Editor’s Note: The article has been updated to reflect that the Wolf-Rayet star is in the constellation Sagitta.
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. With its powerful instruments to view the infrared, Webb shows the star, named WR 124, in unprecedented detail. The star is 15,000 light-years away in the constellation of Saggitta.
Massive stars go through their life cycles very quickly, with only a few of them experiencing a brief Wolf-Rayet phase before going supernovae, making Webb’s detailed observations of this rare phase valuable to scientists. astronomers. Wolf-Rayet stars are in the process of shedding their outer layers, resulting in their characteristic halos of gas and dust. The star WR 124 has 30 times the mass of the Sun and, so far, has shed 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 universe’s total “dust budget” is of great interest to astronomers for a number of 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 molecules to form and clump together, 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 of 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 the longer mid-infrared wavelengths, showing the structure of the WR 124 nebula.
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 at wavelengths of infrared light. Webb’s Near Infrared Camera (NIRCam) balances the brightness of WR 124’s stellar core and gnarled details in the fainter surrounding gas. The telescope’s Mid-Infrared Instrument (MIRI) reveals the lumpy structure of the nebula of gas and dust from ejected material that now surrounds the star. Before Webb, dust-loving astronomers simply did not have enough detailed information to examine questions about dust production in environments like WR 124, and whether dust grains were large and abundant enough to survive the supernova and become in a significant contribution to the total dust budget. Now those questions can be investigated with real data.
Stars like WR 124 also serve as an analogy to help astronomers understand a pivotal period in the history of the early universe. Similar dying stars first seeded the young universe with heavy elements forged in their cores, elements that are now common in the current era, even on Earth.
Webb’s detailed image of WR 124 preserves a brief and turbulent moment of transformation forever, and promises future discoveries that will reveal long-hidden mysteries of cosmic dust.
The James Webb Space Telescope is the world’s premier space science observatory. Webb will solve the mysteries of our solar system, see beyond 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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