Vocabulary:

©1995 The Regents of the University of California

Angle:

The space within two lines that diverge from a common point measured in degrees (360 = complete circle). minutes ' (60 minutes in one degree) and seconds " (60 seconds in one minute)

Angular velocity:

How fast something is spinning in the units of angle per unit time, such as degrees per second (also called rotation rate)

Arc:

A portion of a circle

Axis:

An imaginary line about which something spins or rotates

Longitude:

Lines that extend from north to south pole. The measure of longitude is an angular distance between any two of these lines. Pretend you're in the center of the planet and looking out toward the surface; the measure of the angle between two points on the surface is longitude

Magnetogram:

Picture taken of the magnetosphere of a planet or the Sun

Magnetosphere:

A level of a planet's or Sun's atmosphere that is controlled by and a reflection of its magnetic field

Period of Rotation

The time it takes for an object to make one complete turn (360 degrees)

Planetary features:

Distinguishing marks or physical characteristics on the solid surface or in the (gaseous) atmosphere of a planet such as sunspots, cometary impact sites, meteor crater, or even an atmospheric storm

Planets:

The (nine) heavenly bodies that revolve around the Sun

Rotate:

To move around an axis passing through the rotating body

Solar System:

Collection of Sun, planets, satellites, comets, and asteroids

Speed:

How fast something is moving measured in miles per hour or meters per second or any distance divided by any time

Spin:

Rotate; to move around an imaginary line (axis) that is INSIDE the object

Sunspots:

Relatively dark/cool areas on the photosphere of the Sun that are caused by the Sun's magnetic field

Terminator:

The edge of the shadow that marks the edge of night-- sunrise or sunset on the surface of a planet or satellite

UT:

Universal time; local (mean) time on the prime meridian--the line of longitude that passes through Greenwich, England. UT is expressed on a 24-hour clock with zero hours occurring at 6 P.M. Central Standard Time

Velocity:

How fast and in what direction something is moving...like 40 mph due north is a velocity