Happy Birthday Fritz Zwicky

February 14, 2008 marks the 110^th anniversary of the birth of astrophysicist Fritz Zwicky. His amazing scientific career is relatively unknown to the general public, but he remains a giant in the astronomical community.

Zwicky came to Caltech in 1925 and was a faculty member there for more than 40 years. He was a member of the staff of the Mount Wilson and Palomar Observatories until his retirement in 1968. He also worked as the research director Aerojet Engineering Corporation from 1943 to 1961.

Telescope operator Ben Traxler worked with Zwicky, Hubble, and all the astronomers from the early days at Palomar. Traxler remarked that Zwicky’s “very fertile intellect was busy at all times” and his research efforts certainly confirm that.

In an article titled “Idea Man” published in 2001 Stephen M. Maurer wrote that Zwicky will be “remembered as a gifted observational astronomer who had discovered more supernovae than everyone else in human history combined. Today, Zwicky’s reputation is bigger than ever, except that now astronomers think of him as a theorist. When researchers talk about neutron stars, dark matter, and gravitational lenses, they all start the same way: ‘Zwicky noticed this problem in the 1930s. Back then, nobody listened . . .’”

That’s right, supernovae, neutron stars, dark matter and gravitational lenses. Those are all active topics of modern astronomy that Zwicky was exploring more than 70 years ago. Much of his thinking in those areas was brought about by his work with the wide-angle 18-inch and later the 48-inch Schmidt telescopes at Palomar. The Schmidt telescope was a brand-new concept in astronomy that made it possible to photograph wide areas of the sky quickly with little distortion even on the edge of the field of view. It was Zwicky who brought Bernhardt Schmidt’s invention to Palomar and the world.

Starting in 1936 Zwicky used the 18-inch Schmidt to make the first rapid survey of the heavens, mapping out hundreds of thousands of galaxies. With it he also began his searches for exploding stars known as supernovae (With Walter Baade he even coined the term “supernova”), discovered that galaxies come in clusters and obtained the first evidence for dark matter. His searches for supernovae were extremely fruitful, having discovered more than 120 of them during his lifetime – at the time that was more supernovae than all other astronomers combined. He was the first to suggest, and correctly so, that a supernova marks an ordinary star’s transition to a collapsed, super dense object known as a neutron star.

Fritz Zwicky passed away in 1974. He received many honors during his lifetime. In 1949 he was presented with the Presidential Medal of Freedom by president Truman, for his work on rocket propulsion during World War II. The Royal Astronomical Society presented him with their most prestigious award, the Gold Medal, for "distinguished contributions to astronomy and cosmology", acknowledging his work on neutron stars, dark matter, and cataloging of galaxies. Zwicky was also honored by having an asteroid (1803 Zwicky) and a lunar crater named for him.

Today’s astronomers are still following in Zwicky’s footsteps. Palomar’s 48-inch Schmidt (since renamed the Samuel Oschin Telescope) is used nightly to survey the sky, hunting for supernovae, gravitational lenses and more. Astronomers have found a renewed interest in Zwicky’s concept of sky surveys. Entire giant telescopes are about to be built for that purpose. Beyond his observational work Zwicky’s theoretical advances laid the foundation for modern astrophysics, which owes him a great debt.