AstronomyAstronomy, which etymologically means "law of the stars", (from Greek: αστρονομία = άστρον + νόμος) is a science involving the observation and explanation of events occurring outside Earth and its atmosphere. It studies the origins, evolution, physical and chemical properties of objects that can be observed in the sky (and are outside the earth), as well as the processes involving them.
, photographed by the crew of Apollo 11 as they circled the Moon in 1969. Located near the center of the far side of Earth's Moon, its diameter is about 93 kilometers (58 miles).]]
Astronomy is one of the few sciences where amateurs still play an active role, especially in the discovery and monitoring of transient phenomena. Astronomy is not to be confused with astrology, a pseudoscience that attempts to predict a person's destiny by tracking the paths of astronomical objects. Although the two fields share a common origin, they are quite different; astronomers embrace the scientific method, while astrologers do not.
Divisions of astronomy
In its earliest days, going back to ancient Greece and other ancient civilizations, astronomy consisted largely of astrometry, measuring positions of stars and planets in the sky. Later, the work of Kepler and Newton paved the way for celestial mechanics, mathematically predicting the motions of celestial bodies interacting under gravity, and solar system objects in particular. Much of the effort in these two areas, once done largely by hand, is highly automated nowadays, to the extent that they are rarely considered as independent disciplines anymore. Motions and positions of objects are now easily known, and modern astronomy concerns itself much more with trying to observe and understand the actual physical nature of celestial objects—what makes them "tick".
Ever since the twentieth century the field of professional astronomy has tended to split into observational astronomy and theoretical astrophysics. Although most astronomers incorporate elements of both into their research, because of the different skills involved, most professional astronomers tend to specialize in one or the other. Observational astronomy is concerned mostly with getting data, which involves building and maintaining instruments and processing the resulting data; this branch is at times referred to as "astrometry" or simply as "astronomy." Theoretical astrophysics is concerned mainly with figuring out the observational implications of different models, and involves working with computer or analytic models.
The fields of study are also categorized in another two ways: by "subject", usually according to the region of space (e.g. Galactic astronomy) or "problems addressed" (such as star formation or cosmology); or by the way used for obtaining information.
By subject or problem addressed
on Mars. Photographed by Mars Global Surveyor, the long dark streak is formed by a moving swirling column of Martian atmosphere (with similarities to a terrestrial tornado). The dust devil itself (the black spot) is climbing the crater wall. The streaks on the right are sand dunes on the crater floor.]]
Also, there are other disciplines that may be considered part of astronomy:
- Astrobiology: the study of the advent and evolution of biological systems in the universe.
- Astrometry: the study of the position of objects in the sky and their changes of position. Defines the system of coordinates used and the kinematics of objects in our galaxy.
- Cosmology: the study of the universe as a whole and its evolution.
- Galactic astronomy: the study of the structure and components of our galaxy and of other galaxies.
- Extragalactic astronomy: the study of objects (mainly galaxies) outside our galaxy.
- Galaxy formation and evolution: the study of the formation of the galaxies, and their evolution.
- Planetary Sciences: the study of the planets of the solar system.
- Stellar astronomy: the study of the stars.
- Stellar evolution: the study of the evolution of stars from their formation to their end as a stellar remnant.
- Star formation: the study of the condition and processes that led to the formation of stars in the interior of gas clouds, and the process of formation itself.
See list of astronomical topics for a more exhaustive list of astronomy-related pages.
Ways of obtaining information
In astronomy, information is mainly received from the detection and analysis of electromagnetic radiation,
photons, but information is also carried by cosmic rays, neutrinos, meteors, and, in the near future, gravitational waves (see LIGO and LISA).
A traditional division of astronomy is given by the region of the electromagnetic spectrum observed:
. This image shows several blue, loop-shaped objects that are multiple images of the same galaxy. They have been duplicated by the gravitational lens effect of the cluster of yellow galaxies near the photograph's center. The lens is produced by the cluster's gravitational field that bends light to magnify and distort the image of a more distant object.]]
- Optical astronomy describes the techniques used to detect and analyze light in and slightly around the wavelengths that can be detected with the eyes (about 400 - 800 nm). The most common tool is the telescope, with electronic imagers and spectrographs.
