JWST Releases New Image of Famous Supernova Remnant—Offering a New Perspective

NASA has released a new image of the supernova remnant Cassiopeia A (Cas A) captured by the James Webb Space Telescope (JWST). Using its Near-Infrared Camera (NIRCam), JWST has provided a fresh view of Cas A, one of the most extensively studied supernova remnants.

Cas A, located about 11,000 light-years from Earth in the constellation Cassiopeia, consists of the debris from a massive star that is believed to have exploded approximately 340 years ago. Previous observations by NASA’s Chandra X-Ray Observatory, the Hubble Space Telescope, and the now-retired Spitzer Space Telescope have provided a multiwavelength view of this stellar explosion’s remnants. JWST’s new observations at different wavelengths reveal more intricate details of the expanding shell of material interacting with the gas ejected by the star prior to the explosion.

In April, JWST’s Mid-Infrared Instrument provided an image that uncovered surprising features in the inner shell of Cas A. The latest NIRCam image offers a different perspective, and astronomers are investigating why some of these features are also visible in this new view.

To the human eye, infrared light is invisible. To make such wavelengths visible, image processors and scientists convert them into colors. In this image, various filters from JWST’s Near-Infrared Camera (NIRCam) are assigned specific colors to represent different features within Cassiopeia A (Cas A).

The bright orange and light pink areas in the image represent the inner shell of the supernova remnant. JWST has detected small knots of gas containing sulfur, oxygen, argon, and neon, which originated from the exploded star. Embedded within this gas are dust and molecules that could eventually contribute to the formation of new stars and planetary systems.

Purdue University astronomer Danny Milisavljevic commented, “With NIRCam’s resolution, we can now see how the dying star was shattered during the explosion, leaving behind filaments similar to tiny shards of glass. It’s remarkable to resolve these details after so many years of studying Cas A, as they provide transformational insight into the explosion.”

The new near-infrared view shows that Cas A’s inner cavity and outer shell are less colorful compared to the mid-infrared view previously captured by JWST’s Mid-Infrared Instrument (MIRI). Features that appeared deep orange and red in the MIRI image now look more like white smoke in the NIRCam image. This change in appearance reflects where the explosion’s blast wave is interacting with surrounding material. Dust, too cool to be seen in near-infrared, becomes visible in the mid-infrared as it heats up.

The team suspects that the smoke-like areas in the image are due to synchrotron radiation, which is emitted across various wavelengths, including near-infrared. This type of radiation is produced by high-speed charged particles spiraling around magnetic fields.

Additionally, the “Green Monster,” a green loop seen in earlier images, is not visible in the NIRCam view. Researchers had previously described it as “challenging to understand.” Although absent from the NIRCam image, faint outlines of circular holes seen in the MIRI image are now visible as white and purple regions, representing ionized gas. This ionized gas is likely the result of supernova debris interacting with the surrounding gas ejected by the star before its explosion.

A new feature, nicknamed “Baby Cas A,” appears as a large blob in the bottom right corner of the NIRCam image. This blob is a light echo, where the light from the ancient explosion warms distant dust, causing it to glow as it cools. Baby Cas A is thought to be about 170 light-years behind the main supernova remnant, and its intricate dust pattern and proximity to Cas A are of particular interest to the team.