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This page is where the articles to be featured on the Outer space portal are listed. Feel free to make an entry for any article from Wikipedia:Featured articles#Physics and astronomy. It also contains an archive of Articles of the Month below.

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Selected articles list

Selected article: 1-10

Portal:Outer space/Selected article/1

The ISS seen by Space Shuttle Atlantis during the final flyaround of the ISS by the Space Shuttle on STS-135,19 July 2011

The

Canadian robotics. In 1993 the partially built components for a Soviet/Russian space station Mir-2, the proposed American Freedom, and the proposed European Columbus
merged into a single multinational programme. The ISS is arguably the most expensive single item ever constructed.

Portal:Outer space/Selected article/2

The dwarf planet Ceres

A

gravity but has not cleared its neighbouring region of planetesimals and is not a satellite. They are smaller than planets, but more massive than small solar system bodies. The term was adopted in 2006 by the International Astronomical Union (IAU) as a result of the increase in discoveries of trans-Neptunian objects that rivaled Pluto in size, and finally precipitated by the discovery of an even more massive object, Eris. The IAU currently recognizes five dwarf planets—Ceres (pictured), Pluto, Haumea, Makemake, and Eris. It is suspected that at least another 40 known objects in the Solar System
are dwarf planets, but the number might be as high as 2,000. The 2006 definition has been both praised and criticized, and has been disputed by some scientists.

Portal:Outer space/Selected article/3

The Earth seen from Apollo 17

extrasolar planets
—beginning in 1995 and accelerating thereafter—was the second milestone. It confirmed that the Sun is not unique in hosting planets and expanded the habitability research horizon beyond our own solar system.

Portal:Outer space/Selected article/4

The Hubble Deep Field

The

scientific papers since it was created. Three years after the HDF observations were taken, a region in the south celestial hemisphere was imaged in a similar way and named the Hubble Deep Field South. The similarities between the two regions strengthened the belief that the universe is uniform over large scales and that the Earth occupies a typical region in the universe (the cosmological principle
).

Portal:Outer space/Selected article/5

Comet P/Halley as taken March 8, 1986, by W. Liller

dirty snowball" model, which correctly surmised that Halley would be composed of a mixture of volatile ices, such as water, carbon dioxide and ammonia
, and dust. However, the missions also provided data which substantially reformed and reconfigured these ideas.

Portal:Outer space/Selected article/6

Image of Space Shuttle Challenger's smoke plume

The

Rogers Commission, a special commission appointed by President Ronald Reagan to investigate the accident. The Rogers Commission found that NASA's organizational culture
and decision-making processes had been a key contributing factor to the accident. The Challenger disaster has been used as a case study in many discussions of engineering safety and workplace ethics.

Portal:Outer space/Selected article/7

Known objects in the Kuiper belt

The

plutoids
".

Portal:Outer space/Selected article/8

The official NASA patch for the Shuttle-Mir Program, showing a docked to the Russian ', flying above a stylised Earth. The patch is bordered by the colours of the flags of Russia and the USA.

The

Soyuz flight and almost 1000 days in space for American astronauts over seven expeditions. The program was, however, marred by various concerns, notably the safety of Mir following a fire and collision on board the station, financial issues with the cash-strapped Russian Space Program and worries from astronauts about the attitudes of the program administrators. Nevertheless, a large amount of science, expertise in space station construction and knowledge in working in a cooperative space venture was gained from the combined operations, allowing 'Phase Two' of the joint project, the construction of the International Space Station
, to proceed much more smoothly than otherwise possible.

