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Variable Stars
A star whose brightness changes periodically. There are many types of variable stars and their brightnesses vary for many different reasons. For example, the brightness of a Cepheid variable star changes because its luminosity changes; the luminosity change is related to the internal structure of the star and the processes that occur there. Variable stars can also be caused by eclipsing dark or bright companions.
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Vega
A blue-white star 26 light-years away in the constellation Lyra; a dust disk that surrounds it may harbor a planet.
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Venus
The second planet from the Sun in the solar system. Venus orbits the Sun at an average distance 0.7 AU. The planet has a mass of 0.08 times the mass of Earth and a radius 0.95 times the radius of Earth. It is made of solid, rocky material and has a predominantly carbon dioxide atmosphere. Clouds of sulfuric acid cover the entire planet. Venus has no moons.
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Venus Express
The first Venus exploration mission of the European Space Agency. Launched in 2005, Venus Express has been continuously sending back science data from its polar orbit around Venus. Equipped with seven science instruments, the main objective of the mission is the long term observation of the Venusian atmosphere.
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Venusian Surface
The second planet from the Sun in the solar system. Venus orbits the Sun at an average distance 0.7 AU. The planet has a mass of 0.08 times the mass of Earth and a radius 0.95 times the radius of Earth. It is made of solid, rocky material and has a predominantly carbon dioxide atmosphere. Clouds of sulfuric acid cover the entire planet. Venus has no moons.
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Viking to Mars
NASA’s Viking 1 and 2 landers became the first spacecraft to touch down safely on Mars in 1976. From opposite sides of Mars, they photographed and analyzed their environments, finding a surface of iron-rich clay and a frigid atmosphere battered by giant dust storms. Experiments designed to look for signs of life produced inconclusive results, which scientists interpreted as meaning the Martian surface is sterile.
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Virgo, the Virgin
A constellation of the zodiac.
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Volcanoes and Earthquakes
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Voyager Probes
Voyager 1 and 2 conducted a “grand tour” of the outer planets during the 1970s and ’80s. Voyager 1 flew past Jupiter and Saturn, discovering new moons and rings, compiling movies of the motions of both planets’ atmospheres, and conducting other observations. Voyager 2 followed the same path, but was then targeted to fly past Uranus and Neptune. Its encounters provided the first detailed looks at both giant planets and their moons. No other spacecraft has flown past either planet. Both Voyagers still operate today, and have detected signs of the “edge” of the solar system.
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Vulpecula, the Fox
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