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Topic: Variable star


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  Variable star - Wikipedia, the free encyclopedia
Variable stars are generally analysed using photometry and photospectrometry.
Of the brighter stars in the sky, Polaris is a Cepheid, although a somewhat unusual one.
Stars with sizable sunspots may show significant variations in brightness as they rotate, and brighter areas of the surface are brought into view.
en.wikipedia.org /wiki/Variable_star   (3578 words)

  
 variable star. The Columbia Encyclopedia, Sixth Edition. 2001-05
star that varies, either periodically or irregularly, in the intensity of the light it emits.
The class to which a variable star belongs is determined by a plot of its light curve, which is a graph of the star’s apparent brightness versus time.
Cepheid variables are classed as either population I Cepheids, which are found in the spiral arms of galaxies, or population II Cepheids, also known as W Virginis stars, which are found in star clusters (see also stellar populations).
www.bartleby.com /65/va/variable.html   (712 words)

  
 Variable star designation - Wikipedia, the free encyclopedia
Variable stars are named using a variation on the Bayer designation format of an identifying label (as described below) combined with the Latin genitive of the name of the constellation in which the star lies.
In the early 19th century few variable stars were known, so it seemed reasonable to use the letters of the Roman alphabet, starting from the letter R so as to avoid confusion with letter spectral types or the (now rarely used) Latin-letter Bayer designations.
With the advent of photography the number of variables piled up quickly, and variable star names soon fell into the Bayer trap of reaching the end of the alphabet while still having stars to name.
en.wikipedia.org /wiki/Variable_star_designation   (358 words)

  
 Cataclysmic variable star: Facts and details from Encyclopedia Topic   (Site not responding. Last check: 2007-11-07)
A nova is a cataclysmic nuclear explosion caused by the accretion of hydrogen onto the surface of a white dwarf star....
A neutron star is a compact star in which the weight of the star is carried by the pressure of free neutrons....
Acrux (α cru / α crucis / alpha crucis) is the brightest star in constellation crux (the southern cross) and the thirteeth brightest star in the...
www.absoluteastronomy.com /encyclopedia/c/ca/cataclysmic_variable_star.htm   (1393 words)

  
 variable star on Encyclopedia.com
VARIABLE STAR [variable star] star that varies, either periodically or irregularly, in the intensity of the light it emits.
Relatively rare among this subclass are the Cepheid variables ; these yellow supergiant stars are historically important because, having periods roughly proportional to their absolute brightness, they provide a means of measuring galactic and extragalactic distances.
Bright shining stars: the mediating effect of organizational image on the relationship between work variables and army officers' intentions to leave the service for a job in high-tech industry.
www.encyclopedia.com /html/v1/variable.asp   (914 words)

  
 variable star articles on Encyclopedia.com   (Site not responding. Last check: 2007-11-07)
variable star VARIABLE STAR [variable star] star that varies, either periodically or irregularly, in the intensity of the light it emits.
star STAR [star] hot incandescent sphere of gas, held together by its own gravitation, and emitting light and other forms of electromagnetic radiation whose ultimate source is nuclear energy.
Algol's variation in apparent magnitude, from 2.06 to 3.28, is due to the fact that it is an eclipsing binary star, with one component revolving about the
www.encyclopedia.com /articles/13358.html   (473 words)

  
 Variable Star Naming   (Site not responding. Last check: 2007-11-07)
Variable stars are those stars that change their apparent brightness (or sometimes their color) over time.
The second variable star discovered in that constellation is called S, the third T, then U, then V, then W, then X, then Y, and then Z. This covers the first nine variable stars discovered in any given constellation.
The tenth variable star to be discovered in a constellation is named RR.
www.stellar-database.com /variable.html   (317 words)

  
 BGSU Variable Star Project
The REU students at Cerro Tololo Inter-American Observatory (Chile) are contributing to this effort by observing RR Lyrae stars in the Southern hemisphere using the Curtis Schmidt telescope.
The orbital characteristics of a binary star are used to determine the masses of the two stars.
By measuring the apparent (B-V) color of an RRL near the plane and comparing it to the un-reddened (or "intrinsic") color of stars far from the plane, he was able to measure the reddening (and thus absorption) due to dust along the line of site to the star.
physics.bgsu.edu /~layden/VarStarProj/vsp_main.html   (2072 words)

