The James Webb Space Telescope amazes once again with new images of the remnants of the Cassiopeia A (Cas A) supernova. This material is composed of clouds of gas, dust, and other matter that was expelled when the star exploded.
Danny Milisavljevic, a physics and astronomy professor at the College of Science at Purdue University, studies supernova remnants and leads a year-long research group on the James Webb examining Cas A. “I’ve spent 17 years studying stars and their titanic explosions. I’ve used dozens of telescopes, both ground-based and space-based, covering the electromagnetic spectrum from gamma rays to radio wavelengths” said Milisavljevic. “Yet, I was still unprepared for the data that James Webb has provided us. I am stunned by their quality and beauty.”
Remnants of Cas A
Cassiopeia A is the most recent “remnant” of a massive star that exploded in the Milky Way. Studying this material offers a unique opportunity to learn more about how supernova phenomena occur. The light from the explosion first reached Earth about 340 years ago. “Cas A represents our best opportunity to observe the debris field of an exploded star. Performing a sort of stellar autopsy allows us to understand what kind of star was there before and how that star died” said Milisavljevic.
Supernovae like the one that formed Cas A are crucial to life. Stars create a variety of elements, and subsequent supernovae create additional elements. From calcium in our bones to iron in our blood and many other surrounding elements. The explosion spreads them into interstellar space, sowing new generations of stars and planets. “By understanding the process of star explosion, we are reading our history of origin” Milisavljevic added.
Located about 11,000 light-years away, the material cloud is located in the section of the sky of the Cassiopeia constellation. For decades, scientists have studied Cas A using different wavelengths. The new image captured by James Webb’s 18 golden hexagonal mirrors shows incredible details never seen before of the supernova remnants. The mid-infrared light has been translated into visible light, allowing scientists to analyze details and structures. Large curtains of material, fading in red and orange, represent the point where the star’s material is colliding with circumstellar gas and dust. Among those pink stripes, explosions of pink show where the composite elements of the star, including oxygen, argon, and neon, are shining.
For researchers, one of the most perplexing elements of the image is the large green ring in the picture. “We’ve nicknamed it the Green Monster, in honor of Fenway Park in Boston” said Milisavljevic. “If you look closely, it appears to be made up of tiny bubbles. The shape and complexity are unexpected and difficult to understand at the moment”. Higher-resolution images, at multiple wavelengths, particularly in the infrared, give astronomers a clearer view of the complexity of the structure.
Just as taking hold of binoculars can help resolve colors and patterns on a bird’s wing, the more details scientists have, the more information they can deduce and analyze. “Compared to previous infrared images, we see incredible details that we’ve never been able to access before” said Tea Temim, a co-investigator in the program at Princeton University.
For scientists, the most interesting aspect of the gas is the dust. Huge amounts of dust pervade very young galaxies in the early universe. It’s difficult to explain the origins of this dust without taking into account supernovae, which eject large amounts of heavy elements into space. But supernovae can also destroy dust, and it’s still unclear how much survives the journey through interstellar space.
The origin of matter and life
By studying the remnants of the Cas A supernova with the James Webb Space Telescope, astronomers hope to gain a better understanding of its dust content. The research is essential for understanding where the constituent elements of planets and us humans are created. “In Cas A, we can observe regions that have different gas compositions and understand what types of dust formed in those zones,” said Temim.
Carl Sagan long ago revealed to humanity that we are made of “star stuff”. Milisavljevic’s team and James Webb’s observations are helping scientists understand how all of this is possible. “The James Webb Telescope is incredible. I feel lucky to be among the first scientists testing its unparalleled power to explore the universe. I will spend the rest of my career trying to understand what’s in this data set”.