Asrtonomy Megathread OP

[release][url=http://en.wikipedia.org/wiki/Astronomy]Astronomy[/url] is a natural science that deals with the study of celestial objects (such as stars, planets, comets, nebulae, star clusters and galaxies) and phenomena that originate outside the Earth's atmosphere (such as the cosmic background radiation). It is concerned with the evolution, physics, chemistry, meteorology, and motion of celestial objects, as well as the formation and development of the universe.

Astronomy is one of the oldest sciences. Prehistoric cultures left behind astronomical artifacts such as the Egyptian monuments and Stonehenge, and early civilizations such as the Babylonians, Greeks, Chinese, Indians, and Maya performed methodical observations of the night sky. However, the invention of the telescope was required before astronomy was able to develop into a modern science. Historically, astronomy has included disciplines as diverse as astrometry, celestial navigation, observational astronomy, the making of calendars, and even astrology, but professional astronomy is nowadays often considered to be synonymous with astrophysics.

During the 20th century, the field of professional astronomy split into observational and theoretical branches. Observational astronomy is focused on acquiring data from observations of celestial objects, which is then analyzed using basic principles of physics. Theoretical astronomy is oriented towards the development of computer or analytical models to describe astronomical objects and phenomena. The two fields complement each other, with theoretical astronomy seeking to explain the observational results, and observations being used to confirm theoretical results.

Amateur astronomers have contributed to many important astronomical discoveries, and astronomy is one of the few sciences where amateurs can still play an active role, especially in the discovery and observation of transient phenomena.

Ancient astronomy is not to be confused with astrology, the belief system which claims that human affairs are correlated with the positions of celestial objects. Although the two fields share a common origin and a part of their methods (namely, the use of ephemerides), they are distinct.[/release]

