Astronomy

{{Astronomy}}
{{cquote|Astronomy compels the soul to look upwards, and leads us from this world to another.|||[[Plato]]<ref>''The Republic'' Book 7. Accessible at [https://gutenberg.org/cache/epub/1497/pg1497-images.html Project Gutenberg]</ref>}}
'''Astronomy''' is the science behind all pretty lights in the sky. It developed from purely studying the position and motion of said lights into actually discovering what they are and what makes them actually work. It arguably developed from the [[protoscience]] of [[astrology]] – which associated [[star]]s and [[planet]]s with special powers that influenced daily human life here on [[Earth]]. Now with added science, we know that they don't really care about us. Indeed, there isn't a "they" at all. These days, the best way to annoy an astronomer is to refer to them as an astrologer – watch the fur fly if you dare.

==Stars==
[[File:Star life cycles red dwarf en.svg|thumb|right|Stellar evolution of low-mass (left cycle) and high-mass (right cycle) stars, with examples in italics]]
{{main|Star}}
In fact, pretty much all of the pretty lights in the sky are [[Rush Limbaugh|great glowing gas bags]], gigantic space ovens slowly [[nuclear fusion|fusing]] four [[hydrogen]] nuclei into [[helium]] and a few other light elements (which converts seven-tenths of one percent of the mass into energy). Once stars have finished the longest stage of their evolution, having consumed most of their hydrogen, they get hard at work at making some heavier elements, up to iron. These nuclear reactions produce a tremendous amount of energy, and make them glow in the dark.

Thanks to [[spectroscopy]], we can tell what elements – and in what relative quantity – are present in the photosphere of a star. It also gives us clues as to the star's surface temperature, resulting in the modern "spectral class" designation system that runs O B A F G K M.

The nearest star is the god we call Helios, Sol, or, colloquially, the [[Sun]]. Because it is so near, it appears very bright to us and makes the side of the Earth facing it warm and well-lit. All the others, even though some may be much bigger, are so far away that they look like little backlit pinholes cut into a dark velvet canopy in the sky.  

Eventually, stars that are massive enough may undergo an implosion/explosion effect, resulting in a (Data General) supernova<ref group=note>Don't confuse a supernova with a nova. A nova (without the super) is the result of a white dwarf in a mass-exchange binary system with another star. When the white dwarf accretes enough hydrogen from its companion, the outer layers get hot enough and pressurized enough to undergo nuclear fusion. This produces helium, but no heavy elements are synthesized.</ref> in which elements heavier than iron can be synthesized. [[God]] made a supernova to alert some shepherds to the birth of the Baby [[Jesus]].<ref group=note>Apparently. There are no reasonable candidates for such a supernova.</ref> Depending on the original mass of a star, following its collapse or explosion the remnants can take various forms ranging from a white dwarf, to a neutron star, to a black hole.

==Planets==
{{main|Planet}}
A few other pretty lights are what we call 'planets,' or wanderers. They got that name because a planet's position against the 'fixed' stars changes day by day. It moves across the constellations in a narrowish band of sky (the [[zodiac]]) above and below the 'celestial equator.' Planets sometimes loop the loop, going backwards briefly. This was very complicated to explain for people who thought that planets orbited the Earth. [[Copernicus]] realised that having all the planets (including the Earth) orbit the Sun made things easier. Unfortunately Mr C was stuck on the old idea that the orbits must be circular, so his theoretical maths still had to be a bit complicated to match the observed timings of planets around their orbits. This is because orbits are not circles, but ellipses (well done, Mr [[Kepler]]!). 

Planets are rocks or gas bags that, like the Earth, orbit the Sun, and are only visible due to the light they reflect from the Sun. Some of them also have moons (more on that in a moment) orbiting them in turn. The most famous, astronomically speaking history-wise, are the four largest moons of [[Jupiter]], which were observed by [[Galileo]] with a primitive homemade telescope. A [[Star Trek|Federation]] shuttlecraft is named for him for this reason. [[Saturn]] is also known for its rings, which are made up of billions of tiny pieces of rock and ice.

Planets closer to the Sun tend to be formed of rock because the central part of the solar [[nebula]] was hotter while the solar system was forming, boiling off the lighter elements. Those that are farther away, such as Saturn and Jupiter, tend to be less dense as a result.

When you get as far out as the tiny [[Pluto]], it is hard to tell if you are dealing with a planet or a large [[asteroid]], one of the miscellaneous pieces of rock left over while the planets were forming. In fact Pluto was demoted (and the largest asteroid, Ceres, promoted) to a Dwarf planet in 2006<ref>Britt, Robert Roy. [http://www.space.com/2791-pluto-demoted-longer-planet-highly-controversial-definition.html Pluto Demoted: No Longer a Planet in Highly Controversial Definition.] space.com.</ref>).

===Extrasolar planets===
Extrasolar planets, a.k.a. [[exoplanet]]s, are planets orbiting stars other than the Sun, including our nearest neighbor {{wpl|Proxima Centauri}}<ref>{{wpa|Proxima Centauri b}}</ref>, less than 4 light years away. There are also {{wpl|rogue planet||s}} wandering about without a star to orbit. As of February 1st 2023, [[atheist]] intellectuals with devil machines claim to have confirmed over 5000 exoplanets.<ref>[https://exoplanetarchive.ipac.caltech.edu/docs/counts_detail.html Exoplanet and Candidacy Statistics] - Caltech</ref> We have photos of some of them.<ref>"[https://www.accuweather.com/en/space-news/chilean-telescope-captures-images-of-bright-exoplanet/1486589 Very Large Telescope captures direct images of bright exoplanet]" - Accuweather</ref> Scientists working in this area now predict that a majority of stars will turn out to have planets.

We spot stars with planets either by watching them wobble side to side (position change), wobble in and out (Doppler spectrum change), or dim briefly as planets cross in front of them. As the [[Bible]] mentions no such thing, it is safe to ignore the godless monkey-men, 'cos the Mayans are coming to get them on [[Niburu]].

==Moons==
Moons are small rocky bodies orbiting planets. Most notable is our own [[Moon]]. It is a big rock that is no longer geologically active. Humans have been there and left sundry trash lying around (mostly golf carts and balls), as we usually do, but also large retroreflectors, which are useful for trotting out when people claim that [[Moon landing hoax|humans never made it up there]].

==Miscellaneous==
In addition to the pretty lights, there are lots of leftover detritus (rock, dust, ice, etc.) floating around at various distances and in variously warped orbits. These include asteroids, [[comet]]s and large amounts of space junk.<ref>[http://globalpublicsquare.blogs.cnn.com/2011/09/24/the-danger-of-space-debris/ "The Danger of Space Debris" by Micah Zenko. CNN, 24 September 2011]</ref>

==Caution==
When you go outside at night and look up, be careful not to trip over anything, or fall in a 
[[black hole|black]]
 hole.

==Astronomy woo==
This is a list of relevant topics
*[[Astrology]]
*[[Comet Elenin]]
*[[Flat Earth]]
*[[Nibiru]]
*[[Planet X]]
*[[Pseudoastronomy]]
*[[Immanuel Velikovsky]]

==See also==
*[[Astrophysics]]
*[[Starlight problem]]
==Notes==
{{reflist|group=note}}
==References==
{{reflist}}

[[Category:Science]] <!-- but just barely, the way I wrote it -->
[[Category:Astronomy| ]]

Categories: Science, Astronomy