Webb and Chandra join forces to solve mystery behind the Green Monster in star debris

By combining data from NASA's Chandra X-ray Observatory and James Webb Space Telescope (JWST), researchers have solved the mystery surrounding the Green Monster in the well-known supernova remnant Cassiopeia A (Cas A).

The curious structure was first discovered in Webb data in April 2023. Following an in-depth analysis, the researchers found that filaments in the outer part of Cas A, from the blast wave, closely matched the X-ray properties of the Green Monster, including less iron and silicon than in the supernova debris.

The researchers concluded that the Green Monster was formed as a result of a blast wave from the exploded star colliding with the material surrounding it. This finding provides robust support to earlier suggestions based on Webb data alone.

For the first time scientists have combined the powers of @NASA's Chandra & Webb Space Telescopes to study the famous supernova remnant Cassiopeia A, helping to solve the mystery behind the remnant's "Green Monster": https://t.co/ycBcpEnNxL #AAS243 pic.twitter.com/TSN8NOmEOr

— Chandra Observatory (@chandraxray) January 8, 2024

The research also revealed other details about the explosion that resulted in the creation of Cas A about 340 years ago, from Earth's perspective.

The Webb view of the pristine debris was compared with X-ray maps of radioactive elements that were created in the supernova and by using NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) data, the researchers mapped radioactive titanium while Chandra pinpointed the locations of radioactive nickel by measuring the distribution of iron.

Some filaments of pristine debris near the remnant's center, seen with Webb, are connected to the iron seen by Chandra farther out. Radioactive titanium is seen where pristine debris is relatively weak, according to the researchers.

According to observations made by the Webb telescope and X-ray maps, radioactive material observed in X-rays played a significant role in forming cavities within the pristine debris at the center of Cas A. These structures likely originated from the violent mixing of the star's inner layers with the hot, radioactive matter produced during the collapse of the core under gravity.