Newcomb, Simon (1835-1909) - in 1899 published a comprehensive table of the motion of the Moon. He was a prolific writer who in an early paper, objected to the theory that the asteroid belt was formed by the breakup of a planet between Mars and Jupiter. Nicholson, Seth Barnes (1891-1963) - American astronomer who took careful measurements of temperatures of the Moon. The results led to the theory that the Moon was covered with a thin layer of dust, acting as an insulator. He also discovered four new moons of Jupiter.