Abell 21. Medusa Nebula

Click on the image for a full resolution version     See this image also in Instagram   Abell 21 is a planetary Nebula that was discovered and catalogued as such, in 1955, by George Abell. During the following nearly two decades, there was a debate whether this nebula was, in fact, a supernova remnant (SNR). … Continue reading Abell 21. Medusa Nebula