Portal:Astronomy

The Astronomy Portal

Topics: Culture; Geography; Health; History; Mathematics; Nature; People; Philosophy; Religion; Society; Technology

A man sitting on a chair mounted to a moving platform, staring through a large telescope.

Astronomy is a natural science that is the study of celestial objects (such as moons, planets, stars, nebulae, and galaxies), the physics, chemistry, and evolution of such objects, and phenomena that originate outside the atmosphere of Earth, including supernovae explosions, gamma ray bursts, and cosmic background radiation.

Astronomy is one of the oldest sciences. Prehistoric cultures have left astronomical artifacts such as the Egyptian monuments and Nubian monuments, and early civilizations such as the Babylonians, Greeks, Chinese, Indians, Iranians and Maya performed methodical observations of the night sky. However, the invention of the telescope was required before astronomy was able to develop into a modern science. Historically, astronomy has included disciplines as diverse as astrometry, celestial navigation, observational astronomy, and the making of calendars, but professional astronomy is nowadays often considered to be synonymous with astrophysics. Template:/box-footer

Show new selections

Lua error in package.lua at line 80: module 'Module:Box-header/colours' not found.

Photograph of the crescent planet Neptune (top) and its moon Triton (center), taken by Voyager 2 during its 1989 flyby

The definition of planet has included a wide range of celestial bodies. Early use of the term was never strict and its meaning has blurred to include or exclude a variety of objects. By the end of the 19th century, the word planet had a more firm definition: it applied only to objects in the Solar System, a number small enough that any differences could be dealt with on an individual basis. After 1992 however, astronomers began to discover many additional objects beyond the orbit of Neptune, as well as hundreds of extrasolar planets. These discoveries not only increased the number of potential planets, but expanded their variety and peculiarity. The issue of a clear definition for planet came to a head in 2005 with the discovery of the trans-Neptunian object Eris, a body larger than the smallest then-accepted planet, Pluto. In its 2006 response to the discovery, the International Astronomical Union released its decision on the matter. Its definition, which applies only to the Solar System, states that a planet is a body that orbits the Sun, is massive enough for its own gravity to make it round, and has "cleared its neighbourhood" of smaller objects around its orbit. Under this new definition, Pluto and the other trans-Neptunian objects do not qualify as planets. (more...)

...Archive/Nominations

Read more...

Lua error in package.lua at line 80: module 'Module:Box-header/colours' not found.

... 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?

Biographies : Astronomers - Other people - Amateur Astronomers

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

Spaceflight : Human spaceflight - Satellites - SETI - Spacecraft Template:/box-footer

Template:/box-header

WikiProject Astronomy	WikiProject Solar System



WikiProject Cosmology	WikiProject Spaceflight

Template:/box-footer

Template:/box-header

Star	Spaceflight	Moon


Space	Solar System	Mars

X-ray astronomy	Cosmology	Jupiter

Template:/box-footer

Lua error in package.lua at line 80: module 'Module:Box-header/colours' not found.

Credit: NASA

Sunspots are temporary phenomena on the surface of the Sun (the photosphere) that appear visibly as dark spots compared to surrounding regions. They are caused by intense magnetic activity, which inhibits convection, forming areas of reduced surface temperature. Although they are at temperatures of roughly 3,000–4,500 K (4,940–7,640 °F), the contrast with the surrounding material at about 5,780 K leaves them clearly visible as dark spots, as the intensity of a heated black body (closely approximated by the photosphere) is a function of T (temperature) to the fourth power.

More selected pictures...

Read more...

Template:/box-header

14 December 1962 - Mariner 2 becomes the first space probe to perform a flyby of a planet, when it passes within 35,000 kilometers of Venus
19 December 2013 - Gaia was launched. Its mission is to study billions of stars in the Milky Way
21 December 1968 - Apollo 8, the first crewed spacecraft to leave Earth orbit, reach the Moon, orbit it, and return safely to Earth, is launched

Template:/box-footer

Template:/box-header

Here are some Open Tasks :