A Cosmic Landscape of Debris

The remnants of the supernova explosion in Cas A, visualized in the near-infrared spectrum of the James Webb Space Telescope. NASA, ESA, CSA, STScI, Danny Milisavljevic (Purdue University), Ilse De Looze (UGent), Tea Temim (Princeton University)

This colorful interplay of vivid orange and delicate pink is the remnant of a stellar explosion that occurred 340 years ago in the constellation Cassiopeia. By capturing the stellar graveyard and its debris for the first time with the high-resolution near-infrared camera of the James Webb Space Telescope, researchers have uncovered numerous new details about the supernova remnant located 11,000 light-years away.

When a massive star reaches the end of its life cycle, it collapses and explodes in a supernova. The remnants of such a stellar explosion can be observed, for example, in the Cassiopeia constellation, located 11,000 light-years away. Following a supernova in 1680, we can now use space telescopes to observe the aftermath of this explosion in the form of the Cassiopeia A supernova relic, or simply Cas A.

Traces of the Explosion in Space

Due to its relatively close proximity to Earth, Cassiopeia A, composed of glowing gases and a central neutron star, is one of the most extensively studied supernova remnants in the entire cosmos. Various observatories, including NASA’s Chandra X-ray Observatory and the Hubble Space Telescope, have already imaged the celestial object in different wavelength ranges.

Now, the high-resolution Near-Infrared Camera (NIRCam) of the James Webb Space Telescope has captured its first snapshot of Cas A—specifically in the near-infrared range. “With the resolution of NIRCam, we can now see how the dying star completely shattered during its explosion, leaving behind filaments resembling tiny shards of glass,” explains Danny Milisavljevic of Purdue University.

A “Landscape” of Debris Made of Gas and Dust

Among these filaments is the inner shell of the supernova remnant, which appears in this image in bright orange and light pink. It consists of elements such as sulfur, oxygen, argon, and neon, all of which were once part of the star. However, some of these “gas remnants” are too small, even for the James Webb Telescope to detail, where tiny in this case means smaller than 16 billion kilometers. For comparison, Cas A itself spans a diameter of ten light-years, equivalent to around 97 trillion kilometers.

Amidst its gas remnants, Cas A harbors a mixture of dust and molecules that could serve as building materials for new stars and planetary systems in the distant future.

Smoke and Holes

Around the inner shell of the supernova remnant, a white shimmer is also visible, resembling the smoke from a campfire. This area marks where the shockwave of the stellar explosion penetrates the surrounding circumstellar material, according to Milisavljevic and his colleagues. They believe that the white shimmer is synchrotron radiation, which results from charged particles spiraling around magnetic field lines at extremely high speeds.

In even subtler colors than synchrotron radiation, numerous circular holes are discernible in the Cas A supernova remnant. Researchers speculate that these are ionized gases, penetrated and shaped by the supernova debris.

A “Baby” of Cassiopeia A

Another detail drawing astronomers’ attention is the golden shimmering field in the bottom right corner of the image. They have named it “Baby Cas A” because it appears to be a descendant of the main supernova. Milisavljevic and his team reported that, despite appearing to be right next to Cas A, the debris baby is actually about 170 light-years away from the supernova remnant.

Baby Cas A is most likely a field of dust that received heat from the explosion wave long after the star’s explosion. Hence, it appears to glow in the near-infrared snapshot. Besides Baby Cas A, the James Webb Space Telescope was able to capture other such light echoes scattered throughout the debris portrait.

Featured Image: The remnants of the supernova explosion in Cas A, visualized in the near-infrared spectrum of the James Webb Space Telescope. NASA, ESA, CSA, STScI, Danny Milisavljevic (Purdue University), Ilse De Looze (UGent), Tea Temim (Princeton University)