From Wikipedia, the free encyclopedia
The Astronomy Portal


A man sitting on a chair mounted to a moving platform, staring through a large telescope.
Percival Lowell observing Venus from the Lowell Observatory telescope in 1914

Astronomy is a natural science that studies celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and 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.

Featured article - show another

This is a Featured article, which represents some of the best content on English Wikipedia.

A Hertzsprung–Russell diagram plots the luminosity (or absolute magnitude) of a star against its color index (represented as B−V). The main sequence is visible as a prominent diagonal band from upper left to lower right. This plot shows 22,000 stars from the Hipparcos Catalog together with 1,000 low-luminosity stars (red and white dwarfs) from the Gliese Catalogue of Nearby Stars.

In astronomy, the main sequence is a classification of stars which appear on plots of stellar color versus brightness as a continuous and distinctive band. Stars on this band are known as main-sequence stars or dwarf stars, and positions of stars on and off the band are believed to indicate their physical properties, as well as their progress through several types of star life-cycles. These are the most numerous true stars in the universe and include the Sun. Color-magnitude plots are known as Hertzsprung–Russell diagrams after Ejnar Hertzsprung and Henry Norris Russell.

After condensation and ignition of a star, it generates thermal energy in its dense core region through nuclear fusion of hydrogen into helium. During this stage of the star's lifetime, it is located on the main sequence at a position determined primarily by its mass but also based on its chemical composition and age. The cores of main-sequence stars are in hydrostatic equilibrium, where outward thermal pressure from the hot core is balanced by the inward pressure of gravitational collapse from the overlying layers. The strong dependence of the rate of energy generation on temperature and pressure helps to sustain this balance. Energy generated at the core makes its way to the surface and is radiated away at the photosphere. The energy is carried by either radiation or convection, with the latter occurring in regions with steeper temperature gradients, higher opacity, or both. (Full article...)

More Did you know (auto generated)


Selected image - show another

Credit: ESA / Hubble / NASA

Antennae Galaxies (also known as NGC 4038/NGC 4039 or Caldwell 60/Caldwell 61) are a pair of interacting galaxies in the constellation Corvus. The Hubble Space Telescope image of NGC 4038 (top) and NGC 4039 (bottom) undergoing a galactic collision.

Astronomy News

24 November 2023 –
Astronomers at the Telescope Array Project in Utah, United States, observe the second largest cosmic ray ever detected, the so-called Amaterasu particle, with an energy of 244 EeV. (Cosmos Magazine)
14 June 2023 –
Astronomers report that the presence of phosphates on Enceladus, moon of the planet Saturn, has been detected, completing the discovery of all the basic chemical ingredients for life on the moon. (New York Times)
12 June 2023 – Discoveries of exoplanets
Astronomers announce in the journal Nature Astronomy the discovery of BEBOP-1c, an exoplanet orbiting the binary star system, TOI-1338. The system is the second discovered to have more than one circumbinary planet. (Space.com)

December anniversaries

  • 7 December 1972 – The “Blue Marble” photograph is taken by the Apollo 17 crew
  • 8 December 1992 – Galileo completes the second Earth flyby
  • 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
  • 17 December 1917 – “2001: A Space Odyssey” science fiction author Arthur C. Clarke is born
  • 19 December 2013 – Gaia is launched for the mission to study billions of stars in the Milky Way
  • 21 December 1968 – Apollo 8, is launched with the first crewed spacecraft to leave Earth orbit, reach the Moon, orbit it, and return safely to Earth
  • 27 December 1571 – Astronomer, mathematician, and astrologer Johannes Kepler is born

Space-related Portals

Astronomical events

All times UT unless otherwise specified. Portal:Astronomy/Events/December 2023



Select [►] to view subcategories

Things you can do

Here are some Open Tasks :

Astronomy featured article candidates:

  • No current candidates

Astronomy articles for which peer review has been requested:

  • No current requests


Wikibooks logo
Wikibooks logo

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


Associated Wikimedia

The following Wikimedia Foundation sister projects provide more on this subject:

Discover Wikipedia using portals

Shortcuts to this page: Astronomy portalP:ASTRO Purge server cache