Portal:Outer space
Portal maintenance status: (April 2019)
|
Introduction
Outer space (or simply space) is the expanse that exists beyond Earth's atmosphere and between celestial bodies. It contains ultra-low levels of particle densities, constituting a near-perfect vacuum of predominantly hydrogen and helium plasma, permeated by electromagnetic radiation, cosmic rays, neutrinos, magnetic fields and dust. The baseline temperature of outer space, as set by the background radiation from the Big Bang, is 2.7 kelvins (−270 °C; −455 °F).
The plasma between galaxies is thought to account for about half of the baryonic (ordinary) matter in the universe, having a number density of less than one hydrogen atom per cubic metre and a kinetic temperature of millions of kelvins. Local concentrations of matter have condensed into stars and galaxies. Intergalactic space takes up most of the volume of the universe, but even galaxies and star systems consist almost entirely of empty space. Most of the remaining mass-energy in the observable universe is made up of an unknown form, dubbed dark matter and dark energy.
Outer space does not begin at a definite altitude above Earth's surface. The Kármán line, an altitude of 100 km (62 mi) above sea level, is conventionally used as the start of outer space in space treaties and for aerospace records keeping. Certain portions of the upper stratosphere and the mesosphere are sometimes referred to as "near space". The framework for international space law was established by the Outer Space Treaty, which entered into force on 10 October 1967. This treaty precludes any claims of national sovereignty and permits all states to freely explore outer space. Despite the drafting of UN resolutions for the peaceful uses of outer space, anti-satellite weapons have been tested in Earth orbit.
The concept that the space between the Earth and the Moon must be a vacuum was first proposed in the 17th century after scientists discovered that air pressure decreased with altitude. The immense scale of outer space was grasped in the 20th century when the distance to the Andromeda galaxy was first measured. Humans began the physical exploration of space later in the same century with the advent of high-altitude balloon flights. This was followed by crewed rocket flights and, then, crewed Earth orbit, first achieved by Yuri Gagarin of the Soviet Union in 1961. The economic cost of putting objects, including humans, into space is very high, limiting human spaceflight to low Earth orbit and the Moon. On the other hand, uncrewed spacecraft have reached all of the known planets in the Solar System. Outer space represents a challenging environment for human exploration because of the hazards of vacuum and radiation. Microgravity has a negative effect on human physiology that causes both muscle atrophy and bone loss. (Full article...)
Selected article
The Solar System consists of the Sun and its planetary system of eight planets, their moons, and other non-stellar objects. It formed 4.6 billion years ago from the gravitational collapse of a giant molecular cloud. The vast majority of the system's mass is in the Sun, with most of the remaining mass contained in Jupiter. The four smaller inner planets, the terrestrial planets, are primarily composed of rock and metal. The four outer planets, the giant planets, are substantially more massive than the terrestrials. The Solar System also contains a number of regions populated by smaller objects. The asteroid belt, which lies between Mars and Jupiter, is composed of material similar to that of the terrestrial planets. Beyond Neptune's orbit lie the Kuiper belt and scattered disc, linked populations of trans-Neptunian objects composed mostly of ices. These populations include objects large enough to have been rounded by their own gravity, termed dwarf planets. Identified dwarf planets include the asteroid Ceres and the trans-Neptunian objects Pluto, Eris, Haumea, and Makemake. Six of the planets, at least three of the dwarf planets, and many of the smaller bodies are orbited by natural satellites, usually termed "moons" after the Moon, Earth's natural satellite.
Selected picture
-
Image 1Credit: NASAMars, the fourth planet from the Sun, is named after the Roman god of war because of its blood red color. Mars has two small, oddly-shaped moons, Phobos and Deimos, named after the sons of the Greek god Ares. At some point in the future Phobos will be broken up by gravitational forces. The atmosphere on Mars is 95% carbon dioxide. In 2003 methane was also discovered in the atmosphere. Since methane is an unstable gas, this indicates that there must be (or have been within the last few hundred years) a source of the gas on the planet.
-
Image 2Pale Blue Dot is the name given to this 1990 photo of Earth taken from Voyager 1 when its vantage point reached the edge of the Solar System, a distance of roughly 3.7 billion miles (6 billion kilometres). Earth can be seen as a blueish-white speck approximately halfway down the brown band to the right. The light band over Earth is an artifact of sunlight scattering in the camera's lens, resulting from the small angle between Earth and the Sun. Carl Sagan came up with the idea of turning the spacecraft around to take a composite image of the Solar System. Six years later, he reflected, "All of human history has happened on that tiny pixel, which is our only home."
