NASA has released an image of the supernova remnants Cassiopeia A, or simply Cas A, captured by the WISE space telescope at infrareds. There’s no historical record of that supernova even though its light reached Earth around 1667 A.D., probably because a large amount of dust between it and the Earth greatly dimmed its brightness. Its various emissions made it possible to study it with different instruments over the last few decades. WISE detected the echoes of the light burst that are generating ripples outwards from the star that exploded.
About 11,000 light-years from Earth, the supernova remnants Cassiopeia A were discovered in 1947 thanks to their radio emissions, of which it’s one of the brightest extrasolar known sources. This made them an object of study in various bands of the electromagnetic spectrum, as its emissions reach up to X-rays.
According to the reconstructions, over 11,000 years ago a supergiant star exploded in a supernova that left a neutron star and remnants around it. In 1667 A.D. the supernova’s light reached Earth, but interstellar dust in the middle probably partially obscured it. The consequence is that at best it was barely visible to the naked eye and no one was aware of that extraordinary event, so it wasn’t recorded.
The astronomical instruments built during the 20th century made it possible to identify the supernova remnants Cassiopeia A and to study them in an increasingly sophisticated way. This allowed to reconstruct the history of the supernova and the evolution of its remnants. It was also the target chosen for the so-called first light, which is the first use, of NASA’s Chandra X-ray Observatory.
NASA’s WISE (Wide-field Infrared Survey Explorer) space telescope made it possible to detect infrared emissions from the supernova remnants Cassiopeia A, shown in false colors in the image. At its center, it’s possible to see the blast wave generated by the supernova in a bright cloud of dust.
The blast wave travels at a very high speed, about 6% of the speed of light. When WISE captured this image, the blast wave had expanded to a distance of approximately 21 light-years from the explosion. The flash of the explosion covered over 300 light-years when seen from Earth. The orange echoes, even farther from the central remnants, are made up of interstellar dust that was heated by the supernova flash centuries after the original explosion.
The analysis of the supernova remnants Cassiopeia A and the reconstruction of their history offer new information on the death of a supergiant star and on the evolution of what remains after its explosion. Among the results of the analyzes conducted using various telescopes is the discovery of enormous amounts of elements generated by the progenitor star partly before its explosion and partly by the supernova. Those elements include oxygen, sulfur, calcium, iron, nitrogen, and phosphorus, all of which are essential for Earth-like life forms. The elements in supernova remnants Cassiopeia A are dispersing into interstellar space and could end up in some star system in formation.
