The expanding shell of hot gas and debris left behind after a supernova explosion, visible for thousands of years as it sweeps up and heats surrounding interstellar material. These remnants are important sources of cosmic rays and help distribute heavy elements throughout galaxies.
From 'supernova' and Latin 'remnant' (remaining behind), the term developed in the mid-20th century as radio astronomy revealed the extended structures surrounding historical supernova sites. The concept expanded understanding of stellar explosions from brief events to long-lasting cosmic phenomena.
Supernova remnants are like cosmic snow plows that create giant bubbles in space! The Crab Nebula, from a supernova observed by Chinese astronomers in 1054 AD, is still expanding at 1,500 kilometers per second and won't fade away for another 100,000 years.
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