-
Image 3Photo: Yuri Beletsky, ESOA laser shoots towards the centre of the Milky Way from the Very Large Telescope facility in Chile, to provide a laser guide star, a reference point in the sky for the telescope's adaptive optics (AO) system. AO technology improves the performance of optical systems by reducing the effect of atmospheric distortion. AO was first envisioned by Horace W. Babcock in 1953, but did not come into common usage until advances in computer technology during the 1990s made the technique practical.
-
Image 4Realistic-color mosaic of images of Jupiter's moon Europa taken by NASA's Jupiter orbiter Galileo in 1995 and 1998. This view of the moon's anti-Jovian hemisphere shows numerous lineae, linear features created via a tectonic process in which crustal plates of water ice floating on a subsurface ocean (kept warm by tidal flexing) shift in relative position. Reddish regions are areas where the ice has a higher mineral content. The north polar region is at right. (Geologic features are annotated in Commons.)
-
Image 5An animated view of Voyager I's approach to Jupiter. One frame of this image was taken each Jupiter day (approximately 10 hours) between January 6 and February 9, 1979, as the space probe flew from 58 million to 31 million kilometers from Jupiter during that time. The small, round, dark spots appearing in some frames are the shadows cast by the moons passing between Jupiter and the Sun, while the small, white flashes around the planet, are the moons themselves.
-
Image 6Image credit: SeavAn animated image showing the apparent retrograde motion of Mars in 2003 as seen from Earth. All the true planets appear to periodically switch direction as they cross the sky. Because Earth completes its orbit in a shorter period of time than the planets outside its orbit, we periodically overtake them, like a faster car on a multi-lane highway. When this occurs, the planet will first appear to stop its eastward drift, and then drift back toward the west. Then, as Earth swings past the planet in its orbit, it appears to resume its normal motion west to east.
-
Image 7Credit: NASAExtra-vehicular activity (EVA) is work done by an astronaut away from the Earth and outside of his or her spacecraft. EVAs may be made outside a craft orbiting Earth (a spacewalk) or on the surface of the Moon (a moonwalk). Shown here is Steve Robinson on the first EVA to perform an in-flight repair of the Space Shuttle (August 3 2005).
-
Image 8Image credit: United States Geological SurveyA composite image of Olympus Mons on Mars, the tallest known volcano and mountain in the Solar System. This image was created from black-and-white imagery from the USGS's Mars Global Digital Image Mosaic and color imagery acquired from the 1978 visit of Viking 1.
-
Image 9A TRACE image of sunspots on the surface, or photosphere, of the sun from September 2002, is taken in the far ultraviolet on a relatively quiet day for solar activity. However, the image still shows a large sunspot group visible as a bright area near the horizon. Although sunspots are relatively cool regions on the surface of the sun, the bright glowing gas flowing around the sunspots have a temperature of over one million °C (1.8 million °F). The high temperatures are thought to be related to the rapidly changing magnetic field loops that channel solar plasma.
-
Image 10Photo credit: Spirit roverA 360° panorama taken during the descent from the summit of Husband Hill, one of the Columbia Hills in Gusev crater, Mars. This stitched image is composed of 405 individual images taken with five different filters on the panoramic camera over the course of five Martian days.
-
Image 11Photograph credit: European Space AgencyMars is the fourth planet from the Sun and is known as the "Red Planet" due to its reddish appearance as seen from Earth. The planet is named after Mars, the Roman god of war. A terrestrial planet, Mars has a thin atmosphere and surface features reminiscent both of the impact craters of the Moon and the volcanoes, valleys, deserts and polar ice caps of the Earth. The planet has the highest mountain in the Solar System, Olympus Mons, as well as the largest canyon, Valles Marineris. Mars's rotation period and seasonal cycles are also similar to those of the Earth. Of all the planets in the Solar System other than Earth, Mars is the most likely to harbour liquid water and perhaps life. There are ongoing investigations assessing Mars's past potential for habitability, as well as the possibility of extant life. Future astrobiology missions are planned, including NASA's Mars 2020 rover and the European Space Agency (ESA)'s Rosalind Franklin rover. In November 2016, NASA reported finding a large amount of underground ice in the Utopia Planitia region of the planet. The volume of water detected has been estimated to be equivalent to the volume of water in Lake Superior. Mars has two moons, Phobos and Deimos, which are small and irregularly shaped.
