Coma: The dust and gas surrounding an active cometís nucleus

Corona: The very hot outermost layer of a star's atmosphere. Our Sun's corona can only be seen during a total solar eclipse.

Doppler Shift: A shift in an object's spectrum due to a change in the wavelength of light that occurs when an object is moving toward or away from Earth.

Elliptical: Shaped like an elongated closed curve; egg-like shape

Gravitational field: The volume over which an object exerts a gravitational pull.

Kiloparsec: 1000 parsecs. A parsec equals 3.26 light years; kiloparsec equals 3, 260 light years.

Light Year: The distance light travels in one year.  A light year is 9.5 trillion kilometers

Magnetic fields: A region of space near a magnetized body where magnetic forces can be detected.

Magnetosphere: The region of space in which a planetís magnetic field dominates that of the solar wind.

Metric ton: 1000 kilograms. A metric ton equals 2,204 pounds.

Nuclear Fusion: A process where atoms are joined and tremendous amounts of heat energy are released.

Oort Cloud: A huge cloud thought to surround our solar system that is home to large quantities of dust that are frozen and covered with ice.  Area serves as the birthplace of comets.

Penumbra:  Faint outer shadow; partial eclipses are seen from within this shadow.

Spectroscope: An instrument that separates visible light into its various wavelengths. Each wavelength corresponds to a specific color in the spectrum.

Spectrum:  A band of colors which forms when visible light passes through a prism. The band ranges in color from violet (shorter wavelength) to red (longer wavelength).

Umbra:  Dark inner shadow; total eclipses are seen from within this shadow.