SSI 2007
GAGE
Important Terms for Understanding our Sun-Earth-Moon System
and the Solar System
sun
star that is in the center of a solar system; when
referring to our star we capitalize the Sun
star
self-luminous body
satellite
object that revolves around another object
planet
celestial body that revolves around a star; the
Earth is a satellite of the Sun
moon
celestial body that revolves around a planet; the
word is capitalized when referring to Earth’s
moon; the Moon is a satellite of the Earth
axis
imaginary line through the center of an object;
object rotation around their axes
rotation
motion around an axis
day
period of time it takes to make one rotation
revolution
motion around another object
year
period of time it takes to make one revolution
orbit
path of a body that is revolving
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lunar phase
amount of illumination on the Moon’s surface
visible from Earth
ellipse
circle with different diameters
eclipse
when the shadow of one object falls on another
blocking sunlight on the second object; when the
Earth’s shadow falls on the Moon it is a lunar
eclipse; when the Moon’s shadow falls on the
Earth the Sun is blocked so it is a solar eclipse
constellation
pattern of stars
solar system
collection of planets, moons, comets, and
asteroids that orbit a central star
comet
“dirty” snowball made of ice, rock fragments, and
dust
asteroid
rocky body that orbits the Sun; not a planet or
moon
atmosphere
blanket of gases surrounding a planet or moon
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