Cassiopeia A is one of the Milky Way’s most well-studied supernova remnants. From our perspective, the plasma shell has been growing at a pace of between 4,000 and 6,000 kilometers per second for 350 years. However, not all of it is true. The supernova looks to be traveling backwards in one place. The discovery, which has been approved for publication in the Astrophysical Journal and is accessible as a preprint on the ArXiv, is based on 19 years of data that implies the remnant’s western portion has collided with something. Another possibility is that there is a hole in the shell, although models point to a collision.
In a statement, main author Jacco Vink of the University of Amsterdam noted, “The backward shift in the west can signify two things.” “Either there is a hole in the supernova material, a form of vacuum, forcing the hot shell to abruptly slide inwards locally. Alternatively, the nebula may have collided with something.” NASA’s Chandra X-ray Observatory was used to make the observations. The inner and outer shells of the supernova were measured for acceleration (or deceleration). Vink’s discoveries drew the attention of an Italian group of astronomers when he initially presented them at a specialty conference in 2019. They were intrigued, so they set out to mimic what would happen if they collided.
When a star enters the red giant phase, and then the super red giant phase, it loses a lot of material. These stars are massive, with loosely linked outer layers. When a star goes supernova, a cataclysmic explosion towards the end of its life, the material is hurled at tremendous speeds, allowing it to catch up with previously discharged material. The situation between the impact and the shell having a hole, according to the Italian group, may be distinguished. The shock wave lessens at first after a collision, but later accelerates. This is exactly what Vink discovered in his observations.
“The jigsaw pieces came into place when we just discovered an acceleration and they expected it in their models,” Vink added. In the constellation Cassiopea, Cassiopea A is situated 11,000 light-years distant. The supernova’s light would have reached Earth in 1670, but due to intervening dust and inadequate telescope capabilities, no one could see it at the time. Since then, many observations have caught up with us, and it is now a favored target for many observatories. Last month, NASA’s newest X-ray observatory, IXPE, produced its first image, which was of a supernova remnant. The JWST will investigate it in infrared later this year, which is exciting.
