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Topic: Spectral classification

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spectral type

spectral line

spectral theorem

spectral theory

spectral density

spectral sequence

Spectral Bat

spectral radius

spectral envelope

spectral space

spectral decomposition

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	Stellar classification - Wikipedia
		Spectral characteristics offer a way to classify stars which gives information about temperature in a different way - particular absorption lines can be observed only for a certain range of temperatures because only in that range are the involved atomic energy levels populated.
		The Yerkes spectral classification, also called the MKK system, is a system of stellar spectral classification introduced in 1943 by William W. Morgen[?], Phillip C. Keenan[?] and Edith Kellman[?] of Yerkes Observatory.
		This classification is based on spectral lines sensitive to stellar surface gravity which is related to luminosity, as opposed to the Harvard classification which is based on surface temperature.
	wikipedia.findthelinks.com /sp/Spectral_type.html (1343 words)

	Stellar classification - Wikipedia, the free encyclopedia
		In astronomy, stellar classification is a classification of stars based initially on photospheric temperature and its associated spectral characteristics, and subsequenly refined in terms of other characteristics.
		Note the letters are not related to the letters used in the classification of true stars, but instead indicate the composition of the white dwarf's outer layer or "atmosphere".
		The Yerkes spectral classification, also called the MKK system from the authors' initials, is a system of stellar spectral classification introduced in 1943 by William W. Morgan, Phillip C. Keenan and Edith Kellman of Yerkes Observatory.
	en.wikipedia.org /wiki/Stellar_classification (2049 words)

	Spectral Classification
		Each spectral type is divided into 10 subclasses, A0, A1, A2,...A9 etc. The spectral types and sub-classes represent a temperature sequence, from hotter (O stars) to cooler (M stars), and from hotter (subclass 0) to cooler (subclass 9).
		Luminosity classes are determined from spectral features and photometric measurements, coupled with information regarding the distance to the star and theamount of extinction of the starlight from interstellar material.
		For larger stars of a given spectral type, the surface gravity decreases relative to what it was on the main sequence, and this decreases the equivalent widths of the absorption lines.
	cfa-www.harvard.edu /~pberlind/atlas/htmls/note.html (337 words)

	Spectral classification of late-type dwarfs
		Spectral classification is astronomical botany: it is an ordering and organisation of observations based solely on appearance.
		A spectral classification system tied to physical parameters must change with each revision of the theoretical models, and a changing system makes it very difficult to establish the readily-understood common reference system which is essential for spectral types to be of any use.
		Spectral class M is characterised by the presence of strong absorption bands due to the diatomic molecule titanium oxide, TiO (Morgan, Keenan \& Kellman, 1943).
	www-int.stsci.edu /%7Einr/ldwarf.html (2629 words)

	The Classification of Stellar Spectra
		The current spectral classification scheme was developed at Harvard Observatory in the early 20th century.
		The standard scheme used for this is called the Yerkes classification (or MMK, based on the initials of the authors William W. Morgan, Philip C. Keenan, and Edith Kellman).
		Composite spectrum; two spectral types are blended, indicating that the star is an unresolved binary.
	www.shef.ac.uk /physics/people/pacrowther/spectral_classification.html (1913 words)

	The Classification of Stellar Spectra (Site not responding. Last check: 2007-10-25)
		The early spectral classification system was based on the appearance of the spectra, but the physical reason for these differences in spectra were not understood until the 1930’s and 1940’s.
		The spectral classification system used today is a refinement called the MK system, introduced in the 1940’s and 1950’s by W. Morgan and P.C. Keenan at Yerkes Observatory to take account of the fact that stars at the same temperature can have different sizes.
		Thus spectral classification is, in many ways, as fundamental to astronomy as is the Linnean system of classifying plants and animals by genus and species.
	users.anderson.edu /~dibales/CLEA/Spectra.htm (6697 words)

	William Wilson Morgan, January 3, 1906—June 21, 1994 \| By Donald E. Osterbrock \| Biographical Memoirs
		Morgan's work on the classification of the forms of galaxies, based largely on close inspection of direct photographs in the Mount Wilson and Palomar Observatories plate files, was one of his most important contributions to galaxy research.
		Morgan was elected to the National Academy of Sciences in 1956, and was awarded the Bruce Medal of the Astronomical Society of the Pacific in 1958, the Henry Norris Russell Lectureship of the American Astronomical Society in 1961, and the Henry Draper Medal of the NAS in 1980.
		Later Morgan and Keenan were honored by a workshop on spectral classification, dedicated to them, at the University of Toronto, and by another held under the auspices of the Vatican Observatory in Tucson in 1993, the fiftieth anniversary of the publication of the MKK Spectral Atlas.
	www.nap.edu /readingroom/books/biomems/wmorgan.html (6283 words)

	eSky: Spectral Classification
		The classification of stars according to their spectra; each major spectral classification is given a letter, with additional numbers providing further subdivisions.
		A star's full spectral classification often also includes a 'luminosity class', a Roman numeral from I to VII indicating the star's luminosity, which correlates with its mass.
		For example, the full spectral classification for Achernar is B3Vp, with 'p' indicating that it has a peculiar spectrum, while Castor in Gemini is classified as A2Vm, with 'm' demonstrating that the spectrum contains strong metal lines, and so on.
	www.glyphweb.com /esky/concepts/spectralclassification.html (1065 words)

