Space science 28434 225183576 2008-07-12T09:40:58Z Gaius Cornelius 293907 Revert addition of non-English link. {{Cleanup|date=March 2007}} '''Space science''' is an all-encompassing term that describes all of the various science fields that are concerned with the study of the [[Universe]], generally also meaning "excluding the Earth" and "outside of the Earth's atmosphere". Originally, all of these fields were considered part of [[astronomy]]. However, in recent years the major sub-fields within astronomy, such as [[astrophysics]], have grown so large that they are now considered separate fields on their own. There are eight overall categories that can generally be described on their own; Astrophysics, Galactic Science, Stellar Science, non-Earth Planetary Science, Biology of Other Planets, Astronautics/Space Travel, Space Colonization and Space Defense. The [[Library of Congress]] and [[Dewey Decimal System]] have a major classification "Descriptive Astronomy" which they use instead of placing descriptive works into their huge "Geography" collections. ==Astronomy== === Astronomical Methods === [[Image:palomar.arp.600pix.jpg|thumb|right|250px|Palomar Telescope.]] {{Main|Astronomy|}} Astronomical methods are the equipment and techniques used to collect data about the objects in Space. Galileo's first astronomical method was to find and buy the best telescope of the time and then point that telescope to the heavens. Methods can be categorized according to the wavelength they are attempting to record. [[Radio astronomy]] includes [[radio telescope]]s; devices that receive and record radio waves from outside the Earth. They record [[cosmic microwave background radiation]] resulting from the [[Big Bang]], [[Pulsar]]s and other sources. [[Optical astronomy]] is the oldest kind of astronomy. [[X-ray astronomy|X-ray]] observatories include the [[Chandra X-ray Observatory]] and others. [[Gamma ray astronomy|gamma ray]] includes the [[Compton Gamma Ray Observatory]] and others. [[Neutrino astronomy]] observatories have also been built, primarily to study our Sun. [[Gravitational wave]] observatories have been theorized. A [[space telescope]] is a telescope orbiting or travelling from the Earth, such as the [[Hubble space telescope]]. [[RXTE]] is Long Exposure Time Astronomy used to study [[millisecond pulsar]]s and [[Rotation-powered pulsar|pulsar deceleration]]. [[Spectroscopy]] '''Astronomy teaching tools''' include [[Planetarium]]s and others. Further information can be found at Library of Congress Classification QB1-139 General Astronomy (Dewey 520), QB140-237 Practical and spherical astronomy (Dewey 522), (Observatories Dewey 522), QB468-480 Non-optical methods of astronomy === Descriptive Astronomy === Galileo's second astronomical method was to describe what he saw in the telescope. Descriptive Astronomy is the highest sub-category of Astronomy used by the Library of Congress and Dewey Decimal systems to classify any knowledge related to describing celestial objects. Because we are seeing today portions of the Universe as they actually looked millions or billions of years ago we should have a historical section within Descriptive astronomy: '''History of The Universe''' includes the size, shape and structure of the historical universe), '''Cartography of The Historical Universe''', [[Early Universe]] and others. '''The Current Universe''' includes size shape and structure of the current Universe, cartography of the current Universe and others. '''Cartography of Space Bodies'''. Recording photographic or similar images of the Earths surface from space is a well developed science, yet still expanding because of advances in the actual resolution of images taken from space or atmosphere and because of advances in digitizing and manipulating the images. Most of these advances are being applied to the cartography of space-located bodies, even though acquiring the original images of those bodies is extremely complicated and expensive, usually requiring long distance probes to carry the cameras. Further information is available at Library of Congress Classification: G3190-3191 Celestial maps. Visible matter in the universe is apparently organized geographically into structures with large amounts of space between them; either the space between planets, the space between stars or the space between galaxies. Even galaxies themselves are not spread uniformly but appear to be located in filaments. Therefore The Universe can be divided geographically into regions that follow this structure '''The Filaments of Galaxies''' are the furthest visible structures. Those filaments are made