![]() As the ejected gas moves away from the star and cools, cosmic dust forms and glows in the infrared light detectable by Webb. The star WR 124 is 30 times the mass of the Sun and has shed 10 Suns’ worth of material-so far. Wolf-Rayet stars are in the process of casting off their outer layers, resulting in their characteristic halos of gas and dust. Massive stars race through their lifecycles, and only some of them go through a brief Wolf-Rayet phase before going supernova, making Webb’s detailed observations of this rare phase valuable to astronomers. The star is 15,000 light-years away in the constellation Sagitta. Webb shows the star, WR 124, in unprecedented detail with its powerful infrared instruments. John S.The rare sight of a Wolf-Rayet star – among the most luminous, most massive, and most briefly-detectable stars known – was one of the first observations made by NASA’s James Webb Space Telescope in June 2022. Calculations show that even graphite, which is black in bulk, reflects visible light well when dispersed into small particles. Grains reflect light almost as well as fresh snow, more because of their favourable size (which promotes scattering rather than absorption) than their chemical composition. ![]() Optical observations suggest that about 60–70 percent of the light is reflected rather than absorbed, while the corresponding fraction for Earth is only 35 percent and for the Moon a mere 5 percent. The extent and brightness of reflection nebulae show conclusively that dust grains are excellent reflectors in the broad range of wavelengths extending from the ultraviolet (as determined from observations from space) through the visible. ![]() The brightest reflection nebulae are illuminated by B-type stars that are very luminous but have temperatures lower than about 25,000 K, cooler than the O-type stars that would ionize the hydrogen in the gas and produce an H II region. The famous nebulosity in the Pleiades star cluster is of this type it was discovered in 1912 that the spectrum of this nebula mimics the absorption lines of the nearby stars, whereas bright nebulae that emit their own light show their own characteristic emission lines. Reflection nebula, interstellar cloud that would normally be a dark nebula (or molecular cloud) but whose dust reflects the light from a nearby bright star that is not hot enough to ionize the cloud’s hydrogen. SpaceNext50 Britannica presents SpaceNext50, From the race to the Moon to space stewardship, we explore a wide range of subjects that feed our curiosity about space!.Learn about the major environmental problems facing our planet and what can be done about them! Saving Earth Britannica Presents Earth’s To-Do List for the 21st Century.Britannica Beyond We’ve created a new place where questions are at the center of learning.100 Women Britannica celebrates the centennial of the Nineteenth Amendment, highlighting suffragists and history-making politicians.COVID-19 Portal While this global health crisis continues to evolve, it can be useful to look to past pandemics to better understand how to respond today.Student Portal Britannica is the ultimate student resource for key school subjects like history, government, literature, and more.Demystified Videos In Demystified, Britannica has all the answers to your burning questions.This Time in History In these videos, find out what happened this month (or any month!) in history.#WTFact Videos In #WTFact Britannica shares some of the most bizarre facts we can find. ![]() Britannica Classics Check out these retro videos from Encyclopedia Britannica’s archives.Britannica Explains In these videos, Britannica explains a variety of topics and answers frequently asked questions.
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