  
 Smoothing Data from Variable Stars
Variable stars are stars for which the intensity of the emitted energy changes over time; for periodic variable stars the change of intensity is periodic over time.
Eclipsing binaries consist of two stars orbiting each other in a conformation relative to the observer such that brightness variability occurs as one star passes in front of the other in turn; as the stars may be of different brightness, the drop in light flux depends on which star is in the front.
The brightness changes in the remaining classes of periodic variables is caused by periodic pulsation (contraction and expansion) of the stars and their outer layers.
www.stat.berkeley.edu /users/rice/UBCWorkshop   (1096 words)

  
 VMI: Astronomical Research   (Site not responding. Last check: 2007-11-07)
The VMI Observatory includes a 20-inch telescope which is ideal for obtaining professional-quality observations of pulsating variable stars.
A sample light curve is shown to the left, for the variable star HZ Persei, a Cepheid variable which completes a pulsation cycle in 11.28 days, and undergoes a change in apparent magnitude of approximately 0.6 mag (a factor of 1.7 in brightness).
This particular Cepheid variable star shows very little scatter in the light curve, which is typical for this type of variable star.
www.vmi.edu /departments.asp?durki=2055&site=63&return=2246   (956 words)

  
 variable star
Variable stars fall into two general categories: intrinsic variables, in which physical changes, such as pulsations or eruptions, are involved, and extrinsic variables, in which the light output fluctuates due to eclipses or stellar rotation.
Further classification is complex; originally it was based on a star’s light-curve, amplitude, and periodicity (or lack of it), but is now more closely linked to the physical processes underlying the variability.
Specific types of variable star are often named after a prototype (see variable star naming).
www.daviddarling.info /encyclopedia/V/variablestar.html   (473 words)

  
 Variable star   (Site not responding. Last check: 2007-11-07)
These are stars which have intrinsic variations brightness that is the star itself gets and dimmer.
Extrinsic variables have variations in their brightness seen by terrestrial observers due to some source.
One of the most common reasons this is the presence of a binary star so that the two together form binary star.
www.freeglossary.com /Variable_stars   (378 words)

  
 Binary & Variable Star Links
Weighing Ultra-Cool Stars is a press release from ESO explaining how VLT adaptive optics images were combined with those from the HST to measure the mass of an ultra-cool L-type star and its brown dwarf companion in a binary system.
ASSA: Variable Star Group is part of the Astronomical Society of South Australia, an amateur society with a keen interest in variable star observations.
Roller Coaster Stars - Astronomy in Your Hands is an observational exercise where you observe a northern or southern hemisphere Cepheid variable star to produce a light curve and then determine the distance to the star.
outreach.atnf.csiro.au /education/senior/astrophysics/binary_variable_links.html   (1030 words)

  
 Mike Simonsen's Variable Star Pages
The AAVSO is a worldwide organization of amateur and professional astronomers who are interested in the study of variable stars.
Its purpose is to collect, archive, analyze and publish variable star observations, and to make these observations available to professional astronomers, researchers, and educators.
Variable star research is one of the few areas in astronomy where amateurs can make an exciting and significant contribution to science.
home.mindspring.com /~mikesimonsen   (495 words)

  
 SurfWax: News, Reviews and Articles On Variable Star
Cepheids' brightness variations are used to measure the distances of galaxies and the expansion rate of the universe.
The North Star, Polaris A is a bright supergiant variable star...
These kinds of stars are used by astronomers to measure the distance to various galaxies and to chart the expansion rate of the universe, so it is essential to know about their physics and evolution, including their mass.
news.surfwax.com /astronomy/files/Variable_Star_Astronomy.html   (1043 words)

  
 Variable Star Projects at SSUO
An eclipsing binary is a binary star for which the solar system is very nearly in the orbital plane for the system.
Preliminary reductions to differential magnitude for the variable and comparison, and a check star and comparison are presented in the following plot.
A preliminary analysis of the check and comparison star observations suggests a mean error for a single magnitude difference of approximately +/- 0.015 magnitude.
www.phys-astro.sonoma.edu /observatory/research/varstarp.html   (861 words)

  
 Chandra :: Educational Materials :: Variable Stars
Stars appear to shine with a constant light; however, thousands of stars vary in brightness.
Amateur astronomers around the world observe variable stars and assist professional astronomers by sending their data to variable star organizations, such as the American Association of Variable Star Observers (AAVSO) in Cambridge, Massachusetts.
The collection and study of variable star data requires the ability to estimate the apparent magnitudes of stars.
chandra.harvard.edu /edu/formal/variable_stars   (302 words)