of [[supercluster]]s, tending to line up in filaments. Our Milky Way Galaxy is a galaxy in what is called the '''Our Supercluster of Galaxies''' by the National Geographic Society. Some 150 million light-years across, Our Supercluster is a great aggregation of perhaps thousands of smaller clusters of galaxies. The largest of these smaller clusters is called the Virgo Cluster. According to National Geographic, The Virgo Cluster contains the center of mass of Our Supercluster. Although The Milky Way Galaxy is a part of Our Supercluster, it is not a part of the Virgo Cluster. Our Milky Way Galaxy is part of a cluster called the Local Group. Gravitationally, our Local Group plays a small role in Our Supercluster because it is a small and distant cluster from the center. A much larger cluster within in Our Supercluster is the Ursa Major Cluster. The following objects are located within Our Supercluster but not within the Local Group; they are objects 100,000,000 light-years to 10,000,000 light-years from the Sun: [[Elliptical Galaxy M49|M49]], [[Whirlpool Galaxy|M51]], [[Messier 58|M58]], [[Elliptical Galaxy M59|M59]], [[NGC 4649|M60]], [[Spiral Galaxy M61|M61]], [[Sunflower Galaxy|M63]], [[Black Eye Galaxy|M64]], [[Spiral Galaxy M65|M65]], [[Messier 66|M66]]. National Geographic magazine has produced a very good drawing of this region in its Map of the Universe Supplement, October 1999 issue. '''Local Group''': Our Milky Way Galaxy is one of about 30 galaxies called the Local Group. The Local Group is about 4 million light-years across. In the Local Group our Milky Way Galaxy plays a large gravitational part because our galaxy is the second largest galaxy in our Local Group, second only to the Andromeda Galaxy. All of the other galaxies in our Local Group are gravitationally bound either to the Andromeda Galaxy or to our Milky Way Galaxy. Inside of our local group but outside of our Galaxy are objects 4,000,000 LY to 1,000,000 LY from the Sun: [[Andromeda Galaxy|M31]], [[Elliptical Galaxy M32|M32]], [[Triangulum Galaxy|M33]]. [[Image:Orion Arm.JPG|thumb|left|250px|Image of the Orion and neighbouring arms]] '''Milky Way Galaxy''': Our Milky Way Galaxy is a massive mass-containing structure 100,000 light-years across and 30,000 light-years tall. Most of its billions of suns are organized into approximately 12 structures called "arms". Our Sun is located in what is called the "Orion Arm". The next arm outside of us is called the "Perseus Arm". The Crab Nebula [[Crab Nebula|M1]] is located in the Perseus Arm. The arm outside of the Perseus Arm is called the Outer Arm. Palomar 1 is located in the Outer Arm. The next arm inside of us is called the Sagittarius Arm. The Ring Nebula [[Ring Nebula|M57]] and the Carina Nebula (NGC 3372) are located in the Sagittarius Arm. The next arm inside of the Sagittarius Arm is called the Crux Arm. The inner arms are much shorter, obviously from being shifted by gravitational forces. Arms beside each other today may have at an earlier time been one. '''Orion Arm''': The Orion Nebula [[Orion Nebula|M42]] is located in our Arm. '''Celestial Objects 1000 LY to 100 LY from the Sun''': [[Open Cluster M39|M39]], [[Beehive Cluster|M44]], [[Pleiades (star cluster)|M45]]. '''Celestial Objects 100 LY to 16LY From the Sun'''. '''Celestial Objects less than 16 LY from the Sun''': [[List of nearest stars]] '''Nearby-Stars Solar Systems''': By measuring the extremely small movements of nearby stars astronomers have been able to prove that there are planets going around these Suns, therefore these suns have become "Solar Systems". [[Solar system]] includes '''Scientific Study of Solar System Planets''', [[Venus]], [[Mercury (planet)|Mercury]], [[Saturn]], [[Jupiter]], [[Uranus]], [[Neptune]], [[Mars]], and [[Moon]] Further reading can be found in the Library of Congress Classification QB495-903 Descriptive astronomy (Dewey 523) Galileo's second astronomical method was to describe what he saw in the telescope. == Physics Of The Universe / Astrophysics == [[Image:CMB Timeline75.jpg|thumb|right|250px|Timeline of Origin of Space.]] {{Main|Astrophysics|}} After first looking at the planets, then second describing what he saw, Galileo's third astronomical method was to theorize about the reasons for what he saw in the telescope, specifically to theorize that the Earth goes around the Sun. The Physics of the Universe can be divided into several broad categories: '''Astrophysical Theory''' includes [[general relativity]] and others. '''Astrophysical Processes''' includes [[baryon]]ic and others. '''Physical Processes, General''' includes [[Mechanics]], [[Electromagnetism]], [[electromagnetic