German-American astronomer, it be important discoveries in the field of stellar evolution and Intergalactic distances. He/She remained in the observatories on Mount Wilson and mount Palomar in California (United States of America) during the second world war, period that took advantage of to study the Andromeda galaxy with a 2.5 m telescope, taking advantage of the blackout that took place in Los Angeles and that increased the clarity of the night sky. He/She managed to be the first photographs of stars in our Galaxy, thus identifying two main groups: Star old that they are in the Galactic core and are red or star population II, and star young people who are on the periphery, in the arms in a spiral of the Galaxy, and are blue, also known as population I stars. With this distinction could be a crucial test for the theories of the evolution of galaxies.
Baade also determined the true distance of the Andromeda Galaxy, reaching 2 million light-years (previously underestimated in 800,000), thus, expanding the scale of distances between galaxies and, therefore, the ideas about the effective dimensions of the universe.