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Starts With A Bang

JWST uncovers new secrets within the Horsehead Nebula

The most iconic “dark nebula” of all lights up under JWST’s infrared gaze. Here’s what’s newly discovered inside.
A vibrant image of the Horsehead Nebula captured by JWST, featuring a radiant blue and white glow against a deep red starry background.
The edge of the "mane" of the Horsehead Nebula, highlighted here by new JWST NIRCam imagery, provides us with our deepest-ever look at this iconic astronomical sight. What we found inside is richer than anyone expected.
Credit: NASA, ESA, CSA, Karl Misselt (University of Arizona), Alain Abergel (IAS, CNRS)
Key Takeaways
  • Located 1300 light-years away, the Horsehead Nebula is an iconic astronomical sight that’s delighted astronomers for centuries.
  • But only recently have we looked at it with infrared, rather than merely visible, light, illuminating many of its dusty, internal secrets.
  • Already, with JWST’s first NIRCam and MIRI glimpses of this object, we’re finding more inside it than most astronomers had imagined. Here’s what we’ve revealed so far.

The Horsehead Nebula is an iconic astronomical sight.

A vibrant cosmic image captured by the JWST featuring a shadowy horsehead nebula silhouetted against a luminous pink and purple gas cloud sprinkled with scattered stars.
A dark molecular cloud of neutral gas sits in front of an active star-forming region: IC 434, creating the iconic sight of the Horsehead Nebula. Located about 1300 light-years away in the constellation of Orion, the dark cloud is quite large in extent, explaining why more stars are visible “above” the nebula than below it.
Credit: T.A.Rector (NOIRLab/NSF/AURA) and Hubble Heritage Team (STScI/AURA/NASA)

Most nebulae are luminous: shining red and/or blue.

Eagle nebula wide field
This ground-based, wide-field image of the Eagle Nebula shows the star-forming region in all its glory, with new stars, reflection and emission nebulae, and dusty features all present. The reddish glow coming from many of the gaseous components is a result of hydrogen atoms recombining, and a photon of precisely 656.3 nanometers being emitted every time an electron transitions from the n=3 to the n=2 energy state.
Credit: ESO

Energetic light ionizes hydrogen atoms, leading to red “emission” nebulae as electrons de-excite after recombining.

Wolf-Rayet star cosmic reef
This portion of the Cosmic Reef composition highlights the blue reflection nebula created by winds blown off of a hot, massive, giant blue star that are then illuminated in reflected light by the original star that created it. The Wolf-Rayet star that powers it may be destined, in short order, for a stellar cataclysm such as a core-collapse supernova, but we can only see the presence of the cold, expelled gas from its outer layers as they reflect the starlight from the luminous, blue star powering it.
Credit: NASA, ESA and STScI

Neutral atoms also reflect bright starlight, creating bluish “reflection” nebulae.

molecular dust cloud
Dark, dusty molecular clouds, like Barnard 59, part of the Pipe Nebula, appear prominent as they block out the light from background objects: stars, heated gas, and light-reflecting material. These dark nebulae themselves are composed of neutral gas which blocks visible light, but which will also collapse and eventually form new stars inside of them if they persist for long enough. Many of the dark nebulae are clouds of gas in the Milky Way’s plane, a precursor to new episodes of star-formation.
Credit: ESO

But the Horsehead is a different beast: a dark nebula.

A vibrant image captured by the JWST of the Horsehead Nebula, featuring swirling red clouds and bright stars scattered across a dark sky.
Near Orion’s Belt, the reflection nebula known as the Flame Nebula (left) as well as the star-forming emission nebula known as IC 434 (in red) are joined by a series of dark molecular clouds in the foreground that create spectacular silhouettes known as dark nebulae. The Horsehead Nebula (at center) is arguably the most famous dark nebula of them all.
Credit: Stephanh/Wikimedia Commons

Cool gas clouds in the foreground of stars and star-forming regions block the background light.

A detailed image of the Horsehead Nebula, captured by JWST, showing a dense, dark cloud of dust and gas with tiny glowing stars scattered around.
This optical image of the Horsehead Nebula was taken by the Hubble Space Telescope back in 2001, and showcases not only the shape and density of the light-blocking nebula itself, but reveals many faint, reddened stars located behind the nebula where the light still penetrates and escapes the light-blocking neutral matter.
Credit: NASA, NOAO, ESA and The Hubble Heritage Team (STScI/AURA); Acknowledgment: K. Noll (Hubble Heritage PI/STScI), C. Luginbuhl (USNO), F. Hamilton (Hubble Heritage/STScI)

Their silhouettes create intricate “dark nebulae” against the illuminated backdrop.

A vibrant cosmic image captured by the JWST showing a nebula with swirling purple and red colors against a star-studded dark sky.
This view of the Horsehead Nebula comes courtesy of the ESA’s Euclid mission, which is an optical-and-infrared space telescope that took this panoramic, detailed view of this region of the constellation Orion, also known as Barnard 33. The Horsehead Nebula sits just to the south of star Alnitak, the easternmost of Orion’s famous three-star belt, and is part of the vast Orion molecular cloud.
Credit: ESA/Euclid/Euclid Consortium/NASA; Processing: J.-C. Cuillandre (CEA Paris-Saclay), G. Anselmi

With internal and external heating, infrared eyes reveal intricate features within the Horsehead Nebula.

A striking image of the horsehead nebula captured by the JWST, featuring rich red and blue colors with bright stars scattered around it.
Unlike visible-light images of the Horsehead Nebula, this near-infrared view is sensitive to the relatively warm gas within the optically dark nebula itself, lighting it up for Hubble’s infrared instruments. Intricate, wispy features within the gas, as well as partially obscured background and internal stars and proto-stars, all appear illuminated in this view.
Credit: NASA, ESA, and the Hubble Heritage Team (AURA/STScI)

Euclid, Hubble, and JWST’s NIRCam views all expose this neutral gas.

