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( Planet)
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, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.[a][1][2] The term planet is ancient, with ties to history, science, myth, and religion. The planets were originally seen by many early cultures as divine, or as emissaries of the gods. Even today, many people believe in astrology, which holds that the movement of the planets affects people's lives, although such a causation is rejected by the scientific community. As scientific knowledge advanced, human perception of the planets changed, 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 thought by Ptolemy to orbit the Earth in deferent and epicycle motions. Though the idea that the planets orbited the Sun had been suggested many times, it was not until the 17th century that this view was supported by evidence from the first telescopic astronomical observations, performed by Galileo Galilei. By careful analysis of the observation data, 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, and some share 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 understand that planets throughout the Milky Way Galaxy share characteristics in common with our own. Planets are generally divided into two main types large, low-density gas giants, and smaller, rocky terrestrials. Under IAU definitions, there are eight planets in the Solar System. In order from the Sun, they are the four terrestrials, Mercury, Venus, Earth, and Mars, then the four gas giants, Jupiter, Saturn, Uranus, and Neptune. Many of these planets are orbited by one or more moons, which can be larger than small planets. As of September 2008, there are 314 known extrasolar planets, ranging from the size of gas giants to that of terrestrial planets.[3] This brings the total number of identified planets to at least 322. The Solar System also contains at least five dwarf planets Ceres, Pluto (formerly considered to be the Solar System's ninth planet), Makemake, Haumea and Eris. No extrasolar dwarf planets have yet been detected.
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Planet Subcategories
Planet Articles
Yoga And Salute To The Sun by Jeff Seward
One of the all-around yoga exercises is the 12-step salute to the sun. Do it once or twice when you get up in the morning to help relieve stiffness and invigorate the body. Multiple repetitions at night will help you to relax; insomniacs often find t...
Save Yourself and the Planet with Safe Personal Care Products by Anne Harvester
To call safe personal care products “chemical free” might be a bit misleading, as chemicals are nothing more than arrangements of atoms and molecules; in fact, a chemical known as dihydrogen oxide is necessa...
Trends in Men's Cosmetics by Jishnu Raj
Gone are those days when cosmetics were considered only for women. Today more than eighty percent of the men are very much concerned about their looks and the way they dress up. Men have begun to take lot of care for their skin and they still want to...
Killer Disease Sweeps Planet by Sheila Wolf, RDH "Mama Gums"
"KILLER DISEASE SWEEPS PLANET!" If you saw this unforgettable headline in your local paper, would you be alarmed? Would you read the article to discover the "what, who, where, and why" about this dreadful killer disease? Or simply run naked and screa...
Sexual Health by Nutrovita1 Nutrovita1
SEXUAL HEALTH
Sexuality is an integral part of being human. Love, affection and sexual intimacy contribute to healthy relationships and individual well-being. But along with the po...
The MOST Powerful Dieting Tip on the Planet by Marc David
Copyright 2006 Marc David
Most people are going about this weight reduction thing all wrong. They simply want to reduce the pounds giving no thought as to what it is they are losing. I'm about to give you the most powerful dieting formula on ...
The Best Foods on the Planet for a Lean Body by Mike Geary
In most of my newsletters, I like to provide a healthy snack or meal recipe that not only is delicious, but also helps to get you closer to that hard-body appearance that everyone is looking for. In this article, I'd like to give you healthy ...
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