Fly me (partway) to the moon

Last week, scientists from the National Institute of Standards and Technology (NIST), the National Aeronautics and Space Administration (NASA), the United States Geological Survey (USGS) and the University of Guelph sent ...

Production sites of stars are rare

Astronomers using the Nobeyama Radio Obeservatory (NRO) 45-meter telescope found that high-density gas, the material for stars, accounts for only 3 percent of the total mass of gas distributed in the Milky Way. This result ...

Sudden turbulence that injured dozens is hard to predict

Passengers on a flight from Canada to Australia said they had no warning about turbulence that suddenly slammed people into the ceiling of the plane and injured more than three dozen—a phenomenon that experts say can be ...

Saudi carrier cancels troubled Boeing 737 order for Airbus

Boeing's campaign to restore the reputation of its best-selling plane after two deadly crashes suffered a blow with a Saudi airline canceling an order worth up to $5.9 billion in favor of a European rival of the U.S. manufacturer.

Boeing shares hit as FAA finds new 737 MAX issue

Shares of Boeing tumbled Thursday, a day after US regulators identified a new issue in the Boeing 737 MAX that will likely slow the plane's return to service following two deadly crashes.

Airline group advocates more training for Boeing 737 Max

A trade group representing hundreds of airlines is renewing its push for additional pilot training and coordination among global aviation regulators to ensure that the Boeing 737 Max is safe before it is allowed to fly again ...

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Planet

A planet (from Greek πλανήτης, from the verb πλανώμαι planōmai I wander), 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]

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. The Solar System also contains at least five dwarf planets: Ceres, Pluto (originally classified as the Solar System's ninth planet), Makemake, Haumea and Eris. With the exception of Mercury, Venus, Ceres and Makemake, all of these are orbited by one or more natural satellites.

As of June 2009, there are 353 known extrasolar planets, ranging from the size of gas giants to that of terrestrial planets.

This text uses material from Wikipedia, licensed under CC BY-SA