1512 N. Copernicus States the Earth is not the center of the Universe.
1577 Tycho Brahe Showed comets are distant objects which are not in the atmosphere through parallax measurements.
1609 Johannes Kepler Stated his 3 laws of planetary motion.
1610 Galileo Galilei Found the first moons around another planet.
1656 Huygens Identifies nature of Saturn's rings.
1705 E. Halley Applied Newton's laws of motion to predict the return of comet Halley.
1772 Lagrange determined 5 stable points for a 3rd body when 2 bodies are much more massive than it. Only L4(lead) and L5(trail) points are stable.
1781 William Herschel Found Uranus.
1796 Pierce Laplace States his hypothesis for formation of solar system from a spinning gas and dust nebula.
1801 G. Piazzi Found the first asteriod Ceres.
1846 Johann Galle Found Neptune from Jean LeVerrier prediction. -Louis d'Arrest also with Galle (student). -John Adams made prediction earlier too.
1849 E. Roche Stated Roche Law.
1898 Witt Found first NEO 433 Eros.
19?? Robertson Described Poynting-Robertson effect.
1906 Max Wolf Found first Jovian Trojan Archilles.
1920 Baade Found comet/asteroid Hidalgo.
1930 Clyde Tombaugh Found Pluto (1961).
1949 K. Edgeworth Stated there should be a disk of comets beyond Neptune because the solar nebula shouldn't have truncated at Neptune but would have small bodies from the slow accumulation at such large distances.
1950 Fred Whipple Stated comets are weak conglomerates of volatile and solid material (dirty snowball).
1950 J. Oort Stated long period comets come from a spherical cloud at a distance greater than 10000 AU. Spherical cloud came from scattered inner small bodies.
1951 G. Kuiper Stated there should be a disk of small bodies from the outer part of the solar nebula.
1969 Dohnanyi Found power law size distribution dN=c*a^-3.5*da for collisional evolved system.
1972 Everhart Stated long period comets could become short period comets through Jupiter interactions. -Joss(1973) and Delsemme(1974) argued this wasn't efficient enough to give all the observed short period comets.
1977 Kowal Found first Centaur 2060 Chiron 1977UB (1989).
1978 J. Christy Found Charon satellite of Pluto.
1980 J. Fernandez Stated a Kuiper disk would be a good source for short period comets with low inclinations.
1981 Hills To make Oort cloud stable need inner Oort cloud from about 3000 AU to 10000 AU. -smaller than minimum semi-major axis known for a long period comet. Don't see long period comets with semi-major axis < 10000 AU because need strong perturber to dislodge this comets.
1984 Aumann et. al Alpha Lyrae (Vega) has an IR excess (from IRAS).
1984 Smith & Terrile Found Beta Pic has a large disk 1000 AU in radius.
1984 P. Weissman Vega excess in IR from small body ring such as a Oort cloud or Kuiper Belt.
1987 Duncan et al. Planets perturb small bodies semi-major axis while galactic tides perturb small bodies perihelion distance.
1988 Duncan,Quinn,Tre. Stated need low inclination source region for low inclination Jupiter Family short period comets.
1992 Jewitt & Luu Found first Kuiper Belt Object 1992QB1 (1993)
1995 Malholtra Demonstrated the resonance capturing of KBOs by Neptune through Fernandez & Ip (1984) statement of Jupiter migrating inward and the other gas giants migrating outward due to conservation of momentum from scattering of small planetismals in the early solar system.