solar system
the sun and all of the planets and other bodies that travel around it
planet
a celestial body that orbits the sun, is round because of its own gravity, and has cleared the neighborhood around its orbital path
solar nebula
a rotating cloud of gas and dust from which the sun and planets formed; also any nebula from which stars and exoplanets may form
planetismal
a small body from which a planet originated in the early stages of development of the solar system
eccentricity
the degree of elongation of an elliptical orbit
orbital period
the time required for a body to complete a single orbit
inertia
the tendency of an object to resist a change in motion unless an outside force acts on the other
terrestrial planet
one of the highly dense planets nearest to the sun; Mercury, Venus, Earth, and Mars
gas giant
a planet that has a deep, massive atmosphere; Jupiter, Saturn, Uranus, and Neptune
Kuiper Belt
a region of the solar system that starts just beyond the orbit of Neptune and contains dwarf planets and other small bodies made mostly of ice
Galilean moon
any one of the four largest satellites of Jupiter- Io, Europa, Ganymede, and Callisto- discovered by Galileo in 1610
asteroid
a small, rocky object that orbits the sun; most asteroids are located in a band between the orbits of Mars and Jupiter
comet
a small body of rock, ice, and cosmic dust that follows an elliptical orbit around the sun and that gives off gas and dust in the form of a tail as it passes close to the sun
Oort cloud
a spherical region that surrounds the solar system, that extends from the Kuiper Belt to almost halfway to the nearest star, and contains billions of comets
meteoroid
a relatively small, rocky body that travels through space
meteor
a bright streak of light that results when a meteoroid burns up in Earth's atmosphere