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waning

The sunlit part of the moon is getting smaller

waxing

the sunlit part of the moon is getting larger

Charon

Pluto's only moon

Inner Planets

Mercury, Venus, Earth, Mars: four planets closest to sun

Outer Planets

Jupiter, Saturn, Uranus, Neptune, Pluto

Mercury

A terrestrial planet; closest to the Sun

Venus

similar to earth in size and mass

Venus

the sun rises in the west and sets in the east

Earth

the sun rises in the east and sets in the west

Earth

the only planet we know of that supports life

Mars

the red planet

Saturn

the second largest planet in the solar system

Jupiter

a giant among giants; made primarily of hydrogen and helium

Uranus

the planet that is tilted on its side

Neptune

the blue world

Pluto

The furthest planet from the sun

Pluto

the smallest planet

Mercury

its year is only 88 Earth days long

Annular

eclipse a solar eclipse during which the outer ring of the sun can be seen around the moon

Asteroid

a small, rocky body that revolves around the sun

Asteroid belt

the region of the solar system most asteroids occupy; roughly between the orbits of Mars and Jupiter

Astronomical unit (AU)

the average distance between the Earth and the sun, or approximately 150,000,000 km

Comet

a small body of ice, rock, and cosmic dust loosely packed together that gives off gas and dust in the form of a tail as it passes close to the sun

Eclipse

an event in which the shadow of one celestial body falls on another

Gas giants

the large, gaseous planets of the outer solar system

Greenhouse Effect

the natural heating process of a planet, such as the Earth, by which gases in the atmosphere trap heat

Kuiper Belt

the region of the solar system outside the orbit of Neptune that is occupied by small, icy, cometlike bodies

Light-minute

a unit of length equal to the distance light travels in space in 1 minute, or 18,000,000 km

Lunar eclipse

an event in which the shadow of the Earth falls on the moon

Meteor

a streak of light caused when a meteoroid or comet dust burns up in the Earth's atmosphere before it reaches the ground

Meteorite

"a meteoroid that reaches the Earth's surface without burning up completely"

Meteoroid

a very small, rocky body that revolves around the sun

Moon

a natural satellite of a planet

Oort cloud

"a spherical region of space that surrounds the solar system in which distant comets revolve around the sun"

Period of revolution

the time it takes for one body to make one complete orbit, or revolution, around another body in space

Period of rotation

the time it takes for an object to rotate once

Phases

"the different appearances of the moon due to varying amounts of sunlight on the side of the moon that faces the Earth; results from the changing relative positions of the moon, Earth, and the sun"

Prograde rotation

the counterclockwise spin of a planet or moon as seen from above the planet's north pole

Retrograde orbit

the clockwise revolution of a satellite around a planet as seen from above the north pole of the planet

Retrograde rotation

the clockwise spin of a planet or moon as seen from above the planet's or moon's north pole

Revolution

the elliptical motion of a body as it orbits another body in space

Rotation

the spinning motion of a body on its axis

Satellite

a natural or artificial body that revolves around a planet

Solar eclipse

an event in which the shadow of the moon falls on the Earth's surface

Surface gravity

the percentage of your Earth weight you would experience on another planet; the weight you would experience on another planet

Terrestrial planets

the small, dense, rocky planets of the inner solar sys

Mercury

which planet has no moons

Venus

which planet has no moons

Luna

the Earth's moon is called

Mars

this planet has two moons

Jupiter

this planet has twenty-eight known moons

Saturn

this planet has thirty known moons

Uranus

this planet has twenty-one moons

Neptune

this planet has eight moons

Ions

Electrically charged particles

nucleus

the solid center of a comet

ellipses

circles that are somewhat stretched out of shape

meteor showers

occur when earth passes through dusty debris left behind in the orbit of a comet

stony

this is one of the three major types of meteorites

metallic

this is one of the three major types of meteorites

stony-iron

this is one of the three major types of meteorites

Io

the most volcanically active body in the solar system

Ganymede

the largest moon of Jupiter

Titan

scientists hope to answer questions about how life began on earth by studying this satellite

inner planets

small, dense and rocky

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