Mercury
From Gwn
| Mercury (OMa-1) | |
| |
| Discovered: | 3rd millennium BCE |
| Named After: | Named after the Roman God |
| Relative Size: | 0.055 Earths |
| Satellites: | None |
Mercury is the innermost and smallest planet in the Olympus Major solar system, orbiting the Sun once every 88 days. Physically, Mercury is similar in appearance to the Earth's 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 1% as strong as that of the Earth. Surface temperatures on Mercury range from about -180 to 430°C, with the subsolar point being the hottest and the bottoms of craters near the poles being the coldest.
History
Mercury has been known since at least the 3rd millennium BC, when it was known to the Sumerians of Mesopotamia as Ubu-idim-gud-ud, among other names. The Babylonians (2000–1000 BC) succeeded the Sumerians, and early Babylonians may have recorded observations of the planet: although no records have survived, late Babylonian records from the 7th century BC refer to much earlier records. The Babylonians called the planet Nabu or Nebu after the messenger to the Gods in their mythology.
The ancient Greeks gave the planet two names: Apollo when it was visible in the morning sky and Hermes when visible in the evening. However, Greek astronomers came to understand that the two names referred to the same body, with Pythagoras being the first to propose the idea.
The first telescopic observations of Mercury were made by Galileo in the early 17th century. Although he observed phases when he looked at Venus, his telescope was not powerful enough to see the phases of Mercury. In 1631 Pierre Gassendi made the first observations of the transit of a planet across the Sun when he saw a transit of Mercury predicted by Johannes Kepler. In 1639 Giovanni Zupi used a telescope to discover that the planet had orbital phases similar to Venus and the Moon. The observation demonstrated conclusively that Mercury orbited around the Sun.
Meaning of the Name
The Romans named the planet after the fleet-footed messenger god Mercury, probably for its fast apparent motion in the twilight sky. The astronomical symbol for Mercury, displayed at the top of the infobox, is a stylized version of the god's head and winged hat atop his caduceus, an ancient astrological symbol. 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 (बुध), after the son of Chandra (the Moon). The Chinese, Korean, Japanese, and Vietnamese cultures refer to the planet as the water star (水星), based on the Five Elements. The Hebrews named it Kokhav Hamah (כוכב חמה), "the star of the hot one" ("the hot one" being the Sun).
