The Outer space Portal
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
Titan is the largest moon of Saturn, the only natural satellite known to have a dense atmosphere, and the only object other than Earth for which clear evidence of stable bodies of surface liquid has been found. Discovered on 25 March 1655 by the Dutch astronomer Christiaan Huygens, Titan is the sixth ellipsoidal moon from Saturn. Frequently described as a planet-like moon, it is the second-largest natural satellite in the Solar System, after Jupiter's moon Ganymede, and it is larger by volume than the smallest planet, Mercury. Titan itself is primarily composed of water ice and rocky material. Its dense, opaque atmosphere meant that little was known of the surface features or conditions until the Cassini–Huygens mission in 2004. Although mountains and several possible cryovolcanoes have been discovered, its surface is relatively smooth and few impact craters have been found. Owing to the existence of stable bodies of surface liquids and its thick nitrogen-based atmosphere, Titan has been cited as a possible host for microbial extraterrestrial life or, at least, as a prebiotic environment rich in complex organic chemistry.
Selected picture
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Mercury is the smallest and closest to the Sun of the eight planets in the Solar System. It has no known natural satellites. The planet is named after the Roman deity Mercury, the messenger to the gods. -
Diagram: Kelvin SongA diagram of Jupiter showing a model of the planet's interior, with a rocky core overlaid by a deep layer of liquid metallic hydrogen and an outer layer predominantly of molecular hydrogen. Jupiter's true interior composition is uncertain. For instance, the core may have shrunk as convection currents of hot liquid metallic hydrogen mixed with the molten core and carried its contents to higher levels in the planetary interior. Furthermore, there is no clear physical boundary between the hydrogen layers—with increasing depth the gas increases smoothly in temperature and density, ultimately becoming liquid. -
Image 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. -
Photo credit: Mars Reconnaissance OrbiterFalse-color Mars Reconnaissance Orbiter image of a side of the Chasma Boreale, a canyon in the polar ice cap of the Planum Boreum (north pole of Mars). Light browns are layers of surface dust, greys and blues are layers of water and carbon dioxide ice. Regular geometric cracking is indicative of higher concentrations of water ice.
The Planum Boreum's permanent ice cap has a maximum depth of 3 km (1.9 mi). It is roughly 1200 km (750 mi) in diameter, an area equivalent to about 1½ times the size of Texas. The Chasma Boreale is up to 100 km (62.5 mi) wide and features scarps up to 2 km (1.25 mi) high. For a comparison, the Grand Canyon is approximately 1.6 km (1 mi) deep in some places and 446 km (279 mi) long but only up to 24 km (15 mi) wide. -
Photo 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. -
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Image: Tom RuenAn 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. -
Planet Mars Credit: 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. -
Color-composite image of the Pleiades from the Digitized Sky Survey Credit: 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. -
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. -
Photograph: 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. -
Sombrero Galaxy 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. -
Image credit: Dave JarvisAn 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. -
NGC 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. -
Space Shuttle Atlantis launch plume 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. -
NASA astronaut Robert Curbeam (left) and European Space Agency (ESA) astronaut Christer Fuglesang participate in STS-116's first of three planned sessions of extra-vehicular activity (EVA) as construction resumes on the International Space Station. The landmasses depicted in the background are the South Island (left) and North Island (right) of New Zealand. -
Earth "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. -
The asteroid 433 Eros was named after the Greek god of love Eros. This S-type asteroid is the second-largest near-Earth asteroid. This image shows the view looking from one end of the asteroid across the gouge on its underside and toward the opposite end.
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The Day the Earth Smiled refers to the date July 19, 2013, on which the Cassini spacecraft turned to image Saturn, its entire ring system, and the Earth from a position where Saturn eclipsed the Sun. Cassini imaging team leader and planetary scientist Carolyn Porco called for all the world's people to reflect on humanity's place in the cosmos, to marvel at life on Earth, and to look up and smile in celebration. The final mosaic, shown here, was released four months later and includes planets Earth, Mars, and Venus, and a host of Saturnian moons. -
Photograph: 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. -
Kepler's Supernova Credit: NASAThis Supernova remnant of Kepler's Supernova (SN 1604) is made up of the materials left behind by the gigantic explosion of a star. There are two possible routes to this end: either a massive star may cease to generate fusion energy in its core, and collapse inward under the force of its own gravity, or a white dwarf star may accumulate material from a companion star until it reaches a critical mass and undergoes a similar collapse. In either case, the resulting supernova explosion expels much or all of the stellar material with great force. -
Photo: NASA/Crew of Expedition 22Space Shuttle Endeavour in a photograph taken from the International Space Station, in which the shuttle appears to straddle the stratosphere and mesosphere. During this mission, STS-130, the shuttle's primary payloads were the Tranquility module and the Cupola, a robotic control station which provides a 360-degree view around the station.