Read more

Portal:Outer space/Selected article/9

Ariel as seen by Voyager 2 in 1986

flyby of Uranus performed by the spacecraft Voyager 2 in 1986, which managed to image 35% of the moon's surface. There are no plans at present to return to study the moon in more detail. After Miranda, Ariel is the second-smallest of Uranus's five round satellites, and the second-closest to its planet. Among the smallest of the Solar System's 19 known spherical moons (it ranks 14th among them in diameter), Ariel is composed of roughly equal parts ice and rocky material. Like all of Uranus's moons, Ariel probably formed from an accretion disk that surrounded the planet shortly after its formation, and, like other large moons, it may be differentiated, with an inner core of rock surrounded by a mantle of ice. Ariel has a complex surface comprising extensive cratered terrain cross-cut by a system of scarps, canyons and ridges. The surface shows signs of more recent geological activity than other Uranian moons, most likely due to tidal heating
.

Portal:Outer space/Selected article/10

Ceres

core and ice mantle. It may harbour an ocean of liquid water underneath its surface. From the Earth, Ceres' apparent magnitude ranges from 6.7 to 9.3, and hence at its brightest it is still too dim to be seen with the naked eye. The unmanned Dawnspacecraft, launched on 27 September 2007 by NASA
, is expected to be the first to explore Ceres after its scheduled arrival there in 2015.

Selected article: 11-20

Portal:Outer space/Selected article/11

Uranus in 1986 by Voyager 2

space probe showed Uranus as a virtually featureless planet in visible light without the cloud bands or storms associated with the other giants. The wind
speeds on Uranus can reach 250 m/s (560 mph).

Portal:Outer space/Selected article/12

Neptune, as photographed by Voyager 2

ring system
, which may have been detected during the 1960s but was only indisputably confirmed by Voyager 2.

Portal:Outer space/Selected article/13

The Earth seen from Apollo 17

inner core. Earth interacts with other objects in outer space, including the Sun and the Moon. The mineral
resources of Earth, as well as the products of the biosphere, contribute resources that are used to support a global human population. The human inhabitants are grouped into about 200 independent sovereign states and have developed many views of the planet.

Portal:Outer space/Selected article/14

The Moon as seen by an observer from Earth

The

celestial body that humans have traveled to and landed on. The first artificial object to escape Earth's gravity and pass near the Moon was the Soviet Union's Luna 1, the first artificial object to impact the lunar surface was Luna 2, and the first photographs of the normally occluded far side of the Moon were made by Luna 3, all in 1959. The U.S. Apollo program
has achieved the first (and only) manned missions to date, resulting in six landings between 1969 and 1972. Human exploration of the Moon ceased with the conclusion of the Apollo program, although as of 2024, several countries have announced plans to send either people or robotic spacecraft to the Moon.

Portal:Outer space/Selected article/15

The Apollo 8 crew portrait

Apollo space program. Commander Frank Borman, Command Module Pilot James Lovell and Lunar Module Pilot William Anders became the first humans to travel beyond Earth orbit and into an orbit around the Moon. It was also the first manned launch of the Saturn V rocket. NASA prepared for the mission in only four months. The hardware involved had only been used a few times—the Saturn V had only launched twice before, and the Apollo spacecraft had only just finished its first manned mission, Apollo 7. However the success of the mission paved the way for the successful completion of John F. Kennedy's goal of landing on the Moon before the end of the decade. After launching on December 21, 1968, the crew took three days to travel to the Moon, which they orbited for twenty hours. While in lunar orbit they made a Christmas Eve
television broadcast that is thought to be one of the most watched of all time.

Portal:Outer space/Selected article/16

Jupiter, as seen from Voyager (1979)

largest planet within the Solar System. It is two and a half times as massive as all of the other planets in our Solar System combined. Jupiter, along with Saturn, Uranus, and Neptune, is classified as a gas giant. When viewed from Earth, Jupiter can reach an apparent magnitude of -2.8, making it the fourth brightest object in the night sky. The planet was known by astronomers of ancient times and was associated with the mythology and religious beliefs of many cultures. Jupiter is primarily composed of hydrogen with only a small proportion of helium; it may also have a rocky core of heavier elements. The outer atmosphere is visibly segregated into several bands at different latitudes, resulting in turbulence and storms along their interacting boundaries. A prominent result is the Great Red Spot, a giant storm that is known to have existed since at least the seventeenth century. Surrounding the planet is a faint planetary ring system and a powerful magnetosphere. There are also at least 67 moons, including the four large moons called the Galilean moons that were first discovered by Galileo Galilei in 1610. Jupiter has been explored on several occasions by robotic spacecraft, most notably during the early Pioneer and Voyager fly-by missions and later by the Galileo orbiter
.

