Science

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