The James Webb photographed the Horsehead Nebula with unprecedented resolution

There Horsehead Nebula (HorseHead nebula, Barnard 33) is one of the most characteristic and well-known objects in our skies. It is located 1300 light years from here in the constellation of Orion, in particular on the western side of the Orion B molecular cloud, and is made up of large waves of dust and gas, collapsing material that shines because it is illuminated by a nearby hot star.

This region is also one of the most photographed ever, both by amateurs and by telescopes on Earth and in space. One of the first images from the Euclid space telescope, published on November 7, 2023, represents the Horsehead Nebula.

Now, the James Webb Space Telescope has captured it the sharpest infrared images to date of the nebula. They show it in a completely new light, highlighting its complexity with unprecedented spatial resolution. Webb’s view, in particular, focuses on the illuminated edge of the upper part of the nebula’s characteristic dust and gas structure. He then outlines it features and structures never appreciated before at this level of detail.

The photodissociation mechanism in the Horsehead Nebula

The Horsehead Nebula is a well-known one photodissociation region (in English PhotoDissociation Region, PDR): Ultraviolet light from young, massive stars creates an area of ​​mostly neutral gas, amidst the fully ionized gas that surrounds massive stars and the clouds in which they are born. This ultraviolet radiation heavily influences the chemistry of the gas of these regions, and serves as the main source of heat.

This process occurs 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 in PDRs provides a unique tool for study the physical and chemical processes that drive the evolution of interstellar matter in our Galaxy and throughout the Universe, from the formation of the first stars to the present day.

Thanks to its proximity to us and its geometric structure, the Horsehead Nebula is an ideal target for scientists to study the structure of PDRs and the evolution of the chemical characteristics of gas and dust in these environments. In fact, it is considered one of the best objects in the sky for studying how radiation interacts with interstellar matter.

Always unique details, thanks to Webb

Using the James Webb MIRI (Mid InfraRed Instrument) and NIRCam (Near InfraRed Camera) instruments, researchers have revealed for the first time the small-scale structures of the illuminated edge of the Horse’s Head. They also detected a network of striated structures extending perpendicular to the PDR, containing particles of dust and ionized gas swept up by the nebula.

The observations, in particular the very high level of detail that Webb’s instruments can achieve, have also allowed astronomers to study the effects of attenuation and dust emission and to better understand the multidimensional shape of the nebula.

The astronomers intend to analyze the spectroscopic data obtained on the nebula even more deeply, to highlight the evolution of the physical and chemical properties of the observed material.

The study presenting these results, accepted for publication in Astronomy & Astrophysicscan be found here in pre-print version.

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