force]]s, [[Statistical Mechanics]], [[Thermodynamics]], [[Quantum Mechanics]], [[theory of relativity|relativity]], [[gravity]] and others. '''Origins Of The Universe''' [[Universe]] Theories of the Origins of the Universe, [[Big bang theory|Big Bang Theory]], Early Universe, Evidence, [[Cosmic Microwave Background]], Dark Ages, '''Interstellar Medium ''', [[void (astronomy)|voids]], Filaments of Galaxies, [[galaxy cluster]]s and others. '''Astrophysical Plasma''' includes [[Plasma (physics)|plasma]] and [[Plasma (physics)#Potentials|''quasineutrality'']] and others. '''Cosmic Plasmas Between Stars, (Diffuse Plasmas)''' includes [[intergalactic space]], [[intergalactic medium]], [[interstellar medium]], [[interplanetary medium]], [[interstellar space]], [[heliospheric current sheet]], [[interplanetary medium]], [[Solar wind]] and others. '''Cosmic Plasmas Inside Stars, (Dense Plasma)''' includes [[Stars]], [[plasma physics|plasma physicists]], [[active galactic nucleus|active galactic nuclei]], [[fusion power]], [[magnetohydrodynamics|magnetohydrodynamic]], [[X-ray]]s , [[bremsstrahlung]], [[Physical Cosmology|Cosmology]] , [[reionization|reionized]], [[ambipolar diffusion]], [[Particle Physics]] and others. Further information can be found at Library of Congress Classification QB460-466 Astrophysics, QB349-421 Theoretical astronomy and celestial mechanics, and QB980-991 Cosmogony. Cosmology (PHYSICAL COSMOLOGY ONLY), (Dewey "Theoretical Astronomy" 521) == Cosmology/Cosmonauts == [[Image:Hubble deep field.jpg|thumb|right|250px|Galaxies in the Hubble Deep Field.]] {{Main|Galaxy|}} Physics can explain the underlying physical science of any galaxy, yet many aspects of galaxies are not best described through their physics. '''Galactic physical science''' is the general term for all physical sciences that can be applied to any galaxy in the Universe or to a particular galaxy. '''Galaxy Formation and Evolution''' includes [[Galaxy|Galaxies]], [[Elliptical galaxy|elliptical galaxies]] Giant Galaxies, '''Spiral Galaxies''', [[Andromeda Galaxy|M31]] The [[Andromeda Galaxy]] and others. '''Intra-Galaxy Processes, General '''includes [[Black Hole]], [[Globular Cluster]]s, [[Satellite]] Galaxy, [[Prograde and Retrograde Motion|Retrograde Rotation]], Halo [[star]]s, [[High Velocity Cloud]]s, [[Monoceros Ring]], '''accretion disc''', [[Gravitation]], [[Angular Momentum]], [[Centripetal force]], [[Tidal Force|tidal effects]], [[Viscosity]], [[orbit]]al momentum, [[Accretion disk]], [[Active galactic nuclei]], [[Protoplanetary disc]]s, [[Gamma ray burst]]s and others. '''Milky Way Galactic Physical Science''' is the overall science containing all the physical sciences related directly to the Milky Way Galaxy: Halo [[star]]s, Milky Way [[High Velocity Cloud]]s, Milky Way [[Monoceros Ring]], Milky Way '''accretion disc''', Milky Way [[Gravitation]], Milky Way [[Angular Momentum]], Milky Way [[Centripetal force]], Milky Way [[Tidal Force|tidal effects]], Milky Way [[Viscosity]], Milky Way [[orbit]]al momentum, Milky Way [[event horizon]], Milky Way [[black hole]] and others. == Stellar science == [[Image:GPN-2000-000908.jpg|thumb|left|250px|Quintuplet Cluster- Very young and near the Galactic Center.]] Physics is the underlying physical science of any star, yet many aspects of stars are not best described through their physics. '''Stellar science''' is the general term for ALL physical sciences that can be applied to any star in the Universe or to a particular star. '''Solar science of the Sun''' [[Sun]] is the overall science containing all of the physical sciences related directly to our local Sun. '''Stellar-Processes, General''' [[Stellar dynamics]], [[star]]s, [[Stellar Evolution]], [[event horizon]], [[black hole]], [[x-ray]]s, [[nuclear fusion]] and others. In [[astronomy]], '''stellar evolution''' is the sequence of changes that a [[star]] undergoes during its lifetime; the hundreds of thousands, millions or billions of years during which it emits light and heat. Over the course of that time, the star will change radically. Stellar evolution is not studied by [[observation|observing]] the life cycle of a single star&mdash;most stellar changes occur too slowly to be detected even over many centuries. Instead, [[astrophysics|astrophysicists]] come to understand how stars evolve by observing numerous stars, each at a different point in its life cycle, and simulating [[stellar structure]] with [[computer model]]s. '''Birth''' of stars is discussed in ''Main article: [[Star formation|Star Formation]]'' '''Stellar evolution''' begins with a [[Dark nebula|giant