The Lake County Astronomical Society

Astronomy Bio...Gerard Kuiper

Jay Bitterman

Gerard Peter Kuiper was born on December 7, 1905, in Harenkarspel, The Netherlands. In 1933 he immigrated to the United States and in 1937 became a naturalized American citizen. He joined the staff of the Yerkes Observatory, affiliated with the University of Chicago. He was director of the Observatory from 1947 to 1949 and again, for a second term, from 1957 to 1960. From 1960 until his death in 1973 he held similar positions at the Lunar and Planetary Laboratory at the University of Arizona, and he was closely linked with the American space program.

He worked on the origin of the planets because there were theoretical discrepancies arising from the new twentieth century hypotheses on galactic evolution. The most favored of these theories is that stars, and probably planets, are formed from the condensation products of interstellar gas clouds. For this condensation to occur, the gravitational effects forcing the cloud together must exceed the expansive effect of the gas pressure of the cloud. Nonetheless, calculations of this hypothetical process indicated that under certain conditions of temperature and density, there was a lower limit to the size of the condensation products. As a matter of fact, it was found that this condensation theory was insufficient to account for the temperature or the amount of material that make up the bulk of the planets in the Solar System. To make up for this, Kuiper and his colleagues suggested that the mass of the cloud from which the planets were formed was much greater than the present mass of the planets. They indicated that the mass of the original interstellar gas cloud was approximately one-tenth the mass of the Sun, or 70 times the total mass of the planets. This condensation, according to these new conditions, would produce "protoplanets". But the idea of the formation of protoplanets appears to be unworkable, partly because it involves the condensation of only 1.5 per cent of the original interstellar gas cloud, and could not account for the balance of the material.

His work on planetary features was far more fruitful. In 1948 he predicted that carbon dioxide was one of the chief constituents of the Martian atmosphere. In 1965, with the Mariner space probes to Mars, his theory was confirmed. In 1948 he discovered the fifth moon of Uranus, which he called Miranda. In 1949 he discovered the second moon of Neptune, Nereid. When compared with Neptune's first moon, Triton, whose diameter is 3,000 km., Nereid is a dwarf. Nereid also has an eccentric orbit and its distance from Neptune varies by several million kilometers.

Kuiper's spectroscopic studies of the planets Uranus and Neptune led to the discovery of features afterwards named "Kuiper bands", found at wavelengths of 7,500 Å, which have been identified and indicate the presence of methane.

During his working life, Kuiper proposed many planetary research programs, besides playing a vital role in the United States' space probe program during the late 1960s and early 1970s. In recognition of his work, the International Astronomical Union has named a ray crater on the planet Mercury after him.