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Astrobiology Glossary

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Term Definition
Van Allen Belt A region containing charged particles trapped in the Earth's magnetic force field (magnetosphere). The belt's lower boundary begins at about 800 kilometers (496 miles) above the Earth's surface and extends thousands of kilometers into space.
Variable Star A star whose luminosity (brightness) changes with time.
Vela Satellite Launched by the U.S. in the 1960s to monitor the Limited Nuclear Test Ban Treaty. The satellite's mission was to detect the gamma rays produced during nuclear blasts. Although not intended for astronomical studies, the Vela satellite provided useful celestial data, detecting an unexpected blast of cosmic gamma radiation in 1967. The satellite discovered several other gamma-rays bursts during the years of the Vela project, which ceased operation in 1979.
Velocity The speed of an object moving in a specific direction. A car traveling at 35 miles per hour is a measurement of speed. Observing that a car is traveling 35 miles per hour due north is a measurement of velocity.
Venus An inner, terrestrial (rocky) planet that is slightly smaller than Earth. Located between the orbits of Mercury and Earth, Venus has a very thick atmosphere that is covered by a layer of clouds that produce a 'greenhouse effect' on the planet. Venus's surface temperature is roughly 480° C (900° F), making it the hottest planet in the solar system.
Very Large Array (VLA) One of the world's premier radio observatories, consisting of 27 antennas arranged in a huge 'Y' pattern. The VLA spans up to 22 miles (36 km) across, which is roughly one and a half times the size of Washington, D.C. Each antenna is 81 feet (25 meters) in diameter. Located in Socorro, New Mexico, the telescopes work in tandem to produce a sharper image than any single telescope could record.
Visible Light Electromagnetic radiation that human eyes can detect; also known as the visible spectrum. The visible colors are red, orange, yellow, green, blue, indigo, and violet, along with various combinations and shades of these colors. Within the visible part of the spectrum, red light has a longer wavelength than blue light.
Volcano A break or vent in the crust of a planet or moon that can spew extremely hot ash, scorching gases, and molten rock. The term volcano also refers to the mountain formed by volcanic material.

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Quote of the Day

Science means simply the aggregate of all the recipes that are always successful. All the rest is literature.
- Paul Valéry (1871 - 1945)

Quiz Me

Which of the following vocalizations are not used by cheetahs?
Purring
Chirping
Roaring
Growling
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Fact of the Day

A day on Jupiter is only 9 hours and 48 minutes long. Such fast rotation causes Jupiter to be somewhat squashed due to centrifugal force: its polar radius is 4000 km less than its equatorial radius (the latter being 71,392 km). That means you'd weigh almost 25% more at Jupiter's poles than at its equator, that is, if you could find a place to stand! So a 100 pound person (on Earth) would weigh 230 pounds at Jupiter's equator but 285 pounds at the pole!

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