molecular cloud]] (GMC), also known as a [[stellar nursery]]. Most of the 'empty' space inside a [[galaxy]] actually contains around 0.1 to 1 particle per cm³, but inside a GMC, the typical density is a few million particles per cm³. A GMC contains 100,000 to 10,000,000 times as much mass as our [[Sun]] by virtue of its size: 50 to 300 [[light-year]]s across. Very small protostars never reach temperatures high enough for [[nuclear fusion]] of hydrogen to begin; these are [[brown dwarf]]s of less than 0.1 solar mass. Brown dwarfs heavier than 13 [[Jupiter]] masses (<math>M_J</math>) do fuse [[deuterium]], and some astronomers prefer to call only these objects brown dwarfs, classifying anything larger than a planet but smaller than this a sub-stellar object. Both types, deuterium-burning or not, shine dimly and die away slowly, cooling gradually over hundreds of millions of years. The central temperature in more massive protostars, however, will eventually reach 10 [[megakelvin]]s, at which point [[hydrogen]] begins to fuse by way of the [[proton-proton chain reaction]] to deuterium and then to [[helium]]. The onset of nuclear fusion leads over a relatively short time to a [[hydrostatic equilibrium]] in which energy released by the core prevents further gravitational collapse. The star thus evolves rapidly to a stable state. New stars come in a variety of sizes and colors. They range in [[spectral type]] from hot and blue to cool and red, and in mass from less than 0.5 to more than 20 solar masses. The brightness and color of a star depend on its surface temperature, which in turn depends on its mass. A new star will fall at a specific point on the [[main sequence]] of the [[Hertzsprung-Russell diagram]]. Small, cool [[red dwarf]]s burn hydrogen slowly and may remain on the main sequence for hundreds of billions of years, while massive hot [[supergiant]]s will leave the main sequence after just a few million years. A mid-sized star like the Sun will remain on the main sequence for about 10 billion years. The Sun is thought to be in the middle of its lifespan; thus, it is on the main sequence. Once a star expends most of the [[hydrogen]] in its core, it moves off the main sequence. '''Maturity'''After millions to billions of years, depending on its initial mass, the continuous fusion of hydrogen into helium will cause a build-up of helium in the core. The later years and death of stars: '''Low-mass star''' Some stars may fuse helium in core hot-spots, causing an unstable and uneven reaction as well as a heavy [[solar wind]]. In this case, the star will form no [[planetary nebula]] but simply evaporate, leaving little more than a [[brown dwarf]]. But a star of less than about 0.5 solar mass will never be able to fuse helium even after the core ceases hydrogen fusion. There simply is not a stellar envelope massive enough to bear down enough pressure on the core. These are the [[red dwarf]]s, such as [[Proxima Centauri]], some of which will live thousands of times longer than the Sun. Recent astrophysical models suggest that red dwarfs of 0.1 solar masses may stay on the main sequence for almost six trillion years, and take several hundred billion more to slowly collapse into a [[white dwarf]]. (S&T, 22) '''Mid-sized stars''' Once a medium-size star (between 0.4 and 3.4 solar masses) has reached the [[red giant]] phase, its outer layers continue to expand, the core contracts inward, and helium begins to fuse into carbon. In stars of less than 1.4 solar masses, the helium fusion process begins with an explosive burst of energy generation known as a [[helium flash]].<ref>{{cite journal | author=Alan C. Edwards | title=The hydrodynamics of the helium flash | journal=Monthly Notices of the Royal Astronomical Society | year=1969 | volume=146 | pages=445 | url=http://adsabs.harvard.edu/abs/1969MNRAS.146..445E }}</ref> Helium burning reactions are extremely sensitive to temperature, which causes great instability. Huge pulsations build up, which eventually give the outer layers of the star enough [[kinetic energy]] to be ejected as a [[planetary nebula]]. At the center of the nebula remains the core of the star, which cools down to become a small but dense [[white dwarf]], typically weighing about 0.6 solar masses, but only the volume of the Earth. '''White dwarfs''' ''Main article: [[white dwarf]]s'' White dwarfs are stable because the inward pull of gravity is balanced by the [[degeneracy pressure]] of the star's electrons. (This is a consequence of the [[Pauli exclusion principle]].) With no fuel left to burn, the star radiates its remaining heat into space for thousands