Portal:Outer space

The Outer space Portal

Introduction

Because of the hazards of a vacuum, astronauts must wear a pressurized space suit while off-Earth and outside their spacecraft.

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 Kuiper belt is a region of the Solar System beyond the planets extending from the orbit of Neptune (at 30 AU) to approximately 50 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. It consists mainly of small bodies, or remnants from the Solar System's formation. While the asteroid belt is composed primarily of rock, ices, and metal, the Kuiper objects are composed largely of frozen volatiles, such as methane, ammonia and water. The classical (low-eccentricity) 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. Since the belt was discovered in 1992, the number of known Kuiper belt objects has increased to over a thousand, and more than 70,000 KBOs over 100 km (62 mi) in diameter are believed to exist. Pluto is the largest known member of the Kuiper belt, if the scattered disc is excluded. In Pluto's honour, the four currently accepted dwarf planets beyond Neptune's orbit are called "plutoids".

Selected picture

• 

  

  Astronaut Steve Robinson on a spacewalk, August 2005

  Extra-vehicular activity

  Credit: NASA

  Extra-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).
• 
  Helix Nebula

  Photograph: NASA/JPL-Caltech/University of Arizona

  The 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.
• 
  Husband Hill

  Photo credit: Spirit rover

  A 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.
• 

  

  Space Shuttle Atlantis launch plume

  Space Shuttle program

  Credit: NASA/Fir0002

  The launch of Space Shuttle Atlantis on STS-98, February 7 2001, at sunset. The sun is behind the camera, and the shape of the plume is cast across the vault of the sky, intersecting the rising full moon. The top portion of the plume is bright because it is illuminated directly by the sun; the lower portions are in the Earth's shadow. After launch, the shuttle must engage in a pitch and roll program so that the vehicle is below the external tank and SRBs, as evidenced in the plume trail. The vehicle climbs in a progressively flattening arc, because achieving low orbit requires much more horizontal than vertical acceleration.

  
  
  
• 
  Lunar rover

  Photo credit: Harrison Schmitt

  Astronaut 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.
• 
  Tvashtar Paterae

  Photo credit: New Horizons probe

  An 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.
• 
  Order of magnitude

  Image credit: Dave Jarvis

  An illustration of relative astronomical orders of magnitude, starting with the terrestrial planets of the Solar System in image 1 (top left) and ending with the largest known star, VY Canis Majoris, at the bottom right. The biggest celestial body in each image is shown on the left of the next frame.
• 
  Jupiter

  Image credit: NASA

  An 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.
• 
  Pale Blue Dot

  Photo credit: NASA/JPL

  Pale 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."
• 
  Solar flare

  Photo: Goddard Space Flight Center

  A solar flare, a sudden flash of brightness observed over the Sun's surface or the solar limb which is interpreted as a large energy release, recorded on August 31, 2012. Such flares are often, but not always, followed by a colossal coronal mass ejection; in this instance, the ejection traveled at over 900 miles (1,400 km) per second.
• 
  Uranus

  Photo: NASA/JPL/Voyager 2 mission

  Uranus is the seventh planet from the Sun and the fourth most massive in the Solar System. In this photograph from 1986 the planet appears almost featureless, but recent terrestrial observations have found seasonal changes to be occurring.
• 

  

  Planet Mars

  Mars (planet)

  Credit: NASA

  Mars, 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.
• 

  

  Sombrero Galaxy

  Sombrero Galaxy M104

  Credit: NASA / STScI

  The Sombrero Galaxy is a spiral galaxy in the Virgo constellation. It was discovered in the late 1700s. It is about 28 million light years away and is just faint enough to be invisible to the naked eye but easily visible with small telescopes. In our sky, it is about one-fifth the diameter of the full moon. M104 is moving away from Earth at about 1,000 kilometers per second.

  
  
  
• 

  

  Earth

  The Blue Marble

  Credit: The Apollo 17 crew

  "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.
• 

  

  Orion Nebula

  Orion Nebula

  Credit: Hubble Space Telescope

  A composite photo of the Orion Nebula, the closest region of star formation to Earth. It is composed of 520 separate images and NASA calls it "one of the most detailed astronomical images ever produced". The nebula is located below Orion's Belt and is visible to the naked eye at night. It is one of the most scrutinized and photographed objects in the night sky, and is among the most intensely-studied celestial features.
• 
  Geostationary orbit

  Animation credit: Cmglee

  This 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).
• 
  STS-1

  Photo credit: NASA

  A timed exposure of the first Space Shuttle mission, STS-1. The shuttle Columbia stands on launch pad A at Kennedy Space Center, the night before launch. The objectives of the maiden flight were to check out the overall Shuttle system, accomplish a safe ascent into orbit and to return to Earth for a safe landing.
• 

  

  Earthrise, as seen by Apollo 8

  Apollo 8

  Credit: 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.