	The Classification of Stellar Spectra
		Classification by spectral features quickly proved to be a powerful tool for understanding stars.
		If the convective cells created during this helium fusion runaways reach all the way to the hydrogen fusion layer, this would potentially provide a mechanism for material deep within the star to be dredged up to its surface.
		Spectral lines also show Doppler shifts with respect to the rest velocity of the star, indicating that matter is streaming out from them.
	www.star.ucl.ac.uk /~pac/spectral_classification.html (1913 words)

	Automated Classification of a Large Database of Stellar Spectra
		The classification of a large database of stellar spectra, which would be a Herculean task for human classifiers if done visually, is an ideal problem for the ANN technique, which can handle such problems without manual intervention.
		Instead of using the full spectral information, a set of 161 wavelength positions was used to monitor the fluxes which are diagnostic of the spectral classes as given by human experts (Jaschek and Jaschek 1990).
		The catalog classification was taken from this catalog, where like MK classification, the UV classification is given as O, B, F, etc., as main classes, subclasses ranging from 0.0 to 9.5, and luminosity classes represented as s, g, and d for super-giants, giants, and dwarfs, respectively.
	www.adass.org /adass/proceedings/adass94/gulatir.html (1538 words)

	Andre HECK - Papers on classification
		Spectral classification, photometry and statistical analysis, in Spectral Classification of the Future, Eds.
		Prediction of spectral classification from photometric observations - Application to the uvby beta photometry and the MK spectral classification.
		UV stellar spectral classification, in Exploring the Universe with the IUE Satellite, Eds.
	cdsweb.u-strasbg.fr /~heck/p-class.htm (992 words)

	Automated Spectral Classification
		A large part of the effort in automating stellar spectral classification has focused on automating the MK system, and most of this effort has concentrated on the application of supervised feed-forward neural networks.
		These authors focused primarily on spectral type classification of intermediate to low resolution spectra (1-15Å) in the optical and UV.
		Spectral classification is a means to an end, namely the determination of physical stellar parameters.
	www.iap.fr /SitesHeberges/com45uai/rapport99/node11.html (948 words)

	Galaxy Classification Lab - Astro 113 - Matthew A. Bershady
		This hoped-for insight is prompted most directly by how the spectral classification of stars provided astronomers with the impetus and framework to comprehend the physics that make stars shine.
		There have been many subsequent variants, but largely the classification has been based on subjective, qualitative assessments of the distribution of optical light -- what is often referred to as 'galaxy morphology.' There are many problems with the approach, yet it has remained paramount for over 70 years.
		Not coincidentally, it was Morgan who quantified and developed the stellar spectral classification scheme you used in Lab #3 (Spectral Classification of Stars).
	www.astro.wisc.edu /~mab/education/astro113/galclass_lab.html (2607 words)

	Classification of spectral types (from star) -- Encyclopædia Britannica (Site not responding. Last check: 2007-10-25)
		The Henry Draper Catalogue lists spectral classes from the hottest to the coolest stars.
		These types are designated, in order of decreasing temperature, by the letters O, B, A, F, G, K, and M. This group is supplemented by R- and N-type stars (today often referred to as carbon, or C-type, stars) and S-type stars.
		More results on "Classification of spectral types (from star)" when you join.
	www.britannica.com /eb/article-52823 (876 words)

	Major MIRA Results in Stellar Classification (Site not responding. Last check: 2007-10-25)
		Like the classification of plants and animals, the classification of stars is the basic language of astrophysical research.
		Temperatures, luminosities, sizes, even the ages of stars are keyed to their spectral classification.
		The article, entitled “Neural Network Classification of the Near-Infrared Spectra of A Type Stars” presented the next step in a series of results in the creation of a new spectral classification system based in the near-infrared part of the spectrum.
	www.wardsystems.com /pages.asp?7 (672 words)

	Automated Stellar Spectral Classification (Site not responding. Last check: 2007-10-25)
		Nonetheless, if stellar classification is to continue as a useful tool in stellar surveys, then it must adapt to keep pace with the large amounts of data which will be acquired as magnitude limits are pushed ever deeper.
		We are working on a project to automate the multi-parameter classification of visual stellar spectra, using artificial neural networks and other techniques.
		In addition to classification using the whole spectrum over the MK range, we have investigated the use of Principal Components Analysis as a front-end compression of the data.
	www.aas.org /publications/baas/v28n2/aas188/abs/S087004.html (228 words)

	Spectral Classification
		So each spectral class will have a letter designation (O, B, A, F, G, K, or M) and a single digit designation.
		For example, the sun is spectral class G2.
		Draw a graph using the spectral type on the vertical (y) axis and the B - V value on the horizontal (x) axis.
	wind.cc.whecn.edu /~marquard/astronomy/spectral_class.htm (453 words)

