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Astronomy

Webb reveals new features from Sagittarius C, in the heart of the Milky Way

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Webb reveals new features from Sagittarius C, in the heart of the Milky Way

The latest image from the NASA/ESA/CSA James Webb Space Telescope shows a portion of the dense centre of our galaxy in unprecedented detail, including never-before-seen features astronomers have yet to explain. The star-forming region, named Sagittarius C (Sgr C), is about 300 light-years from the Milky Way’s central supermassive black hole, Sagittarius A*.

[Image description: In a field crowded with stars, a funnel-shaped region of space appears darker than its surroundings with fewer stars. It is wider at the top edge of the image, narrowing towards the bottom. Toward the narrow end of this dark region a small clump of red and white appears to shoot out streamers upward and left. A large, bright cyan-colored area surrounds the lower portion of the funnel-shaped dark area, forming a rough U shape. The cyan-coloured area has needle-like, linear structures and becomes more diffuse in the center of the image. The right side of the image is dominated by clouds of orange and red, with a purple haze.]
The full view of the NASA/ESA/CSA James Webb Space Telescope’s NIRCam (Near-Infrared Camera) instrument reveals a 50 light-years-wide portion of the Milky Way’s dense centre. An estimated 500,000 stars shine in this image of the Sagittarius C (Sgr C) region, along with some as-yet unidentified features.
A vast region of ionised hydrogen, shown in cyan, wraps around an infrared-dark cloud, which is so dense that it blocks the light from distant stars behind it. Intriguing needle-like structures in the ionised hydrogen emission lack any uniform orientation. Researchers note the surprising extent of the ionised region, covering about 25 light-years.
A cluster of protostars – stars that are still forming and gaining mass – are producing outflows that glow like a bonfire at the base of the large infrared-dark cloud, indicating that they are emerging from the cloud’s protective cocoon and will soon join the ranks of the more mature stars around them. Smaller infrared-dark clouds dot the scene, appearing like holes in the starfield.
Researchers say they have only begun to dig into the wealth of unprecedented high-resolution data that Webb has provided on this region, and many features bear detailed study. This includes the rose-coloured clouds on the right side of the image, which have never been seen in such detail.
Credit: NASA, ESA, CSA, STScI, S. Crowe (UVA)
Amid the estimated 500,000 stars in the image is a cluster of protostars – stars that are still forming and gaining mass – producing outflows that glow like a bonfire in the midst of an infrared-dark cloud. At the heart of this young cluster is a previously known, massive protostar over 30 times the mass of our Sun. The cloud the protostars are emerging from is so dense that the light from stars behind it cannot reach Webb, making it appear less crowded when in fact it is one of the most densely packed areas of the image. Smaller infrared-dark clouds dot the image, looking like holes in the starfield. That’s where future stars are forming.

Webb’s NIRCam (Near-Infrared Camera) instrument also captured large-scale emission from ionised hydrogen surrounding the lower side of the dark cloud, shown cyan-coloured in the image. Typically, this is the result of energetic photons being emitted by young massive stars, but the vast extent of the region shown by Webb is something of a surprise that bears further investigation. Another feature of the region that scientists plans to examine further is the needle-like structures in the ionised hydrogen, which appear oriented chaotically in many directions.

Around 25,000 light-years from Earth, the galactic centre is close enough to study individual stars with the Webb telescope, allowing astronomers to gather unprecedented information on how stars form, and how this process may depend on the cosmic environment, especially compared to other regions of the galaxy. For example, are more massive stars formed in the centre of the Milky Way, as opposed to the edges of its spiral arms?

Webb Sagittarius C[Image description: In a field crowded with stars, a funnel-shaped region of space appears darker than its surroundings with fewer stars. It is wider at the top edge of the image, narrowing towards the bottom. Toward the narrow end of this dark region a small clump of red and white appears to shoot out streamers upward and left. A large, bright cyan-coloured area surrounds the lower portion of the funnel-shaped dark area, forming a rough U shape. The cyan-coloured area has needle-like, linear structures and becomes more diffuse in the center of the image. The right side of the image is dominated by clouds of orange and red, with a purple haze.]
This image of Sagittarius C (Sgr), captured by Webb’s Near-Infrared Camera (NIRCam), shows compass arrows, scale bar, and colour key for reference.
The north and east compass arrows show the orientation of the image on the sky. Note that the relationship between north and east on the sky (as seen from below) is flipped relative to direction arrows on a map of the ground (as seen from above).
The scale bar is labelled in light-years, which is the distance that light travels in one Earth-year. (It takes 3 years for light to travel a distance equal to the length of the scale bar.) One light-year is equal to about 5.88 trillion miles or 9.46 trillion kilometres. The field of view shown in this image is approximately 50 light-years long.
This image shows invisible near-infrared wavelengths of light that have been translated into visible-light colours. The colour key shows which NIRCam filters were used when collecting the light. The colour of each filter name is the visible light colour used to represent the infrared light that passes through that filter.
Credit: NASA, ESA, CSA, STScI, S. Crowe (UVA)
Press release from ESA Webb.

ScientifiCult è una Testata Giornalistica registrata presso il Tribunale di Bari numero R.G. 5296/2021 - R.S. 21. Direttrice Responsabile: Alessandra Randazzo

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