Difference between revisions of "Venus"
(Enhancement with new template and more sections) |
m (fix link) |
||
| Line 33: | Line 33: | ||
}} | }} | ||
| − | '''Venus''' is one of the [[planet]]s and is named for [[Venus ( | + | '''Venus''' is one of the [[planet]]s and is named for [[Venus (goddess)|Venus]], the Roman goddess of love. |
When the planet is visible, it is the brightest, most conspicuous, and easiest to recognize of all the planets. | When the planet is visible, it is the brightest, most conspicuous, and easiest to recognize of all the planets. | ||
Revision as of 02:12, March 31, 2008
| Venus | |
|---|---|
 Venus silhouetted against the Sun during one of the rare transits of Venus, 6/8/2004 | |
| Symbol | 
|
| Name of discoverer | Known to the ancients |
| Name origin | Roman goddess of love and beauty |
| Orbital characteristics | |
| Primary | Sun |
| Order from primary | 2 |
| Perihelion | 107,476,259 km (0.718 AU) |
| Aphelion | 108,942,109 km (0.728 AU) |
| Semi-major axis | 108,208,930 km (0.723 AU) |
| Titius-Bode prediction | 0.7 AU |
| Orbital eccentricity | 0.0068 |
| Sidereal year | 224.70069 da (0.615 a) |
| Synodic year | 583.92 da (1.599 a) |
| Avg. orbital speed | 35.02 km/s |
| Inclination | 3.39471° to the ecliptic |
| Rotational characteristics | |
| Sidereal day | -243.0187 da |
| Rotational speed | 6.52 km/h |
| Axial tilt | 177.36° |
| Physical characteristics | |
| Mass | 4.8685 * 1024 kg (81.468% earth) |
| Density | 5250 kg/m³ |
| Mean radius | 6051.8 km |
| Surface gravity | 8.87 m/s² (0.904 g) |
| Escape speed | 10.36 km/s |
| Surface area | 460,235,000 km² (90.229% earth) |
| Mean temperature | 730 K |
| Number of moons | None |
| Composition | Rock |
| Albedo | 0.65 |
Venus is one of the planets and is named for Venus, the Roman goddess of love.
When the planet is visible, it is the brightest, most conspicuous, and easiest to recognize of all the planets.
Contents
Evening and Morning Stars
When Venus is the "evening star," it shines brightly in the West in the hours after sunset. It is visible long before the sky is dark enough to see any other star, and when people "wish upon a star" very often they are actually wishing upon Venus. You can see it shining through a window in a lit room, just like the "wishing star" in the opening of Walt Disney's animated cartoon, Pinocchio.
Astronomy books sometimes claim that "planets do not twinkle." This is not quite true, but Venus in particular does shine with a steadier light than any star. When looking at Venus, it is quite possible to wonder whether one is looking at a plane, until one has watched for long enough to be sure that it is not moving (or, at least, not moving quickly enough to notice).
Venus alternates back and forth between being the "evening star" and the "morning star." As the evening star, it sets in the West after the sun does. As the morning star, it rises in the East before the sun does. In between, it rises and sets at about the same time as the Sun and is lost in the sun's glare. Pythagoras is traditionally recorded as the person who realized that both the evening star and the morning star were the same object.
Through a small telescope—binoculars will not do, but any real astronomical telescope will—it is possible to see that Venus often does not appear round, but goes through phases like the Moon, depending on how the light of the Sun strikes it.
Transits of Venus
About every two years, Venus "catches up with" and passes the Earth as they both orbit the Sun. This is called a "conjunction" of Venus and the Earth. During a conjunction, Venus is almost directly between the Earth and the Sun. It would seem as if Venus could be seen silhouetted against the Sun on every conjunction, but in fact the orbits of the planets are slightly tilted with respect to each other, so at a conjunction Venus almost never lines up perfectly, but appears to pass above or below the Sun. Very rarely—at intervals of over a century—conjunction occurs at the point in the orbits where they are both in the same plane. When this occurs, a transit of Venus can be observed. Transits of Venus occur in pairs, eight years apart; then over a century passes before the next one.
One of the rare transits of Venus occurred on June 8, 2004; another will occur on June 6, 2012; then there will be no more until 2117, probably not within the lifetime of those reading this. A transit of Venus cannot be seen with the naked eye. Observing a transit of Venus requires great attention to eye safety and a telescope equipped with a safe sun filter or a special transit viewer.
The planet Venus is about the same size as the Earth. Before explorations made by spacecraft made it clear just how harsh conditions on Venus are, science-fiction writers used to speculate that the temperature and climate of Venus might be within the range of life as we know it on Earth.
Theoretical considerations
- Venus possesses very few impact craters. Therefore, uniformitarian geologists regard Venus as geologically young (estimated apparent age 800 million Julian years). Attempts to explain this feature of Venus have been lacking, and the very slow surface winds and lack of water on Venus complicates the matter further.
- Venus rotates retrograde to its orbit around the Sun. (Note the negative value for a Venusian sidereal day.) Nearly every other Solar System body rotates prograde. This presents a serious theoretical problem for the nebular hypothesis of the origin of the solar system.
In popular culture
Many science-fiction stories have been set on Venus. C. S. Lewis' novel Perelandra which takes place on Venus, and is a retelling of the story of the Garden of Eden. Other motion picture projects have speculated on the consequences of the importation of an extraterrestrial creature or creatures from Venus to Earth.
External links
- TransitofVenus.org, website about the upcoming 2012 transit
- NASA "Venus"
- Venus: Cauldon of Fire
- Magellan Project home page
| |||||||||||||||||||||||||||||