This picture is a true-colour image of Mars, taken from a distance of about 240,000 kilometres (150,000 mi) by the OSIRIS instrument on ESA's Rosetta spacecraft, during its February 2007 flyby of the planet. The image was generated using OSIRIS's orange (red), green and blue filters. -
Image 12Photo credit: New Horizons probeAn animation of an eruption by the Tvashtar Paterae volcanic region on the innermost of Jupiter's Galilean moons, Io. The ejecta plume is 330 km (205 mi) high, though only its uppermost half is visible in this image, as its source lies over the moon's limb on its far side. This animation consists of a sequence of five images taken by NASA's New Horizons probe on March 1, 2007, over the course of eight minutes from 23:50 UTC.
-
Image 13Animation credit: CmgleeThis is an animation showing geocentric satellite orbits, to scale with the Earth, at 3,600 times actual speed. The second-outermost (shown in grey) is a geostationary orbit, 35,786 kilometres (22,236 miles) above Earth's equator and following the direction of Earth's rotation, with an orbital period matching the planet's rotation period (a geosynchronous orbit). An object in such an orbit will appear to occupy a fixed position in the sky. Some 300 kilometres (190 miles) farther away is the graveyard orbit (brown), used for satellites at the end of their operational lives. Nearer to the Earth are the orbits of navigational satellites, such as Galileo (turquoise), BeiDou (beige), GPS (blue) and GLONASS (red), in medium Earth orbits. Much closer to the planet, and within the inner Van Allen belt, are satellites in low Earth orbit, such as the Iridium satellite constellation (purple), the Hubble Space Telescope (green) and the International Space Station (magenta).
-
Image 14Photograph: NASA/JPL-Caltech/University of ArizonaThe Helix Nebula is a large planetary nebula located in the constellation Aquarius. Discovered by Karl Ludwig Harding, probably before 1824, it is one of the closest to Earth of all the bright planetary nebulae, about 215 parsecs (700 light-years) away. It is similar in appearance to the Cat's Eye Nebula and the Ring Nebula.
-
Image 15Photograph: NASA, ESA, A. Aloisi (STScI/ESA), and The Hubble Heritage (STScI/AURA)-ESA/Hubble CollaborationAn image of NGC 4449, highlighting its qualities as a starburst galaxy. NGC 4449, an irregular galaxy in the constellation Canes Venatici located about 12 million light years from Earth, has a rate of star formation twice that of the Milky Way's satellite galaxy, the Large Magellanic Cloud. Interactions with nearby galaxies are thought to have influenced this star formation.
-
Image 16The Pioneer plaque, which was included on both Pioneer 10 and Pioneer 11 unmanned spacecraft, the first man-made objects to leave the Solar System. Made from gold-anodised aluminium, the plaque shows the figures of a man and a woman along with several symbols that are designed to provide information about the origin of the spacecraft. However, the mean time for the spacecraft to come within 30 astronomical units of a star is longer than the current age of our galaxy.
-
Image 17NGC 6357 is a diffuse nebula in the constellation Scorpius. This composite image of the nebula contains X-ray data from the Chandra X-ray Observatory and the ROSAT telescope (purple), infrared data from the Spitzer Space Telescope (orange), and optical data from the SuperCosmos Sky Survey (blue). Radiation from hot, young stars is energizing the cooler gas in the clouds that surround them. Often known as the Lobster Nebula, the astronomical object has also been termed the Madokami Nebula by fans of the anime Madoka Magica due to its supposed resemblance to the main character. Scientists at the Midcourse Space Experiment prefer the name War and Peace Nebula, because the bright, western part resembles a dove, while the eastern part looks like a skull in infrared images.
-
Image 18"The Blue Marble" is a famous photograph of Earth. NASA officially credits the image to the entire Apollo 17 crew — Eugene Cernan, Ronald Evans and Jack Schmitt — all of whom took photographic images during the mission. Apollo 17 passed over Africa during daylight hours and Antarctica is also illuminated. The photograph was taken approximately five hours after the spacecraft's launch, while en route to the Moon. Apollo 17, notably, was the last manned lunar mission; no humans since have been at a range where taking a "whole-Earth" photograph such as "The Blue Marble" would be possible.
