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Astronomy portal

Percival Lowell observing Venus from the Lowell Observatory in 1914.jpg

Astronomy (from Ancient Greek ἄστρον (astron), meaning "star", and νόμος (nomos), meaning "law, culture") is the study of the evolution and physical and chemical properties of celestial objects. Astronomical observations are not only relevant for astronomy as such, but provide essential information for the verification of fundamental theories in physics, such as the general relativity theory. Complementary to observational astronomy, theoretical astrophysics seeks to explain astronomical phenomena.

Selected article

Ariel as seen by Voyager 2 in 1986. The canyon system Kachina Chasma stretches across the upper part of the image.
Ariel is the brightest and third most massive of the 27 known moons of Uranus. Discovered on 24 October 1851 by William Lassell, it is named for a sky spirit in Alexander Pope's The Rape of the Lock and Shakespeare's The Tempest. Like its parent planet, Ariel orbits on its side, giving it an extreme seasonal cycle. As of 2011, almost all knowledge of Ariel derives from a single flyby of Uranus performed by the spacecraft Voyager 2 in 1986, which managed to image 35% of the moon's surface. There are no plans at present to return to study the moon in more detail.

After Miranda, Ariel is the second-smallest of Uranus's five round satellites, and the second-closest to its planet. Among the smallest of the Solar System's 19 known spherical moons (it ranks 14th among them in diameter), Ariel is composed of roughly equal parts ice and rocky material. Like all of Uranus's moons, Ariel probably formed from an accretion disc that surrounded the planet shortly after its formation, and, like other large moons, it may be differentiated, with an inner core of rock surrounded by a mantle of ice. Ariel has a complex surface comprising extensive cratered terrain cross-cut by a system of scarps, canyons and ridges. The surface shows signs of more recent geological activity than other Uranian moons, most likely due to tidal heating.

Did you know

40-foot Telescope

... that William Herschel's 40-foot telescope (pictured) was the largest telescope in the world for 50 years?

...that Zeeman-Doppler imaging is a technique used to map the surface magnetic field of stars?

...that Astronomische Nachrichten, founded by H. C. Schumacher in 1821, is the world's oldest existent astronomical journal?

...that the Stingray Nebula, thought to have formed around 1987, is the youngest known planetary nebula?

...that the Mark II radio telescope built in 1964 at Jodrell Bank Observatory, UK was the first ever telescope to be controlled by a digital computer?

...that Comet Shoemaker-Levy 9 passed within Jupiter's Roche limit in 1992, causing it to break up into smaller pieces two years before it collided with the planet?

...that the Kaidun meteorite fell on March 12, 1980 on a Soviet military base in Yemen and may be from Phobos?


Astronomy : Archaeoastronomy - Astrophysics - Calendars - Catalogues - Celestial coordinate system - Celestial mechanics - Cosmology - Images - Large-scale structure of the cosmos - Observatories - Planetary science - Telescopes

Biographies : Astronomers - Other people

Astronomical objects : Lists - Galaxies - Nebulae - Planets - Stars

Spaceflight : Human spaceflight - Satellites - SETI - Spacecraft


Crab Nebula.jpg
Solar system.jpg
WikiProject Astronomy WikiProject Solar System

Io highest resolution true color.jpg
WikiProject Astronomical objects WikiProject Spaceflight

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X-ray astronomy Science Jupiter

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Cassiopeia A

Cassiopeia A (Cas A) is a supernova remnant in the constellation Cassiopeia and the brightest astronomical radio source in the sky, with a flux of 2720 Jy at 1 GHz. The supernova occurred approximately 11,000 light-years (3.4 kpc) away in the Milky Way.

Astronomy News

Wikinews Space portal

  • January 31: Main belt asteroid No. 274301 named 'Wikipedia'
  • June 17: Study says young stars 'shoot water bullets'
  • January 11: Moon water possibly originated from comets, data shows
  • October 15: Brazilian astronomers propose new model of our galaxy
  • October 1: New planet found in 'Habitable Zone'
  • September 19: Jupiter at its brightest in 47 years
  • August 25: Astronomers discover large exo-solar system
  • August 22: Scientists say the moon is slowly shrinking

March anniversaries

  • 13 March 1781 – William Herschel discovers the planet Uranus.

Things you can do

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  • Copyedit: Roque de los Muchachos Observatory, Europa (moon) More...
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  • Requests: Borde-Vilenkin-Guth Theorem, Antigalaxy, Sunspot index, undefined names in the List of astronomers, More...
  • Stubs: D Ring, Diffraction spike More...
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Astronomy featured article candidates:

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Astronomy articles for which peer review has been requested:

  • Epsilon Eridani ( entry)
  • Jupiter Trojan ( entry)


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These books may be in various stages of development. See also the related Science and Mathematics bookshelves.

  • Astronomy
  • GAT: A Glossary of Astronomical Terms
  • Introduction to Astrophysics
  • General relativity
  • Observing the Sky from 30°S
  • Observing the Sky from 40°N


  • Solar System

Astronomical events

All times UT unless otherwise specified.

4 March, 13:00 Mercury at inferior conjunction
5 March, 23:14 Moon at perigee
9 March, 20:42 Comet PANSTARRS at max brightness
11 March, 19:51 New moon
13 March, 15:00 Gamma Normids peak
19 March, 03:14 Moon at apogee
20 March, 11:02 Earth at northward equinox
20 March, 23:42 Comet Lemmon at max brightness
27 March, 09:27 Full moon
28 March Uranus at conjunction
28 March, 17:06 Venus at superior conjunction
31 March, 04:00 Moon at perigee
31 March, 21:48 Mercury at greatest western elongation

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