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 2The Antikythera Mechanism was an analog computer from 150 to 100 BC designed to calculate the positions of astronomical objects. (from History of astronomy)
Image 3The Oort cloud, one of the most successful theoretical models about the Solar System (from Theoretical astronomy)
Image 4Amateur astronomy groups are often involved in outreach to introduce astronomy to the general public (from Amateur astronomy)
Image 5An 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 6Babylonian tablet in the British Museum recording Halley's Comet in 164 BC (from History of astronomy)
Image 7Southern Hemisphere (from History of astronomy)
Image 8A voting session is conducted in 2006 International Astronomical Union's general assembly for determining a new definition of a planet (from Astronomer)
Image 9The 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 10Amateur astronomer recording observations of the sun. (from Amateur astronomy)
Image 11Portrait 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 12Historical accuracy of atomic clocks from NIST. (from Theoretical astronomy)
Image 13The 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 14An amateur astrophotography setup with an automated guide system connected to a laptop (from Observational astronomy)
Image 15Calendrical functions of the Berlin Gold Hat c. 1000 BC (from History of astronomy)
Image 16Segment 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 17Artist 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 18Arabic astrolabe from 1079 to 1080 AD (from History of astronomy)
Image 19"El Caracol" observatory temple at Chichen Itza, Mexico (from History of astronomy)
Image 20An assembly in Estonia to observe meteors (from Observational astronomy)
$Image 2150 cm refracting telescope at Nice Observatory (from Observational astronomy)$

Image 2150 cm refracting telescope at Nice Observatory (from Observational astronomy)
Image 22Ultra HD photography taken at La Silla Observatory (from Observational astronomy)
Image 23Comparison of CMB (Cosmic microwave background) results from satellites COBE, WMAP and Planck documenting a progress in 1989–2013 (from History of astronomy)
Image 24ALMA is the world's most powerful telescope for studying the Universe at submillimeter and millimeter wavelengths. (from Observational astronomy)
Image 25History 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 26Historical Jantar Mantar observatory in Jaipur, India (from History of astronomy)
Image 27Sir Patrick Moore was one of the world's leading popularisers of astronomy. (from Amateur astronomy)
Image 28The main platform at La Silla hosts a huge range of telescopes with which astronomers can explore the Universe. (from Observational astronomy)
Image 29Mayall telescope at Kitt Peak National Observatory (from Observational astronomy)
Image 30Overview of types of observational astronomy by observed wavelengths and their observability. (from Observational astronomy)
Image 31An 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 32The Crab Nebula as seen in various wavelengths (from Observational astronomy)
Image 339th-century diagram of the positions of the seven planets on 18 March 816, from the Leiden Aratea (from History of astronomy)
Image 34One 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 35The Hubble Space Telescope (from History of astronomy)
Image 36Sunset at the equinox from the prehistoric site of Pizzo Vento at Fondachelli Fantina, Sicily (from History of astronomy)
Image 37The Nebra sky disk, Germany, 1800–1600 BC (from History of astronomy)
Image 38Map 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)

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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 British mathematician Margaret Meyer was the first woman to be elected to the Royal Astronomical Society?
... that the star cluster Messier 103 can be observed with the use of binoculars?
... that NASA has plans to tug an asteroid to the Moon?
... that MOA-2009-BLG-387Lb is the eleventh planet discovered using the gravitational microlensing phenomenon?
... that the first Dutch satellite, the Astronomical Netherlands Satellite, had the Main Belt asteroid 9996 ANS named after it?

More Did you know facts

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... that in many works of fiction, the asteroid belt is the remnants of a destroyed planet?
... that the Passive Seismic Experiment Package recorded one of the first instances of humans littering on another planetary body?
... that the active galaxy 3C 120 was given the variable-star designation BW Tauri because of its variability in the visible spectrum?
... 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 Susan Murabana created Africa's first permanent planetarium?
... that examples of artificial planets in science fiction include Riverworld, the Well World, and the Death Star?

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WikiProjects

WikiProject Astronomy	WikiProject Solar System



WikiProject Cosmology	WikiProject Spaceflight

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Credit: NASA / ESA / Andrew Fruchter (STScI) / ERO team (STScI + ST-ECF)

The Eskimo Nebula (NGC 2392), also known as the Clown-faced Nebula, Lion Nebula or Caldwell 39, is a bipolar planetary nebula (PN) discovered by astronomer William Herschel in 1787. Image of NGC 2392, the Eskimo Nebula is by HST in 1999.

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Astronomy News

21 November 2024 –: The European Southern Observatory announces that its astronomers in Chile capture the first close-up image of a star outside the Milky Way. (The New York Times)
20 November 2024 – Discoveries of exoplanets: In a study published by the Nature journal, astronomers announce the discovery of IRAS 04125+2902 b, a newborn exoplanet. The discovery was made by Madyson Barber, a graduate student at the University of North Carolina at Chapel Hill. (Nature) (ABC 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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January anniversaries

1 January 1925 – Astronomer Edwin Hubble formally presents his discovery of galaxies outside the Milky Way at a meeting of the American Astronomical Society
1 January 1952 – The Kyiv Planetarium opens in Kyiv, Ukraine
3 January 1888 – The 91-centimeter refracting telescope at Lick Observatory, the world's largest telescope from 1888 to 1897, sees its first light
3 January 1999 – The Mars Polar Lander is launched by NASA to study the soil and climate of Planum Australe, a region near the south pole on Mars
4 January 2004 – The Mars rover Spirit lands, three weeks ahead of twin rover Opportunity, and begins exploring the Red Planet
14 January 2005 – The probe Huygens lands on Titan, a moon of Saturn, in the first successful landing in the outer Solar System
26 January 1949 – Hale Telescope, which introduced several innovations to telescope construction and was the world's largest telescope for nearly 30 years, has its first light

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Space-related Portals

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Astronomical events

All times UT unless otherwise specified.

3 January, 15:24	Quadrantids peak
4 January, 07:59	Earth at perihelion
4 January, 17:24	Moon occults Saturn
5 January, 15:17	Moon occults Neptune
7 January, 23:35	Moon at perigee
10 January, 03:59	Venus at greatest eastern elongation
13 January	Comet ATLAS at maximum brightness
13 January, 22:27	Full moon
14 January, 03:43	Moon occults Mars
16 January, 01:17	Mars at opposition
21 January, 04:55	Moon at apogee
29 January, 12:36	New moon