THE SINGLE BEST STRATEGY TO USE FOR GALACTIC ELEMENTS

prior to the 20th century, we failed to know that galaxies other than the Milky Way existed; earlier astronomers had classified them as as “nebulae,” given that they seemed like fuzzy clouds. But during the 1920s, astronomer Edwin Hubble showed that the Andromeda “nebula” was a galaxy in its own ideal. A composite image of the Messier 81 (