NASA’s Webb Uncovers Star Formation in Cluster’s Dusty Ribbons

Jan 11, 2023

NGC 346, a notably dynamic star-forming region nestled within nearby galaxies, holds enigmatic qualities. Situated within the Small Magellanic Cloud (SMC), a dwarf galaxy proximate to the Milky Way, NGC 346 exists within an environment characterized by diminished concentrations of elements beyond hydrogen and helium, commonly referred to as metals. The presence of these metals, which compose a substantial portion of space dust, was anticipated to be scarce and elusive due to the SMC's composition. However, fresh insights from the James Webb Space Telescope (Webb) contradict this assumption.

NGC 346, shown here in this image from NASA’s James Webb Space Telescope Near-Infrared Camera (NIRCam), is a dynamic star cluster that lies within a nebula 200,000 light years away. Webb reveals the presence of many more building blocks than previously expected, not only for stars, but also planets, in the form of clouds packed with dust and hydrogen. The plumes and arcs of gas in this image contains two types of hydrogen. The pink gas represents energized hydrogen, which is typically as hot as around 10,000 °C (approximately 18,000 °F) or more, while the more orange gas represents dense, molecular hydrogen, which is much colder at around -200 °C or less (approximately -300 °F), and associated dust. The colder gas provides an excellent environment for stars to form, and, as they do, they change the environment around them. The effect of this is seen in the various ridges throughout, which are created as the light of these young stars breaks down the dense clouds. The many pillars of glowing gas show the effects of this stellar erosion throughout the region. In this image blue was assigned to the wavelength of 2.0 microns (F200W), green was assigned to 2.77 microns (F277W), orange was assigned to 3.35 microns (F335M), and red was assigned to 4.44 microns (F444W). Credits: NASA, ESA, CSA, O. Jones (UK ATC), G. De Marchi (ESTEC), and M. Meixner (USRA). Image processing: A. Pagan (STScI), N. Habel (USRA), L. Lenkic (USRA) and L. Chu (NASA)

In an image captured by Webb's Near-Infrared Camera (NIRCam), NGC 346 emerges as a vibrant star cluster within a nebula situated 200,000 light years away. This image underscores the discovery of an unexpectedly higher prevalence of foundational components, not solely conducive to star formation, but also to planetary genesis, manifested as dust and hydrogen-rich clouds. The gas formations depicted in the image comprise two categories of hydrogen. Pink hues denote energized hydrogen, with temperatures reaching approximately 10,000 °C (roughly 18,000 °F) or higher, whereas orange tints signify dense molecular hydrogen at much colder temperatures of approximately -200 °C or lower (around -300 °F), accompanied by associated dust. The frigid hydrogen environment fosters optimal conditions for star formation, catalyzing transformative impacts on the surrounding milieu. Evident in the manifold ridges, the light radiated by nascent stars disintegrates the dense clouds, generating the distinctive features observed. A color scheme was applied to the image: blue corresponds to a wavelength of 2.0 microns (F200W), green to 2.77 microns (F277W), orange to 3.35 microns (F335M), and red to 4.44 microns (F444W).

Astronomers directed their investigation towards this region due to its resonance with the conditions and metal composition observed in galaxies billions of years in the past, an epoch dubbed "cosmic noon," marked by a zenith in star formation activity. This parallels a period 2 to 3 billion years subsequent to the cosmic birth, during which galaxies underwent intense star formation. These primal cosmic fireworks continue to influence the contemporary galaxy landscape.

Examination of protostars, currently in the process of materializing, permits an evaluation of potential disparities in the star formation mechanisms within the SMC when juxtaposed with those observed in our Milky Way. During the star formation process, these protostars amass surrounding gas and dust, resulting in ribbon-like formations discernible in Webb's imagery. Such matter coalesces into an accretion disk that nourishes the central protostar. While gas encompassing protostars within NGC 346 has been detected previously, Webb's near-infrared observations have, for the first time, identified dust particles within these disks. The research team also possesses spectroscopic data from Webb's NIRSpec instrument, an ongoing analysis of which is anticipated to yield novel insights into material accretion onto individual protostars, as well as their immediate surroundings.

These results were presented Jan. 11 in a press conference at the 241st meeting of the American Astronomical Society.

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Source: NASA. "NASA’s Webb Uncovers Star Formation in Cluster’s Dusty Ribbons". https://www.nasa.gov/feature/goddard/2023/nasa-s-webb-uncovers-star-formation-in-cluster-s-dusty-ribbons. Jan 11, 2023. [Accessed: Jan 12, 2023].