Mysterious features hidden in near-infrared light
Like a shiny, round ornament ready to hang in the perfect spot on your holiday tree, the supernova remnant Cassiopeia A (Cas A) shines in new images from NASA’s James Webb Space Telescope. As part of the Vacation at the White House in 2023, U.S. First Lady Dr. Jill Biden debuts the first-ever White House Advent Calendar. To showcase the “magic, wonder, and joy” of the holiday season, Dr. Biden and NASA are celebrating with this new image from the web.
Although everything is bright, this scene is not the proverbial quiet night. Her NIRCam (near-infrared camera) view of Cas A’s web shows this stellar explosion at a resolution previously unattainable at these wavelengths. This high-resolution look reveals intricate details of the expanding shell of material that hits the star’s gas vent before it explodes.
Cas A is one of the most well-studied supernova remnants in the entire universe. For many years, ground and space observatories, including NASA, Chandra X-ray Observatory, hubble space telescopeand retired Spitzer Space Telescope They assembled multi-wavelength images of the object’s remains.
But astronomers are now entering a new era in Cas A research. In April 2023, Webb’s MIRI (Mid-Infrared Instrument) Started this chapter, new and unexpected features within the inner shell of a supernova remnant have been revealed. Many of those features are not visible in his new NIRCam images, and astronomers are investigating why.
Image: Cassiopeia A (NIRCam)
“Like broken glass”
Infrared light is invisible to our eyes, so image processors and scientists convert these wavelengths of light into visible colors. In this latest image of Cas A, NIRCam’s different filters are assigned colors, each suggesting a different activity occurring within the object.
At first glance, NIRCam images may appear lighter in color than MIRI images. However, this simply depends on the wavelength at which the object’s material is emitting light.
The most striking color in Webb’s latest image is the bright orange and bright pink blobs that make up the inner shell of the supernova remnant. Webb’s razor-sharp vision can detect the tiniest clumps of gas consisting of sulfur, oxygen, argon, and neon from the star itself. Embedded in this gas is a mixture of dust and molecules that will eventually become the building blocks of new stars and planetary systems. Some filaments of debris are too small to be resolved even with a web. This means its diameter is equal to or less than 10 billion miles (about 100 astronomical units). By comparison, the entirety of Cas A is 10 light years across, or 60 trillion miles.
“NIRCam’s resolution allows us to see how a dying star could have completely shattered when it exploded, leaving behind filaments that resemble tiny shards of glass,” said Danny Milisavljevic of Purdue University, who led the research team. I started to understand,” he said. “After all these years of studying Cas A, it’s really exciting to now know its details and provide us with transformative insight into how this star exploded. It’s unbelievable.”
Image: Cassiopeia A NIRCam/MIRI
hidden green monster
Comparing Webb’s new near-infrared and mid-infrared images of Cas A, curiously, its inner cavity and outermost shell are devoid of color.
The area around the main inner shell, which appeared as deep orange and red in the MIRI image, now looks like campfire smoke. This shows where the supernova explosion wave is impacting the surrounding circumstellar material. Dust in the circumstellar medium is too cold to be directly detected at near-infrared wavelengths, but it emits light in the mid-infrared.
The researchers say the white color is synchrotron radiation, which is emitted across the electromagnetic spectrum, including near-infrared radiation. It is produced by charged particles that move at extremely high speeds in a spiral around magnetic field lines. Synchrotron radiation is also visible in the bubble-like shell in the lower half of the internal cavity.
Also missing from the near-infrared images is a loop of green light in Cas A’s central cavity, which glows in mid-infrared light and has been dubbed the “green monster” by the research team. This feature was described as “difficult to understand” when researchers first investigated it.
Although the Green Monster’s “green color” is not visible in NIRCam, what remains in the near-infrared of its region may provide insight into its mysterious features. The circular hole visible in the MIRI image is faintly outlined with white and purple luminescence in the NIRCam image. This represents ionized gas. Researchers believe this is because supernova debris penetrated the star and scraped away at the gas left behind by the star before exploding.
Image: Characteristics of Cassiopeia A
Baby Cass A
The researchers were also completely surprised by one fascinating feature in the bottom right corner of NIRCam’s field of view. They call the large striped blob Baby Cass A – because it looks like the offspring of a major supernova.
This is an echo of light, shining as light from a long-ago explosion of a star reaches distant dust, warming it and cooling it. The complexity of the dust pattern and the apparent proximity of Baby Cas A to Cas A itself are of particular interest to researchers. In fact, Baby Cass A is located about 170 light-years behind the supernova remnant.
There are several other small echoes of light scattered throughout Webb’s new portrait.
The Cas A supernova remnant is located 11,000 light-years away in the constellation Cassiopeia. From our point of view, it is estimated that it exploded about 340 years ago.
The James Webb Space Telescope is the world’s premier space science observatory. Webb unravels the mysteries of our solar system, looks to distant worlds around other stars, and explores the mysterious structure and origins of our universe and our place in it. Webb is an international program led by NASA and its partners ESA (European Space Agency) and Canadian Space Agency.
media contact
Laura Betts – laura.e.betz@nasa.gov, Rob Gutro– rob.gutro@nasa.gov
NASA’s Goddard Space Flight Center, Greenbelt, Maryland.
hannah brown – hbraun@stsci.edu , Christine Pulliam – cpulliam@stsci.edu
Space Telescope Science InstituteBaltimore, Maryland.
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Related information
Other web news – https://science.nasa.gov/mission/webb/latestnews/
Other web images – https://science.nasa.gov/mission/webb/multimedia/images/
web mission page – https://science.nasa.gov/mission/webb/
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