Astronomers using the NASA/ESA/CSA James Webb Space Telescope have captured the most detailed images yet of one of the most distinctive objects in our skies, the Horsehead nebula.
At the bottom of this Webb/NIRCam image a small portion of the Horsehead nebula is seen close-in, as a curved wall of thick, smoky gas and dust. Above the nebula various distant stars and galaxies can be seen up to the top of the image. Image credit: NASA / CSA / ESA / Webb / K. Misselt, University of Arizona / A. Abergel, IAS, University Paris-Saclay & CNRS.
The Horsehead nebula is located about 1,500 light years from Earth in the constellation of Orion.
Also known as Barnard 33, the nebula is visible only because its obscuring dust is silhouetted against the bright nebula IC 434.
The Horsehead nebula is only one small feature in the Orion molecular cloud complex, dominated in the center of this view by the brilliant Flame nebula.
The nebula was first recorded on February 6, 1888, by the Scottish astronomer Williamina Fleming.
The object formed from a collapsing interstellar cloud of material, and glows as it is illuminated by a nearby hot star.
The gas clouds surrounding the Horsehead have already dissipated, but the jutting pillar is made of stronger stuff that is harder to erode.
Astronomers estimate that the Horsehead formation has about 5 million years left before it too disintegrates.
The new images from Webb focus on the illuminated edge of the top of the nebula’s distinctive dust and gas structure.
This Webb/MIRI image is more than half-filled by a small section of the Horsehead nebula, from the bottom up. Image credit: NASA / CSA / ESA / Webb / K. Misselt, University of Arizona / A. Abergel, IAS, University Paris-Saclay & CNRS.
“The Horsehead nebula is a well-known photodissociation region (PDR),” the Webb astronomers said.
“In such a region ultraviolet light from young, massive stars creates a mostly neutral, warm area of gas and dust between the fully ionized gas surrounding the massive stars and the clouds in which they are born.”
“This ultraviolet radiation strongly influences the gas chemistry of these regions and acts as the most important source of heat.”
“These regions occur where interstellar gas is dense enough to remain neutral, but not dense enough to prevent the penetration of far-ultraviolet light from massive stars.”
“The light emitted from such PDRs provides a unique tool to study 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.”
“Owing to its proximity and its nearly edge-on geometry, the Horsehead nebula is an ideal target for astronomers to study the physical structures of PDRs and the evolution of the chemical characteristics of the gas and dust within their respective environments, and the transition regions between them.”
“It is considered one of the best objects in the sky to study how radiation interacts with interstellar matter.”
“Thanks to Webb’s MIRI (Mid-Infrared Instrument) and NIRCam (Near Infrared Camera) instruments, we revealed for the first time the small-scale structures of the illuminated edge of the Horsehead,” they said.
“We also detected a network of striated features extending perpendicular to the PDR front and containing dust particles and ionised gas entrained in the photo-evaporative flow of the nebula.”
“The observations also allowed us to investigate the effects of dust attenuation and emission, and to better understand the multidimensional shape of the nebula.”
“Next, we intend to study the spectroscopic data that have been obtained of the nebula to evidence the evolution of the physical and chemical properties of the material observed across the nebula.”
The results appear in the journal Astronomy & Astrophysics.
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A. Abergel et al. 2024. JWST observations of the Horsehead photon-dominated region I. First results from multi-band near- and mid-infrared imaging. A&A, in press; doi: 10.1051/0004-6361/202449198