Tattered Remnants of a Star

10,000 light-years away in the constellation of Cassiopeia, a massive star went supernova, collapsing under the weight of its own gravity and blowing its outer layers into space, causing its own explosive demise. Shattered fragments are all that remain of the star—a huge swirls of debris and stellar ejecta called Cassiopeia A. It contains gases of 10 million degrees Celsius, created when the supernova flung out materials that smashed into surrounding dust and gas at speeds of 16 million km/hour. Cas A is actually the strongest radio source in the sky beyond our solar system, and the images above show the remnants in both optical and X-ray wavelengths, capturing the complex, intricate structure of the debris, fascinating in its utter destruction. The false colours indicate chemical compositions: bright green filaments are rich in oxygen, red and purple are sulphur, and blue are hydrogen and nitrogen. The light of Cas A first reached Earth just 340 years ago, so it’s one of the youngest and freshest such remnants we know of in the Milky Way. Studying it will help us understand the evolution of the universe. But it still holds some mysteries—take a closer look at the last image, and note the small turquoise dot right in the centre. Astronomers believe this is a neutron star—an ultra-dense star created during the supernova. Years of observation have shown unexpected rapid cooling of the star, which is thought to be caused by superfluids in its dense core. Superfluids are extremely bizarre but super cool, and you can read more about them from NASA.

(Image credit: Hubble/Chandra)