Mystery Behind Green Lights From Supernova Remnant Cassiopeia A Finally Solved

James Webb Space Telescope helped astronomers solve the mysterious green light observed from a supernova remnant. It was first observed last year from the remains of an exploded star.

Green Monster From a Supernova Remnant Cassiopeia A Explained

The remarkable "wall of emission" in front of Cassiopeia A, also known as Cas A, is an expanding shell of hot gas, approximately 11,000 light-years from Earth, whose light first reached us 340 years ago. It was captured on camera by NASA's James Webb Space Telescope (JWST or Webb) in April of last year. Astronomers have been attempting to explain its origin and existence in the thoroughly examined supernova remnant for the past year.

The new image, which was released on Monday (Jan. 8), both online and at the American Astronomical Society conference in New Orleans, combines Webb's and NASA's Chandra, Spitzer, and Hubble space telescopes' combined observing powers to reveal Cas A in never-before-seen detail.

Stretching across ten light-years, the ball of light appears to be laced with red clouds, exposing dust that has probably been warmed due to its residence in gas that has been heated to millions of degrees. A stunning new picture of the stellar debris is presented by streaks of white, green, and orange light scattered throughout, giving the impression of cosmic chaos.

The wispy green light dubbed "Green Monster" appears to be spattered with "remarkably round holes," according to Danny Milisavljevic of Purdue University, who led the new study. The intriguing "holes" might have developed due to knots of supernova ejecta breaking through the star's earlier released expanding cloud of stellar gas.

"There's very few mechanisms in the universe that can make such round objects," he added. "This is the one that seems to be the best explanation."

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What Is Cassiopeia A?

Cassiopeia A (Cas A) is the remnant after a huge supernova burst about 300 years ago. An expanding shell of hot gas created by the explosion is visible in the X-ray image.

The star exploded 10,000 years before the light from the Milky Way galaxy reached Earth in the late 1600s. Cas A is the youngest known supernova remnant in the Milky Way Galaxy, located 10,000 light-years away in the constellation Cassiopeia.

The supernova remnant is easily noticeable as it appears as gaseous streamers that glow in red, white, blue, green, and pink light up the sky like fireworks on July Fourth. The explosion was assumed to be very powerful but may have occurred behind an interstellar dust cloud as there is no current record of it being seen, except a potential sighting by English astronomer John Flamsteed in 1680.

The remnant can be poorly observed in visible, infrared, and X-ray wavelengths. It forms a growing ring of material with a roughly five-arc-minute diameter. The remnant's expansion rate has been used to calculate the explosion's age. The neutron star, the first known to have a carbon atmosphere, is at the center of the remnant.