Maarten Schmidt

1929-

Dutch-American Astronomer

In 1963 Dutch-American astronomer Maarten Schmidt discovered what are now called quasars, or quasi-stellar radio sources (QSOs). Having found what appeared to be invisible stars that emitted radio waves, he observed that the objects' light spectrum was like nothing ever seen. These source of ultra-intense radio emissions remain somewhat mysterious; they are no bigger than stars, yet they produce more energy than an entire galaxy. In later years, this fact has led to speculation that black holes are the source of quasars; as for Schmidt, he has continued to investigate the spectral qualities of quasars.

Born on December 28, 1929, Schmidt was raised in Groningen, Holland. He attended the University of Leiden, where he studied under Jan H. Oort and earned his Ph.D. in 1956. In 1959 he moved to the California Institute of Technology (Cal Tech), where he was initially concerned with questions involving the galaxy's mass distribution and dynamics. In the early 1960s, however, astronomer Rudolph Minkowski retired from Cal Tech, and Schmidt assumed leadership of the project Minkowski had directed, the analysis of spectra of radio-emitting objects.

With the advent of radio astronomy in the 1930s and 1940s, scientists were able to observe stars not only in terms of their light waves but also their radio emissions—a development that greatly expanded the reach of the known universe. At this time radio astronomers first became aware of faint blue star-like objects that emitted extraordinary amounts of radio waves and ultraviolet radiation. While observing these objects at California's Mount Palomar Observatory in 1963, Schmidt had a great insight.

The light spectrum associated with these objects contained a few strangely wide lines, which initially looked like nothing ever seen, but Schmidt soon realized that these lines were normal spectral lines for hydrogen that had been shifted toward the red end of the visible spectrum, and this shift had made the configuration difficult to recognize. The red coloring indicated that the object was moving away from Earth—at a rate of about 30,000 miles per second (48,280 km/s).

These odd red-shifting objects came to be known as quasi-stellar radio sources, or quasars. Since 1963, thousands more have been discovered, and the majority of quasars are now believed to emit no radio waves at all—only an intense ultraviolet light. These "radio-quiet" quasars now constitute about 99% of all known quasars.

Since the mid-1960s, Schmidt has turned his attention to a number of subjects involving quasars. Analyzing their evolution and distribution, he found that there were far more quasars in an earlier epoch. This finding helped lead to the decline of the steady-state theory, which had once competed with the Big Bang theory as a model for how the universe came into being.

Schmidt, who retired as a professor in 1996, has served in a variety of roles at Cal Tech: executive officer for astronomy from 1972 to 1975; chairman of the Division of Physics, Mathematics, and Astronomy from 1976 to 1978; and director of the Hale Observatories from 1978 to 1980. Winner of the 1992 Bruce Medal and other honors, he continues to investigate quasars with a high red shift, his aim being to find the "red shift cutoff," above which no quasars exist.

JUDSON KNIGHT