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 1Amateur astronomer recording observations of the sun. (from Amateur astronomy)
Image 29th-century diagram of the positions of the seven planets on 18 March 816, from the Leiden Aratea (from History of astronomy)
Image 3An 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 4Segment 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 5Overview of types of observational astronomy by observed wavelengths and their observability. (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 8Sunset at the equinox from the prehistoric site of Pizzo Vento at Fondachelli Fantina, Sicily (from History of astronomy)
Image 9Arabic astrolabe from 1079 to 1080 AD (from History of astronomy)
Image 10The main platform at La Silla hosts a huge range of telescopes with which astronomers can explore the Universe. (from Observational astronomy)
Image 11An 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 12The Oort cloud, one of the most successful theoretical models about the Solar System (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 14Portrait 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 15The Antikythera Mechanism was an analog computer from 150 to 100 BC designed to calculate the positions of astronomical objects. (from History of astronomy)
Image 16The 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 17History 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 18Artist 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 19An amateur astrophotography setup with an automated guide system connected to a laptop (from Observational astronomy)
Image 20Historical Jantar Mantar observatory in Jaipur, India (from History of astronomy)
Image 21Map 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 22A voting session is conducted in 2006 International Astronomical Union's general assembly for determining a new definition of a planet (from Astronomer)
Image 23Places like Paranal Observatory offer crystal clear skies for observing astronomical objects with or without instruments. (from Amateur astronomy)
Image 24Ultra HD photography taken at La Silla Observatory (from Observational astronomy)
Image 25Amateur astronomy groups are often involved in outreach to introduce astronomy to the general public (from Amateur astronomy)
Image 26The Nebra sky disk, Germany, 1800–1600 BC (from History of astronomy)
Image 27Southern Hemisphere (from History of astronomy)
Image 28Babylonian tablet in the British Museum recording Halley's Comet in 164 BC (from History of astronomy)
Image 29"El Caracol" observatory temple at Chichen Itza, Mexico (from History of astronomy)
Image 30The Hubble Space Telescope (from History of astronomy)
Image 31Sir Patrick Moore was one of the world's leading popularisers of astronomy. (from Amateur astronomy)
$Image 3250 cm refracting telescope at Nice Observatory (from Observational astronomy)$

Image 3250 cm refracting telescope at Nice Observatory (from Observational astronomy)
Image 33ALMA is the world's most powerful telescope for studying the Universe at submillimeter and millimeter wavelengths. (from Observational astronomy)
Image 34Mayall telescope at Kitt Peak National Observatory (from Observational astronomy)
Image 35One 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 36The Crab Nebula as seen in various wavelengths (from Observational astronomy)
Image 37An assembly in Estonia to observe meteors (from Observational 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.

Absorption lines in the visible spectrum of a supercluster of distant galaxies (right), as compared to absorption lines in the visible spectrum of the Sun (left). Arrows indicate redshift. Wavelength increases up towards the red and beyond (frequency decreases).

In physics, a redshift is an increase in the wavelength, and corresponding decrease in the frequency and photon energy, of electromagnetic radiation (such as light). The opposite change, a decrease in wavelength and increase in frequency and energy, is known as a blueshift, or negative redshift. The terms derive from the colours red and blue which form the extremes of the visible light spectrum. The main causes of electromagnetic redshift in astronomy and cosmology are the relative motions of radiation sources, which give rise to the relativistic Doppler effect, and gravitational potentials, which gravitationally redshift escaping radiation. All sufficiently distant light sources show cosmological redshift corresponding to recession speeds proportional to their distances from Earth, a fact known as Hubble's law that implies the universe is expanding.

All redshifts can be understood under the umbrella of frame transformation laws. Gravitational waves, which also travel at the speed of light, are subject to the same redshift phenomena. The value of a redshift is often denoted by the letter $z$ , corresponding to the fractional change in wavelength (positive for redshifts, negative for blueshifts), and by the wavelength ratio $1 + z$ (which is greater than 1 for redshifts and less than 1 for blueshifts). (Full article...)

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Did you know - show different entries

... that the new Astronomy and Astrophysics Decadal Survey lays out a roadmap for exploring extrasolar planetary systems and investigating the nature of dark energy?
... that the constellation of Microscopium can't be seen from locations affected by light pollution?
... that the atmosphere of Triton produces a surface pressure only 1/70,000th of that on Earth?
... that in May 2008, an amateur astronomer discovered an unusual supernova-like object in the galaxy NGC 300?
... that the "Beethoven Burst" was a powerful gamma-ray burst which occurred on the birthday of Ludwig van Beethoven?

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... that Michael Collins has been called "one of the best clarinettists walking the planet" by The Times?
... that in early depictions of Uranus in fiction, the planet was portrayed as solid
... that fictional depictions of Jupiter have portrayed human habitation on the planet and its moons both by altering the environment to suit humans and altering humans to be suited to the environment?
... that examples of artificial planets in science fiction include Riverworld, the Well World, and the Death Star?
... 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: Jschulman555

Medusa Nebula is a planetary nebula in the constellation of Gemini. It is also known as Abell 21 and Sharpless 2-274. It was originally discovered in 1955 by University of California, Los Angeles astronomer George O. Abell. Image of Medusa nebula from 24 inch telescope on Mt. Lemmon, AZ.

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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