Cas A (MIRI image)

Cassiopeia A (Cas A) is a supernova remnant located about 11 000 light-years from Earth in the constellation Cassiopeia. It spans approximately 10 light-years. This image, released in April 2023, uses data from Webb’s Mid-Infrared Instrument (MIRI) to reveal Cas A in a new light.

On the remnant’s exterior, particularly at the top and left, lie curtains of material ,appearing orange and red, that are due to emission from warm dust. This marks where ejected material from the exploded star is ramming into surrounding circumstellar material.

Interior to this outer shell lie mottled filaments of bright pink studded with clumps and knots. This is material from the star itself, and likely shines due to a mix of various heavy elements and dust emission. The stellar material can also be seen as fainter wisps near the cavity’s interior.

A loop represented in green extends across the right side of the central cavity. Its shape and complexity are unexpected and challenging for scientists to understand.

[Image description: A roughly square image is rotated clockwise about 45 degrees. Within the image is a roughly circular nebula with a complex structure. On the circle’s exterior lie curtains of material glowing orange. Interior to this outer shell lies a ring of mottled filaments of bright pink studded with clumps and knots. At centre right, a greenish loop extends from the right side of the ring into the central cavity. Translucent wisps of blue, green, and red appear throughout the image.]