M27: 不是彗星
2019 August 29 M27: Not a Comet Image Credit & Copyright: Bob Franke Explanation: While hunting for comets in the skies above 18th century France, astronomer Charles Messier diligently kept a list of the things he encountered that were definitely not comets. This is number 27 on his now famous not-a-comet list. In fact, 21st century astronomers would ide...