a rotating cloud of gas and dust from which the sun and planets formed; also any nebula from which stars and planets may form
theory that the sun and the planets condensed out of a spinning cloud of gas and dust
Premise that stars and planets accumulated from contracting, accreting clouds of galactic gas, dust, and debris.
the formation of a celestial object by the effect of gravity pulling together surrounding objects and gases
Regions of condensed matter that serve as a starting point for the formation of a planet.
the state when period of rotation is exactly equal to orbital period. the moon is in this and thus presents the same face toward the earth at all times.
planet closest to the Sun; has a thin atmosphere with temperature extremes, an iron core, and many craters and high cliffs
models of the universe based on the assumption that the sun, moon, and planets all orbit Earth
a model of the solar system in which Earth and the other planets revolve around the sun
small particles or grains of matter, primarily carbon and silicates, distributed throughout interstellar space
Mercury, Venus, Earth, and Mars. They all have rocky crusts and dense mantles and cores.