	Spectral Classification of Stars
		This lab teaches the basic techniques and criteria of the Morgan-Keenan system of spectral classification.
		Classification lies at the foundation of nearly every science.
		Scientists develop classification systems based upon perceived patterns in and relationships among natural objects.
	www.astro.washington.edu /labs/clearinghouse/labs/Spectclass/spectralclassweb.html (771 words)

	CLEA Spectroscopy manual
		In the course of the Harvard classification study, some of the old spectral types were consolidated together, and the types were re-arranged to reflect a steady change in the strengths of representative spectral lines.
		Because the spectral types represent a sequence of stars of different surface temperatures two things are notable: (1) The different spectral types show different absorption lines, and (2) The overall shape of the continuum changes.
		Having both the spectral classification and the apparent magnitude, m, of a star enables one to determine its distance, since there is a relation between the spectral type of a star and its absolute magnitude.
	www.mines.edu /Academic/courses/physics/phgn324/CLEA/spectrometry.html (7661 words)

	Spectral Classification of Galaxies: An Orthogonal Approach (Site not responding. Last check: 2007-10-25)
		The derived eigenbasis is affected by the normalization of the original spectral energy distributions.
		Projecting the spectral energy distributions on to their eigenspectra we find that the coefficients define a simple spectral classification scheme.
		The galaxy spectral types can then be described in terms of a one parameter family (the angle in the plane of the first two eigenvectors).
	tarkus.pha.jhu.edu /%7Eajc/papers/spec/spec.html (210 words)

	1.6\mum Spectral Classification of Bright Sources Discovered during 2MASS Prototyping (Site not responding. Last check: 2007-10-25)
		Spectral classification of a subset of the sources indicates that approximately 65% have spectral types typical of asymptotic giant branch stars (M, C, and S).
		These spectra have high SNR, and there is sufficient detail to differentiate between M, C, and S stars and to determine spectral type to within two subclasses.
		Our long range goal is to use radial velocities together with photometrically determined distances for spectrally identified AGB stars to probe the underlying structure of the Galaxy.
	www.aas.org /publications/baas/v27n4/aas187/S075005.html (264 words)

	The Data Fusion Server (Site not responding. Last check: 2007-10-25)
		The performance of the new procedure is assessed relative to those of the classification procedure combining spectral feature and textural measures based on the grey-level co-occurrence matrix from the near-infrared band of the SPOT bands and the per-pixel classification procedure.
		The testing result shows that the classification accuracy with the new procedure can be improved more than 10%, compared to those with the other two procedures.
		Testing results also show that the new procedure has considerable potential for the land cover and land use classifications in multi-spectral images, and it is particularly suitable for the land use and land cover classifications containing complex spectral components, like urban regions.
	www.data-fusion.org /print.php?sid=56 (335 words)

	Stellar Classification
		The work was funded from the estate of the American astronomer Henry Draper, and performed by a corps of women (and the commonly held belief is that women were chosen because they would work for less pay than men).
		Stars were categorised into a number of classes, distinguished by the strength of the spectral lines of different elements, beginning with hydrogen, and were originally assigned letters which ran in order.
		The classification of the spectral types of stars has become more complicated over the years as astronomers have discovered interesting features that they wanted to include.
	www.peripatus.gen.nz /Astronomy/SteCla.html (951 words)

	BBC - h2g2 - Spectral Classification System - A337312
		The Spectral Classification System is used by astronomers to group stars according to the properties of their electromagnetic spectra.
		When the spectral classification system was invented, stars were assigned a letter of the alphabet depending on how pronounced the Balmer lines were in the star's spectrum.
		To remember the order of the spectral classes, astronomy students use mnemonics such as 'Oh Be A Fine Girl/Guy Kiss Me!'.
	www.bbc.co.uk /dna/h2g2/alabaster/A337312 (619 words)

	Classification of hot sub-dwarfs
		The aim of this classification scheme is to establish reference standards which would be suitable for subsequent fine analysis.
		These classifications are designed to eliminate, for 2A resolution spectra, the confusion which arises from the use of acronyms such as sdO, sdOB, sdO(B), sdB.
		Note that the current two-dimensional classification depends primarily on the relative strengths of H-gamma, He I 4713, He I 4471, He II 4686 and He II 4543.
	star.arm.ac.uk /%7Ecsj/abstracts/sdb_class.html (224 words)

	Free Virtual Galaxy Project-Spectral Classification (Site not responding. Last check: 2007-10-25)
		The lines corresponding to a particular frequency may be narrow for one star and wider in another, or, in other cases, the intensity of the lines may differ.
		When Spectral Class and Luminosity are plotted against one another by placing the former along the x-axis and the latter along the y-axis of a graph, we are looking at a
		Main Sequence stars exhibit Luminosities typical for their Spectral Class and are in the prime of their existence.
	www.ccm.net /~jrsmith/spclass.html (1093 words)

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