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Space-related portals
General images
The following are images from various outer space-related articles on Wikipedia.
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Cosmic dust of the Andromeda Galaxy as revealed in infrared light by the Spitzer Space Telescope. (from Cosmic dust) -
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The Long Duration Exposure Facility (LDEF) is an important source of information on small-particle space debris. (from Space debris) -
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Astronaut Buzz Aldrin had a personal Communion service when he first arrived on the surface of the Moon. (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) -
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) -
The diversity found in the different types and scales of astronomical objects make the field of study increasingly specialized. (from Outline of space science) -
A computer-generated map of objects orbiting Earth, as of 2005. About 95% are debris, not working artificial satellites (from Outer space) -
Smooth chondrite interplanetary dust particle. (from Cosmic dust) -
Reconstruction of solar activity over 11,400 years. Period of equally high activity over 8,000 years ago marked. (from Space climate) -
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Comet 103P/Hartley (2010) (from Space exploration) -
This light-year-long knot of interstellar gas and dust resembles a caterpillar. (from Interstellar medium) -
Known orbit planes of Fengyun-1C debris one month after the weather satellite's disintegration by the Chinese ASAT (from Space debris) -
Objects in Earth orbit including fragmentation debris, November 2020, NASA: ODPO (from Space debris) -
A micrometeoroid left this crater on the surface of Space Shuttle Challenger's front window on STS-7. (from Space debris) -
Voyager 1 is the first artificial object to reach the interstellar medium. (from Interstellar medium) -
A dusty trail from the early Solar System to carbonaceous dust today. (from Cosmic dust) -
The original Magdeburg hemispheres (left) used to demonstrate Otto von Guericke's vacuum pump (right) -
Saudi officials inspect a crashed PAM-D module in January 2001. (from Space debris) -
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) -
After reentry, Delta 2 second stage pieces were found in South Africa. (from Space debris) -
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) -
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) -
The first image of Earth taken by a person. South is up. (from Outer space) -
Baker-Nunn cameras were widely used to study space debris. (from Space debris) -
Artist's impression of dust formation around a supernova explosion. (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) -
Because of the hazards of a vacuum, astronauts must wear a pressurized space suit while outside their spacecraft. -
Perseverance's backshell sitting upright on the surface of Jezero Crater (from Space debris) -
First television image of Earth from space, taken by TIROS-1 (1960) (from Space exploration) -
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) -
Model of Vostok spacecraft (from Space exploration) -
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) -
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) -
Earth and the Moon as seen from cislunar space on the 2022 Artemis 1 mission (from Outer space) -
NASA computer-generated image of debris objects in Earth orbit, c. 2005. (from Space debris)
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Vanguard 1 is expected to remain in orbit for 240 years. (from Space debris) -
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V-2 Rocket in the Peenemünde Museum (from Space exploration) -
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) -
Concept art for a NASA Vision mission (from Space exploration) -
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) -
Space debris identified as WT1190F, burning up in a fireball over Sri Lanka. (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) -
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) -
A proposed timeline of the origin of space, from physical cosmology (from Outline of space science)
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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) -
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) -
Bow shock formed by the magnetosphere of the young star LL Orionis (center) as it collides with the Orion Nebula flow -
View of an orbital debris hole made in the panel of the Solar Max satellite. (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) -
Illustration of a satellite breaking up into multiple pieces at higher altitudes. (from Space debris) -
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) -
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) -
Concept for a space-based solar power system to beam energy down to Earth (from Outer space) -
Interstellar medium and astrosphere meeting (from Interstellar medium) -
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. -
Apollo 16 LEM Orion, the Lunar Roving Vehicle and astronaut John Young (1972) (from Space exploration) -
A MESSENGER image from 18,000 km showing a region about 500 km across (2008) (from Space exploration) -
Three-dimensional structure in Pillars of Creation. (from Interstellar medium) -
Porous chondrite dust particle (from Cosmic dust) -
Artistic image of a rocket lifting from a Saturn moon (from Space exploration) -
Illustration of Earth's atmosphere gradual transition into outer space (from Outer space) -
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Delta-v's in km/s for various orbital maneuvers (from Space exploration) -
Crew quarters on Zvezda, the base ISS crew module (from Space exploration) -
Infographic showing the space debris situation in different kinds of orbits around Earth (from Space debris) -
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) -
Astronaut Piers Sellers during the third spacewalk of STS-121, a demonstration of orbiter heat shield repair techniques (from Outline of space science) -
Apollo Command Service Module in lunar orbit (from Space exploration) -
Major elements of 200 stratospheric interplanetary dust particles. (from Cosmic dust) -
Debris density in low Earth orbit (from Space debris) -
Tupan Patera on Jupiter's moon Io (from Space exploration) -
Zodiacal light caused by cosmic dust. (from Cosmic dust) -
Surface of Mars by the Spirit rover (2004) (from Space exploration) -
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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?
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