The brink of stellar death is a tumultuous time, and the sight of a massive star casting out enormous quantities of heated gas into space is a spectacle to behold. This monumental event, seen surrounding the star, was captured with striking detail by Webb's Mid-Infrared Instrument.
In June 2022, one of NASA's James Webb Space Telescope's earliest observations showcased a Wolf-Rayet star - WR 124, a celestial marvel, known for its fleeting lifespan, staggering mass, and brilliant luminosity. Webb's sophisticated infrared equipment allowed us to witness the star in an unparalleled degree of detail. This stellar titan, resting in the constellation Sagittarius, lies a staggering 15,000 light-years from Earth.
These behemoth stars burn through their lifecycles at an accelerated pace, with a select few experiencing the brief Wolf-Rayet phase before they explode in a supernova. Webb's intricate observations of this uncommon stage prove invaluable to astronomers. Wolf-Rayet stars, such as WR 124, weighing in at 30 times the mass of our Sun, and having already discarded ten solar masses worth of material, are in the throes of shedding their outer layers. This process leaves behind distinctive halos of gas and dust that, when cooled, form cosmic dust that glows under the gaze of Webb's infrared detection.
The image captured by Webb's Mid-Infrared Instrument reveals WR 124's nebula's structure in long mid-infrared wavelengths, glowing as a result of cooler cosmic dust. This nebula is the byproduct of sporadic ejections from the aging star and the turbulence-infused creation of cosmic dust. The origins of cosmic dust capable of weathering a supernova explosion and contributing to the universe's overall "dust budget" captivate astronomers. Despite its significance in star formation, planet creation, and the genesis of life-building molecules, the universe surprisingly hosts more dust than current theories can account for.
Webb's advanced technology enables an in-depth study of cosmic dust in unprecedented detail, which is most effectively observed in infrared light. Its Near-Infrared Camera (NIRCam) juxtaposes the brightness of WR 124's stellar core against the intricacies of the surrounding gas, while the Mid-Infrared Instrument (MIRI) exposes the nebulous structure of ejected material encircling the star. Before Webb, astronomers didn't have the necessary detail to scrutinize dust formation in environments like WR 124 and determine if the dust grains were plentiful and large enough to survive a supernova and significantly contribute to the dust budget. These questions can now be tackled with actual data.
Stars like WR 124 also serve as a proxy for astronomers to better understand a pivotal time in the universe's early history. Similar dying stars initially imbued the young universe with heavy elements forged in their cores, elements now prevalent in our current era, including on Earth. The detailed image captured by Webb of WR 124 immortalizes a fleeting, turbulent period of transformation and augurs future discoveries that will unravel the long-concealed enigmas of cosmic dust.