of millions of years. In the end, all that remains is a cold dark mass sometimes called a [[black dwarf]]. However, the universe is not old enough for any black dwarf stars to exist. '''Supermassive stars''' After the outer layers of a star greater than five solar masses have swollen into a gigantic red [[supergiant]], the core begins to yield to gravity and starts to shrink. As it shrinks, it grows hotter and denser, and a new series of nuclear reactions begin to occur. These reactions fuse progressively heavier elements, temporarily halting the collapse of the core. '''Neutron stars''' ''Main article: [[neutron star]]'' It is known that in some supernovae, the intense gravity inside the supergiant forces the [[electron]]s into the atomic nuclei, where they combine with the [[proton]]s to form [[neutron]]s. The electromagnetic forces keeping separate nuclei apart are gone (proportionally, if nuclei were the size of dust motes, atoms would be as large as football stadiums), and the entire core of the star becomes nothing but a dense ball of contiguous neutrons or a single atomic nucleus. '''Black holes''' ''Main article: [[black hole]]s'' It is widely believed that not all supernovae form neutron stars. If the stellar mass is high enough, the neutrons themselves will be crushed and the star will collapse until its radius is smaller than the [[Schwarzschild radius]]. The star has then become a black hole. == Non-Earth Planetary Science == [[Image:Solar system.jpg|thumb|right|250px|Solar System Planets.]] '''Planetary Processes, General''' includes [[Planetary science]], [[Planets]], [[Extrasolar Planet]], [[Dwarf Planets]], [[Comets]], [[Asteroid]]s and others. '''Geophysics''' is the study of the [[Earth]] by quantitative [[physics|physical]] methods, especially by [[reflection seismology|seismic]], [[electromagnetic]], and [[radioactivity]] methods, therefore '''Planetary Geophysics''' is the study of the [[planets]] by quantitative [[physics|physical]] methods, especially by [[reflection seismology|seismic]], [[electromagnetic]], and [[radioactivity]] methods. It includes the branches of: [[Seismology]] ([[earthquake]]s and elastic [[wave]]s), planetary gravity, [[geodesy]],[[Tectonophysics]] (geological processes in the planets), [[Mineral Physics]] and others. Geophysics can be both a part of physics and a part of Geology. '''Geodesy of The Solar System''', also called '''geodetics''' of the solar system, is the scientific discipline that deals with the measurement and representation of the planets of the Solar System, their [[gravitation]]al fields and geodynamic phenomena ([[polar motion]] in three-dimensional, time-varying space. The science of geodesy has elements of both astrophysics and planetary sciences. The shape of the Earth is to a large extent the result of its rotation, which causes its equatorial bulge, and the competition of geologic processes such as the collision of plates and of [[Volcano|vulcanism]], resisted by the Earth's [[gravity]] field. These principles can be applied to the solid surface of Earth ([[orogeny]]; Few mountains are higher than 10 km, few deep sea trenches deeper than that because quite simply, a mountain as tall as, for example, 15 km, would develop so much [[pressure]] at its base, due to gravity, that the rock there would become [[plastic]], and the mountain would slump back to a height of roughly 10 km in a geologically insignificant time. Some or all of these geologic principles can be applied to other planets besides Earth. For instance on Mars, whose surface gravity is much less, the largest volcano, [[Olympus Mons]], is 27 km high at its peak, a height that could not be maintained on Earth. The Earth [[geoid]] is essentially the figure of the Earth abstracted from its topographic features. Therefore the Mars geoid is essentially the figure of Mars abstracted from its topographic features. [[Surveying]] and [[mapping]] are two important fields of application of geodesy. Physics is the underlying physical science of any planet, yet many aspects of planets are not best described through their physics. '''Planetary science''' is the general term for ALL physical sciences that can be applied to planets in the Universe or else to a particular planet. '''Planetary science of the Earth''' is the overall physical science containing all the physical sciences related directly to our Earth. Planetary Science can be broadly divided into several major sciences: Geology, Oceanography and Atmospheres. '''Geology of Solar System Planets''' contains [[Geology of Mercury]], [[Geology of Venus]], [[Geology of the Moon]], [[Geology of