- Infrared astronomy deals with the detection of infrared radiation (wavelengths longer than red light). The most common tool is the telescope but with the instrument optimized for infrared. Space telescopes are also used to eliminate noise (electromagnetic interference) from the atmosphere.
- Radio astronomy uses completely different instruments to detect radiation of wavelengths of mm to cm. The receivers are similar to those used in radio broadcast transmission (which uses those wavelengths of radiation). See also Radio telescopes.
- High-energy astronomy
Optical and radio astronomy can be performed with ground-based observatories, because the atmosphere is transparent at those wavelengths. Infrared light is heavily absorbed by
water vapor, so infrared observatories have to be located in high, dry places or in space.
The atmosphere is opaque at the wavelengths used by X-ray astronomy, gamma-ray astronomy, UV astronomy and, except for a few wavelength "windows", Far infrared astronomy, so observations
can be carried out only from balloons or space observatories.
In the early part of its history, astronomy involved only the observation and predictions of the motions of the objects in the sky that could be seen with the naked eye. The Rigveda refers to the 27 constellations associated with the motions of the sun and also the 12 zodiacal divisions of the sky. The ancient Greeks made important contributions to astronomy, among them the definition of the magnitude system. The Bible contains a number of statements on the position of the earth in the universe and the nature of the stars and planets, most of which are poetic rather than literal; see Biblical cosmology. In 500 AD, Aryabhata presented a mathematical system that took the earth to spin on its axis and considered the motions of the planets with respect to the sun.
Astronomy was mostly stagnant in medieval Europe, but flourished meanwhile in the Arab world. The late 9th century Islamic astronomer al-Farghani (Abu'l-Abbas Ahmad ibn Muhammad ibn Kathir al-Farghani) wrote extensively on the motion of celestial bodies. His work was translated into Latin in the 12th century. In the late 10th century, a huge observatory was built near Tehran, Iran, by the astronomer al-Khujandi who observed a series of meridian transits of the Sun, which allowed him to calculate the obliquity of the ecliptic. In Persia, Omar Khayyam (Ghiyath al-Din Abu'l-Fath Umar ibn Ibrahim al-Nisaburi al-Khayyami) compiled many tables and performed a reformation of the calendar that was more accurate than the Julian and came close to the Gregorian.
During the Renaissance Copernicus proposed a heliocentric model of the Solar System. His work was defended, expanded upon, and corrected by Galileo Galilei and Johannes Kepler. Kepler was the first to devise a system that described correctly the details of the motion of the planets with the Sun at the center. However, Kepler did not succeed in formulating a theory behind the laws he wrote down. It was left to Newton's invention of celestial dynamics and his law of gravitation to finally explain the motions of the planets.
Stars were found to be faraway objects. With the advent of spectroscopy it was proved that they were similar to our own sun, but with a wide range of temperatures, masses and sizes. The existence of our galaxy, the Milky Way, as a separate group of stars was only proven in the 20th century, along with the existence of "external" galaxies, and soon after, the expansion of the universe seen in the recession of most galaxies from us. Cosmology made huge advances during the 20th century, with the model of the big bang heavily supported by the evidence provided by astronomy and physics, such as the cosmic microwave background radiation, Hubble's Law and cosmological abundances of elements.
For a more detailed history of astronomy, see the history of astronomy.
. The ejection of gas, from the dying star at the center, has symmetrical patterns unlike the chaotic patterns expected from an ordinary explosion.]]
Timelines in astronomy
References: Formulas and Constants
Source | Copyright
Webmasters: Add your website here:
Readers: Edit |
Astronomy by Frank
Gallery of astrophotography attempts, links, and suggestions and tips for buying that first telescope.
Astronomy, Physics, and Soaring Page by Larry Bogan
A collection of Astronomical projects, lectures, and calculations. Orbits, Sunspots, Occultations, and Magnitudes.
Personal treasury of astronomical observing reports, advice for beginners, and links to other astronomy sites.
Chodakowski's Freeware Links
Links to astronomy, weather, and other science related freeware. Business spreadsheet freeware download.
The Astronomy WebCams Paradise
Amateur astronomy with webcams. Also illustrated lessons and photos in 3D.
