Neptune: Difference between revisions

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'''Neptune''' is the eighth [[planet]] from the [[Sun]]. It is a [[gas giant]] (also known as a Jovian planet, after the planet [[Jupiter]]).
#REDIRECT [[Neptune (planet)]]
[[Image:Neptune NASA-JPL.jpg|right|thumb|350px|{{#ifexist:Template:Neptune NASA-JPL.jpg/credit|{{Neptune NASA-JPL.jpg/credit}}<br/>|}}Voyager 2 photo of Neptune taken in 1989]]
==Parameters for classification as a planet==
Neptune is classified as a planet by the International Astronomical Union for meeting the following criteria:<ref>[http://www.nasa.gov/vision/universe/solarsystem/planetsf-20060824.html Honey, I Shrunk the Solar System] NASA. “The International Astronomical Union has decided that, to be called a planet, an object must have three traits. It must orbit the sun, be massive enough that its own gravity pulls it into a nearly round shape, and be dominant enough to clear away objects in its neighborhood.”</ref>
*Orbits the sun;
*Has mass sufficient for its gravity to form a nearly round shape;
*Has mass sufficient for gravity to clear a path in its orbit.
 
==Physical Characteristics==
Neptune is approximately 30 times as far from the sun as Earth (30 AU), though slightly smaller than Uranus, is more dense and is about seventeen times more massive than Earth (17 Earth masses).  At its distance from the Sun, it receives about one thousandth of the same sunlight as Earth.<ref name= NeptuneSouthPole>[http://www.nasa.gov/vision/universe/solarsystem/neptune-20070918.html A warm south pole on Neptune] NASA 18/09/07. Retrieved 4/11/07</ref> It radiates more internal heat than it receives from the sun, though less than Jupiter or Saturn, indicating a radioactive inner core.<ref>{{cite web|title=Post Voyager comparisons of the interiors of Uranus and Neptune|author=Podolak, M.; Reynolds, R. T.; Young, R.|work=NASA, Ames Research Center|year=1990|url=http://adsabs.harvard.edu/abs/1990GeoRL..17.1737P|accessdate= 2006-01-16 }}</ref>
[[Image:Thermal images of Neptune's polar region.jpg|right|thumb|350px|{{#ifexist:Template:Thermal images of Neptune's polar region.jpg/credit|{{Thermal images of Neptune's polar region.jpg/credit}}<br/>|}}ESO Very Large Telescope thermal images of Neptune's south polar region showing variation in temperature.]]
The average temperature on Neptune is -200° C (392° F). Recent measurements have show the southern pole to be about 10° C hotter than the planet average. This results in the vaporisation of the frozen methane and its circulation to the upper layers of the atmosphere. Neptune is comprised predominantly of hydrogen and helium. However, its methane  component reaches the upper atmosphere absorbing red light from sunlight and reflects the blue spectrum making Neptune appear blue.<ref name= NeptuneSouthPole/>
 
==Rotational Characteristics==
Neptune’s polar orientation is similar to Earth’s with the northern pole tilting toward or away from the Sun in season. The northern hemisphere summers and winters lasts approximately 40 years each. The variation in polar tilts and increased temperature may be a contributing factor to the winds on Neptune which reach velocities of about 2,000 k/h (1,240 m/h)<ref name= NeptuneSouthPole/>
 
==Orbital Characteristics==
Neptune has an orbital period (sidereal year) of 164.79 earth years. At is closest approach to the Sun (perihelion) it is nearly 30 times the distance of the Earth from the Sun (29.80 AU). At its furthest distance from the Sun (aphelion) it is 30.32 AU from the Sun.<ref>[http://www.nmm.ac.uk/server/show/conWebDoc.393 The orbits of the planets] National Maritime Museum</ref>
 
==Natural Satellites==
Neptune has thirteen moons. The largest, [[Triton (moon)|Triton]], is geologically active, with geysers of [[liquid nitrogen]].<ref>{{cite web|title=The Plausibility of Boiling Geysers on Triton|author=Duxbury, N.S., Brown, R.H.|work=Beacon eSpace|year=1995|url=http://trs-new.jpl.nasa.gov/dspace/handle/2014/28034?mode=full|accessdate= 2006-01-16 }}</ref> Triton is the only large satellite with a [[Retrograde and direct motion|retrograde]] orbit. Neptune possesses a number of [[Neptune Trojan|Trojan asteroid]]s.
 
==References==
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==External Links ==
 
[[Category:Astronomy Workgroup]]
[[Category:CZ Live]]

Revision as of 13:34, 20 November 2007

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