Mars]], [[Jupiter#Physical characteristics|Geology of Jupiter]],[[Saturn#Physical characteristics|Geology of Saturn]], [[Uranus#Physical characteristics|Geology of Uranus]] [[Neptune#Physical characteristics|Geology of Neptune]], [[Pluto#Physical characteristics|Geology of Pluto]] '''Geology of Other Planets''' [[Planetary geology]] (sometimes known as Astrogeology) refers to the application of geologic principles to other bodies of the solar system. However, specialised terms such as ''selenology'' (studies of the [[Moon]]), ''areology'' (of [[Mars (planet)|Mars]]), etc., are also in use. Most of the geological sciences related to the Earth can be directly applied to the study of non-Earth planets: '''Geology Fields or related disciplines''' [[Structural geology]], [[Geomorphology]]., [[Economic geology]], [[Mining|Mining geology]], [[Geodetics]], [[Geomorphology]], [[Geophysics]], [[Historical geology]], [[Hydrogeology]] or [[geohydrology]], [[Mineralogy]], [[Paleoclimatology]], [[Sedimentology]], [[Seismology]], [[Stratigraphy]], [[Structural geology]], [[Volcanology]],'''Hydrology'''. [[Geothermometry]] (heating of the earth, heat flow, [[volcano]]logy, and hot springs), [[Hydrology]] (ground and surface water, sometimes including [[glaciology]]). '''Extrasolar Geology''' is currently a young science because only recently have extrasolar planets been found. '''Atmospheres of Solar System Planets''' refers to the application of meteorological principles to other bodies of the solar system including the application of: [[Atmospheric electricity]] and [[Earth's magnetic field|terrestrial magnetism]] (including [[ionosphere]], [[Van Allen radiation belt|Van Allen belts]], [[telluric current]]s, [[Radiant energy]], etc.), [[Meteorology]] and [[Climatology]]. [[Aeronomy]] the study of the physical structure and chemistry of the atmosphere. '''Atmosphere of Planets of The Solar System''' includes http://www.astronomy.org/astronomy-survival/outer.html '''Mars Atmosphere''' includes [[Atmosphere of Mars|Mars Atmosphere]], [[Venus#Atmospheric entry|Venus Atmosphere]]. '''Jupiter Atmosphere''' [http://en.wikipedia.org/wiki/Jupiter#Magnetosph] [[Jupiter#Atmosphere|Jupiter Atmosphere]][[Jupiter#The|Great Red Spot Great Red Spot]] http://www2.jpl.nasa.gov/galileo/mess44/promysso.html, Atmosphere on Jupiters-Moons, '''Atmosphere on Saturn''' http://www.nasm.si.edu/ceps/rpif/saturn/saturn.html http://www.physics.purdue.edu/astr263l/SStour/saturn.html http://www.abc.net.au/science/news/stories/s872839.htm. '''Atmosphere on Urnaus''' http://www.physics.purdue.edu/astr263l/SStour/uranus.html '''Atmospheres of Extrasolar Planets''' is currently a young science because only recently have extrasolar planets been found. Astronomers are currently theorizing that the recently discovered extrasolar Jupiter-sized planets have continuous surface winds of many thousands of miles per hour caused by their highly elliptical orbit which brings them close to their parent star. == Exobiology / Extraterrestrial Life == [[Image:Silane.png|thumb|right|250px|Silicon Based Life. A picture of [[silane]], the silicon-based analogue of [[methane]].]] Earth telescopes can resolve some surface features of the nearby planets and so far, no life can be seen through the telescopes. However, Earth telescopes cannot resolve the surface features of any planet outside the solar system, so the search for life on other planets continues. While no incontestable evidence has been found for life outside of Earth, the scientific study of the theoretical basis for life on other bodies is progressing. Some scientists are trying to theorize which kinds of stars would have planets that hold life. Because life has overall fragile parameters for survival the general consensus is that only older stars would have planets circling them with life. From this they theorize which sections of our Milky Way Galaxy would most likely hold life. Other scientists theorize the quantity of civilizations that might exist in a galaxy and others are actually listening for the possible radio chatter of extraterrestrial technical civilizations. These sub-sciences of exobilogy can be categorized as follows: '''Habitable Zone Astrobiology ''' is discussed in [[Galactic Habitable Zone]] and [[Solar System Habitable Zone]]. '''Astrobiochemistry''' [[Exogenesis]] Most scientists hold that if extraterrestrial life exists, its [[evolution]] would have occurred independently in different places in the [[universe]]. An alternative hypothesis, held by a minority, is [[panspermia]], which suggests that life in the universe could have stemmed from a smaller number of points of origin, and then spread across the universe, from [[Planetary habitability|habitable planet]] to habitable planet. These two hypotheses are not [[mutually exclusive]]. '''Alternative biochemistry''' includes '''Alternative Carbon Biochemistry''' where water is not the Solvent of Carbon Chains: Life forms based in [[ammonia]] rather than water are also considered, though this solution appears less optimal than water.