The Astronomy Corner
Offers a monthly astronomy column, short essays and editorials.
Curt Hall's Amateur Astronomy Site
Astronomy website created for the amateur astronomer and casual observer.
Alohacyberian of Hawaii
Travels of Keith Martin.
Amateur Astronomy Resources
Categorized links, books and product reviews.
An Astronomy Linkpage
Links, articles and papers sorted in astronomy, space flight and SETI@home.
Dans Astrophotography site
Some of my Astrophotos.
Dan's Astronomy and Physics
Links to astronomy and physics sites.
Earth, Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto.
Anomalous X-ray pulsars.
Dublin Night Sky Observer
Provides astronomy and space news, and monthly observing notes.
The Event Inventor by Kye's World
Learn about astronomy and geometry using the position from a shadow stick. Learn to make a sundial.
Explore The Universe
Explore the Universe on the net!
Jerry Pool's images of the Moon and Constellations.
Member of Calar Alto Observatory. Information about his work, publications, projects, and co-workers.
The guide to the universe
Four educational trips to the universe.
Fermin's Astronomy Page
Basic facts about planets in our solor system and the moon. Also over 50 pictures of galaxies, nebulae, and star clusters.
Favorite Astronomy Links
Links to news, what's up, research, institutions, observatories, history of astronomy, and astronomy as a hobby, by Prof. J.S. Tenn, Sonoma State University.
The Final Frontier
Search for Extra Terrestrial Intelligence; news about the universe.
An astronomy site with links including a NGC - Messier search tool. Also captures hummingbirds from a web cam.
Glenn Schneider's Home Page @ Steward Observatory
HST/NICMOS and other recent astronomical endeavors, professional and personal.
Gaze Upon the Heavens
Contains links to some of my favorite sites as well as photos and research paper.
Images, information and advise for getting started stargazing. The title is really where the Observatory is: Cool, Calif..
Colliding Galaxies and the Fate of the Milky Way
Continuing discussion of the fate of the Milky Way Galaxy and ultimately the universe.
Cycles, resonances, synchronizations
Cyclical phenomena in the solar system.
Dave's Astronomy Stuff
Links to useful astronomy resources, including satellite and comet tracking, space exploration, observatories, world space agencies, education, software and photographs.
Personal webpage of astronomy photographs
Dimitris Gouliermis in the Sternwarte der Universitaet Bonn.
David Paul Green's Astronomy Homepage
Software, book and site reviews, dark sky survey and resume.
Astronomy with Peter Enzerink
Astronomy information from an Australian perspective. Includes some helpful tips for astronomy software.
Garcia, Fredrik Anthony
Contains information about our solorsystem.
Henry's Astronomy Page
Projects in stargazing, astrophotos, ccd imaging and travel experiences.
Facts and information on various topics including our universe.
Mike's AstroCam Website
CCD astrophotography created with modified color and B&W Quick Cam cameras.
An astronomy and space site, original eclipse and comet images, impact hazards, meteor news, weather information.
Mars Pathfinder Mission - Genuine Pictures
These slightly adjusted pictures prove that there is life on Mars [ed: contains parodies of NASA images of Mars and of Mars exploration].
X-ray astronomy West Chester University astronomy education astrophysics publications NASA Chandra X-ray Observatory
Site about our solar system.
Mini Dome Observatory
Aben Brown designed a small domed observatory to mount above a rooftop hatchway.
Michele's Home Page
Information on research projects primarily dealing with variable stars (XX Leo eclipsing binary star, SMC variable stars, novae). Provides links to a growing number of astronomy, space, and science related sites.
Descriptions of author books, listings of her reviews, biographical information, and e-mail contact.
Niall Glynn's Space and Astronomy Online
An easy-to-use site providing daily updated news with pictures and weather pages, as well as a shop where you can buy books, scopes, and accessories.
Mark Allison's Astro Site
Information and observations from an amateur Deep Sky astronomer based in Salford.
Martin Chick Astronomy
Includes information on my interest, astronomy.
Mr. C's Science World of Astronomy
Collection of astronomical links.
Night Sky Observers
Louisville,KY based club, member of the Astronomical League. Includes an astrophoto gallery and telescope buying guide.
