Portal:Astronomy

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The Astronomy Portal

Introduction

Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest include planets, moons, stars, nebulae, galaxies, meteoroids, asteroids, and comets. Relevant phenomena include supernova explosions, gamma ray bursts, quasars, blazars, pulsars, and cosmic microwave background radiation. More generally, astronomy studies everything that originates beyond Earth's atmosphere. Cosmology is a branch of astronomy that studies the universe as a whole.

Astronomy is one of the oldest natural sciences. The early civilizations in recorded history made methodical observations of the night sky. These include the Egyptians, Babylonians, Greeks, Indians, Chinese, Maya, and many ancient indigenous peoples of the Americas. In the past, astronomy included disciplines as diverse as astrometry, celestial navigation, observational astronomy, and the making of calendars.

Professional astronomy is split into observational and theoretical branches. Observational astronomy is focused on acquiring data from observations of astronomical objects. This data is then analyzed using basic principles of physics. Theoretical astronomy is oriented toward the development of computer or analytical models to describe astronomical objects and phenomena. These two fields complement each other. Theoretical astronomy seeks to explain observational results and observations are used to confirm theoretical results.

Astronomy is one of the few sciences in which amateurs play an active role. This is especially true for the discovery and observation of transient events. Amateur astronomers have helped with many important discoveries, such as finding new comets. (Full article...)

General images - load new batch

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

Image 1Places like Paranal Observatory offer crystal clear skies for observing astronomical objects with or without instruments. (from Amateur astronomy)
Image 2Calendrical functions of the Berlin Gold Hat c. 1000 BC (from History of astronomy)
Image 3History of the Universe – gravitational waves are hypothesized to arise from cosmic inflation, a rapidly accelerated expansion just after the Big Bang (from Physical cosmology)
Image 4An assembly in Estonia to observe meteors (from Observational astronomy)
Image 5"El Caracol" observatory temple at Chichen Itza, Mexico (from History of astronomy)
Image 6ALMA is the world's most powerful telescope for studying the Universe at submillimeter and millimeter wavelengths. (from Observational astronomy)
Image 7Amateur astronomy groups are often involved in outreach to introduce astronomy to the general public (from Amateur astronomy)
Image 8Ultra HD photography taken at La Silla Observatory (from Observational astronomy)
Image 9Southern Hemisphere (from History of astronomy)
Image 10An example of a gravitational lens found in the DESI Legacy Surveys data. There are four sets of lensed images in DESI-090.9854-35.9683, corresponding to four distinct background galaxies—from the outermost giant red arc to the innermost bright blue arc, arranged in four concentric circles. All of them are gravitationally warped—or lensed—by the orange galaxy at the very center. Dark matter is expected to produce gravitational lensing also. (from Physical cosmology)
Image 11One of the Oldest Observatories in South America is the Quito Astronomical Observatory, founded in 1873 and located 12 minutes south of the Equator in Quito, Ecuador. The Quito Astronomical Observatory is the National Observatory of Ecuador and is located in the Historic Center of Quito and is managed by the National Polytechnic School. (from Observational astronomy)
Image 12Portrait of the Flemish astronomer Ferdinand Verbiest who became head of the Mathematical Board and director of the Observatory of the Chinese emperor in 1669 (from Astronomer)
Image 13The Antikythera Mechanism was an analog computer from 150 to 100 BC designed to calculate the positions of astronomical objects. (from History of astronomy)
Image 14Historical Jantar Mantar observatory in Jaipur, India (from History of astronomy)
Image 15A voting session is conducted in 2006 International Astronomical Union's general assembly for determining a new definition of a planet (from Astronomer)
Image 16Sir Patrick Moore was one of the world's leading popularisers of astronomy. (from Amateur astronomy)
Image 17The Hubble Space Telescope (from History of astronomy)
Image 18An amateur astrophotography setup with an automated guide system connected to a laptop (from Observational astronomy)
Image 19The Crab Nebula as seen in various wavelengths (from Observational astronomy)
Image 20Overview of types of observational astronomy by observed wavelengths and their observability. (from Observational astronomy)
Image 21Comparison of CMB (Cosmic microwave background) results from satellites COBE, WMAP and Planck documenting a progress in 1989–2013 (from History of astronomy)
Image 22Artist conception of the Big Bang cosmological model, the most widely accepted out of all in physical cosmology (neither time nor size to scale) (from Physical cosmology)
Image 23Amateur astronomer recording observations of the sun. (from Amateur astronomy)
Image 24Sunset at the equinox from the prehistoric site of Pizzo Vento at Fondachelli Fantina, Sicily (from History of astronomy)
Image 25The inflationary theory as an augmentation to the Big Bang theory was first proposed by Alan Guth of MIT. Inflation solves the 'horizon problem' by making the early universe much more compact than was assumed in the standard model. Given such smaller size, causal contact (i.e., thermal communication) would have been possible among all regions of the early universe. The image was an adaptation from various generic charts depicting the growth of the size of the observable universe, for both the standard model and inflationary model respectively, of the Big Bang theory. (from Physical cosmology)
Image 26The main platform at La Silla hosts a huge range of telescopes with which astronomers can explore the Universe. (from Observational astronomy)
Image 27Map of the Milky Way Galaxy, with the constellations that cross the galactic plane in each direction and the known prominent components annotated including main arms, spurs, bar, nucleus/bulge, notable nebulae and globular clusters (from History of astronomy)
Image 289th-century diagram of the positions of the seven planets on 18 March 816, from the Leiden Aratea (from History of astronomy)
Image 29Segment of the astronomical ceiling of Senenmut's Tomb (circa 1479–1458 BC), depicting constellations, protective deities, and twenty-four segmented wheels for the hours of the day and the months of the year (from History of astronomy)
Image 30Historical accuracy of atomic clocks from NIST. (from Theoretical astronomy)
Image 31Arabic astrolabe from 1079 to 1080 AD (from History of astronomy)
Image 32The Nebra sky disk, Germany, 1800–1600 BC (from History of astronomy)
Image 33Babylonian tablet in the British Museum recording Halley's Comet in 164 BC (from History of astronomy)
$Image 3450 cm refracting telescope at Nice Observatory (from Observational astronomy)$