-
Image 19Credit: William Anders"Earthrise," the first occasion in which humans saw the Earth seemingly rising above the surface of the Moon, taken during the Apollo 8 mission on December 24, 1968. This view was seen by the crew at the beginning of its fourth orbit around the Moon, although the very first photograph taken was in black-and-white. Note that the Earth is in shadow here. A photo of a fully lit Earth would not be taken until the Apollo 17 mission.
-
Image 20Photo credit: Harrison SchmittAstronaut Eugene Cernan makes a short test drive of the lunar rover (officially, Lunar Roving Vehicle or LRV) during the early part of the first Apollo 17 extravehicular activity. The LRV was only used in the last three Apollo missions, but it performed without any major problems and allowed the astronauts to cover far more ground than in previous missions. All three LRVs were abandoned on the Moon.
-
Image 21Credit: NASA, ESA, AURA/Caltech, Palomar ObservatoryThe Pleiades (also known as M45 or the Seven Sisters) is an open cluster in the constellation of Taurus. It is among the nearest to the Earth of all open clusters, probably the best known and certainly the most striking to the naked eye.
-
Image 22Six beryllium mirror segments of the James Webb Space Telescope (JWST) undergoing a series of cryogenic tests at NASA's Marshall Space Flight Center in Huntsville, Alabama. The JWST is a planned space telescope that is a joint collaboration of 20 countries. It will orbit the Sun approximately 1,500,000 km (930,000 mi) beyond the Earth, around the L2 Lagrange point. It is expected to launch in December 2021.
Space-related portals
General images
-
Image 2Vanguard 1 is expected to remain in orbit for 240 years. (from Space debris)
-
Image 3Bow shock formed by the magnetosphere of the young star LL Orionis (center) as it collides with the Orion Nebula flow
-
Image 4Astronomers used the James Webb Space Telescope to image the warm dust around a nearby young star, Fomalhaut, in order to study the first asteroid belt ever seen outside of the Solar System in infrared light. (from Cosmic dust)
-
Image 5Apollo 16 LEM Orion, the Lunar Roving Vehicle and astronaut John Young (1972) (from Space exploration)
-
Image 6Apollo Command Service Module in lunar orbit (from Space exploration)
-
Image 8Model of Vostok spacecraft (from Space exploration)
-
Image 9Astronaut Piers Sellers during the third spacewalk of STS-121, a demonstration of orbiter heat shield repair techniques (from Outline of space science)
-
Image 11The Long Duration Exposure Facility (LDEF) is an important source of information on small-particle space debris. (from Space debris)
-
Image 12Perseverance's backshell sitting upright on the surface of Jezero Crater (from Space debris)
-
Image 13A computer-generated animation by the European Space Agency representing space debris in low earth orbit at the current rate of growth compared to mitigation measures being taken. (from Space debris)
-
Image 14The International Space Station is an orbiting laboratory for space applications and habitability. Visible in the background is yellow-green airglow of Earth's ionosphere and the interstellar field of the Milky Way. (from Outer space)
-
Image 16A computer-generated map of objects orbiting Earth, as of 2005. About 95% are debris, not working artificial satellites (from Outer space)
-
Image 17For the first time, the NASA / ESA / Canadian Space Agency / James Webb Space Telescope has observed the chemical signature of carbon-rich dust grains at redshift z ≈ 7, which is roughly equivalent to one billion years after the birth of the Universe, this observation suggests exciting avenues of investigation into both the production of cosmic dust and the earliest stellar populations in our Universe. (from Cosmic dust)
-
Image 19Illustration of a satellite breaking up into multiple pieces at higher altitudes. (from Space debris)
-
Image 20Concept for a space-based solar power system to beam energy down to Earth (from Outer space)
-
Image 22The original Magdeburg hemispheres (left) used to demonstrate Otto von Guericke's vacuum pump (right)
-
Image 23Buzz Aldrin taking a core sample of the Moon during the Apollo 11 mission (from Space exploration)
-
Image 27Timeline of the expansion of the universe, where visible space is represented by the circular sections. At left, a dramatic expansion occurs in the inflationary epoch, and at the center, the expansion accelerates. Neither time nor size are to scale. (from Outer space)
-
Image 28Major elements of 200 stratospheric interplanetary dust particles. (from Cosmic dust)
-
Image 29Earth and the Moon as seen from cislunar space on the 2022 Artemis 1 mission (from Outer space)
-
Image 30NASA computer-generated image of debris objects in Earth orbit, c. 2005. (from Space debris)
-
Image 31A wide field view of outer space as seen from Earth's surface at night. The interplanetary dust cloud is visible as the horizontal band of zodiacal light, including the false dawn (edges) and gegenschein (center), which is visually crossed by the Milky Way (from Outer space)
-
Image 33Space Shuttle Endeavour had a major impact on its radiator during STS-118. The entry hole is about 5.5 mm (0.22 in), and the exit hole is twice as large. (from Space debris)
-
Image 34Cosmic dust of the Andromeda Galaxy as revealed in infrared light by the Spitzer Space Telescope. (from Cosmic dust)
-
Image 35Gabbard diagram of almost 300 pieces of debris from the disintegration of the five-month-old third stage of the Chinese Long March 4 booster on 11 March 2000 (from Space debris)
-
Image 36Conventional anti-satellite weapons such as the SM-3 missile remain legal under space law, even though they create hazardous space debris (from Outer space)
-
Image 37The sparse plasma (blue) and dust (white) in the tail of comet Hale–Bopp are being shaped by pressure from solar radiation and the solar wind, respectively.
