Atmosphere

The gas that surrounds a planet or star. The Earth's atmosphere is made up mostly of nitrogen, while the Sun's atmoshere consists of mostly hydrogen.

Aurora

A display of coloured light given off by collisions between charged particles trapped in a planet's magnetic fields and atoms of atmospheric gases near the planet's magnetic poles.

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Cassini Division

a 4,700 kilometer gap within he rings of Saturn

Crustal Deformation

Deformation is a general term that refers to all changes in the original form and/or size of a rock body Most crustal deformation occurs along plate margins.

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Density

The ratio between the mass of an object and its volume. In the metrtic system, density is measured in grams per cubic centimeter or kilograms per liter.

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Electron

A stable elementary particle that is a primary constituent of ordinary matter, contained in the atoms of all elements and described as having a charge of -1.602 x 10-19 coulombs, a rest mass of 9.11 x 10-31 kg., and a spin of 1/2. Electrons flowing in a conductor constitute an electric current

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F-ring, G-ring

Saturn's ring system is divided up into 7 major divisions with alphabetic designators in the order of discovery. From the innermost ring to the outermost ring the designators are D, C, B, A, F, G and E. Each major division is further subdivided into thousands of individual ringlets. The F and G rings are very thin and difficult to see while the A, B, and C rings are broad and quite visible. Between the A and B rings is a gap called the Cassini division named after Giovanni Cassini who discovered the Gap in 1676. At the outermost part of the A ring lies the Keeler (Encke) gap.

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Gigabyte

A measure of computer data storage capacity and is "roughly" a billion bytes. A gigabyte is two to the 30th power, or 1,073,741,824 in decimal notation.

Gravity-Assist

Technique whereby a spacecraft takes angular momentum from a planet's solar orbit (or a satellite's orbit) to accelerate the spacecraft, or the reverse.

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Heat flux

The rate of heat flowing past a celestial body. Its units are W/m2.

Hubble Space Telescope

Hubble orbits 600 kilometers (375 miles) above Earth, using excellent pointing precision, powerful optics, and state-of-the-art instruments to provide stunning views of the Universe that cannot be made using ground-based telescopes or other satellites. Hubble was originally designed in the 1970s and launched in 1990.

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Ionosphere

The ionizing action of the sun's radiation on the earth's upper atmosphere produces free electrons. Above about 60km the number of these free electrons is sufficient to affect the propagation of electromagnetic waves. This "ionized" region of the atmosphere is a plasma and is referred to as the ionosphere.

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Kronos (sometimes spelled Cronos or Cronus)

Titan ruler and the father of Zeus. Kronos was the Greek god of agriculture (not to be confused with Chronos, the personification of time).

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Magnetosphere

that area of space around a planet that is controlled by that planet's magnetic field.

Mass

A measure of the total amount of material in a body, defined either by the inert properties of the body or by its gravitational influence on other bodies.

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Newton

Named in honor the famous mathematician, a Newton is the force needed to give an object weighing 1 kilogram (2.2 pounds) an acceleration of 1 meter (3.28 feet) per second squared.

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Orbit

The path of an object that is moving around a second object or point.

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Payload

Cargo being transported by a vehicle. Context - The Hubble Telescope was a payload carried in the Space Shuttle's cargo bay, removed from the cargo bay and placed into its own orbit around the Earth.

Phobos

International project PHOBOS was devoted to the investigations of Mars and its satellites. Two interplanetary probes were launched in 1988, one of them had reached the Phobos and carried out some experiments before it was lost.

Pioneer 11

Launched on 5 April 1973, Pioneer 11 followed its sister ship to Jupiter (1974), made the first direct observations of Saturn (1979) and studied energetic particles in the outer heliosphere. The Pioneer 11 Mission ended on 30 September 1995, when the last transmission from the spacecraft was received. The spacecraft is headed toward the constellation of Aquila (The Eagle), Northwest of the constellation of Sagittarius. Pioneer 11 will pass near one of the stars in the constellation in about 4 million years.

Proton

A proton is a subatomic particle found in the nucleus of every atom. The particle has a positive electrical charge.

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Trajectory

The curve described by a projectile in flight.

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Voyager 1, Voyager 2

The twin spacecraft Voyager 1 and Voyager 2 were launched by NASA in separate months in the summer of 1977 from Cape Canaveral, Florida. As originally designed, the Voyagers were to conduct closeup studies of Jupiter and Saturn, Saturn's rings, and the larger moons of the two planets.

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