Astronomy portal

Astronomy (Greek: αστρονομία = άστρον + νόμος, astronomia = astron + nomos, literally "law of the stars") 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.

Article of the month

The Big Bang is the cosmological model of the initial conditions and subsequent development of the Universe that is supported by the most comprehensive and accurate explanations from current scientific evidence and observation. As used by cosmologists, the term Big Bang generally refers to the idea that the Universe has expanded from a primordial hot and dense initial condition at some finite time in the past (currently estimated to have been approximately 13.7 billion years ago), and continues to expand to this day.

Georges Lemaître proposed what became known as the Big Bang theory of the origin of the Universe, although he called it his "hypothesis of the primeval atom". The framework for the model relies on Albert Einstein's general relativity and on simplifying assumptions (such as homogeneity and isotropy of space). The governing equations had been formulated by Alexander Friedmann. After Edwin Hubble discovered in 1929 that the distances to far away galaxies were generally proportional to their redshifts, as suggested by Lemaître in 1927, this observation was taken to indicate that all very distant galaxies and clusters have an apparent velocity directly away from our vantage point: the farther away, the higher the apparent velocity.

Recently featured: Main sequence – Zhang Heng – Atmosphere of Jupiter

Did you know

... 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 existant 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?

Categories

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

Space exploration : Human spaceflight - Satellites - SETI - Spacecraft

Projects

• Space
• Astronomy
• Astronomical objects

Space-related Portals

Picture of the week

NGC 1427A is an irregular galaxy in the constellation Eridanus.

Astronomy News

• October 18, 2009: IBEX satellite releases first all sky map
• October 7, 2009: New ring discovered around Saturn, could explain dark side of its moon
• September 27, 2009: Indian lunar mission Chandrayaan finds water on moon
• September 22, 2009: Images show new dimension to Saturn's rings
• August 27, 2009: Extrasolar planet will most probably fall into its star
• July 21, 2009: Black spot on Jupiter is impact site, says NASA
• June 25, 2009: Saturn moon may contain liquid water
• April 23, 2009: Gamma-ray burst, dubbed GRB 090423, was detected by Swift satellite
• January 16, 2009: International Year of Astronomy is launched

More astronomy news from Wikinews…

Astronomical events in November 2009

All times UT unless otherwise specified.

Things you can do

Wikibooks

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

Wikijunior

• Solar System