Portal:Outer space/Selected article/17

NASA soil target on Mars named after Laika

Samoyed terrier weighing approximately 6 kg (13 lb). Laika died on November 4, 1957, a few hours after launch, due to overheating, and her remains were destroyed during re-entry on April 14, 1958. Her true cause of death was not made public until years after the flight, with officials always stating that she was either euthanized by poisoned
food or died when the oxygen supply ran out. Russian officials have since expressed regret for allowing Laika to die.

Portal:Outer space/Selected article/18

View of Mars from Hubble Space Telescope

Opportunity). Geological evidence gathered by these and preceding missions suggests that Mars previously had large-scale water coverage, while observations also indicate that small geyser-like water flows have occurred in recent years. Mars has two moons, Phobos and Deimos
, which are small and irregularly shaped.

Portal:Outer space/Selected article/19

The Hubble Space Telescope as seen from the departing Space Shuttle Atlantis, flying Servicing Mission 4 (STS-125), the fifth and final human spaceflight to visit the observatory.

The

near infrared. The telescope is named after the astronomer Edwin Hubble. Although not the first space telescope, Hubble is one of the largest and most versatile, and is well known as both a vital research tool and a public relations boon for astronomy. The HST was built by the United States space agency NASA, with contributions from the European Space Agency, and is operated by the Space Telescope Science Institute. Space telescopes were proposed as early as 1923. Hubble was funded in the 1970s, with a proposed launch in 1983, but the project was beset by technical delays, budget problems, and the Challenger disaster
. When finally launched in 1990, scientists found that the main mirror had been ground incorrectly, compromising the telescope's capabilities. The telescope was restored to its intended quality by a servicing mission in 1993.

Portal:Outer space/Selected article/20

Pluto and its three moons

S/2012 (134340) 1
, discovered in 2012.

Selected article: 21-30

Portal:Outer space/Selected article/21

Photograph of the planet Neptune (large, background) and its moon Triton (small, foreground), taken by Voyager 2 as it entered the outer Solar System

The

cleared its neighbourhood
" of smaller objects around its orbit. Under this new definition, Pluto and the other trans-Neptunian objects do not qualify as planets.

Portal:Outer space/Selected article/22

Galileo spacecraft image of Io. The dark spot just left of center is the erupting volcano Prometheus. Whitish plains on either side of it are coated with volcanically emplaced sulfur dioxide frost, while yellower regions are encrusted with a higher proportion of sulfur.

Io is the innermost of the four Galilean moons of the planet Jupiter and, with a diameter of 3,642 kilometres (2,263 mi), the fourth-largest moon in the Solar System. It was named after the mythological character of Io, a priestess of Hera who became one of the lovers of Zeus. With over 400 active volcanoes, Io is the most geologically active object in the Solar System. This extreme geologic activity is the result of tidal heating from friction generated within Io's interior as it is pulled between Jupiter and the other Galilean satellites—Europa, Ganymede and Callisto. Several volcanoes produce plumes of sulfur and sulfur dioxide that climb as high as 500 km (300 mi) above the surface. Io's surface is also dotted with more than 100 mountains that have been uplifted by extensive compression at the base of the moon's silicate crust. Some of these peaks are taller than Earth's Mount Everest. Unlike most satellites in the outer Solar System, which are mostly composed of water-ice, Io is primarily composed of silicate rock surrounding a molten iron or iron sulfide core. Most of Io's surface is characterized by extensive plains coated with sulfur and sulfur dioxide frost. Io's volcanism is responsible for many of the satellite's unique features. Its volcanic plumes and lava flows produce large surface changes and paint the surface in various shades of yellow, red, white, black, and green, largely due to allotropes and compounds of sulfur. Numerous extensive lava flows, several more than 500 km (300 mi) in length, also mark the surface. The materials produced by this volcanism provide material for Io's thin, patchy atmosphere and Jupiter's extensive magnetosphere. Io's volcanic ejecta also produce a large plasma torus around Jupiter.

