| Term | Definition |
|---|
| Revolution orbital period | The movement of one object around a central object |
| Rotation | The movement of one object as it turns or spins around a central point or axis |
| Solar noon | time of day when the sun reaches it's highest point in the sky |
| Angle of Seperation | Angle between lines originating from the eye of the obserce toward objects, such as a star. The sun- and the horizon. |
| Apparent | seeming real or true; for example, the sun's apparent motion across the sky is due to earth's rotation, not the sun's motion |
| Horizon | The plane that extends from one's eye to the edge of Earth; the apparent connection between Earth and the sky |
| Orbit | The curved point of one object, such as a planet, or moon around an object (Verb) To move in a circular or electrical path around a central object. |
| Plane | A flat surface; an imaginary surface along which the planets orbit. |
| Polaris | The current star to which the North Celestial pole of Earth points; also called the North Star. |
| Eliptic | The apparent path of the sun, planets, and moon in the sky as seen from Earth; the plane along which the sun, planets, moon and other solar system objects orbit. |
| Equinox | Either of two times of the year (fall or spring) during a planet's orbit when the North and South Poles are equdistant from the sun, causing day and night to be of equal length. |
| NASA | The National Aeronautics and Space Adminstration, an organization that oversees the United States' space program, established in 1958. |
| Solstice | Either of two times of the year during which the north pole (around June 21) or the south pole (around December 21) is most directed toward the sun. |
| First Quarter | The phase of the Moon in which only the right half of the Moon's side is that faces Earth is illuminated; occurs when the Moon, Earth, and Sun form a 90 degree angle. |
| Full Moon | The phase of the Moon in which the entire side of the Moon that faces Earth is fully illuminated; occurs when Earth is between the Moon and Sun. |
| New Moon | A phase of the Moon in which the side of the Moon that faces Earth is not illuminated at all; occurs when the Moon is between Earth and the Sun. |
| Third Quarter | The phase of the Moon in which only the left half of the Moon's side that faces Earth is illuminated; occurs when the Moon, Earth and the Sun form a 90 degree angle. |
| Waning Crescent | Phase of the Moon in which a narrow strip of the Moon's lighted hemisphere is visible from Earth; shaped like a crescent; light is on the left; occurs before a new moon. |
| Waning Gibbous | Phase of the Moon in which the lighted portion of the Moon's side that faces Earth is getting smaller; occurs after a full moon. |
| Waxing Crescent | Phase of the Moon in which a narrow strip of the Moon's lighted hemisphere is visible from Earth; shaped like a crescent; light is on the right; occurs after a new moon. |
| Waxing Gibbous | Phase of the Moon in which the lighted portion of the Moon's side that faces Earth is getting larger; occurs before a full moon. |
| Lunar Eclipse | The blocking of sunlight to the Moon; occurs during a full moon, when Earth's shadow lands on the Moon. |
| Penumbra | The lighter, outer part of a shadow cone. |
| Solar Eclipse | The blocking of the Sun's light that occurs during a new moon when the Moon's shadow falls on Earth. |
| Umbra | The inner, darker part of a shadow. |
| Radiation | The process by which energy is transferred from one object, such as the Sun, to another object, such as a planet, without the space between them being heated. |
| Solar Flare | A sudden brightness near a sunspot; explosion of gas from the Sun's surface. |
| Solar Wind | A stream of electrically charged particles (primarily protons and electrons) that flow outward from the Sun's corona. |
| Sunspot | A relatively darker, cooler area on the Sun's surface that emits charged particles. |
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