Strange pair of stars that produce dust shells like a clockwork mechanism

The James Webb Space Telescope has identified an intriguing object created by a rare pair of stars surrounded by rings of dust. The pair, known as Wolf-Rayet 140, are 5,000 light-years away and we may know the interstellar medium between stars and how stars form.

This system consists of two stars, one older and more massive of a type called the Wolf-Rayet star, and the other hot a blue-white type called an O-type star. And they orbit in such a way that they approach once every eight years. . When this happens, the stellar winds emitted by each star begin to interact. This interaction causes the large Wolf-Rayet star to lose some of its stellar material, which forms dust.

Cosmic dust shells created by the interaction of binary stars appear as tree rings around Wolf-Rayet 140. The remarkable regularity of the shell spacing indicates that they form as a clockwork mechanism during the stars’ eight-year orbital cycle. when the two members of the rails approach each other. In this image, blue, green and red have been assigned to Webb’s MIRI (Midi-Infrared Instrument) data at 7.7, 15 and 21 microns (filters F770W, F1500W and F2100W respectively). NASA, ESA, CSA, STScI, NASA-JPL, Caltech

It is this formation of dust every eight years that creates the dust shells seen in the image above. Each interaction creates a new shell, and at least 17 of these shells are visible in the Webb data, showing over 130 years of history between the two stars.

“We are looking at over a century of dust production from this system,” lead author Ryan Lau, NSF’s NOIRLab astronomer, said in a statement. “The image also illustrates how sensitive this telescope is. Before, we were only able to see two dust rings, using ground-based telescopes. Now we see at least 17 “.

Webb was able to see the numerous bullets using his mid-infrared instrument, which allowed the researchers to use different filters to see the chemical composition of the dust shells. They found that they are made up of compounds called polycyclic aromatic hydrocarbons (PAHs), which are found in the space between stars – called the interstellar medium – and which play an important role in how stars form. There are only about 600 known Wolf-Rayet stars, but there may be evidence of many more in our galaxy.

“Although Wolf-Rayet stars are rare in our galaxy because they are short-lived as far as stars are concerned, it is possible that they have produced a lot of dust over the course of the galaxy’s history before they explode and / or form black holes,” he said. said co-author Patrick Morris of Caltech, “I think with NASA’s new space telescope we will learn a lot more about how these stars shape the material between stars and trigger new star formation in galaxies.”

The research is published in the journal Nature Astronomy.

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