[media]http://upload.wikimedia.org/wikipedia/commons/a/a4/The_Sun_by_the_Atmospheric_Imaging_Assembly_of_NASA%27s_Solar_Dynamics_Observatory_-_20100801.jpg[/media]
The fucking gigantic ball of superheated [url=http://en.wikipedia.org/wiki/Plasma_%28physics%29]plasma[/url] that our Earth orbits, the [url=http://en.wikipedia.org/wiki/Sun]sun[/url].
[media]http://upload.wikimedia.org/wikipedia/commons/3/30/Mercury_in_color_-_Prockter07_centered.jpg[/media]
[url=http://en.wikipedia.org/wiki/Mercury_%28planet%29]Mercury[/url], the closest planet to the sun.
[media]http://upload.wikimedia.org/wikipedia/commons/5/51/Venus-real.jpg[/media]
[url=http://en.wikipedia.org/wiki/Venus]Venus[/url], one of the hottest and generally just uninhabitable planets in the solar system.
[media]http://upload.wikimedia.org/wikipedia/commons/9/97/The_Earth_seen_from_Apollo_17.jpg[/media]
[url=http://en.wikipedia.org/wiki/Earth]Earth[/url]. The best planet in existence.
[media]http://upload.wikimedia.org/wikipedia/commons/d/dd/Full_Moon_Luc_Viatour.jpg[/media]
Our [url=http://en.wikipedia.org/wiki/Moon]Moon[/url].
[media]http://upload.wikimedia.org/wikipedia/commons/5/56/Mars_Valles_Marineris.jpeg[/media]
[url=http://en.wikipedia.org/wiki/Mars]Mars[/url], the second best planet. It's believed at one point long ago it could possibly have had life on it or at least would have been capable of hosting life.
[media]http://upload.wikimedia.org/wikipedia/commons/f/f3/InnerSolarSystem-en.png[/media]
The main [url=http://en.wikipedia.org/wiki/Asteroid_belt]asteroid belt[/url] of our solar system. It's located between Mars and Jupiter.
[media]http://upload.wikimedia.org/wikipedia/commons/5/5a/Jupiter_by_Cassini-Huygens.jpg[/media]
[url=http://en.wikipedia.org/wiki/Jupiter]Jupiter[/url]. The largest planet in our solar system. Has an absolutely insane amount of moons.
[media]http://upload.wikimedia.org/wikipedia/commons/c/c7/Saturn_during_Equinox.jpg[/media]
[url=http://en.wikipedia.org/wiki/Saturn]Saturn[/url], most well know for it's giant rings of ice and rock.
[media]http://en.wikipedia.org/wiki/File:Uranus2.jpg[/media]
[url=http://en.wikipedia.org/wiki/Uranus]Uranus[/url]. How your anus got so distended and cold and so far away from the Earth, we'll never know. [sp]Bad joke, I know. Bear with me here.[/sp]
[media]http://en.wikipedia.org/wiki/File:Neptune.jpg[/media]
[url=http://en.wikipedia.org/wiki/Neptune]Neptune[/url], the last full planet in the solar system.
[media]http://upload.wikimedia.org/wikipedia/commons/9/91/EightTNOs.png[/media]
Eight [url=http://en.wikipedia.org/wiki/Trans-Neptunian_object]tran-Neptune objects[/url] including ex-planet Pluto and the other four official [url=http://en.wikipedia.org/wiki/Plutoid]plutoids[/url]. ([url=http://en.wikipedia.org/wiki/Pluto]Pluto[/url], [url=http://en.wikipedia.org/wiki/Eris_%28dwarf_planet%29]Eris[/url], [url=http://en.wikipedia.org/wiki/Haumea_%28dwarf_planet%29]Haumea[/url], and [url=http://en.wikipedia.org/wiki/Makemake_%28dwarf_planet%29]Makemake[/url])
[release][b]OBJECTS PAST NEPTUNE[/b]
[b][u]The [url=http://en.wikipedia.org/wiki/Kuiper_belt]Kuiper Belt/[url][/u] -[/b] The Kuiper belt, sometimes called the Edgeworth–Kuiper belt, is a region of the Solar System beyond the planets extending from the orbit of Neptune (at 30 AU) to approximately 55 AU from the Sun. It is similar to the asteroid belt, although it is far larger—20 times as wide and 20 to 200 times as massive. Like the asteroid belt, it consists mainly of small bodies, or remnants from the Solar System's formation. While the asteroid belt is composed primarily of rock and metal, the Kuiper objects are composed largely of frozen volatiles (termed "ices"), such as methane, ammonia and water. The belt is home to at least three dwarf planets – Pluto, Haumea, and Makemake. Some of the Solar System's moons, such as Neptune's Triton and Saturn's Phoebe, are also believed to have originated in the region.

[b][u]The [url=http://en.wikipedia.org/wiki/Oort_cloud]Oort Cloud[/url][/u] -[/b] The Oort cloud is a hypothesized spherical cloud of comets which may lie roughly 50,000 AU, or nearly a light-year, from the Sun. This places the cloud at nearly a quarter of the distance to [url=http://en.wikipedia.org/wiki/Proxima_centauri]Proxima Centauri[/url], the nearest star to the Sun. The Kuiper belt and scattered disc, the other two reservoirs of trans-Neptunian objects, are less than one thousandth the Oort cloud's distance. The outer extent of the Oort cloud defines the gravitational boundary of our Solar System.

The Oort cloud is thought to comprise two separate regions: a spherical outer Oort cloud and a disc-shaped inner Oort cloud, or Hills cloud. Objects in the Oort cloud are largely composed of ices, such as water, ammonia, and methane. Astronomers believe that the matter composing the Oort cloud formed closer to the Sun and was scattered far out into space by the gravitational effects of the giant planets early in the Solar System's evolution.

