Portal:Astronomy
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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.
Gamma-ray bursts (GRBs) are flashes of gamma rays associated with extremely energetic explosions in distant galaxies. They are the most luminous electromagnetic events in the universe since the Big Bang. Bursts can last from milliseconds to nearly an hour, although a typical burst lasts a few seconds. The initial burst is usually followed by a longer-lived "afterglow" emitting at longer wavelengths (X-ray, ultraviolet, optical, infrared, and radio).
Most observed GRBs are believed to be a narrow beam of intense radiation released during a supernova event, as a rapidly rotating, high-mass star collapses to form a black hole. A subclass of GRBs (the "short" bursts) appear to originate from a different process, possibly the merger of binary neutron stars.
The sources of most GRBs are billions of light years away from Earth, implying that the explosions are both extremely energetic (a typical burst releases as much energy in a few seconds as the Sun will in its entire 10 billion year lifetime) and extremely rare (a few per galaxy per million years). All observed GRBs have originated from outside the Milky Way galaxy, although a related class of phenomena, soft gamma repeater flares, are associated with magnetars within the Milky Way. It has been hypothesized that a gamma-ray burst in the Milky Way could cause a mass extinction on Earth.
Recently featured: Tau Ceti – Rings of Uranus – Redshift
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... 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?
Astronomy : Archaeoastronomy - Astrophysics - Calendars - Catalogues - Celestial coordinate system - Celestial mechanics - Cosmology - Images - Large-scale structure of the cosmos - Observatories - Planetary science - Telescopes - Wikipedia Books on Astronomy
Biographies : Astronomers - Other people
Astronomical objects : Lists - Galaxies - Nebulae - Planets - Stars
Space exploration : Human spaceflight - Satellites - SETI - Spacecraft
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| Space | Solar System | Mars |
Artist's rendering shows a view of our own Milky Way Galaxy and its central bar as it might appear if viewed from above
- 23 April2009: Gamma-ray burst, dubbed GRB 090423, was detected by Swift satellite
- 16 January2009: International Year of Astronomy is launched
- 13 December2008: Scientists detect black hole at center of Milky Way Galaxy
- 22 November 2008: Saturn's rings are much older than previously thought
- 29 October 2008: Mars orbiter finds widespread evidence of water-bearing minerals
All times UT unless otherwise specified.
| 4 July, 07:00 | Earth at aphelion |
| 7 July, 09:39 | Full moon and penumbral lunar eclipse |
| 7 July, 22:00 | Moon at apogee |
| 14 July, 02:00 | Mercury at superior conjunction |
| 21 July, 20:00 | Moon at perigee |
| 22 July, 02:35 | New moon and total solar eclipse |
| 28 July | Southern Delta Aquariids peak |
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Here are some Open Tasks :
Astronomy featured article candidates:
Astronomy articles for which peer review has been requested: |
These books may be in various stages of development. See also the related Science and Mathematics bookshelves.
