Free Astronomy Magazine November-December 2023

44 NOVEMBER-DECEMBER 2023 ASTRO PUBLISHING 20,000-year-old explosion continues expanding into space by NASA/ESA Ray Villard T hough a doomed star ex- ploded some 20,000 years ago, its tattered remnants continue racing into space at breakneck speeds – and NASA’s Hubble Space Telescope has caught the action. rial in space. Hubble images taken from 2001 to 2020 clearly demon- strate how the remnant’s shock front has expanded over time, and they used the crisp images to clock its speed. By analyzing the shock’s location, astronomers found that the shock hasn’t slowed down at all in the last 20 years, and is speeding into inter- stellar space at over half a million miles per hour – fast enough to The nebula, called the Cygnus Loop, forms a bubble-like shape that is about 120 light-years in diameter. The distance to its center is approx- imately 2,600 light-years. The entire nebula has a width of six full Moons as seen on the sky. Astronomers used Hubble to zoom into a very small slice of the leading edge of this expanding supernova bubble, where the supernova blast wave plows into surrounding mate-