A stunning photograph from NASA's James Webb Space Telescope shows an incredible cosmic sight: at least 17 concentric dust rings erupting from a pair of stars in a fingerprint-like pattern. These two stars, jointly known as Wolf-Rayet 140, are located at a distance of somewhat more than five thousand light-years from our home planet.
As the two stars neared one another, their stellar winds interacted, compressing the gas and creating dust to create the rings. The orbits of the stars bring them close together about once every eight years, and the dust loops act as timekeepers by marking the passage of time like tree rings.
Creating dust from gas needs the same circumstances and materials as baking bread from flour. Hydrogen is the most abundant element in stars, yet it cannot create dust on its own. Wolf-Rayet stars lose so much mass, however, that they also release more complicated elements like carbon, which are usually located deep inside a star. Where the winds of the two stars meet, the heavier components are squeezed, much as bread is when it is kneaded by two people.
Even though the dust rings, or shells as Lau and his colleagues call to them, are thicker and broader than they seem in the picture, the Mid-Infrared Instrument (MIRI) on Webb and the telescope's overall sensitivity make it especially equipped to examine them. Webb's scientific instruments are able to detect infrared light, a spectrum of which is beyond the range of human vision.
MIRI is able to view colder things, such as the dust rings, since it detects longer infrared wavelengths than Webb's other sensors. The MIRI spectrometer also showed the dust's composition, which consisted mostly of debris expelled by a class of stars known as Wolf-Rayet stars.
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To collapse into a black hole, Wolf-Rayet stars, which are O-type stars but were born at least 25 times as massive as our Sun, are on their last legs. Wolf-Rayet stars burn hotter than they did when they were young, creating tremendous winds that drive enormous volumes of gas into space. It's possible that the Wolf-Rayet star in this binary system lost more than half its mass via this mechanism.
Although it is known that other Wolf-Rayet systems generate dust, no such systems have been found to generate rings. Wolf-Rayet star WR 140 has an unusual ring pattern due to its extended orbit. Before the stars are roughly as close together as the distance between the Earth and the Sun, and their winds clash, the gas isn't under enough pressure to generate dust. In a circular orbit, Wolf-Rayet binaries may generate dust continuously.
