August 4, 2022
On this date in 1181, Chinese and Japanese astronomers noticed a bright “new” star appear in the W-shaped constellation of Cassiopeia. The star was approximately the same brightness as the summer star Vega – the fifth brightest star in the sky. This was light from a supernova that was visible for approximately 6 months. It is thought that this supernova was responsible for creating the 3C58 nebula, which contains a rapidly spinning neutron star at its center.
This Chandra image shows 3C58 as a central neutron star surrounded by a thick layer of X-ray emission. Although it has not been confirmed, it is hypothesized that this nebula is the remnants of a supernova observed in 1181. Image credit: NASA/CXC/SAO