Man at the Window

When a German baby, soon to be named Walter Baade, was born in 1893, the universe seemed relatively small and cozy, although full of unknowns. No one knew the size of the stars, what they were made of, or where they got their energy. No one dreamed that the stars are only the doorstep of the universe. When Baade got his doctorate at the University of Gottingen in 1919, most of the mysteries still remained; but in the U.S. new telescopes, bigger and more accurate than anything in Europe, were beginning to probe the sky with new farsightedness. After earning a reputation at Hamburg Observatory, Baade (pronounced bah-de) got the call that all young astronomers there hoped for. In 1931 he went to work at Mount Wilson, Calif, with the 100-in. telescope, at that time the biggest of them all.

Mount Wilson was the world's best window on the universe, and Baade quickly won recognition as a superb observer. His first search was for supernovae, those incredible stars that burst like giant nuclear bombs and shine for a few weeks with the glare of 100 million suns. They happen in an average galaxy only once in about 300 years. But by patrolling distant galaxies with the 100-incher, Baade photographed many of them--and developed an explanation of their explosive physics.

Star Populations. Another of Baade's absorbing interests was the evolution of stars. After long and subtle observing, Baade found that there are two sorts of star "populations." Population I contains brilliant giant stars that are found chiefly in the outer spiral arms of a galaxy. Population II, of which the sun is a member, contains the less spectacular stars that make up most of any given galaxy's central disk. Baade concluded that the stars of Population I were recently formed out of cosmic dust and gas, and that they are rapidly burning themselves out. The stars of Population II are much older, dating back to the formation of the galaxy. Most of them will shine almost unchanged for billions of years.

In 1948 the 200-in. telescope on Palomar Mountain was finished, and Baade had an even better window to look through. He fought for time on this marvelous instrument, and when he got it, he spent all night in the instrument cage. Every trip to Palomar cost him three or four pounds because of excitement and skipped meals.

Colliding Galaxies. As Baade grew oM, his hair grew white, but his blue eyes were always bright and alert, and his good spirits and accomplishments in astronomy did not diminish. He re-examined the special stars that astronomers had used for a generation to measure great distances--and found that they had been misinterpreted. Thus the observed universe, through Baade's work, doubled in size. In 1952, in collaboration with Rudolph Minkowski (TIME, June 27), he found the first pair of galaxies in collision. This proved that galaxies do in fact collide. Baade therefore examined close clus ters of galaxies for evidence that some of them may have collided in the past. Sure enough, such cluster galaxies contained few of the young stars of Population I, meaning that they had indeed collided. During the encounter, their stars inter-passed without individual collisions, but the dust and gas between them was combed out. Conclusion: galaxies that have collided contain no material to gather into youthful, fast-burning, quick-dying stars of Population I.

At 65, Baade retired. Last week he died in Gottingen, the ancient university town where he started his scholarly career. In his 67 years, the man at the window had seen the universe increase and become more interesting by 1,000,000 times.

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