Although no confirmed direct observations of the Oort cloud have been made, astronomers believe that it is the source of all long-period and Halley-type comets entering the inner Solar System and many of the Centaurs and Jupiter-family comets as well. The outer Oort cloud is only loosely bound to the Solar System, and thus is easily affected by the gravitational pull both of passing stars and of the Milky Way Galaxy itself. These forces occasionally dislodge comets from their orbits within the cloud and send them towards the inner Solar System. Based on their orbits, most of the short-period comets may come from the scattered disc, but some may still have originated from the Oort cloud. Although the Kuiper belt and the farther scattered disc have been observed and mapped, only four currently known trans-Neptunian objects—[url=http://en.wikipedia.org/wiki/90377_Sedna]90377 Sedna[/url], [url=http://en.wikipedia.org/wiki/2000_CR105]2000 CR105[/url], [url=http://en.wikipedia.org/wiki/2006_SQ372]2006 SQ372[/url], and [url=http://en.wikipedia.org/wiki/2008_KV42]2008 KV42[/url]—are considered possible members of the inner Oort cloud.

[b][u]The [url=http://en.wikipedia.org/wiki/Scattered_disk]Scattered Disk[/url][/u] -[/b] The scattered disc (or scattered disk) is a distant region of the [url=http://en.wikipedia.org/wiki/Solar_system]Solar System[/url] that is sparsely populated by icy minor planets, a subset of the broader family of trans-Neptunian objects. The scattered disc objects (SDOs) have orbital eccentricities ranging as high as 0.8, inclinations as high as 40°, and perihelia greater than 30 astronomical units (4.5×109 km; 2.8×109 mi). These extreme orbits are believed to be the result of gravitational "scattering" by the gas giants, and the objects continue to be subject to perturbation by the planet Neptune. While the nearest distance to the Sun approached by scattered objects is about 30–35 AU, their orbits can extend well beyond 100 AU. This makes scattered objects "among the most distant and cold objects in the Solar System". The innermost portion of the scattered disc overlaps with a torus-shaped region of orbiting objects known as the Kuiper belt, but its outer limits reach much farther away from the Sun and farther above and below the ecliptic than the belt proper.

Because of its unstable nature, astronomers now consider the scattered disc to be the place of origin for most periodic comets observed in the Solar System, with the centaurs, a population of icy bodies between Jupiter and Neptune, being the intermediate stage in an object's migration from the disc to the inner Solar System. Eventually, perturbations from the giant planets send such objects towards the Sun, transforming them into periodic comets. Many Oort cloud objects are also believed to have originated in the scattered disc.[/release]
[release][b]ASTRONOMICAL MEASUREMENTS[/b]
[b][u][url=http://en.wikipedia.org/wiki/Astronomical_unit]Astronomical Unit[/url] (AU)[/b][/u] - An astronomical unit (abbreviated as AU, au or a.u.) is a unit of length equal to about 149,597,870.7 kilometers (92,955,807.27 miles) or approximately the mean Earth–Sun distance.
[b][u][url=http://en.wikipedia.org/wiki/Light_year]Light Year[/url] (ly)[/b][/u] - A light-year, also light year or lightyear (symbol: ly) is a unit of length, equal to just under 10 trillion kilometers (1016 meters, 10 petameters or about 6 trillion miles). As defined by the [url=http://en.wikipedia.org/wiki/International_Astronomical_Union]International Astronomical Union[/url] (IAU), a light-year is the distance that light travels in a vacuum in one Julian year.
[b][u][url=http://en.wikipedia.org/wiki/Parsec]Parsec[/url] (pc)[/b][/u] - The parsec (parallax of one arcsecond; symbol: pc) is a unit of length, equal to just under 31 trillion (31×1012) kilometers (about 19 trillion miles), 206,265 AU, or about 3.26 light-years. The parsec measurement unit is used in astronomy. It is defined as the length of the adjacent side of an imaginary right triangle in space. The two dimensions that specify this triangle are the parallax angle (defined as 1 arcsecond) and the opposite side (defined as 1 astronomical unit (AU), the distance from the Earth to the Sun). Given these two measurements, along with the rules of trigonometry, the length of the adjacent side (the parsec) can be found.[/release]