He traveled to California to become a fellow under
Robert Grant Aitken at the
Lick Observatory. In 1935 he left to work at the
Harvard College Observatory, where he met Sarah Parker Fuller (1913-2000), whom he married on 20 June 1936. Although he had planned to move to
Java to work at the
Bosscha Observatory, he took a position at
Yerkes Observatory of the
University of Chicago and received American citizenship in 1937. From 1947 to 1949, Kuiper served as the director of the
Yerkes Observatory, as well as the
McDonald Observatory in west Texas. In 1949, Kuiper initiated the Yerkes–McDonald asteroid survey (1950–1952). From 1950-1960 he was professor at the
University of Chicago, and from 1957 to 1959, Kuiper once again served as the director of the
Yerkes and
McDonald Observatories. In 1959, he sent
Jürgen Stock to Chile, to search for suitable sites of an observatory for the Southern skies, who eventually would identify the spot for the
Cerro Tololo Inter-American Observatory. In 1960 Kuiper moved to
Tucson,
Arizona, to found the
Lunar and Planetary Laboratory at the
University of Arizona, serving as the laboratory's director for the rest of his life, until his death in 1973.
Discoveries and Kuiper answer newsmen's questions at the Interim Scientific Results Conference of the
Ranger program. Kuiper discovered two
natural satellites of
planets in the
Solar System, namely
Uranus's satellite
Miranda and
Neptune's satellite
Nereid. In addition, he discovered
carbon dioxide in the atmosphere of
Mars, and the existence of a
methane-laced
atmosphere above
Saturn's satellite
Titan in 1944. Kuiper also pioneered airborne infrared observing using a
Convair 990 aircraft in the 1960s. In the 1950s Kuiper's interdisciplinary collaboration with the geochemist and Nobel Laureate
Harold C. Urey to understand the Moon's thermal evolution descended into acrimony, as the two engaged in what became known as the "Hot Moon, Cold Moon" controversy. Their falling out, in part a scientific dispute, also reflected the challenge of maintaining professional relationships across overlapping but distinct scientific disciplines. By 1950, Kuiper had contributed a theory for the ongoing problem of solar system origins. Kuiper claimed that gravitational instabilities would form in the solar nebula, which would then condense into protoplanets. However, Kuiper's theory failed to address the
angular momentum problem, simply attributing the loss of momentum to magnetic and electric fields instead of gravity. In another paper, based upon a lecture Kuiper gave in 1950, also called
On the Origin of the Solar System, Kuiper wrote about the "outermost region of the solar nebula, from 38 to 50 astr. units (i.e., just outside proto-Neptune)" where "condensation products (ices of H20, NH3, CH4, etc.) must have formed, and the flakes must have slowly collected and formed larger aggregates, estimated to range up to 1 km or more in size." He continued to write that "these condensations appear to account for the comets, in size, number and composition." According to Kuiper "the planet Pluto, which sweeps through the whole zone from 30 to 50
astr. units, is held responsible for having started the scattering of the comets throughout the solar system." It is said that Kuiper was operating on the assumption, common in his time, that
Pluto was the size of Earth and had therefore scattered these bodies out toward the
Oort cloud or out of the Solar System; there would not be a Kuiper belt today if this were correct. The name "Kuiper belt" was given to the region in the 1980s; it was first used in print by
Scott Tremaine in 1988. In the 1960s, Kuiper helped identify
landing sites on the
Moon for the
Apollo program. Kuiper discovered several binary stars which received "Kuiper numbers" to identify them, such as
KUI 79. == Personal life and death ==