The term planet is ancient, with ties to history, science, mythology, & religion. The planets were originally seen by lots of early cultures as divine, or as emissaries of the gods. As scientific knowledge advanced, human perception of the planets changed, incorporating a lot of disparate objects. In 2006, the International Astronomical Union officially adopted a resolution defining planets within the Solar Method. This definition has been both praised & criticized, & remains disputed by some scientists.
A planet "wandering star") is a celestial body orbiting a star or stellar remnant that is large to be rounded by its own gravity, is not large to cause thermonuclear fusion, & has cleared its neighbouring region of planetesimals.[a][1][2]
The planets were thought by Ptolemy to orbit the Earth in deferent & epicycle motions. Though the idea that the planets orbited the Sun had been suggested lots of times, it was not until the 17th century that this view was supported by facts from the first telescopic astronomical observations, performed by Galileo Galilei. By cautious analysis of the observation information, Johannes Kepler found the planets' orbits to be not circular, but elliptical. As observational tools improved, astronomers saw that, like Earth, the planets rotated around tilted axes, & some shared such features as ice-caps & seasons. Since the dawn of the Space Age, close observation by probes has found that Earth & the other planets share characteristics such as volcanism, hurricanes, tectonics, & even hydrology.Planets are usually divided in to main types: giant, low-density gas giants, and smaller, rocky terrestrials. Under IAU definitions, there's three planets in the Solar System. In order of increasing distance from the Sun, they are the terrestrials, Mercury, Venus, Earth, and Mars, then the gas giants, Jupiter, Saturn, Uranus, and Neptune. Four of the planets are orbited by or more natural satellites. Additionally, the Solar System also contains at least dwarf planets[3] and hundreds of thousands of little Solar System bodies.
Since 1992, hundreds of planets around other stars ("extrasolar planets" or "exoplanets") in the Milky Way Galaxy have been discovered. As of December 2010, over 500 known extrasolar planets are listed in the Extrasolar Planets
A planet "wandering star") is a celestial body orbiting a star or stellar remnant that is large to be rounded by its own gravity, is not large to cause thermonuclear fusion, & has cleared its neighbouring region of planetesimals.[a][1][2]
The planets were thought by Ptolemy to orbit the Earth in deferent & epicycle motions. Though the idea that the planets orbited the Sun had been suggested lots of times, it was not until the 17th century that this view was supported by facts from the first telescopic astronomical observations, performed by Galileo Galilei. By cautious analysis of the observation information, Johannes Kepler found the planets' orbits to be not circular, but elliptical. As observational tools improved, astronomers saw that, like Earth, the planets rotated around tilted axes, & some shared such features as ice-caps & seasons. Since the dawn of the Space Age, close observation by probes has found that Earth & the other planets share characteristics such as volcanism, hurricanes, tectonics, & even hydrology.Planets are usually divided in to main types: giant, low-density gas giants, and smaller, rocky terrestrials. Under IAU definitions, there's three planets in the Solar System. In order of increasing distance from the Sun, they are the terrestrials, Mercury, Venus, Earth, and Mars, then the gas giants, Jupiter, Saturn, Uranus, and Neptune. Four of the planets are orbited by or more natural satellites. Additionally, the Solar System also contains at least dwarf planets[3] and hundreds of thousands of little Solar System bodies.
Since 1992, hundreds of planets around other stars ("extrasolar planets" or "exoplanets") in the Milky Way Galaxy have been discovered. As of December 2010, over 500 known extrasolar planets are listed in the Extrasolar Planets