Free Astronomy Magazine July-August 2024

42 by NASA/ESA/CSA − Bethany Downer Top of iconic Horsehead Nebula in unprecedented detail N ASA’s James Webb Space Tele- scope has captured the sharpest infrared images to date of a zoomed-in portion of one of the most distinctive objects in our skies, the Horsehead Nebula. These observations show the top of the “horse's mane” or edge of this iconic nebula in a whole new light, capturing the region’s complexity with unprecedented spatial resolu- tion. Webb’s new images show part of the sky in the constellation Orion (The Hunter), in the western side of a dense region known as the Orion B molecular cloud. Rising from turbulent waves of dust and gas is the Horsehead Nebula, otherwise known as Barnard 33, which resides roughly 1,300 light-years away. The nebula formed from a collaps- ing interstellar cloud of material, and glows because it is illuminated by a nearby hot star. The gas clouds T his image of the Horsehead Nebula from Webb focuses on a portion of the horse’s “mane” that is about 0.8 light-years in width. It was taken with Webb’s NIRCam. The ethereal clouds that appear blue at the bottom of the image are filled with a variety of ma- terials including hydrogen, methane, and water ice. Red-colored wisps ex- tending above the main nebula repre- sent both atomic and molecular hydrogen. In this area, known as a photodissociation region, ultraviolet light from nearby young, massive stars creates a mostly neutral, warm area of gas and dust between the fully ionized gas above and the nebula below. As with many Webb images, distant gal- axies are sprinkled in the background. This image is composed of light at wavelengths of 1.4 and 2.5 µm (repre- sented in blue), 3.0 and 3.23 µm (cyan), 3.35 µm (green), 4.3 µm (yellow), and 4.7 and 4.05 µm (red). [NASA, ESA, CSA, Karl Misselt (University of Arizona), Alain Abergel (IAS, CNRS)]