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Welcome to 'Hot Rock', fanlisting for the planet Mercury. It is such a pleasure to bring this awesome fanlisting to you. This fanlisting was adopted from Kryz. |
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What is a fanlisting? A fanlisting is a website that devotes itself to a certain subject matter (TV show, actor/ actress, characters, etc.) and asks others from all over to join in and show the world that they're a fan, too! |
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About Mercury... Mercury is the innermost and smallest planet in the solar system, orbiting the Sun once every 88 days. It ranges in brightness from about -2.0 to 5.5 in apparent magnitude, but is not easily seen as its greatest angular separation from the Sun (greatest elongation) is only 28.3°. It can only be seen in morning or evening twilight. Comparatively little is known about the planet: the only spacecraft to approach Mercury was Mariner 10 from 1974 to 1975, which mapped only 40%–45% of the planet’s surface. The period of rotation is 58.6462 days. Physically, Mercury is similar in appearance to the Moon as it is heavily cratered. It has no natural satellites and no substantial atmosphere. The planet has a large iron core which generates a magnetic field about 0.1% as strong as that of the Earth.[1] Surface temperatures on Mercury range from about 90 to 700 K (-180 to 430°C, -292 to 806°F), with the subsolar point being the hottest and the bottoms of craters near the poles being the coldest. Recorded observations of Mercury date back to the time of the Sumerians, in the third millennium BC. The Romans named the planet after the Roman god Mercurius, equated to the Greek Hermes and the Babylonian Nabu. The astronomical symbol for Mercury is a stylized version of the god’s head and winged hat atop his caduceus, an ancient astrological symbol. The Greeks of Hesiod's time called it Stilbon (“the gleaming”) and Hermaon. Before the 5th century BC, Greek astronomers believed the planet to be two separate objects: one visible only at sunrise, the other only at sunset. In India, the planet was named Budha (???), after the son of Chandra (the Moon). The Chinese, Korean, Japanese, and Vietnamese cultures refer to the planet as the water star (??), based on the Five Elements. The Hebrews named it Kokhav Hamah (???? ???), “the star of the hot one” (“the hot one” being the Sun). Mercury is smaller than several of the natural satellites or moons in our solar system. Mercury is one of the four terrestrial planets, being a rocky body like the Earth. It is the smallest of the four, with a diameter of 4879 km at its equator. Mercury consists of approximately 70% metallic and 30% silicate material. The density of the planet is the second-highest in the solar system at 5.43 g/cm³, only slightly less than Earth’s density. If the effect of gravitational compression were to be factored out, the materials of which Mercury is made would be denser, with an uncompressed density of 5.3 g/cm³ versus Earth’s 4.4 g/cm³. Mercury’s density can be used to infer details of its inner structure. While the Earth’s high density results appreciably from gravitational compression, particularly at the core, Mercury is much smaller and its inner regions are not nearly as strongly compressed. Therefore, for it to have such a high density, its core must be large and rich in iron. Geologists estimate that Mercury’s core occupies about 42% of its volume. (For Earth this proportion is 17%.) Recent research strongly suggests Mercury has a molten core. Surrounding the core is a 600 km mantle. It is generally thought that early in Mercury’s history, a giant impact with a body several hundred kilometers across stripped the planet of much of its original mantle material, resulting in the relatively thin mantle compared to the sizable core. Mercury’s crust is thought to be 100–200 km thick. One distinctive feature of Mercury’s surface are numerous narrow ridges, some extending over several hundred kilometers. It is believed that these were formed as Mercury’s core and mantle cooled and contracted at a time when the crust had already solidified. Mercury has a higher iron content than any other major planet in our solar system, and several theories have been proposed to explain this. The most widely accepted theory is that Mercury originally had a metal-silicate ratio similar to common chondrite meteors (thought to be typical of average solar system rocky matter) and a mass approximately 2.25 times its current mass. However, early in the solar system’s history, Mercury was struck by a planetesimal of approximately 1/6 that mass. The impact would have stripped away much of the original crust and mantle, leaving the core behind as a relatively major component. A similar process has been proposed to explain the formation of Earth’s Moon (see giant impact theory). Alternatively, Mercury may have formed from the solar nebula before