Gerard Peter Kuiper ( ; ] ; born Gerrit Pieter Kuiper; December 7, 1905 – December 23, 1973) was a Dutch–American astronomer, planetary scientist, selenographer, author and professor.
 He is the eponymous namesake of the Kuiper belt.
 Kuiper is considered by many to be the father of modern planetary science.
 As professor at the University of Chicago, he was dissertation advisor to Carl Sagan.
 In 1958, the two worked on the classified military Project A119, the secret Air Force plan to detonate a nuclear warhead on the Moon.
Jack Green (18 June 1925 – 5 September 2014) was a geologist and geology professor at California State University Long Beach.
 His active research included general volcanology and economic geology, as well as mineralogy, lunar protolife, lunar volcanism, water on the moon and astrobiology.
 His passion for volcanology and the moon was primarily in trying to prove that lunar craters were volcanic and not asteroid impacts, and therefore, there would be water on the moon which would support life.
 He collaborated with Urey, Shoemaker, Kuiper and others during the "Space Age" heyday, and was active in planning several conferences on remote sensing and the moon.
Miranda, also designated Uranus V, is the smallest and innermost of Uranus's five round satellites.
 It was discovered by Gerard Kuiper on 16 February 1948 at McDonald Observatory, and named after Miranda from William Shakespeare's play "The Tempest".
 Like the other large moons of Uranus, Miranda orbits close to its planet's equatorial plane.
 Because Uranus orbits the Sun on its side, Miranda's orbit is perpendicular to the ecliptic and shares Uranus's extreme seasonal cycle.
Opposition to the Mauna Kea Observatories has existed since the first telescope was built in the late 1960s.
 Originally part of research begun by Gerard Kuiper of the University of Arizona, the site has expanded into the world's largest observatory for infrared and submillimeter telescopes.
 Opposition to the telescope from residents in the city of Hilo, Hawaii were concerned about the visual appearance of the mountain and Native Hawaiians voiced concerns over the site being sacred to the Hawaiian religion as the home of several deities.
 Environmental groups and activists have been expressing concern over endangered species habitat.
 The last proposal in 2006 was canceled after a court order to submit a completed Environmental Impact Statement.
 A current proposal for one of the world's largest optical telescopes, the Thirty Meter Telescope is currently the focus of protests concerning the continued development of the mountain Hawaiians consider the most sacred peak in the island chain.
Kuiper Scarp ( ) is an east–west escarpment running along the south face of Uranus Glacier on the east side of Alexander Island, Antarctica.
 The scarp was photographed by Lincoln Ellsworth, November 23, 1935, in the course of a trans-Antarctic flight and was plotted from the photos by W.L.G. Joerg.
 It was named by the UK Antarctic Place-Names Committee from association with Uranus Glacier after Gerard Kuiper, the Dutch-American astronomer who in 1948 discovered Miranda, one of the satellites of the planet Uranus.
Nereid is the third-largest moon of Neptune.
 It has a highly eccentric orbit.
 It was the second moon of Neptune to be discovered, by Gerard Kuiper in 1949.
Kenneth Essex Edgeworth, DSO, MC (26 February 1880 – 10 October 1972) was an Irish astronomer, economist and engineer.
 He is best known for proposing the existence of a disc of icy bodies beyond the orbit of Neptune in the 1940s in much the same manner as Gerard Kuiper would publish ten years later.
 Observations later confirmed the existence of what has become known, somewhat controversially, as the Kuiper belt.
Kuiper may also refer to a number of items named after the Dutch-American astronomer Gerard Kuiper:
The Gerard P. Kuiper Prize is awarded annually by the Division for Planetary Sciences of the American Astronomical Society for outstanding lifetime achievement in the field of planetary science.
 The prize is named for Gerard P. Kuiper.
Kuiper is a moderate-size crater with a central peak cluster located at on Mercury.
 It is 60 kilometers in diameter and was named after Gerard Kuiper in 1976.
 It is one of very few Mercurian craters which are named not after artists, and one of very few cases when the same name is used for 3 craters (there are also Kuiper craters on Mars and on the Moon).

Question: What profession does Jack Green and Gerard Kuiper have in common?
Answer: professor