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Webb Sheds Light on an Exploded Star

Cassiopeia A, a circular-shaped cloud of gas and dust with complex structure. The inner shell is made of bright pink and orange filaments studded with clumps and knots that look like tiny pieces of shattered glass. Around the exterior of the inner shell, particularly at the upper right, there are curtains of wispy gas that look like campfire smoke. The white smoke-like material also appears to fill the cavity of the inner shell, featuring structures shaped like large bubbles. Around and within the nebula, there are various stars seen as points of blue and white light. Outside the nebula, there are also clumps of yellow dust, with a particularly large clump at the bottom right corner that appears to have very detailed striations.
NASA’s James Webb Space Telescope’s new view of Cassiopeia A (Cas A) in near-infrared light is giving astronomers hints at the dynamical processes occurring within the supernova remnant. Tiny clumps represented in bright pink and orange make up the supernova’s inner shell, and are comprised of sulfur, oxygen, argon, and neon from the star itself. A large, striated blob at the bottom right corner of the image, nicknamed Baby Cas A, is one of the few light echoes visible NIRCam’s field of view. In this image, red, green, and blue were assigned to Webb’s NIRCam data at 4.4, 3.56, and 1.62 microns (F444W, F356W, and F162M, respectively).
NASA, ESA, CSA, STScI, D. Milisavljevic (Purdue University), T. Temim (Princeton University), I. De Looze (University of Gent)

Supernova remnant Cassiopeia A (Cas A) shines in a new image from Dec. 10, 2023, from NASA’s James Webb Space Telescope. Webb’s Near-Infrared Camera (NIRCam) view of Cas A displays this stellar explosion at a resolution previously unreachable at these wavelengths, revealing intricate details of the expanding shell of material slamming into the gas shed by the star before it exploded.

Cas A is one of the most well-studied supernova remnants in all the cosmos. Over the years, ground-based and space-based observatories, including NASA’s Chandra X-Ray ObservatoryHubble Space Telescope, and retired Spitzer Space Telescope have assembled a multiwavelength picture of the object’s remnant.

However, astronomers have now entered a new era in the study of Cas A. In April 2023, Webb’s Mid-Infrared Instrument (MIRI) started this chapter, unveiling new and unexpected features within the inner shell of the supernova remnant. Many of those features are invisible in the new NIRCam image, and astronomers are investigating why.

Read on to find out what we can learn from this new image of Cassiopeia A.

Image Credit: NASA, ESA, CSA, STScI, D. Milisavljevic (Purdue University), T. Temim (Princeton University), I. De Looze (University of Gent)