  
 Early Variable Star Discoverers
In 1784, he discovered the variability of Sheliak (Beta Lyrae), an eclipsing variable, and the variability of Delta Cephei, the second known Cepheid variable and name patron for this class of variable stars.
Over the years, Harding discovered four variable stars, all of Mira type: R Virginis in 1809, R Aquarii in 1810, R Serpentis in 1826, and S Serpentis in 1828.
In 1795, he found the particular variable R Coronae Borealis which is the prototype of an important class of variables, and the RV Tauri variable star R Scuti.
www.seds.org /~spider/spider/Vars/Add/var-dis.html   (728 words)

  
 Visual Variable Star Observing
Variable stars are important because they supply us with much information on specific stellar states.
There are two major groups of variable stars: the intrinsic and the 'apparent' variables.
These stars are used for estimating the visual magnitude of the variable.
www.astroinfo.ch /bbsag/bbsag_e.html   (647 words)

  
 AAVSO: Algol, January 1999 Variable Star Of The Month
Algol's variability was discovered in 1667 by the Italian astronomer Geminiano Montanari making it one of the first ever non-nova variable stars discovered.
The primary star should expand first due to its greater mass, yet we find that the secondary is the older star in the Algol system.
Algol varies in V magnitude from 2.1 at maximum to 3.4 at primary minimum, with a period of 2.867315 days; this period, however, is slowly lengthening.
www.aavso.org /vsotm/0199.stm   (964 words)

  
 Cataclysmic variable star   (Site not responding. Last check: 2007-11-07)
The companion star is usually a red dwarf, although in some cases it is another white dwarf or a slightly evolved star (subgiant).
The stars are so close to each other that the gravity of the white dwarf distorts the secondary, and the white dwarf accretes matter from the companion.
Magnetic systems often show strong and variable polarisation in their optical light, and are therefore sometimes called intermediate polars (in case of a disrupted disk) or polars (in case of prevented disk formation).
www.omniknow.com /common/wiki.php?in=en&term=Cataclysmic_variable   (1889 words)

  
 Variable Star Light Board
In 1997, Bob Gent (a new variable star observer that I'd mentored) asked me to give a talk about observing variables at the upcoming Astronomical League's Starry Nights Festival.
Most of the comparison stars of this field are very close to the variable (which meant I could spread out the "stars" easier on the board.
The "variable" would be at the top center with the comparison stars at either end of the board.
www.genehanson.com /lightbd.htm   (1151 words)

  
 McGraw-Hill AccessScience: Variable star
star that has a detectable change in brightness which is often accompanied by other physical changes.
During the life of a star, changes in brightness occur in the early stages, while it is forming, or in the late stages, close to its death.
Depending upon the type of star, variability in brightness can provide information about its size, radius, mass, temperature, luminosity, internal and external structure, composition, and distance from the Earth.
www.accessscience.com /Encyclopedia/7/72/Est_728000_frameset.html?doi   (139 words)

  
 A Dictionary of Astronomy: variable star @ HighBeam Research   (Site not responding. Last check: 2007-11-07)
Two broad categories are recognized: extrinsic variables, which vary for a mechanical reason (e.g.
rotation); and intrinsic variables, which undergo a real change in luminosity of either an individual star or some element in a binary system.
The standard reference for the classification of types of variable stars and their nomenclature is the General Catalogue of Variable Stars (GCVS).
www.highbeam.com /doc/1O80:variablestar/variable+star.html?refid=ip_hf   (170 words)

  
 Variable Star Observing Biography
Fortunately, this atlas also had variable stars plotted; that is, if their maximum brightness was at least 7.5.
I have observed the cataclysmic variables from the outset.
Though in one sense it was a triumph to have finally found that first variable star without any help, it is also very sad because any experienced variable star observer could have assured me that I had found the variable and that alone could have been all the difference.
www.genehanson.com /aboutgen.htm   (1175 words)

  
 SPA Variable Star Section
The SPA Variable Star Section observes a mixture of naked eye, binocular and telescopic variables.
Also included are charts which show the location of each variable and some nearby comparison stars that can be used when estimating the brightness of the variable.
News of variables, Novae and Supernovae from "The Astronomer"
www.popastro.com /sections/vs.htm   (195 words)

  
 APOD: 2005 May 5 - Mira: The Wonderful Star   (Site not responding. Last check: 2007-11-07)
Modern astronomers now recognize an entire class of long period Mira-type variables as cool, pulsating, red giant stars, 700 or so times the diameter of the Sun.
Mira B is surrounded by a disk of material drawn from the pulsating giant and in such a double star system, the white dwarf star's hot accretion disk is expected to produce
But this sharp, false-color image from the Chandra Observatory also captures the cool giant star strongly flaring at x-ray energies, clearly separated from the x-ray emission of its companion's accretion disk.
antwrp.gsfc.nasa.gov /apod/ap050505.html   (198 words)

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