Astronomers are performing stellar forensics on the youngest-known supernova remnant in the galaxy, probing into its debris for clues about the star and how it exploded.
A research team has captured new images of Cassiopeia A, called “Cas A” for short, with the James Webb Space Telescope, the leading infrared observatory in space, run by NASA and the European and Canadian space agencies.
The Cas A remnant spans about 10 light-years — some 60 trillion miles — and is located 11,000 light-years away in the constellation Cassiopeia. It’s estimated to have exploded about 340 years ago.
Already, scientists have used Webb to discover never-before-seen details in the cataclysmic supernova’s aftermath.
“We can now see how the dying star absolutely shattered when it exploded, leaving filaments akin to tiny shards of glass behind,” said Danny Milisavljevic of Purdue University in Indiana, in a statement.
Supernovas, the biggest, brightest, and most violent explosions in the universe, are element factories, astrophysicists say: They make carbon, for instance, the same chemical on which humans and much of life on Earth are based. They spread metals like calcium found in bones and iron in blood across interstellar space. This dispersal seeds new generations of stars and planets.
This is what astronomer Carl Sagan meant when he said we’re made of “star stuff.” The same substances that make our bodies were literally forged within the cores of stars, then flung through the cosmos when they died.
In April, Milisavljevic’s research team released an image, revealing the cosmic object as a bubble with curtains of fiery red and orange material, caused by warm dust. Within it was a ring of hot pink threads and knots, material from the dead star. The debris field was sprinkled with heavy elements, such as oxygen, argon, and neon.
“We can now see how the dying star absolutely shattered when it exploded, leaving filaments akin to tiny shards of glass behind.”
A prominent green loop, found a little right of the center, provoked the most curiosity. The feature was dotted with more tiny bubbles that experts don’t fully understand.
That image was taken with Webb’s Mid-Infrared Instrument, aka MIRI. But when the team recently pointed the telescope‘s Near-Infrared Camera Instrument, or NIRCam, at the object, many of the details vanished. The new photo, displayed below, is the result of that new study.
Credit: NASA / ESA / CSA / STScI / Danny Milisavljevic / Ilse De Looze / Tea Temim
When comparing the two views taken at different light wavelengths, the near-infrared image is notably less colorful.
Because infrared light is invisible to human eyes, researchers have translated the data into visible-light wavelengths, sort of like playing the same tune but in a lower octave. Each of the assigned colors provides insight into different activities occurring within the debris.
The outer edge of the main inner shell, which appeared orange and red in the April image, now looks like smoke. Researchers believe this is where the supernova blast wave has slammed into surrounding stardust. It’s too cool to be detected at near-infrared wavelengths, but lights up in the mid-infrared.
Credit: NASA / ESA / CSA / STScI / Danny Milisavljevic / Ilse De Looze / Tea Temim
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The white color in the new image is light from charged particles traveling at extremely high speeds and spiraling around magnetic field lines. This so-called “synchrotron radiation” also shows up in the bubble-like shells in the lower half of the inner cavity.
And that prominent green loop — nicknamed the “Green Monster” by the research team — disappears in the near-infrared view.
“The circular holes visible in the MIRI image are faintly outlined in white and purple emission in the NIRCam image – this represents ionized gas,” according to a news release by the Space Telescope Science Institute based in Baltimore. “Researchers believe this is due to the supernova debris pushing through and sculpting gas left behind by the star before it exploded.”
Perhaps the most surprising detail found in the latest Webb image is a streaked blob in the lower right corner. The team has nicknamed it “Baby Cas A” because it looks like the main supernova gave birth to a Mini-me.
In actuality, this is a light echo, according to the experts, where light from the explosion has traveled afar and is warming dust, which glows as it cools. Though Baby Cas A looks like it’s staying close to mama, the cloud is about 170 light-years behind it.
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