Lyman Spitzer 
Until Lyman Spitzer came along, astronomers pretty much ignored the wisps of matter between the stars. They were too busy learning how stars work and plotting the scale of the universe to worry about the near-vacuum of interstellar space.
But Spitzer noticed something important. Elliptical galaxies have a lot of old stars but almost no gas and dust. Spiral galaxies, on the other hand, have a lot of young stars plus vast supplies of gas and dust. Spitzer realized that stars must still be forming from diffuse clouds of gas and dust. His discovery was important to understanding the birth of the stars and the evolution of galaxies. And it led to a new study area for astronomy: the interstellar medium — the stuff between stars.
Spitzer was born in Ohio 100 years ago tomorrow. He studied physics at Yale, then joined the faculty at Princeton under Henry Norris Russell, one of the leaders of American astronomy.
During World War II, he helped develop sonar. After the war, it was back to Princeton, where he succeeded Russell as chairman of the physics and astronomy department — at the age of 33.
Over the decades, Spitzer pursued many research interests. He established an effort to create nuclear fusion — the power source of the stars — in the lab. He studied the evolution of stars, and continued to probe the stuff between the stars.
Yet Spitzer is best known for his advocacy of a new concept in astronomy: the space telescope. More about that tomorrow.
Script by Damond Benningfield, Copyright 2014