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The Horsehead Nebula in unprecedented detail from the James Webb Space Telescope observations

Infrared observations reveal the complex structure and physical processes of the iconic star-forming region

Image: Horsehead Nebula (NASA Webb NIRCam): This image of the Horsehead Nebula, taken by NASA's James Webb Space Telescope, focuses on a portion of the "Horse's Mane" that is about 0.8 light-years across. It was taken using a camera Webb's NIRCam (near-infrared camera) The airy clouds at the bottom of the image are dominated by cold molecular hydrogen. Red streaks extending above the main nebula represent mostly atomic hydrogen gas in this region, known as the photodissociation region and from nearby masses creates a mostly neutral region of gas and dust between the fully ionized gas above and the cooler nebula below. As in many Webb images, distant galaxies are scattered in the background. This image consists of light at wavelengths of 1.4 and 2.5 microns (shown 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). Credit: NASA, ESA, CSA, K. MISSELT (UNIVERSITY OF ARIZONA) and A. ABERGEL (IAS/UNIVERSITY PARIS-SACLAY, CNRS)
Image: Horsehead Nebula (NASA Webb NIRCam): This image of the Horsehead Nebula, taken by NASA's James Webb Space Telescope, focuses on a portion of the "Horse's Mane" that is about 0.8 light-years across. It was taken using Webb's NIRCam (near infrared camera). The airy clouds that appear in blue at the bottom of the image are dominated by cold molecular hydrogen. Red streaks extending above the main nebula represent mostly atomic hydrogen gas. In this region, known as the photodissociation region, ultraviolet light from nearby young, massive stars creates a warm, mostly neutral region of gas and dust between the fully ionized gas above and the cooler nebula below. As in many web images, distant galaxies are scattered in the background. This image consists of light at wavelengths of 1.4 and 2.5 microns (shown in blue), 3.0 and 3.23 microns (cyan), 3.35 microns (green), 4.3 microns (yellow), and 4.7 and 4.05 microns (red). Credit: NASA, ESA, CSA, K. MISSELT (UNIVERSITY OF ARIZONA) and A. ABERGEL (IAS/UNIVERSITY PARIS-SACLAY, CNRS)

NASA's James Webb Space Telescope has captured the sharpest infrared images yet of a magnified portion of one of the most distinct objects in our sky, the Horsehead Nebula. These observations show the top of this iconic "horse's mane" or edge of the nebula in a whole new light, capturing the complexity of the region with unprecedented spatial resolution.

Webb's new images show part of the sky in the constellation Orion (the Hunter), on the western side of a dense region known as the Orion B Molecular Cloud. Through turbulent waves of dust and gas rises the Horsehead Nebula, also known as Barnard 33, about 1,300 light-years away. .

Orientation - Webb's shot focused on a section of the "mane" of the Horsehead Nebula. The bigger picture can be seen in images from the Euclid and Hubble space telescopes. Credit: NASA, ESA, CSA, K. MISSELT (UNIVERSITY OF ARIZONA) and A. ABERGEL (IAS/UNIVERSITY PARIS-SACLAY, CNRS)
Orientation - Webb's photography focused on a section of the "mane" of the Horsehead Nebula. The bigger picture can be seen in images from the Euclid and Hubble space telescopes. Credit: NASA, ESA, CSA, K. MISSELT (UNIVERSITY OF ARIZONA) and A. ABERGEL (IAS/UNIVERSITY PARIS-SACLAY, CNRS)

The nebula was formed from an interstellar cloud of matter, and glows because it is illuminated by a nearby hot star. The gas clouds surrounding the horse's head have already dissipated, but the protruding pillar is made of thick blocks of material and is therefore more difficult to erode. Astronomers estimate that the horse's head has about five million years left before it too will disintegrate. Webb's new observation focuses on the bright edge of the upper part of the nebula's unique dust and gas structure.

The Horsehead Nebula is a known photodissociation region, or PDR. In such a region, ultraviolet (UV) light from young, massive stars creates a warm, mostly neutral region of gas and dust between the fully ionized gas surrounding the massive stars and the clouds in which they are born. This UV radiation greatly affects the chemistry of these areas and acts as a significant heat source.

These regions occur when interstellar gas is dense enough to remain largely neutral, but not dense enough to block the penetration of UV light from massive stars. The light emitted from such PDRs provides a unique tool for studying the physical and chemical processes that drive the evolution of interstellar matter in our galaxy, and throughout the universe from the early era of vigorous star formation to the present day.

Thanks to its proximity and almost edge-to-edge geometry, the Horsehead Nebula is an ideal target for astronomers to study the physical structures of PDRs and the molecular evolution of the gas and dust within their environments, and the transition regions between them. It is considered one of the best areas of the sky for studying how radiation interacts with interstellar matter.

Thanks to Webb's MIRI and NIRCam instruments, an international team of astronomers has revealed for the first time the small-scale structures of the bright end of the horse's head. As UV light vaporizes the dust cloud, dust particles drift out of the cloud, carried along with the heated gas. Webb has identified a network of subtle features that track this movement. The observations also allowed astronomers to investigate how the dust blocks and emits light, and to better understand the multidimensional shape of the nebula.

Next, astronomers intend to study the obtained spectroscopic data to gain insights into the evolution of the physical and chemical properties of the material observed throughout the nebula.

These observations were conducted in the Webb GTO 1192 program, and the results were published on April 29, 2024 in Astronomy & Astrophysics.

The James Webb Space Telescope is the world's leading space science observatory. Webb solves mysteries in our solar system, looks beyond to distant worlds around other stars, and explores the mysterious structures and origins of our universe and our place in it. WEB is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.

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