Portal:Outer space/Selected article/23

Saturn, photographed in July 2008

astronomical symbol (♄) represents the Roman god's sickle. Along with Jupiter, Uranus and Neptune, Saturn is a gas giant. Together, these four planets are sometimes referred to as the Jovian planets, meaning "Jupiter-like". Saturn has a ring system that is divided into nine continuous and three discontinuous main rings (arcs), consisting mostly of ice particles with a smaller amount of rocky debris and dust. Sixty-two known moons orbit the planet; fifty-three are officially named. This does not include the hundreds of "moonlets" within the rings. Titan, Saturn's largest and the Solar System's second largest moon (after Jupiter's Ganymede), is larger than the planet Mercury
and is the only moon in the Solar System to retain a significant atmosphere.

Portal:Outer space/Selected article/24

Ganymede, as from the Galileo spacecraft in 1996

km below Ganymede's surface. Ganymede is the only satellite in the Solar System known to possess a magnetosphere, likely created through convection within the liquid iron core. The satellite has a thin oxygen atmosphere that includes O, O2, and possibly O3. Ganymede's discovery is credited to Galileo Galilei, who observed it in 1610. The satellite's name was soon suggested by astronomer Simon Marius, for the mythological Ganymede, cupbearer of the Greek gods and Zeus's
beloved.

Portal:Outer space/Selected article/25

Titan, as photographed by the Cassini spacecraft in 2009

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.

Portal:Outer space/Selected article/26

Venus in true-color. The surface is obscured by a thick blanket of clouds.

Venus is the second

inferior planet from Earth, it never appears to venture far from the Sun: its elongation
reaches a maximum of 47.8°. Venus reaches its maximum brightness shortly before sunrise or shortly after sunset, for which reason it has been referred to by ancient cultures as the Morning Star or Evening Star.

Venus is a

visible light. Venus may have possessed oceans in the past, but these would have vaporized as the temperature rose due to a runaway greenhouse effect. The water has most probably photodissociated, and, because of the lack of a planetary magnetic field, the free hydrogen has been swept into interplanetary space by the solar wind
.

Portal:Outer space/Selected article/27

The high-resolution Voyager 2 image of Titania taken on January 24, 1986

endogenic processes. It is covered by numerous impact craters reaching 326 km in diameter, but is less heavily cratered than the surface of Uranus' outermost moon, Oberon. Titania probably underwent an early endogenic resurfacing event that obliterated its older, heavily cratered surface. Like all major moons of Uranus, Titania probably formed from an accretion disk that surrounded the planet just after its formation. As of 2013, the Uranian system has been studied up close only once: by the spacecraft Voyager 2
in January 1986. It took several images of Titania, which allowed mapping of about 40% of the moon’s surface.

Portal:Outer space/Selected article/28

MESSENGER image of Mercury with three visible colors mapped to 1000 nm, 700 nm, and 430 nm wavelengths

closer to the Sun than the Earth
), and at times Mercury can technically be regarded as a very bright object when viewed from Earth; however, its proximity in the sky to the Sun makes it more difficult to see than Venus.

Portal:Outer space/Selected article/29

The Sun photographed by the Atmospheric Imaging Assembly (AIA 304) of NASA's Solar Dynamics Observatory (SDO).

