James Webb Telescope Captures Image of Supernova That ‘Absolutely Shattered’ a Star

The new image gives astronomers a near-infrared look at the stellar explosion called Cassiopeia A, located around 11,000 light years away from Earth

A colorized image of the remnants of supernova
The supernova remnant Cassiopeia A, captured by NASA's James Webb Space Telescope in near-infrared light. The image shows the expanding material from the blast colliding with gas released by the star before the explosion. NASA, ESA, CSA, STScI, Danny Milisavljevic (Purdue University), Ilse De Looze (UGent), Tea Temim (Princeton University)

NASA’s James Webb Space Telescope has seen the remains of a supernova explosion in a new light. The remnants, called Cassiopeia A (or Cas A for short), lie 11,000 light-years from Earth, in the constellation Cassiopeia.

In April of this year, Webb imaged the stellar remains in mid-infrared light. Now, the newly released snapshot shows Cas A’s colorful, orb-like wisps captured using Webb’s Near-Infrared Camera (NIRCam).

“With NIRCam’s resolution, we can now see how the dying star absolutely shattered when it exploded, leaving filaments akin to tiny shards of glass behind,” Danny Milisavljevic, an astronomer at Purdue University who led the research, says in a statement from NASA. “It’s really unbelievable after all these years studying Cas A to now resolve those details, which are providing us with transformational insight into how this star exploded.”

Stars burn with fusion, which propels energy outward from their cores. But when aging, giant stars run out of fuel, their own gravity overwhelms fusion’s outward push. The star collapses in an explosion that spews its materials across the cosmos. Heavy elements in the universe are often formed during supernovae.

The light from Cassiopeia A’s explosion reached Earth about 340 years ago. Scientists estimate that in its early days, the star that yielded the explosion had a mass 16 times that of the sun, but it shrank to about five times the size of the sun before it blew. Since the explosion occurred thousands of light-years from Earth, it took thousands of years for its light to reach us.

Previously, the Hubble Space Telescope, Spitzer Space Telescope, Chandra X-Ray Observatory and other telescopes had imaged Cas A, according to NASA. Chandra’s study revealed the amounts of different elements produced by the explosion. The supernova has spat out 10,000 times the mass of the Earth in sulfur, 20,000 times Earth’s mass in silicon, 70,000 Earth masses of iron and a million Earth masses of oxygen.

Webb’s NIRCam detects wavelengths of light that are broader than visible light and thus can’t be seen by the human eye. So, to compose the new image, researchers translated the infrared light in different colors.

The bright orange and light pink areas in the new image represent the supernova’s inner shell and are made up of sulfur, oxygen, argon and neon from the star. Dust and molecules that will one day form new stars are in this gas, per NASA.

A side-by-side comparison of two images of the same supernova remnant
A comparison of the Webb Telescope's new near-infrared image of Cassiopeia A (left) and its mid-infrared image of the supernova from April (right). Some things seen in mid-infrared, like the green loop of light in the center, are not visible in near-infrared. NASA, ESA, CSA, STScI, Danny Milisavljevic (Purdue University), Ilse De Looze (UGent), Tea Temim (Princeton University)

The researchers also compared the new image to the mid-infrared one from earlier this year. Orange and red in April’s image represent the edge of the remnant’s main inner shell, while this detail looks like wisps of smoke in the new picture. This boundary denotes where the supernova explosion collides with surrounding material that isn’t hot enough to be detected in near-infrared.

A green loop of light in the mid-infrared image (which astronomers had nicknamed the “Green Monster”) is also not visible in Webb’s new view. Holes in that part of the image are outlined in ionized gas, appearing white and purple in the near-infrared image. This could be from the explosion pushing through and shaping gas from the star, according to NASA.

With this new look at Cas A, Webb captured another intriguing feature: A blob that appears in the bottom right of the image is an example of a light echo, where light from the supernova is warming far-away dust. As that dust cools, it glows. This light echo, nicknamed Baby Cas A, is about 170 light-years behind the main supernova remnant.

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