-
Image 40Infographic showing the space debris situation in different kinds of orbits around Earth (from Space debris)
-
Image 41Map showing the Sun located near the edge of the Local Interstellar Cloud and Alpha Centauri about 4 light-years away in the neighboring G-Cloud complex (from Interstellar medium)
-
Image 42The distribution of ionized hydrogen (known by astronomers as H II from old spectroscopic terminology) in the parts of the Galactic interstellar medium visible from the Earth's northern hemisphere as observed with the Wisconsin Hα Mapper (Haffner et al. 2003) harv error: no target: CITEREFHaffnerReynoldsTufteMadsen2003 (help). (from Interstellar medium)
-
Image 43Known orbit planes of Fengyun-1C debris one month after the weather satellite's disintegration by the Chinese ASAT (from Space debris)
-
Image 44Reconstruction of solar activity over 11,400 years. Period of equally high activity over 8,000 years ago marked. (from Space climate)
-
Image 45Space debris identified as WT1190F, burning up in a fireball over Sri Lanka. (from Space debris)
-
Image 46Artistic image of a rocket lifting from a Saturn moon (from Space exploration)
-
Image 47View of an orbital debris hole made in the panel of the Solar Max satellite. (from Space debris)
-
Image 48Growth of tracked objects in orbit and related events; efforts to manage outer space global commons have so far not reduced the debris or the growth of objects in orbit (from Space debris)
-
Image 50First television image of Earth from space, taken by TIROS-1 (1960) (from Space exploration)
-
Image 51A laser-guided observation of the Milky Way Galaxy at the Paranal Observatory in Chile in 2010 (from Outline of space science)
-
Image 52Atmospheric attenuation in dB/km as a function of frequency over the EHF band. Peaks in absorption at specific frequencies are a problem, due to atmosphere constituents such as water vapor (H2O) and carbon dioxide (CO2). (from Interstellar medium)
-
Image 53Because of the hazards of a vacuum, astronauts must wear a pressurized space suit while outside their spacecraft.