The

spectral type G2V yellow star at the center of the Solar System. The Earth and many other bodies (including other planets, asteroids, meteoroids, comets and dust) orbit the Sun, which accounts for more than 99% of the Solar System's mass. Different latitudes of the Sun rotate at different rates; a point on the equator takes 25 days, while a point at a pole takes 36 days. The resultant torsion upsets the Sun's very strong magnetic field to create an 11-year solar cycle of activity. Heat and light from the Sun have supported almost all life on Earth. Humans use sunlight to grow crops (see photosynthesis) and power solar cells. The Sun is a ball of plasma with a diameter of 1.392 million km (864,950 mi) and a mass of about 2.0×1030 kg, which is somewhat higher than that of an average star. About 74% of its mass is hydrogen, with 25% helium, and the rest made up of trace quantities of heavier elements. The Sun is about 4.6 billion years old, and is about halfway through its main sequence evolution, during which nuclear fusion
reactions in its core fuse hydrogen into helium.

Portal:Outer space/Selected article/30

Triton, as seen from Voyager 2 in 1989.

seventh-largest moon in the Solar System. Because of its retrograde orbit and composition similar to Pluto's, Triton is thought to have been captured from the Kuiper belt. Triton consists of a crust of frozen nitrogen over an icy mantle believed to cover a substantial core of rock and metal. The core makes up two-thirds of its total mass. Triton has a mean density of 2.061 g/cm3 (1.191 oz/cu in) and is composed of approximately 15–35% water ice. Triton is one of the few moons in the Solar System known to be geologically active. As a consequence, its surface is relatively young, with a complex geological history revealed in intricate and mysterious cryovolcanic and tectonic terrains. Part of its crust is dotted with geysers believed to erupt nitrogen
.

Selected article: 31-40

Portal:Outer space/Selected article/31

Mars

The recorded

originated on Mars
has allowed laboratory examination of the chemical conditions on the planet.

Portal:Outer space/Selected article/32

molecular oxygen, as well as by a rather dense ionosphere
.

Portal:Outer space/Selected article/33

A mockup of the Black Arrow in the rocket park at Woomera.

high test peroxide, a concentrated form of hydrogen peroxide. It was retired after only four launches in favor of using American Scout rockets, which the Ministry of Defense
calculated to be cheaper than maintaining the Black Arrow programme.

Portal:Outer space/Selected article/34

Major features of the Solar System (not to scale)

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.

Portal:Outer space/Selected article/35

GRB 970228 as seen by Hubble

light-years from Earth, providing early evidence that GRBs occur well beyond the Milky Way
.

Portal:Outer space/Selected article/36

The 2004 transit of Venus

A

on 5 and 6 June 2012; the next will be 10–11 December 2117. Historically, Venus transits were of great scientific importance as they were used to gain the first realistic estimates of the size of the Solar System. The 2012 transit provided scientists with a number of other research opportunities, particularly in the refinement of techniques to be used in the search for exoplanets
.

Portal:Outer space/Selected article/37

Image of the Trojan asteroids in front of and behind Jupiter

The

main asteroid belt. Like main belt asteroids, Trojans form families. Jupiter Trojans are dark bodies with reddish, featureless spectra. No firm evidence of the presence of water, organic matter or other chemical compounds has been obtained. The Trojans' densities (as measured by studying binaries or rotational lightcurves) vary from 0.8 to 2.5 g·cm−3. Trojans are thought to have been captured into their orbits during the early stages of the Solar System's formation or slightly later, during the migration
of giant planets.

Read more

Portal:Outer space/Selected article/38

Galileo image of 243 Ida. The tiny dot to the right is its moon, Dactyl.

creatures which inhabited Mount Ida in Greek mythology. Data returned from the flyby pointed to S-type asteroids as the source for the ordinary chondrite
meteorites, the most common type found on the Earth's surface.

Portal:Outer space/Selected article/39

An artist's depiction of the extrasolar planet HD 209458 b orbiting its star

A

Haumea and Eris
. No extrasolar dwarf planets have been detected.

Portal:Outer space/Selected article/40

Artist's rendering of the Kuiper Belt and Oort Cloud

The

Centaurs
and Jupiter-family comets.

Nominations

Feel free to add any featured or good articles to the list above. You can also nominate other articles relating to space here.

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