Portal:Astronomy

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 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 the 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.

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...)

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

$Image 150 cm refracting telescope at Nice Observatory (from Observational astronomy)$
Image 150 cm refracting telescope at Nice Observatory (from Observational astronomy)
Image 2ALMA is the world's most powerful telescope for studying the Universe at submillimeter and millimeter wavelengths. (from Observational astronomy)
Image 3An amateur astrophotography setup with an automated guide system connected to a laptop (from Observational astronomy)
Image 4Sir Patrick Moore was one of the world's leading popularisers of astronomy. (from Amateur astronomy)
Image 5Sunset at the equinox from the prehistoric site of Pizzo Vento at Fondachelli Fantina, Sicily (from History of astronomy)
Image 6A voting session is conducted in 2006 International Astronomical Union's general assembly for determining a new definition of a planet (from Astronomer)
Image 7Babylonian tablet in the British Museum recording Halley's Comet in 164 BC (from History of astronomy)
Image 8This image contains two side-by-side pictures of the night sky comparing the effects of light pollution on the visibility of celestial objects. (from Amateur astronomy)
Image 9The Crab Nebula as seen in various wavelengths (from Observational astronomy)
Image 10Amateur astronomy groups are often involved in outreach to introduce astronomy to the general public (from Amateur astronomy)
Image 11Mayall telescope at Kitt Peak National Observatory (from Observational astronomy)
Image 12The main platform at La Silla hosts a huge range of telescopes with which astronomers can explore the Universe. (from Observational astronomy)
Image 13An 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 14A map of the southern celestial hemisphere, also by Bayer (from History of astronomy)
Image 15Megaliths from Nabta Playa, constructed by Neolithic populations, located in Aswan, Upper Egypt. Excavations of the megalith structures were completed in 2008. (from History of astronomy)
Image 16One 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 17The 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 18Places like Paranal Observatory offer crystal clear skies for observing astronomical objects with or without instruments. (from Amateur astronomy)
Image 19Segment 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 20Historical Jantar Mantar observatory in Jaipur, India (from History of astronomy)
Image 21Overview of types of observational astronomy by observed wavelengths and their observability. (from Observational astronomy)
Image 22Portrait of William Herschel, 1785 (from History of astronomy)
Image 23The Hubble Space Telescope (from History of astronomy)
Image 24A map of the northern celestial hemisphere from Johann Bayer's 1661 edition of Uranometria, the first atlas to feature star charts covering the entire celestial sphere (from History of astronomy)
Image 25An 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 269th-century diagram of the positions of the seven planets on 18 March 816, from the Leiden Aratea (from History of 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 28History 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 29An assembly in Estonia to observe meteors (from Observational astronomy)
Image 30Arabic astrolabe from 1079 to 1080 AD (from History of astronomy)
Image 31Comparison of CMB (Cosmic microwave background) results from satellites COBE, WMAP and Planck documenting a progress in 1989–2013 (from History of astronomy)
Image 32Artist 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 33Amateur astronomer recording observations of the sun. (from Amateur astronomy)
Image 34Calendrical functions of the Berlin Gold Hat c. 1000 BC (from History of astronomy)
Image 35Ultra HD photography taken at La Silla Observatory (from Observational astronomy)
Image 36The Nebra sky disk, Germany, 1800–1600 BC (from History of astronomy)
Image 37"El Caracol" observatory temple at Chichen Itza, Mexico (from History of astronomy)

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The Sun, viewed through a clear solar filter

The Sun is the star located at the centre of the Solar System. It is a massive sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light and infrared radiation with 10% at ultraviolet energies. It is the main source of energy for life on Earth. The Sun has been an object of veneration in many cultures and a central subject of astronomical research since antiquity.

The Sun orbits the Galactic Center at a distance of 24,000 to 28,000 light-years. Its mean distance from Earth is about 1.496×10⁸ kilometres or about 8 light-minutes. The distance between the Sun and the Earth was used to define a unit of length called the astronomical unit (au), now defined to be 149.5978707×10⁶ kilometres. It is the largest and most massive object in the Solar System; its diameter is about 1,391,400 km (864,600 mi), around 109 times that of Earth's. The Sun's mass is around 330,000 times that of Earth's, making up about 99.86% of the total mass of the Solar System. The mass of the Sun's surface layer, its photosphere, consists mostly of hydrogen (~73%) and helium (~25%), with much smaller quantities of heavier elements, including oxygen, carbon, neon, and iron. (Full article...)

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... that light echoes appear to exceed the speed of light due to simple interstellar illusions?
... that the Leo IV dwarf galaxy is one of the smallest satellites of the Milky Way?
... that a hydrocarbon lake on Saturn's moon Titan and an active volcano on Jupiter's moon Io are among the Solar System features named after deities from Māori mythology?
... that the Local Void is an empty region of space, devoid of matter, lying adjacent to our own Milky Way galaxy?
... that William Herschel's 40-foot telescope was the largest telescope in the world for 50 years?

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... that some exoplanets are evaporating catastrophically?
... that the majority of extrasolar planets in fiction are inhabited by native species?
... that Na drugą planetę, published in 1895 as one of the earliest Polish science-fiction novels, was later criticized by communist-era censors for its perceived "adoration for America"?
... that a group of K-pop fans performed a dance with the goal of convincing a company to commit to 100% renewable energy?
... that in many works of fiction, the asteroid belt is the remnants of a destroyed planet?
... that two competing hypotheses seek to explain the unusual orbit of the exoplanet Nu Octantis Ab?

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WikiProjects

More information WikiProject Astronomy, WikiProject Solar System ...

WikiProject Astronomy	WikiProject Solar System



WikiProject Cosmology	WikiProject Spaceflight

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Credit: NRAO / L. Birzan and team (Ohio University)

A galaxy cluster, or cluster of galaxies, is a structure that consists of anywhere from hundreds to thousands of galaxies that are bound together by gravity with typical masses ranging from 10¹⁴–10¹⁵ solar masses. MS 0735.6+7421 is a galaxy cluster located in the constellation Camelopardalis, approximately 2.6 billion light-years away. A composite image from Hubble and Chandra.

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Astronomy News

3 March 2026 –: Astronomers announce the discovery 1,900 light-years from Earth of TIC 120362137, the tightest known quadruple star system, using data from NASA's Transiting Exoplanet Survey Satellite. (Space.com)
10 December 2025 – Brazil–China relations: Brazil and China begin constructing a joint laboratory for radio astronomic technology with the Federal University of Campina Grande and the Federal University of Paraíba to support space research as both countries work on the BINGO radio telescope. (Reuters)

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April anniversaries

2 April 1968 – The epic science fiction film, 2001: A Space Odyssey is released
3 April 2014 – NASA announces that the Cassini orbiter has found evidence of an underground body of water on Enceladus, a moon of Saturn
7 April 2001 – Mars Odyssey orbiter is launched to map and search for water on Mars
12 April 1961 – Cosmonaut Yuri Gagarin becomes the first human to enter outer space when he is launched into orbital flight in Vostok 1
19 April 1971 – The first space station, Salyut 1, is launched into orbit
24 April 1990 – The Hubble Space Telescope, a powerful research tool and public relations boon for astronomy, is launched into orbit

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Astronomical events

All times UT unless otherwise specified.

2 April, 02:12	Full moon
3 April, 22:59	Mercury at greatest western elongation
7 April, 08:32	Moon at apogee
17 April, 11:52	New moon
19 April, 06:57	Moon at perigee
22 April, 19:02	Lyrids peak
25 April	Mars southern solstice