP Philippe Amram, from the Marseille astrophysics laboratory, one of the authors of the study published Thursday in Nature Astronomy and which dissects the recent observations of the telescope.

“Since its discovery by astronomer John Herschel (in 1835, editor’s note), we wonder why the Austral Ring nebula has such a bizarre shape, not really spherical”, rather elongated, continues this CNRS researcher.

The observations of the James Webb come to clear up the mystery: thanks to their vision in the infrared, a wavelength invisible to the human eye, the instruments of the telescope have unearthed the proof of the presence of at least two other stars at the within the nebula.

These discovered stars are located in the center of the nebula, which extends over a diameter equivalent to 1,500 times the distance from the Sun to Pluto. They are farther from the white dwarf than the companion star, but overall the four stars are close enough together to interact.

There are then “exchanges of energy” between this group of stars which “will shape in their wake” the structure of the nebula, according to the astrophysicist. This would finally explain its unique appearance.

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