Image 3450 cm refracting telescope at Nice Observatory (from Observational astronomy)
Image 35The Oort cloud, one of the most successful theoretical models about the Solar System (from Theoretical astronomy)
Image 36The Northern Hemisphere page from Johann Bayer's 1661 edition of Uranometria - the first atlas to have star charts covering the entire celestial sphere (from History of astronomy)
Image 37An image of the Cat's Paw Nebula created combining the work of professional and amateur astronomers. The image is the combination of the 2.2-metre MPG/ESO telescope of the La Silla Observatory in Chile and a 0.4-meter amateur telescope. (from Amateur astronomy)
Image 38Mayall telescope at Kitt Peak National Observatory (from Observational astronomy)

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This is a Featured article, which represents some of the best content on English Wikipedia.

Callisto imaged in approximately true color by the Voyager 2 spacecraft, July 1979

Callisto (/kəˈlɪstoʊ/ kə-LIST-oh), or Jupiter IV, is the second-largest moon of Jupiter, after Ganymede. In the Solar System it is the third-largest moon after Ganymede and Saturn's largest moon Titan, and nearly as large as the smallest planet Mercury. Callisto is, with a diameter of 4,821 km, roughly a third larger than Earth's Moon and orbits Jupiter on average at a distance of 1,883,000 km, which is about six times further out than the Moon orbiting Earth. It is the outermost of the four large Galilean moons of Jupiter, which were discovered in 1610 with one of the first telescopes, being visible from Earth with common binoculars.

The surface of Callisto is the oldest and most heavily cratered in the Solar System. Its surface is completely covered with impact craters. It does not show any signatures of subsurface processes such as plate tectonics or volcanism, with no signs that geological activity in general has ever occurred, and is thought to have evolved predominantly under the influence of impacts. Prominent surface features include multi-ring structures, variously shaped impact craters, and chains of craters (catenae) and associated scarps, ridges and deposits. At a small scale, the surface is varied and made up of small, sparkly frost deposits at the tips of high spots, surrounded by a low-lying, smooth blanket of dark material. This is thought to result from the sublimation-driven degradation of small landforms, which is supported by the general deficit of small impact craters and the presence of numerous small knobs, considered to be their remnants. The absolute ages of the landforms are not known. Callisto is composed of approximately equal amounts of rock and ice, with a density of about 1.83 g/cm³, the lowest density and surface gravity of Jupiter's major moons. Compounds detected spectroscopically on the surface include water ice, carbon dioxide, silicates and organic compounds. Investigation by the Galileo spacecraft revealed that Callisto may have a small silicate core and possibly a subsurface ocean of liquid water at depths greater than 100 km. (Full article...)

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Did you know - show different entries

... that the asteroid 2011 XC2 missed the Earth by less than 1 lunar distance on 3 December 2011?
... that the mass-luminosity relation, first derived by Arthur Eddington in 1924, helps astronomers find the distances to binary star systems?
... that the planetary nebula Abell 39 is unusually spherical, yet its central star is offset from the center?
... that data from Mariner 10 led to the discovery of Mercury's magnetic field in 1974?
... that the Toronto Magnetic Observatory had to be moved as the University of Toronto's electric lighting was interfering with observations?

More Did you know facts

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... that the star TRAPPIST-1 has seven planets, several of which may have temperatures that would allow the existence of liquid water (artist's impression depicted)?
... that Kim Ye-ji's performance in the 10 meter air pistol at the 2024 Summer Olympics led her to be dubbed the "coolest person on the planet"?
... that the active galaxy 3C 120 was given the variable-star designation BW Tauri because of its variability in the visible spectrum?
... that in many works of fiction, the asteroid belt is the remnants of a destroyed planet?
... that Susan Murabana created Africa's first permanent planetarium?
... that the Passive Seismic Experiment Package recorded one of the first instances of humans littering on another planetary body?

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WikiProjects

WikiProject Astronomy	WikiProject Solar System



WikiProject Cosmology	WikiProject Spaceflight

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Credit: NASA

T Tauri is a variable star in the constellation Taurus, the prototype of the T Tauri stars. It was discovered in October 1852 by John Russell Hind.

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Astronomy News

15 July 2024 – Mare Tranquillitatis pit: In the journal Nature Astronomy, American and Italian scientists announce the discovery of a lunar cave, approximately 250 miles (400 km) from the landing site of Apollo 11. (AP) (Nature Astronomy)

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November anniversaries

2 November 1917 – The Hooker Telescope at Mount Wilson Observatory, the largest telescope in the world from 1917 until 1948, sees first light
14 November 1971 – Unmanned probe Mariner 9 arrives at Mars and becomes the first spacecraft to orbit around another planet
18 November 1989 – Explorer 66, a satellite designed to study cosmic microwave background radiation and supply evidence in support of the Big Bang theory, is launched
20 November 1998 – Zarya, the first module of the International Space Station, is launched
28 November 1967 – PSR B1919+21 becomes the first pulsar to be observed when it is discovered by Jocelyn Bell Burnell and Antony Hewish