-
Image 54A MESSENGER image from 18,000 km showing a region about 500 km across (2008) (from Space exploration)
-
Image 55Spatial density of space debris by altitude according to ESA MASTER-2001, without debris from the Chinese ASAT and 2009 collision events (from Space debris)
-
Image 56Astronaut Buzz Aldrin had a personal Communion service when he first arrived on the surface of the Moon. (from Space exploration)
-
Image 57Objects in Earth orbit including fragmentation debris, November 2020, NASA: ODPO (from Space debris)
-
Image 58Spatial density of LEO space debris by altitude, according to 2011 a NASA report to the United Nations Office for Outer Space Affairs (from Space debris)
-
Image 59Voyager 1 is the first artificial object to reach the interstellar medium. (from Interstellar medium)
-
Image 60This light-year-long knot of interstellar gas and dust resembles a caterpillar. (from Interstellar medium)
-
Image 62Smooth chondrite interplanetary dust particle. (from Cosmic dust)
-
Image 64Cosmic dust of the Horsehead Nebula as revealed by the Hubble Space Telescope. (from Cosmic dust)
-
Image 65Spent upper stage of a Delta II rocket, photographed by the XSS 10 satellite (from Space debris)
-
Image 66Near-Earth space showing the low-Earth (blue), medium Earth (green), and high Earth (red) orbits. The last extends beyond the radius of geosynchronous orbits (from Outer space)
-
Image 67The diversity found in the different types and scales of astronomical objects make the field of study increasingly specialized. (from Outline of space science)
-
Image 68A dusty trail from the early Solar System to carbonaceous dust today. (from Cosmic dust)
-
Image 69Large-scale matter distribution in a cubic section of the universe. The blue fiber-like structures represent the matter, and the empty regions in between represent the cosmic voids of the intergalactic medium (from Outer space)
-
Image 70After reentry, Delta 2 second stage pieces were found in South Africa. (from Space debris)
-
Image 71Concept art for a NASA Vision mission (from Space exploration)
-
Image 72Illustration of Earth's atmosphere gradual transition into outer space (from Outer space)
-
Image 73A micrometeoroid left this crater on the surface of Space Shuttle Challenger's front window on STS-7. (from Space debris)
-
Image 75A proposed timeline of the origin of space, from physical cosmology (from Outline of space science)
-
Image 77Debris impacts on Mir's solar panels degraded their performance. The damage is most noticeable on the panel on the right, which is facing the camera with a high degree of contrast. Extensive damage to the smaller panel below is due to impact with a Progress spacecraft. (from Space debris)
-
Image 78Artist's impression of dust formation around a supernova explosion. (from Cosmic dust)
-
Image 79Debris density in low Earth orbit (from Space debris)
Did you know (auto-generated)
- ... that, for the Space 220 Restaurant, Disney reached out to NASA engineers to understand what a space elevator might look like?
- ... that some severe environmental impacts of the invasion of Ukraine can be seen from space?
- ... that the space industry of India has supported the launch of more than 100 domestic satellites and more than 300 foreign satellites?
- ... that Nature's Fynd, producer of microbe-based meat substitutes, is working with NASA to develop a bioreactor for use in space travel?
- ... that Louis W. Roberts was among the highest ranking African-American space program staff at NASA while the Apollo program was underway?
Space news
2024 in space | |||
---|---|---|---|
Space probe launches |
| ||
Impact events | |||
Selected NEOs | |||
Discoveries |
| ||
Comets | |||
Upcoming spaceflight launches
For a full schedule of launches and deep-space rendezvous, see 2024 in spaceflight.
|
Astronomical events
Topics
Biology |
| |||||
---|---|---|---|---|---|---|
Environment | ||||||
Society | ||||||
Technology |
| |||||
2020 in space | ||
---|---|---|
Space probe launches |
| |
Impact events | ||
Selected NEOs |
| |
Exoplanets |
| |
Discoveries |
| |
Comets | ||
Space exploration |
| |
2019 in space | ||
---|---|---|
Space probe launches |
| |
Impact events |
| |
Selected NEOs | ||
Exoplanets |
| |
Discoveries |
| |
Comets | ||
Space exploration |
| |
2018 in space | ||
---|---|---|
Space probe launches |
| |
Impact events | ||
Selected NEOs | ||
Exoplanets |
| |
Discoveries |
| |
Novae |
| |
Comets | ||
Space exploration |
| |
2017 in space | ||
---|---|---|
Space probe launches |
| |
Impact events | ||
Selected NEOs | ||
Exoplanets | ||
Discoveries | ||
Comets | ||
Space exploration |
| |
2016 in space | ||
---|---|---|
Space probe launches |
| |
Impact events | ||
Selected NEOs | ||
Exoplanets |
| |
Discoveries |
| |
Novae | ||
Comets | ||
Space exploration | ||
2015 in space | ||||||
---|---|---|---|---|---|---|
Space probe launches |
| |||||
Impact events | ||||||
Selected NEOs | ||||||
Exoplanets |
| |||||
Discoveries |
| |||||
Comets | ||||||
Space exploration | ||||||
Categories
Wikimedia
The following Wikimedia Foundation sister projects provide more on this subject:
-
Commons
Free media repository -
Wikibooks
Free textbooks and manuals -
Wikidata
Free knowledge base -
Wikinews
Free-content news -
Wikiquote
Collection of quotations -
Wikisource
Free-content library -
Wikiversity
Free learning tools -
Wiktionary
Dictionary and thesaurus