Three panels comparing nebula images from Euclid (visible-infrared), Hubble (infrared), and JWST (infrared) telescopes, highlighting detailed astronomical observations of the Horsehead Nebula
The infrared views of the Horsehead Nebula from Euclid (left), Hubble (center), and JWST (right). The smaller field-of-views of Hubble and JWST are a feature, not a bug, as they image regions of this nebula at far higher resolution than a wide-field telescope like Euclid.
Credit: NASA, ESA, CSA, Karl Misselt (University of Arizona), Alain Abergel (IAS, CNRS), Mahdi Zamani The Euclid Consortium, Hubble Heritage Project (STScI, AURA)

Different features appear at longer, mid-infrared wavelengths in JWST’s MIRI instrument.

Image of a vibrant cosmic scene showing a detailed wave-like structure of the Horsehead Nebula with multicolored stars and interstellar gas in the background.
This image of the Horsehead Nebula from NASA’s James Webb Space Telescope focuses on a portion of the horse’s “mane.” It was taken with Webb’s MIRI (Mid-Infrared Instrument). Mid-infrared light captures the glow of substances like dusty silicates and soot-like molecules called polycyclic aromatic hydrocarbons. This image was assembled using nine different mid-infrared filters, ranging from 5.6 to 25 microns in wavelength.
Credit: NASA, ESA, CSA, Karl Misselt (University of Arizona), Alain Abergel (IAS, CNRS)

But inside, with JWST’s high-resolution instruments, many new secrets are exposed.

A celestial image captured by the JWST showing a bright star at the center with smaller stars and a vibrant, cloud-like Horsehead Nebula in the foreground against a deep red and black space background.
The “mane” of the Horsehead Nebula, as highlighted by JWST’s NIRCam views, shows off simultaneously the intricate features of the gas at the edge of the nebula along with background stars and galaxies, plus wispy features at the edge likely shaped by magnetic fields. Within the gaseous nebula itself, various “lights” are visible inside.
Credit: NASA, ESA, CSA, Karl Misselt (University of Arizona), Alain Abergel (IAS, CNRS)

Background galaxies are just as abundant near the Horsehead’s boundary as they are farther away.

A vibrant image captured by the JWST of space featuring a blue nebulous cloud at the bottom with a scattering of stars and distant galaxies against a deep red backdrop.
With JWST’s unprecedented sensitivity, we can now clearly see that even though substantial amounts of light-blocking material are present near and at the boundary of the Horsehead Nebula itself, the background density of galaxies remains unchanged near the nebula itself. Features and shapes are more difficult to detect, but there are literally galaxies everywhere.
Credit: NASA, ESA, CSA, Karl Misselt (University of Arizona), Alain Abergel (IAS, CNRS)

Individual stars appear to be forming inside the nebula, poking through the neutral gas in infrared light.

Colorful space nebula with swirling clouds of blue and white, highlighted by red accents at the top, resembling the iconic Horsehead Nebula as captured by JWST.
Many lights can be seen in this JWST NIRCam image of the gas within the Horsehead Nebula. Some are due to background galaxies while others are due to partially obscured stars that are either inside or behind the “horse’s head” itself, but unless the diffraction spikes (of a star) or the extended morphological features (of a galaxy) are clearly visible, the nature of these lights cannot so easily be determined.
Credit: NASA, ESA, CSA, Karl Misselt (University of Arizona), Alain Abergel (IAS, CNRS)

Some new stars are identifiable by their diffraction spikes in NIRCam imagery.

One of the telltale signatures of a star in JWST imagery is the “nightmare snowflake” pattern, reminiscent of a series of hexagonal spikes with additional features and distortions, imprinted on point sources due to the optical geometry of the telescope. The object at the lower-left of this image is clearly stellar in nature.
Credit: NASA, ESA, CSA, Karl Misselt (University of Arizona), Alain Abergel (IAS, CNRS)

Other “lights” revealed inside, however, correspond to highly luminous background galaxies.

Close-up view of the Horsehead Nebula with blue and red clouds of gas, highlighted by yellow circles indicating areas of interest.
The objects circled (in yellow) here, despite being located along the same line-of-sight as the neutral gas found in the Horsehead Nebula, can easily be identified as background galaxies due to their extended shapes, still resolvable by JWST’s NIRCam instrument despite the presence of that foreground material. Many of the other lights seen inside may yet be galaxies as well, but a visual inspection is insufficient to reveal their nature.
Credit: NASA, ESA, CSA, Karl Misselt (University of Arizona), Alain Abergel (IAS, CNRS)

One includes a potentially active supermassive black hole.

A detailed image of the Horsehead Nebula, featuring swirling clouds of purple and blue gas interspersed with bright stars.
This portion of the JWST MIRI view of the Horsehead Nebula does not have a NIRCam counterpart, as the field-of-view is centered differently. However, the spike-riddled object at the bottom is likely not a point-like star, but rather an active supermassive black hole in a very distant background galaxy: something that the MIRI instrument is outstanding at picking up. Many previously unknown supermassive black holes have been discovered thanks to the power of MIRI.
Credit: NASA, ESA, CSA, Karl Misselt (University of Arizona), Alain Abergel (IAS, CNRS)

Just 1300 light-years away, infrared views reveal the internal workings within the Horsehead.

Mostly Mute Monday tells an astronomical story in images, visuals, and no more than 200 words.


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