The latest image from the James Webb Space Telescope presents a remarkable spectacle of lights far before the turn of the new year. This is the highest-resolution capture ever made of the supernova remnant Cassiopeia A (Cas A). Without a doubt, it’s an awe-inspiring visual experience.
A Cosmic Explosion Still Visible Today
Located approximately 11,000 light-years away in the constellation Cassiopeia, the visible remnants of the Cas A explosion date back 340 years. As one of the most comprehensively studied supernova remnants in the universe, the Hubble telescope has taken numerous pictures of the remains of this exploded star. The epoch of the James Webb telescope has allowed us even more precise imaging. The MIRI (Mid-Infrared Instrument) showcased in April unexpected and new images of the interior portion of the supernova remnant. Many of the MIRI’s details, however, are missing from the new NIRCam image (Near-Infrared), leaving astronomers with unanswered questions.
Decoding the Light of Cas A
The images were obtained using infrared light, which is invisible to the naked eye. As a result, these wavelengths of light are translated into perceivable colors. In this new image of Cas A, the various filters of the NIRCam emit differing colors, each color signifying a different activity in the object.
At first glance, the NIRCam image may seem less vibrant than its MIRI counterpart. This is due to the wavelengths at which the object’s material emits light. The most striking colors in Webb’s latest image are the bright orange and light pink materials visible in the inner portion of the supernova remnant. Even the tiniest clumps of gas, composed of sulfur, oxygen, argon, and neon from the star itself, are sharply captured by Webb. The gas contains a mix of dust and molecules, which will eventually become part of new stars and planetary systems. Some remnants are even too small for Webb, indicating that they are less than 16 billion kilometers in diameter. For comparison, Cas A as a whole spans ten light years or approximately 96 trillion kilometers.
A New Era of Stellar Observation
“With NIRCam’s resolution, we can now witness the shattered remains of the dying star which exploded and left behind pieces akin to tiny shards of glass,” says research leader Danny Milisavljevic from Purdue University. “It’s truly incredible that after years of studying Cas A, we can discern these details now. It offers us an entirely novel insight into how this star exploded.”
Less Color, More Insight
If you compare NIRCam’s image to the MIRI picture, you can see the internal part and very outer shell displaying very little color. The edges of the inner part that colored deep orange and red on the MIRI image look like the smoke from a bonfire in the NIRCam image. This indicates the juncture where the supernova shockwave collides with the surrounding stellar material, too cold to be detected in near-infrared wavelengths but visible in mid-infrared.
The white color is likely light from synchrotron radiation, emitted across the entire electromagnetic spectrum, including near-infrared. It is generated by charged particles spinning at extremely high speeds around a magnetic field in a spiral. Synchrotron radiation is also visible in the bubble-shaped shell in the lower half of the inner part.
The Green Monster
What’s not visible in the NIRCam image is the green light in the central part of Cas A that was visible in the MIRI picture and was then called the Green Monster. It was an area that researchers found puzzling. Although the green light is no longer visible, NIRCam’s image provides more insight into this mysterious part. The circular holes from the MIRI image are faintly visible in white and purple, indicating ionized gas. Researchers believe that this is a result of supernova fragments pushing through and releasing gas that remained before the star exploded.
The Enigma of Baby Cas A
Finally, astronomers were utterly astonished by one intriguing aspect in the lower-right corner of the NIRCam image. They dub this large, striped ‘blob’ as Baby Cas A, as it seems to be a split-off from the large supernova. However, it is a light echo. The light from the star explosion reached dust far away and heated it up. As it cools down, it glows. The dust pattern and the apparent proximity of Baby Cas A to Cas A itself intrigues researchers. In actuality, Baby Cas A is about 170 light-years behind the supernova remnant. More light echoes can be spotted in Webb’s new portrait, as marked by number 3 in the photo above.