  
  
  
• 
  Adaptive optics

  Photo: Yuri Beletsky, ESO

  A 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.
• 
  Lunar phase

  Image: Tom Ruen

  An animation of the phases of the Moon. As the Moon revolves around the Earth, the Sun lights the Moon from a different side, creating the different phases. In the image, the Moon appears to get bigger as well as "wobble" slightly. Tidal locking synchronizes the Moon's rotation period on its axis to match its orbital period around the earth. These two periods nearly cancel each other out, except that the Moon's orbit is elliptical. This causes its orbital motion to speed up when closer to the Earth, and slow down when farther away, causing the Moon's apparent diameter to change, as well as the wobbling motion observed.
• 
  Milky Way

  Photo credit: Spitzer Space Telescope

  This infrared image shows hundreds of thousands of stars crowded into the swirling core of our spiral Milky Way galaxy. In visible-light pictures, this region cannot be seen at all because cosmic dust lying between Earth and the galactic center blocks our view.
• 
  NGC 4449

  Photograph: NASA, ESA, A. Aloisi (STScI/ESA), and The Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration

  An 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.

Space-related portals

General images

The following are images from various outer space-related articles on Wikipedia.

• 
  Astronaut Piers Sellers during the third spacewalk of STS-121, a demonstration of orbiter heat shield repair techniques (from Outline of space science)
• 
  Perseverance's backshell sitting upright on the surface of Jezero Crater (from Space debris)
• 
  Reconstruction of solar activity over 11,400 years. Period of equally high activity over 8,000 years ago marked. (from Space climate)
• 
  Apollo Command Service Module in lunar orbit (from Space exploration)
• 
  Map 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)
• 
  Objects in Earth orbit including fragmentation debris, November 2020, NASA: ODPO (from Space debris)
• 
  First television image of Earth from space, taken by TIROS-1 (1960) (from Space exploration)
• 
  Buzz Aldrin taking a core sample of the Moon during the Apollo 11 mission (from Space exploration)
• 
  Astronomers 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)
• 
  Large-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)
• 
  Space 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)
• 
  Because of the hazards of a vacuum, astronauts must wear a pressurized space suit while outside their spacecraft.
• 
  Comet 103P/Hartley (2010) (from Space exploration)
• 
  After reentry, Delta 2 second stage pieces were found in South Africa. (from Space debris)
• 
  Spatial density of space debris by altitude according to ESA MASTER-2001, without debris from the Chinese ASAT and 2009 collision events (from Space debris)
• 
  Voyager 1 is the first artificial object to reach the interstellar medium. (from Interstellar medium)
• 
  Timeline 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)
• 
  Artist's impression of dust formation around a supernova explosion. (from Cosmic dust)
• 
  Space debris identified as WT1190F, burning up in a fireball over Sri Lanka. (from Space debris)
• 
  A 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)
• 
  Spent upper stage of a Delta II rocket, photographed by the XSS 10 satellite (from Space debris)
• 
  Artistic image of a rocket lifting from a Saturn moon (from Space exploration)
• 
  The 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.
• 
  A dusty trail from the early Solar System to carbonaceous dust today. (from Cosmic dust)
• 
  NASA computer-generated image of debris objects in Earth orbit, c. 2005. (from Space debris)
• 
  A MESSENGER image from 18,000 km showing a region about 500 km across (2008) (from Space exploration)
• 
  A drifting thermal blanket photographed in 1998 during STS-88 (from Space debris)
• 
  Interstellar medium and astrosphere meeting (from Interstellar medium)
• 
  V-2 Rocket in the Peenemünde Museum (from Space exploration)
• 
  Near-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)
• 
  Debris 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)
• 
  Bow shock formed by the magnetosphere of the young star LL Orionis (center) as it collides with the Orion Nebula flow
• 
  The original Magdeburg hemispheres (left) used to demonstrate Otto von Guericke's vacuum pump (right)
• 
  Concept for a space-based solar power system to beam energy down to Earth (from Outer space)
• 
  Herbig–Haro object HH 110 ejects gas through interstellar space. (from Interstellar medium)
• 
  The Long Duration Exposure Facility (LDEF) is an important source of information on small-particle space debris. (from Space debris)
• 
  Infographic showing the space debris situation in different kinds of orbits around Earth (from Space debris)
• 
  Baker-Nunn cameras were widely used to study space debris. (from Space debris)
