Portal:Astronomy

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Introduction

Astronomy (from Greek: ἀστρονομία) is a natural science that studies celestial objects and phenomena. It applies mathematics, physics, and chemistry in an effort to explain the origin of those objects and phenomena and their evolution. Objects of interest include planets, moons, stars, nebulae, galaxies, and comets; the phenomena also includes supernova explosions, gamma ray bursts, quasars, blazars, pulsars, and cosmic microwave background radiation. More generally, all phenomena that originate outside Earth's atmosphere are within the purview of astronomy. A related but distinct subject is physical cosmology, which is the study of the Universe as a whole.

Astronomy is one of the oldest of the natural sciences. The early civilizations in recorded history, such as the Babylonians, Greeks, Indians, Egyptians, Nubians, Iranians, Chinese, Maya, and many ancient indigenous peoples of the Americas, performed methodical observations of the night sky. Historically, astronomy has included disciplines as diverse as astrometry, celestial navigation, observational astronomy, and the making of calendars, but professional astronomy is now often considered to be synonymous with astrophysics.

Professional astronomy is split into observational and theoretical branches. Observational astronomy is focused on acquiring data from observations of astronomical objects, which 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. The two fields complement each other, with theoretical astronomy seeking to explain observational results and observations being used to confirm theoretical results.

Astronomy is one of the few sciences in which amateurs still play an active role, especially in the discovery and observation of transient events. Amateur astronomers have made and contributed to many important astronomical discoveries, such as finding new comets.

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Selected article

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

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Did you know...

... that the asteroid 2011 XC2 missed the Earth by less than 1 lunar distance on 3 December 2011?
... that the mass-luminosity relation, first derived by Arthur Eddington in 1924, helps astronomers find the distances to binary star systems?
... that the planetary nebula Abell 39 is unusually spherical, yet its central star is offset from the center?
... that data from Mariner 10 led to the discovery of Mercury's magnetic field in 1974?
... that the Toronto Magnetic Observatory had to be moved as the University of Toronto's electric lighting was interfering with observations?

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Subcategories

Select [►] to view subcategories

▼ Astronomy

► Astronomy by location

► Astronomical objects

► Astronomical sub-disciplines

► Outer space

► Space art

► Astronomers

► Astronomical controversies

► Astronomical hypotheses

► Celestial coordinate system

► Astronomical clocks

► Constellations

► Cosmogony

► Dark-sky preserves

► Astronomy data and publications

► Astronomical dynamical systems

► Astronomy education

► Astronomical events

► Astronomy events

► History of astronomy

► Astronomical instruments

► Astronomy-related lists

► Astronomical myths

► Astronomy organizations

► People associated with astronomy

► Philosophy of astronomy

► Astronomy prizes

► Astronomy projects

► Pseudoastronomers

► Sky regions

► Space observatories

► Time in astronomy

► Units of measurement in astronomy

► Unsolved problems in astronomy

► Works about astronomy

► Wikipedia books on astronomy

► Astronomy stubs

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Projects

WikiProject Astronomy	WikiProject Solar System



WikiProject Cosmology	WikiProject Spaceflight

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Space-related Portals

Star	Spaceflight	Moon


Space	Solar System	Mars

X-ray astronomy	Cosmology	Jupiter

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Selected image

Credit: NASA, ESA, and The Hubble Heritage Team STScI/AURA

NGC 1300 is a barred spiral galaxy about 61 million light-years away in the constellation Eridanus. The galaxy is about 110,000 light-years across; just slightly larger than our own galaxy, the Milky Way.

More selected pictures...

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February anniversaries

5 February 1974 – Mariner 10 becomes the first spacecraft to use a gravity assist when it flies by Venus in order to reach Mercury
15 February 1845 – The Leviathan of Parsonstown, the world's largest telescope from 1845 to 1917, sees first light
18 February 1930 – 23-year-old astronomer Clyde Tombaugh discovers Pluto by using a blink comparator on photographs he took in the previous month at Lowell Observatory

More anniversaries

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Things you can do

Here are some Open Tasks :

Copyedit: Roque de los Muchachos Observatory, Europa (moon) More...
Wikify: More...
Merge: More...
Requests: Borde-Vilenkin-Guth Theorem, Antigalaxy, Sunspot index, undefined names in the List of astronomers, More...
Stubs: D Ring, Diffraction spike More...
Discuss deletion: No deletion requests

Astronomy featured article candidates:

No current candidates

Astronomy articles for which peer review has been requested:

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Wikibooks

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

Wikijunior

Solar System

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Wikiversity

Hypervelocity stellar "meteors"

The Hubble Space Telescope image shows four high-velocity, runaway stars plowing through their local interstellar medium. Credit: NASA - Hubble's Advanced Camera for Surveys.{{free media}}

Def. a star moving faster than 65 km/s to 100 km/s relative to the average motion of the stars in the Sun's neighbourhood is called a high-velocity star.

Def. a high-velocity star moving through space with an abnormally high velocity relative to the surrounding interstellar medium is called a runaway star.

Def. a star whose elliptical orbit takes it well outside the plane of its galaxy at steep angles is called a halo star.

...Archive

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Astronomical events

All times UT unless otherwise specified.

2 February, 07:05	Moon occults Saturn
2 February, 20:26	Moon occults Pluto
4 February, 21:04	New moon
5 February, 07:02	Moon occults Mercury
5 February, 09:46	Moon at apogee
12 February	Comet Iwamoto at brightest
19 February, 09:09	Moon at perigee
19 February, 15:54	Full moon
27 February, 01:24	Mercury at greatest eastern elongation