Bright, hot star Wolf-Rayet 124 (WR 124) stands out at the center of the James Webb Space Telescope composite image, which combines the near-infrared and mid-infrared wavelengths of near-infrared and mid-infrared camera light Webb's instrument.

Bright, hot star Wolf-Rayet 124 (WR 124) stands out at the center of the James Webb Space Telescope composite image, which combines the near-infrared and mid-infrared wavelengths of near-infrared and mid-infrared camera light Webb’s instrument.
Credit: NASA, ESA, CSA, STScI, Webb First Scientific Observations (ERO) production team

A rare view of a Wolf-Rayet star – among the most luminous, massive and fleetingly detectable stars known – was one of the first observations made by NASA’s James Webb Space Telescope in June 2022. , Webb shows the star, called WR 124, in unprecedented detail. The star is 15,000 light-years away in the constellation of Sagittarius.

Massive stars go through their life cycles very quickly, with only a few of them going through a brief Wolf-Rayet phase before going supernova, making Webb’s detailed observations of this rare phase invaluable for scientists. Wolf-Rayet stars are in the process of sloughing off their outer layers, resulting in their characteristic halos of gas and dust. The star WR 124 is 30 times the mass of the Sun and has so far spewed out material equivalent to 10 suns. As the ejected gas moves away from the star and cools, it forms cosmic dust that glows in the infrared light detectable by Webb.

The origin of cosmic dust that can survive a supernova explosion and contribute to the total “dust budget” of the universe is of great interest to astronomers for several reasons. Dust is an integral part of how the universe works: It can harbor forming stars, accumulate to form planets, and serve as a platform for the formation and agglomeration of molecules, including the building blocks of life on Earth. Despite the many essential functions that dust performs, there is still more dust in the universe than can be explained by astronomers’ current theories about its formation. The universe is running on a budget surplus of dust.

Wolf-Rayet stars are known to be efficient dust producers, and the mid-infrared instrument on NASA's James Webb Space Telescope shows this to great effect.  The cooler cosmic dust glows in mid-infrared wavelengths, showing the structure of nebula WR 124.

Wolf-Rayet stars are known to be efficient dust producers, and the mid-infrared instrument on NASA’s James Webb Space Telescope shows this to great effect. The cooler cosmic dust glows in mid-infrared wavelengths, showing the structure of nebula WR 124.
Credit: NASA, ESA, CSA, STScI, Webb First Scientific Observations (ERO) production team

Webb opens up new possibilities for studying the details of cosmic dust, which is best seen in infrared light wavelengths. Webb’s near-infrared camera (NIRCam) balances the brightness of WR 124’s stellar core and the fuzzy details in the fainter surrounding gas. The telescope’s Mid-Infrared Instrument (MIRI) reveals the irregular structure of the nebula of gas and dust from the ejected material that now surrounds the star. Before Webb, dust-loving astronomers simply didn’t have enough detailed information to examine questions about dust production in environments like WR 124 and whether the dust grains were large and plentiful enough to survive the supernova and become a significant contributor. for the total dust budget. . Now these questions can be investigated with real data.

Stars like WR 124 also serve as an analogy to help astronomers understand a crucial period in the early history of the universe. Similar dying stars first seeded the young universe with heavy elements forged in their cores, elements that are now commonplace in the current era, even on Earth.

Webb’s detailed image of WR 124 forever preserves a brief, turbulent moment of transformation and promises future discoveries that will reveal long-hidden mysteries of cosmic dust.

The James Webb Space Telescope is the world’s leading space science observatory. Webb will solve the mysteries of our solar system, look beyond the distant worlds around other stars, and explore the mysterious structures and origins of our universe and our place in it. Webb is an international program run by NASA with its partners: the European Space Agency (ESA) and the Canadian Space Agency (CSA).

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