Amateur astro-images from Hawaii.
Jeff MacQuarrie's CCD Astronomy Page
CCD Astrophotography images of nebulae, galaxies, planets and star clusters. Each image contains educational information about the object with links for further research.
Ian's Astronorama Page
Features news, pictures, telescope information, comets, eclipses, and the moon.
Javor Kac - Astrophotography Page
Jupiter-Venus conjunction, planets, comets, meteors, deep-sky.
Keith's Astro Page
Includes comet and night sky photography with a 35mm SLR camera.
Personal deep sky observatory.
Nancy's World of Astronomy
Interesting astronomy links and an online quiz.
CCD images from various equipment on a 10" LX200 F/6.3
Learn astronomy and skateboarding.
Information about Astrophysics, Computational Physics, Numerical Simulation. Contains FORTRAN programs that can be downloaded.
Sam's Astronomy Page
Site devoted to amateur astronomy, including descriptions and pictures of my equipment, tips and links.
The Port Perry Astronomical Observatory
Amateur astronomers share their love of the sky with local students.
Pictures of the Nightsky
This site contains pictures of the earth, moon, planets and the constellations. It contains an explanation of the constellations too.
Resource site for amateur astronomers with telescopes, observing aids, and links.
Planetary Alignment and Magnetic Field Interaction
Magnetic field interactions in planet alignments and sun spots correlation to periodic field polarity reversals.
Photos of Planets and Moons
Photos and information on several of the planets.
Remco Scheepmaker's Astronomy
Personal homepage about my astronomy and astrophotography equipment, telescopes and reviews of the OMC140 and Vixen GP-DX.
Astronomy information with emphasis on the solar system.
Collection of directories, dictionaries, databases, and related products on astronomy and space.
SkyNet Space and Astronomy
Astronomy, Space, Satellite Tracking. Starting point for Astronomy and Space news and information.
Sean's Astro Web Site
Description of my research on ultra high energy cosmic rays.
Simon Nava Home Page
Miscellaneous topics as black holes, space exploration.
Stargazer Online -- Astronomy: First Light
Richard Bell's observing, astrophotography articles and biographies.
An Observation of the Night Sky
This web page is intended for the non-astronomer in the hope that he/she will come to love the night sky the way I do.
Paul Kondratko's Home Page
Contains my scientific and school related publications, presentations and reference material for physics, astrophysics, and mathematics coursework.
Poor Meadow Dyke Observatory
Large telescope-making and CCD-imaging site. DIY frame de-rotation, images, and a hints-and-tips section.
Penny Fischer's Stargazer
Tells you where, and how, and what he likes to observe.
Pete's Astronomy Page
Personal astronomy page with astrophotos.
Pictures From Space!
A collection of Astronomy Photos.
Learn More About the Universe
Links, lectures, and photos.
Sublime64's Home Page
Whats your weight on all the planets? Science, Physics, Astro Picture Gallery. Space.
The Space Technology Center
Documents man's quest for the stars.
Information on spectropolarimetry, dynamo processes.
Space and Computing Newsletter
Newsletter on space topics.
A site for code developers and SETI enthusiasts.
Discussion about controversial topics in astronomy and sci-fi, including links to related sites.
Hints, tips and astrophotography with my Meade LX200 telescope.
Tom's amateur astronomy
Details of my two homemade telescopes, Freeware for astronomy for the low-budget/no-budget amateur.
Treetop's Astronomy Site
Many useful links that are your guide to the heavens.
The Telson Spur -- The Snark Hunter's Page
The Telson Spur is a web of mainly academic resources organized on the theme of necessity vs. contingency in the study of time and evolution. This page, the Snark Hunter's Page, is the top page of The Telson Spur.
Urban astronomy from Singapore. With personal observing reports, various tutorials for newbies on equipment, where to buy, observing.
Offers details about Astronomy; links.
Discoveries made by Voyager 1 and 2 about the giant planets and their moons.
Walter's Extragalactic Homepage
An astronomical picture gallery including observation reports, astronomical articles and astro-links.
World of Astronomy
Brief history on astronomy and quotes.
Weasner's Mighty ETX Site
Resources, discussions and complete information about Meade ETX Astro Telescopes.