• 
  Astronaut Buzz Aldrin had a personal Communion service when he first arrived on the surface of the Moon. (from Space exploration)
• 
  Three-dimensional structure in Pillars of Creation. (from Interstellar medium)
• 
  Surface of Mars by the Spirit rover (2004) (from Space exploration)
• 
  Cosmic dust of the Andromeda Galaxy as revealed in infrared light by the Spitzer Space Telescope. (from Cosmic dust)
• 
  Spatial 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)
• 
  Delta-v's in km/s for various orbital maneuvers (from Space exploration)
• 
  The diversity found in the different types and scales of astronomical objects make the field of study increasingly specialized. (from Outline of space science)
• 
  Model of Vostok spacecraft (from Space exploration)
• 
  Atmospheric 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)
• 
  Debris density in low Earth orbit (from Space debris)
• 
  A 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)
• 
  Self-portrait of Curiosity rover on Mars's surface (from Space exploration)
• 
  A computer-generated map of objects orbiting Earth, as of 2005. About 95% are debris, not working artificial satellites (from Outer space)
• 
  Earth and the Moon as seen from cislunar space on the 2022 Artemis 1 mission (from Outer space)
• 
  Cosmic dust of the Horsehead Nebula as revealed by the Hubble Space Telescope. (from Cosmic dust)
• 
  Illustration of a satellite breaking up into multiple pieces at higher altitudes. (from Space debris)
• 
  A laser-guided observation of the Milky Way Galaxy at the Paranal Observatory in Chile in 2010 (from Outline of space science)
• 
  View of an orbital debris hole made in the panel of the Solar Max satellite. (from Space debris)
• 
  Growth 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)
• 
  The 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). (from Interstellar medium)
• 
  Major elements of 200 stratospheric interplanetary dust particles. (from Cosmic dust)
• 
  For 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)
• 
  A proposed timeline of the origin of space, from physical cosmology (from Outline of space science)
• 
  Apollo 16 LEM Orion, the Lunar Roving Vehicle and astronaut John Young (1972) (from Space exploration)
• 
  Asteroid 4 Vesta, imaged by the Dawn spacecraft (2011) (from Space exploration)
• 
  This light-year-long knot of interstellar gas and dust resembles a caterpillar. (from Interstellar medium)
• 
  Concept art for a NASA Vision mission (from Space exploration)
• 
  Smooth chondrite interplanetary dust particle. (from Cosmic dust)
• 
  Gabbard 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)
• 
  Porous chondrite dust particle (from Cosmic dust)
• 
  A micrometeoroid left this crater on the surface of Space Shuttle Challenger's front window on STS-7. (from Space debris)
• 
  Vanguard 1 is expected to remain in orbit for 240 years. (from Space debris)
• 
  Illustration of Earth's atmosphere gradual transition into outer space (from Outer space)
• 
  Saudi officials inspect a crashed PAM-D module in January 2001. (from Space debris)
• 
  Conventional anti-satellite weapons such as the SM-3 missile remain legal under the law of armed conflict, even though they create hazardous space debris (from Outer space)
• 
  The 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)
• 
  Tupan Patera on Jupiter's moon Io (from Space exploration)
• 
  Zodiacal light caused by cosmic dust. (from Cosmic dust)
• 
  The first image of Earth taken by a person. South is up. (from Outer space)
• 
  Crew quarters on Zvezda, the base ISS crew module (from Space exploration)
• 
  Known orbit planes of Fengyun-1C debris one month after the weather satellite's disintegration by the Chinese ASAT (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

Upcoming spaceflight launches

For a full schedule of launches and deep-space rendezvous, see 2024 in spaceflight.

Astronomical events

Topics

By year

Categories

Category puzzle

Select [►] to view subcategories

Outer space

Outer space lists

Outer space by century

Outer space by decade

Outer space by year

Works about outer space

Space art

Astronomical objects

Astronomy images

Cosmic dust

Space exploration

Industry in space

Intergalactic media

Interstellar media

Life in outer space

Message artifacts

Music in space

People associated with outer space

Satellites

Space applications

Space industry

Space law

Space photography and videography

Space physics

Space robots

Space technology

Spaceflight

Outer space stubs

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

Discover Wikipedia using portals

• 

  List of all portals

• 

  The arts portal

• 

  Biography portal

• 

  Current events portal

• 

  Geography portal

• 

  History portal

• 

  Mathematics portal

• 

  Science portal

• 

  Society portal

• 

  Technology portal

• 

  Random portal

• 

  WikiProject Portals