Pinpointing a Milepost Marker Star that Opened the Realm of Galaxies At the dawn of the 20th century, astronomers faced a ...
SNR 0519 is a supernova remnant (SNR) made up of thin, blood-red shells of gas. It is the remnant of a star that exploded as a supernova about 600 years ago. This image, shows Supernova 1987a (center) ...