Cassiopeia A (Cas A) is a supernova remnant located in the constellation Cassiopeia. It is one of the youngest known remnants, formed from a massive star that exploded approximately 350 years ago. The explosion released a vast amount of energy and material into space, creating a cloud of gas and dust that continues to expand. The remnant is about 11,000 light-years away from Earth and is a significant source of radio waves and X-rays. Astronomers study Cas A to learn more about stellar evolution and the processes involved in supernova explosions, providing insights into the life cycles of massive stars.