The planets

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The planets

Post by Cursakandine on Thu Nov 26, 2009 7:09 pm

A planet, as defined by the International Astronomical Union (IAU), is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.

The term planet is an ancient one having ties to history, science, myth, and religion. The planets were originally seen as a divine presence; as emissaries of the gods. Even today, many people continue to believe the movement of the planets affects their lives, although such a causation is rejected by the scientific community. As scientific knowledge advanced, the human perception of the planets changed over time, incorporating a number of disparate objects. Even now there is no uncontested definition of what a planet is. In 2006, the IAU officially adopted a resolution defining planets within the Solar System. This definition has been both praised and criticized, and remains disputed by some scientists.

The planets were initially thought to orbit the Earth in circular motions; after the development of the telescope, the planets were determined to orbit the Sun, and their orbits were found to be elliptical. As observational tools improved, astronomers saw that, like Earth, the planets rotated around tilted axes and shared such features as ice-caps and seasons. Since the dawn of the Space Age, close observation by probes has found that Earth and the other planets share characteristics such as volcanism, hurricanes, tectonics and even hydrology. Since 1992, through the discovery of hundreds of extrasolar planets (planets around other stars), scientists are beginning to observe similar features throughout the Milky Way Galaxy.The proposal is to call any object that is large enough to make gravity cause it to become round a planet.

Under IAU definitions, there are eight planets in the Solar System (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune) and 270 extrasolar ones. The Solar System also contains at least three dwarf planets (Ceres, Pluto, and Eris). Many of these planets are orbited by one or more moons, which can be larger than small planets. Planets are generally divided into two main types: large, low-density gas giants and smaller, rocky terrestrials.

How many planet are REALLY there?

There are 54 planets around us(including pluto)
In order from closest to furthest, the planets are now:

Mercury
Venus
Earth
Mars
Ceres
Jupiter
Saturn
Uranus
Neptune
2004TY364
2002KX14
2002XV93
2003VS2
1999TC36
2001QF298
Orcus
2003AZ84
Pluto
Ixion
Huya
2005RN43
1995SM55
2002MS4
2004SB60
2004GV9
2002UX25
Varuna
2002TX300
1996TO66
2003OP32
2003EL61
Quaoar
2003QW90
1999CD158
1997CS29
2000CN105
1998WH24
2005FY9
2004PR107
2003MW12
2002CY248
2002KW14
2002AW197
2002WC19
2003QX113
2003FY128
2001UR163
2002TC302
1999DE9
2004XR190
2000YW134
2003UB313
2005RM43
Sedna

The Main planets are
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
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