<ref> http://www.daviddarling.info/encyclopedia/A/ammonialife.html daviddarling.info ''Ammonia based life'']</ref> Also included is '''Alternative Non-Carbon Biochemistry''': Non-carbon based chemistry [[Silicon]] is usually considered the most likely alternative to carbon, though this remains improbable. Silicon life forms are proposed to have a crystalline morphology, and are theorized to be able to exist in high temperatures, such as planets closer to the sun. '''Astrobiosphere''' is the entire area of a planet that supports life and includes [[Biosphere]], Theory of Biosphere, http://en.wikipedia.org/wiki/Planetary_habitability Planetary Habitability [[Extrasolar planets]] Astronomers also search for [[extrasolar]] planets that would be conducive to life, especially those like [[OGLE-2005-BLG-390Lb]] which have been found to have Earth-like qualities. '''Plants On Other Planets''' includes [[Panspermia#Extremophiles|Extremophiles]],<ref>[http://science.nasa.gov/headlines/y2003/02oct_goldilocks.htm?list554307 The Goldilocks Zone<!-- Bot generated title -->]</ref> Theoretical Astrobotany, [[Jupiter#Life on Jupiter|Life On Jupiter]], [[Life|Life on Mars scientific theory]], Independently in [[1996]] structures resembling [[bacterium|bacteria]] were reportedly discovered in a meteorite, [[ALH84001]], thought to be formed of [[martian meteorite|rock ejected from Mars]]. This report is also controversial and scientific debate continues. (See [[Viking biological experiments]].)<ref>{{cite news |url=http://www.cnn.com/2006/TECH/science/06/02/red.rain/index.html |publisher=[[cnn]] |date=2006-06-02 |title= Mysterious red cells might be aliens |accessdate=2006-08-09}} </ref> '''Humanoids-On-Other-Planets''' includes Humanoids-On-Other-Planets Origins- Speculations And Scientific Theory [[Panspermia]]. Extraterrestrial life along with the biochemical basis of extraterrestrial life, there remains a broader consideration of [[evolution]] and [[comparative anatomy|morphology]]. '''Humanoids-On-Other-Planets Technical Civilizations''' includes Humanoids-On-Other-Planets Technical-Civilizations, Speculation And Theory. '''Humanoids-On-Other-Planets Technical-Civilizations, Migrations''' Most scientists hold that if extraterrestrial life exists, its [[evolution]] would have occurred independently in different places in the [[universe]]. An alternative hypothesis, held by a minority, is [[panspermia]], which suggests that life in the universe could have stemmed from a smaller number of points of origin, and then spread across the universe, from [[Planetary habitability|habitable planet]] to habitable planet. '''Humanoids-On-Other-Planets Technical-Civilizations, Quantity of''' [[Drake Equation]] '''Humanoids-On-Other-Planets-Civilizations On Local Stars''' includes Search For Humanoids-On-Other-Planets-Civilizations On Local-Stars, [[SETI]] == Space Exploration Through Space Travel == [[Image:Orion ISS (Sept 2006).jpg|thumb|right|250px|Orion approaching the ISS.]] {{Main|Astronautics|}} Astronomy is exploration of space through instruments based on Earth. Space Exploration through space travel is exploration of space by travel through it, either in person or by drone. Closely associated with Space travel is Space Station, either manned or unmanned. All man-made satellites are a form of unmanned or manned space stations. '''Unmanned Space travel''' includes the sciences of [[Spacecraft Propulsion]], [[Rocket launch technology]], [[Rocket]], [[Astrodynamics]], [[Unmanned space missions]], and others. '''Manned Space travel''' further includes the sciences of [[Microgravity environment]], [[Space transport]], [[Manned space missions]], [[Interplanetary travel]], [[Interstellar travel]] and [[Generation ship]]. ===Unmanned Space Station=== {{Main|Satellite|}} There are [[Astronomical satellite]]s, [[Biosatellite]]s, [[Communications satellite]]s, [[Miniaturized satellites]], [[Navigation satellite]]s, [[Reconnaissance satellite]]s, [[Earth observation satellite]]s, [[communications satellite]]s, [[Earth observation satellite]]s and others. There are many different kinds of orbits possible for these devices. '''Manned Space Station''' includes the sciences of [[Space Station]] and [[Floating cities]]. Further information can be found at Library of Congress Classifications TL787-4050 Astronautics, TL780-785.8 Rocket propulsion, TL787-4050 Space travel. === Space Colonization === {{Main|Space colonization|}} Space colonization is a colossal science that includes all of the scientific disciplines needed to be able to build colonies on non-Earth planets and planetoids. '''Space Colonization Justification''' includes the sciences of [[Space and survival]]. '''Space Colony Research And Development''' Man can practice living on other worlds by building permanently inhabitable cities in extremely hostile environments of the Earth: The poles and the deserts. This is discussed in the articles [[Biosphere 2]] and [[BIOS-3]]. Currently manned Earth hostile-environment stations include [[Amundsen-Scott South Pole Station]], [[Devon Island]], [[Flashline Mars Arctic Research Station|Mars Arctic Research Station]], [[Mars Desert Research Station]], [[climate]], underwater structures for planets with oceans or very heavy atmospheres and others. '''Space Colony Location''' is the science of figuring out the best planets and the best locations on those planets for colonization. Because water is such a necessity for human survival most searches are for locations close to some kind of water. These issues and other related issues are discussed in the articles [[Colonization of Mars]], [[Mars Society]], [[Colonization of Mercury]], [[Colonization of Venus]], [[Venusian terraforming]], [[Colonization of the Moon]], [[Artemis Project]], [[Europa (moon)|Europa]], [[Phobos (moon)|Phobos]], [[Colonization of the asteroids]] and others. '''Space Colonization Habitat''' science includes [[Space habitat]], [[Human adaptation to space]], [[Manmade closed ecological system]], [[Planetary habitability]], [[Domed city]], [[Ocean colonization]], [[Underground city]] and other sub-sciences. Further reading is available at Space Industrialization Dewy 629.44. '''Space Colonization Health''' (Space Medicine Dewey 616.9) '''Space Colonization Agriculture''' includes [[Biosphere 2]] and [[BIOS-3]] and others. '''Space Colonization Food Processing''' includes [[Space food]] and others. '''Space Colonization Housing''' includes [[International Space Station]]. '''Space Colonization Clothing''' includes [[Space suits]] '''Space Colonization Construction''' includes [[Megastructure#Orbital structures|Orbital Megastructures]], [[orbital stationkeeping|station-keeping]], [[Amundsen-Scott South Pole Station]], [[Devon Island]], [[Flashline Mars Arctic Research Station|Mars Arctic Research Station]], [[Mars Desert Research Station]], [[climate]], underwater structures for planets with oceans or very heavy atmospheres and others. '''Space Colonization Transportation''' includes [[Lunar rover]] '''Space Colonization Materials''' includes [[Recycling]] '''Space Colonization Energy''' includes [[Renewable energy]] '''Space Colonization General Manufacturing''' includes [[Space Manufacturing]] '''Space Colonization Economics''' includes [[Space Frontier Foundation]] , [[Private spaceflight]] and [[space tourism]], [[solar power satellite]]s, [[Asteroid mining]], [[space manufacturing]], '''Space Colonization Operations''' includes [[space agency|space agencies]], [[Space advocacy]], [[Colonize the Cosmos]], [[Artemis Project]] , [[National Space Society]], [[Planetary Society]], [[unmanned space mission|robotic exploration]] , [[SETI|search for extraterrestrial life]], [[Space Settlement Institute]], [[Students for the Exploration and Development of Space]], [[NASA]], [[ESA]], [[Project Constellation]] '''Space Colonization Law and Protection'' includes [[Space Law]] == Space Defense == [[Image:Space lasers.jpg|thumb|right|250px|Space Lasers.]]Space Defense is the science of defending the Earth from natural or unnatural threats from Space. Natural threats include [[Near Earth Asteroids]] and similar. Other issues are discussed in [[Missile Defense Command]], [[United States Army Space and Missile Defense Command]], [[Department of Defense Manned Space Flight Support Office]], [[European Aeronautic Defense & Space]] and [[Joint Defense Space Research Facility]]. Further information can be found at Library of Congress Classifications UG1500-1530 Military astronautics, 0UG1500-1530 space warfare, (Dewey 358). ==References== {{reflist}} [[Category:Space science|*]] [[Category:Space exploration]] [[fur:Siencis aerospaziâls]] [[it:Scienze dello spazio]] [[he:מדעי החלל]] [[ja:宇宙科学]] [[pt:Ciência do espaço]] [[ta:விண்வெளி அறிவியல்]] [[ur:علم خلا]] [[yi:ספעיס וויסענשאפט]] [[zh:空间科学]]