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 1The Oort cloud, one of the most successful theoretical models about the Solar System (from Theoretical astronomy)
Image 2An amateur astrophotography setup with an automated guide system connected to a laptop (from Observational astronomy)
Image 3The Antikythera Mechanism was an analog computer from 150 to 100 BC designed to calculate the positions of astronomical objects. (from History of astronomy)
Image 4The Nebra sky disk, Germany, 1800–1600 BC (from History of astronomy)
Image 5The main platform at La Silla hosts a huge range of telescopes with which astronomers can explore the Universe. (from Observational astronomy)
Image 6Historical accuracy of atomic clocks from NIST. (from Theoretical astronomy)
Image 7Calendrical functions of the Berlin Gold Hat c. 1000 BC (from History of astronomy)
Image 8The 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 9An 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 10"El Caracol" observatory temple at Chichen Itza, Mexico (from History of astronomy)
Image 11Artist 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 12The 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 13Sunset at the equinox from the prehistoric site of Pizzo Vento at Fondachelli Fantina, Sicily (from History of astronomy)
Image 14Arabic astrolabe from 1079 to 1080 AD (from History of astronomy)
Image 15Sir Patrick Moore was one of the world's leading popularisers of astronomy. (from Amateur astronomy)
Image 16Amateur astronomer recording observations of the sun. (from Amateur astronomy)
Image 17Map 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 18The Crab Nebula as seen in various wavelengths (from Observational astronomy)
Image 199th-century diagram of the positions of the seven planets on 18 March 816, from the Leiden Aratea (from History of astronomy)
Image 20An assembly in Estonia to observe meteors (from Observational astronomy)
Image 21Segment 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 22Mayall telescope at Kitt Peak National Observatory (from Observational astronomy)
$Image 2350 cm refracting telescope at Nice Observatory (from Observational astronomy)$

Image 2350 cm refracting telescope at Nice Observatory (from Observational astronomy)
Image 24Portrait 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 25Places like Paranal Observatory offer crystal clear skies for observing astronomical objects with or without instruments. (from Amateur astronomy)
Image 26An 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 27Ultra HD photography taken at La Silla Observatory (from Observational astronomy)
Image 28Overview of types of observational astronomy by observed wavelengths and their observability. (from Observational astronomy)
Image 29Historical Jantar Mantar observatory in Jaipur, India (from History of astronomy)
Image 30Southern Hemisphere (from History of astronomy)
Image 31The Hubble Space Telescope (from History of astronomy)
Image 32History 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 33Amateur astronomy groups are often involved in outreach to introduce astronomy to the general public (from Amateur astronomy)
Image 34ALMA is the world's most powerful telescope for studying the Universe at submillimeter and millimeter wavelengths. (from Observational astronomy)
Image 35A voting session is conducted in 2006 International Astronomical Union's general assembly for determining a new definition of a planet (from Astronomer)
Image 36One 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 37Babylonian tablet in the British Museum recording Halley's Comet in 164 BC (from History of astronomy)
Image 38Comparison of CMB (Cosmic microwave background) results from satellites COBE, WMAP and Planck documenting a progress in 1989–2013 (from History of astronomy)

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

General relativity, also known as the general theory of relativity, and as Einstein's theory of gravity, is the geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of gravitation in modern physics. General relativity generalizes special relativity and refines Newton's law of universal gravitation, providing a unified description of gravity as a geometric property of space and time, or four-dimensional spacetime. In particular, the curvature of spacetime is directly related to the energy and momentum of whatever present matter and radiation. The relation is specified by the Einstein field equations, a system of second-order partial differential equations.

Newton's law of universal gravitation, which describes classical gravity, can be seen as a prediction of general relativity for the almost flat spacetime geometry around stationary mass distributions. Some predictions of general relativity, however, are beyond Newton's law of universal gravitation in classical physics. These predictions concern the passage of time, the geometry of space, the motion of bodies in free fall, and the propagation of light, and include gravitational time dilation, gravitational lensing, the gravitational redshift of light, the Shapiro time delay and singularities/black holes. So far, all tests of general relativity have been shown to be in agreement with the theory. The time-dependent solutions of general relativity enable us to talk about the history of the universe and have provided the modern framework for cosmology, thus leading to the discovery of the Big Bang and cosmic microwave background radiation. Despite the introduction of a number of alternative theories, general relativity continues to be the simplest theory consistent with experimental data. (Full article...)

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Did you know - show different entries

... that Jerry Nelson is the principal designer and project scientist for the Keck telescopes?
... that five supernovae have been found in the Messier 100 spiral galaxy?
... that the Antlia Dwarf galaxy may have distorted the shape of its neighbour NGC 3109 one billion years ago?
... that AP Columbae, the closest young star known, formed after the dinosaurs became extinct?
... that a planet was discovered around the star MOA-2009-BLG-387L after it eclipsed a background star, refracting the star's light in a process called gravitational microlensing?

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... that the Passive Seismic Experiment Package recorded one of the first instances of humans littering on another planetary body?
... 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 King Gizzard & the Lizard Wizard's "cli-fi" thrash metal album addresses a mix of current ecological threats and attempts to find another planet to live on?
... that Susan Murabana created Africa's first permanent planetarium?
... that in many works of fiction, the asteroid belt is the remnants of a destroyed planet?
... 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)?

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WikiProjects

WikiProject Astronomy	WikiProject Solar System



WikiProject Cosmology	WikiProject Spaceflight

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Credit: NASA Earth Observatory / STEREO Science Center

A coronal mass ejection (CME) is a significant release of plasma and accompanying magnetic field from the solar corona. They often follow solar flares and are normally present during a solar prominence eruption. Coronal mass ejections release large quantities of matter and electromagnetic radiation into space above the Sun's surface, either near the corona, or farther into the planetary system, or beyond (interplanetary CME).

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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