the Sun’s energy output had stabilized. The planet would initially have had twice its present mass. But as the protosun contracted, temperatures near Mercury could have been between 2500 and 3500 K, and possibly even as high as 10000 K. Much of Mercury’s surface rock could have been vaporized at such temperatures, forming an atmosphere of “rock vapor” which could have been carried away by the solar wind. A third theory proposes that the solar nebula caused drag on the particles from which Mercury was accreting, which meant that lighter particles were lost from the accreting material Each of these theories predicts a different surface composition, and two upcoming space missions, MESSENGER and BepiColombo, both aim to take observations that will allow the theories to be tested. Mercury is too small for its gravity to retain any significant atmosphere over long periods of time; however, it does have a tenuous atmosphere containing hydrogen, helium, oxygen, sodium, calcium and potassium. This atmosphere is not stable—atoms are continuously lost and replenished from a variety of sources. Hydrogen and helium atoms probably come from the solar wind, diffusing into Mercury’s magnetosphere before later escaping back into space. Radioactive decay of elements within Mercury’s crust is another source of helium, as well as sodium and potassium. Water vapor is probably present, being brought to Mercury by comets impacting on its surface. Despite its slow 176-day-long rotation, Mercury has a relatively strong, and apparently global, magnetic field. It is about 0.1% as strong as the Earth’s.[15] It is likely that this magnetic field is generated in a manner similar to Earth’s, by a dynamo of circulating liquid core material. A mechanism that has been suggested for keeping it liquid are particularly strong tidal effects during periods of high orbital eccentricity. Mercury’s magnetic field is strong enough to deflect the solar wind around the planet, creating a magnetosphere inside which the solar wind does not penetrate. This is in contrast to the situation on the Moon, which has a magnetic field too weak to stop the solar wind impacting on its surface and so lacks a magnetosphere. The orbit of Mercury is the most eccentric of the major planets, with the planet’s distance from the Sun ranging from 46,000,000 to 70,000,000 kilometers. It takes 88 days to complete an orbit. The diagram on the left illustrates the effects of the eccentricity, showing Mercury’s orbit overlain with a circular orbit having the same semi-major axis. The higher velocity of the planet when it is near perihelion is clear from the greater distance it covers in each 5-day interval. The size of the spheres, inversely proportional to their distance from the Sun, is used to illustrate the varying heliocentric distance. This varying distance to the Sun, combined with a 3:2 spin-orbit resonance of the planet’s rotation around its axis, result in complex variations of the surface temperature. Mercury’s orbit is inclined by 7° to the plane of Earth’s orbit (the ecliptic), as shown in the diagram on the left. As a result, transits of Mercury across the face of the Sun can only occur when the planet is crossing the plane of the ecliptic at the time it lies between the Earth and the Sun. This occurs about every seven years on average. Mercury’s axial tilt is only 0.01 degrees. This is over 300 times smaller than that of Jupiter, which is the second smallest axial tilt of all planets at 3.1 degrees. This means an observer at Mercury’s equator during local noon would never see the sun more than 1/100 of one degree north or south of the zenith. Conversely, at the poles the Sun never rises more than 0.01° above the horizon. At certain points on Mercury’s surface, an observer would be able to see the Sun rise about halfway, then reverse and set before rising again, all within the same Mercurian day. This is because approximately four days prior to perihelion, Mercury’s angular orbital velocity exactly equals its angular rotational velocity so that the Sun’s apparent motion ceases; at perihelion, Mercury’s angular orbital velocity then exceeds the angular rotational velocity. Thus, the Sun appears to move in a retrograde direction. Four days after perihelion, the Sun’s normal apparent motion resumes at these points. Orbital simulations indicate that the eccentricity of Mercury’s orbit has varied from 0 to 0.47 over the age of the solar system. This is thought to explain Mercury’s 3:2 spin-orbit resonance, since this state is more likely to arise during a period of high eccentricity. |
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About The Webmaster... My name is Amanda and I live in Brooklyn, NY. I am currently the owner of several websites, several fanlistings and namelistings and 3 forums. You can reach me anytime at Sel416331@aol.com and on AIM. All images, html, and codes are the property of me! Please visit the credits page for more info on those who helped out. |