Roughly 340 years ago, light from a massive exploding star reached Earth for the first time. The remnants of this outburst, called a supernova, became known as Cassiopeia A.
Now, thanks to the James Webb Space Telescope, astronomers have a new, highly detailed view of the supernova, which could help them work backward and unravel some of the mysteries surrounding the star before it exploded.
Scientists are particularly interested in this supernova—located about 11,000 light-years from Earth in the constellation Cassiopeia—because it’s the youngest-known leftover from an exploding star in the Milky Way Galaxy. As such, it gives scientists the “best opportunity to look at the debris field of an exploded star and run a kind of stellar autopsy to understand what type of star was there beforehand and how that star exploded,” says Danny Milisavljevic, an astrophysicist at Purdue University and a principal investigator for Webb, in a NASA statement.
Webb captured Cassiopeia A with its Mid-Infrared Instrument (MIRI), which gives scientists a unique view of what’s happening in the supernova outside the realm of visible light. The high-powered telescope’s latest image shows a colorful array of cloud-like shapes and patterns, including a bright green, lasso-shaped structure that astronomers have named the “Green Monster” after Boston’s Fenway Park. Scientists are still trying to decipher the significance of that shape, which is “unexpected and challenging” to understand, says Milisavljevic in the statement.
In Webb’s new mid-infrared view, the supernova also appears to be surrounded by fiery reds and oranges. Astronomers say these hues represent material from the exploded star crashing into surrounding dust and gas. The bright pink sections of the image are full of dust and heavy elements from the star, including neon, argon and oxygen, per NASA.
These heavy elements are important, because they are the building blocks of life, stars and planets, including Earth. Understanding Cassiopeia A, then, is a bit like “reading our own origin story,” says Milisavljevic in the statement.
Scientists have a lot of questions about cosmic dust more broadly, and by studying supernovae like this one, they may be able to uncover some answers. For instance, the universe contains more dust than astronomers’ models can account for, and they’d like to find an explanation for this discrepancy.
“If it wasn’t for the dust, our universe would be a pretty mundane place: flickering stars with nothing around them,” says Matthew Genge, a planetary scientist at Imperial College London who was not involved with the new Webb image, to Quanta Magazine’s Natalie Wolchover. “The dust links stars with everything else, with all the planets, all the living things on those planets. It’s the dust that’s responsible, ultimately.”