National Aeronautics and Space Administration (NASA) solves 2,000-year-old mystery of RCW 86 supernova

Key facts

• Ancient Chinese astronomers recorded a bright guest star in 185 AD, which is now recognised as the first recorded supernova in human history.
• The supernova remnant, known as RCW 86, spans approximately 85 light-years across, a size that previously suggested it was 10,000 years old rather than 2,000.
• Research using the National Aeronautics and Space Administration (NASA) Chandra X-ray Observatory and the European Space Agency (ESA) XMM-Newton revealed the star exploded inside a low-density cavity.
• The cavity or hidden bubble was created by the star's own stellar wind before it died, allowing debris to expand rapidly without resistance from surrounding material.
• A reverse shock or bounce back effect occurred when debris hit denser gas at the cavity's edge, reheating gas to millions of degrees and emitting X-rays detected by NASA.
• The 185 AD event is classified as a Type Ia supernova, a category of stellar explosions used as standard candles to measure distances across the universe.
• The study also utilised data from the Imaging X-ray Polarimetry Explorer (IXPE) and the National Science Foundation (NSF) National Optical-Infrared Astronomy Research Laboratory (NOIRab).
• Understanding these explosions helps scientists refine measurements regarding the expansion of the universe and the nature of dark energy.