Cassiopeia A (Nircam image). * Webb Space Telescope.
Objects in space reveal different aspects of their composition and behavior at different wavelengths of light. The supernova remnant Cassiopeia A (CASA) is one of the most well-studied objects in the wavelength spectrum in the Milky Way. However, there are still secrets hidden in the tattered remains of this star.
The latest tools are being unlocked by the James Webb Space Telescope, one of the newest tools in the researchers' toolbox, and Webb's recent performance in the near-infrared field has surprised researchers.
The supernova remnant Cassiopeia A (CASA) resembles a shiny circular ornament, ready to be placed in the perfect spot on the holiday tree, sparkling in a new image from NASA's James Webb Space Telescope.
As part of the 2023 White House holiday, the First Lady of the United States, Dr. Jill Biden, has unveiled the first-ever White House advent calendar for the first time. To show the "magic, wonder and joy" of the holiday, Dr. Biden and NASA are celebrating with Webb's new **.
While everything was bright, the scene was not the proverbial Silent Night. Webb's Nircam (Near-Infrared Camera) observations of CAS A show this star at a resolution previously unattainable at these wavelengths**. This high-resolution appearance reveals intricate details of the expanding material shell hitting the gas before the star**.
CAS A is one of the most well-studied supernova remnants in all of the universe. Over the years, ground-based and space-based observatories, including NASA's Chandra X-ray Observatory, the Hubble Space Telescope, and the retired Spitzer Space Telescope, have collected multiwavelength images of the object's wreckage.
However, astronomers have now entered a new era of studying CASA. In April 2023, Webb's MIRI (Mid-Infrared Instrument) began the chapter, revealing new and unexpected features within the inner shell of supernova remnants. Many of these features are not visible in the new Nircam images, and astronomers are investigating why.
Infrared light is invisible to our naked eyes, so image processors and scientists convert these wavelengths of light into visible colors. In this latest CAS A image, colors are assigned to different filters from Nircam, each hinting at a different activity taking place within the object.
At first glance, a Nircam image may not look as colorful as a Miri image. However, this only comes down to the wavelength of light emitted by the object's material.
In Webb's latest image, the most striking colors are the clumps represented by bright orange and light pink, which make up the inner shell of the supernova remnant. Webb's keen vision can detect the tiniest gas knots of the star itself, which are made up of sulfur, oxygen, argon, and neon.
This gas is embedded with a mixture of dust and molecules that will eventually become part of new star and planetary systems. Some fragments are filaments too small for even Webb to decipher, meaning they are equivalent to or less than 10 billion miles (about 100 astronomical units) in diameter. By comparison, the entire CAS A spans 10 light-years, or 60 trillion miles.
With Nircam's resolution, we can now see how the dying star shattered completely, leaving behind filaments that resemble tiny glass fragments," said Danny Milis**ljevic of Purdue University, who led the research team. "After so many years of research, it is truly incredible that CAS A has now addressed these details that provide us with transformative insights into how this star is.
Hidden green monsters.
When Weber compared the neo-NIR view of CAS A to the mid-IR view, its inner cavity and outermost outer shell were strangely colorless.
The periphery of the main inner shell, which appears as dark orange and red in the MIRI image, now looks like smoke from a campfire. This marks the location where the supernova shock wave hits the material around the surrounding star. Dust in interstellar matter is too cold to be detected directly at near-infrared wavelengths, but it lights up at mid-infrared rays.
The researchers say that white is light from synchrotron radiation, which is emitted throughout the electromagnetic spectrum, including near-infrared light. It is produced by charged particles circling around magnetic field lines at extremely high speeds. Synchrotron radiation can also be seen in the bubble-like shell in the lower half of the lumen.
Also not visible in the near-infrared view is the green halo in the CAS A** cavity, which glows under mid-infrared light and was nicknamed the Green Monster by the research team. The researchers described this trait as "incomprehensible" at the time of the first study.
While the "green" of the green monster is not visible in the Nircam, what remains in the near-infrared rays of the area can provide insight into mysterious features. The round holes visible in the MIRI image are blurred in white and purple emission in the NIRCAM image, which represents the ionized gas. Researchers believe this is due to supernova fragments passing through and carving the gas left behind by the star in front of the star**.
Infant CAS A
The researchers were also struck by a fascinating feature in the lower right corner of the Nircam visual field. They call this large striped spot Baby Cas A because it looks like a descendant of the main supernova.
It's an echo of light, light from a star a long time ago** has arrived and is heating distant dust that glows as it cools. The intricacies of the dust pattern, as well as the apparent proximity of Baby CAS A to CAS A itself, were particularly interesting to the researchers. In fact, Baby Cas A is located about 170 light-years behind the supernova remnant.
Webb's new portrait is also interspersed with several other smaller light echoes.
The CAS A supernova remnant is located in the constellation Cassiopeia, 11,000 light-years from Earth. From our perspective, it is estimated to be about 340 years ago**.