Results from the Kolkert-Observatory, like a description of the 4" instrumented refractor.
General information on a number of astronomical topics.
Science Fiction Exploration
Hard science fiction and astronomy and the mysteries of the universe revealed.
Tim Printy's Astronomy Web Page
Astrophotography guide specializing in comets, meteors and deep space.
This is a publicly run site for space and space exploration.
This site has general information on Astronomy oriented towards the beginner.
The Sky in the Sun's Shadow
Images of our solar system, the history of astronomy, news, and what to look for in our sky.
SETI for All
Basic information and links about SETI.
Yoonho's Amateur Astronomy
12" LX200 owner, fluorite APO refractor, astro photos.
The World Above
Information plus thought on astronomy and on new exploration. Little information about stars, planets, and galaxies.
A Practical Guide to Astronomy
Resource for the beginner and the experienced backyard astronomer, with facts and photos.
Whitney's Star Finder
A window on the sky for the casual observer, amateur astronomer, or student.
Melissa's Boston University Page
Includes discussion of research and oral presentation about photometry. Includes photos and some related links.
Edward M. Sion
Specializes in white dwarf studies. Includes curriculum vitae and research articles. Professor of Astronomy and Astrophysics at Villanova University.
George P. McCook
Specializes in mathematic analysis of astronomical data. Chairperson and professor of Astronomy at Villanova University. Includes education background and research.
Useful astronomical links, sci.astro.amateur FAQ.
Mt. Regina Observatory
Links to images of comets, NGC objects and planets plus information on telescopes and links to various astronomy-related areas.
Weak Interstellar Messages Pass Us By
Amateur radio project to detect signals from extraterrestrial intelligences.
NJ Night Sky
Amateur astronomy and telescope building.
Michael's Astronomy Home Page
Astrophotos and information about our solar system, information on LaTeX.
A beginner's guide to astronomy with emphasis on the solar system.
Dave & Jeanne's Astronomy Site
Shares the joys of stargazing with the web community.
Specializes in high angular resolution astronomy. Includes publications and research interests. Department of Space, India.
R.. A.. Araya-Gochez
A visiting associate professor in Tapir,India. Currently, working on problems related to the physics of magnetized, fully ionized plasmas. Includes lecture notes and curriculum vitae.
Deb n' Ken's Web Zone: Astronomy
Discusses details about the solar system. Gives information about planets, asteroids, comets, meteors, meteorites, galaxies, nebulae and satellites. Includes image gallery.
The Perfect Sky
Contains some telescope reviews.
It's a Kind of Magic
A refreshing, jargon-free guide to Space, Astronomy, Free PC Games, Utilities, Emulation, MSDOS and Jokes.
Joerg C. Hartmann Astronomie
Movies from moon and sun captured with a Webscope.
Abhijit Dharmadhikari, a self expression.
Astronomy CCD images by Chris Deforeit
Deep sky images, including color pictures.
A few astronomical images taken by the author.
A brief history, links, the Greek mythology of the constellations and some pictures of a solar eclipse, taken in France on August 11 1999.
Lukasz Kanclerski's page - Tips and Photos
Site for beginning stargazers and others too. Lots of astropictures, including photos of the 11 Aug 1999 total solar eclipse over Europe.
An absolute beginner's guide to getting started in astronomy.
Astronomy at WEB
Links to astronomy sites and pictures.
Amateur radioastronomy, macro photography, and philosophy of existence.
Astronomy for the Masses
Articles about measuring angles in the sky, elementary particles, and nuclear forces.
Astronomy and Space Exploration
Information regarding organizations related to space exploration in the Los Angeles area.
Astronomy 4 Dummies
A general information site for those who have a beginner's curiosity about astronomy.
Astronomy - What's Up This Month
Monthly updates on astronomical events, star charts for the month, and photographs.
Basic information on astronomy and astrophysics.
Astro Workgroup Mercator
Amateur astronomy group from Bazel, Belgium.
Astronomy! Reach the Stars!
A window to the universe. Current news, pages for kids, history, links.
Astronomy page of Erik Bryssinck - Belgium
Results of astro-ccd photography, several tips & tricks for quickcam astro-ccd photography.
A general information site for those who have a beginner's curiosity ab