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Topic: Spectral type


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In the News (Mon 23 Oct 17)

  
  CONK! Encyclopedia: Spectral_type   (Site not responding. Last check: 2007-11-07)
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.
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.
Since the radius of a giant star is much larger than a dwarf star while their masses are roughly comparable, the gravity and thus the gas density and pressure on the surface of a giant star are much lower than for a dwarf.
www.conk.com /search/encyclopedia.cgi?q=Spectral_type   (2024 words)

  
 Spectral type   (Site not responding. Last check: 2007-11-07)
Spectral SDK The spectral software development kit (SDK) is a package of OCX (ActiveX) controls to develop own spectral processing programs as easy as possible.
Spectral Methods in MATLAB Forty short m-files which do everything from demonstrating spectral accuracy on functions of varying smoothness to solving the Poisson, biharmonic, Orr-Sommerfeld, KdV, and Allen-Cahn equations.
Spectral Lines Spectral Lines is a science webzine covering everything from the analysis of astronomical data to the detection of zygotes in zoological specimens.
www.serebella.com /encyclopedia/article-Spectral_type.html   (511 words)

  
 eSky: Spectral Classification
Most of the common types have associated colours, which are themselves a consequence of the temperature of the star (hotter stars are bluer, while cooler stars tend to be redder).
Stars of this type are blue in colour and burn hotly, with surface temperatures lying between 11,000 K and 25,000 K.
A-type stars are those whose surface temperatures lie in the approximate range 7,500 K to 11,000 K.
www.glyphweb.com /esky/concepts/spectralclassification.html   (1065 words)

  
 Spectral Type B Stars
The characteristic properties of type B stars – including spectra, mass, and luminosity –; are briefly described, followed by notes about a few well-known examples.
Type B stars are often found in spatial proximity to type O stars; O+B binaries and OB associations are common.
Type O and B stars are short-lived, therefore they are never found too far from their birthplaces in the galactic plane.
www.peripatus.gen.nz /Astronomy/SpeTypB.html   (736 words)

  
 [No title]   (Site not responding. Last check: 2007-11-07)
Stars are assigned to this type on the basis of the following (purely spectroscopic) criteria: spectral types are in the range Fe-Me. The spectra of most typical stars resemble the spectrum of the solar chromosphere.
ISA Rapid irregular variables of the early spectral types, B-A or Ae; ISB Rapid irregular variables of the intermediate and late spectral types, F-M and Fe-Me. RCB Variables of the R Coronae Borealis type.
Spectral type at maximum light is F; at minimum, the types are G-K. The longer the period of light variation, the later is the spectral type.
www.sai.msu.su /groups/cluster/gcvs/gcvs/iii/vartype.txt   (4747 words)

  
 Catalog of Positions of Infrared Stellar Sources -- Original 1994 information   (Site not responding. Last check: 2007-11-07)
If a luminosity class was available, the absolute magnitude was determined from the spectral type using the empirical relationships of Schmidt-Kaler (1982), and distance determined from the difference between the apparent and absolute magnitude (this was calculated in an iterative manner, with the absorption used to correct the distance estimate).
Thus it seems that the spectral types in all the catalogs are consistent for those stars with an observed color, but not for the redder stars without an observed color.
A spectral type and source is given, along with an estimate of the B-V color excess and a flag to indicate the method by which the excess was determined.
ad.usno.navy.mil /cpirss/cpirss_1994.html   (4027 words)

  
 Classifying_Stars
Spectral Type classifies a star on the basis of its spectrum, which depends primarily on the star's temperature and color.
Although spectral type B main-sequence giant and supergiant stars are relatively rare, they are so luminous they can be seen across great distances.
The most luminous stars within thirty light-years of the Sun are spectral type A. Five of the twenty brightest (apparent magnitude) stars in the night sky are spectral type A. Warm to hot, and yellow-white in color.
www.esse.ou.edu /fund_concepts/Fundamental_Concepts1/Universe/Classifying_Stars.html   (898 words)

  
 Spectral Classification
For the standard spectral types, the spectra are sorted into luminosity classes, and displayed in increasing sub-type (decreasing temperature) for each luminosity class.
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).
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)

  
 The Classification of Stellar Spectra
Important lines are the hydrogen Balmer lines, lines of neutral and singly ionized helium, iron lines, the H and K doublet of ionized calcium at 396.8 and 393.3 nm, the G band due to the CH molecule, the 422.7 nm neutral calcium line, several metal lines around 431 nm, and the lines of titanium oxide.
These are isotopes of elements which have been formed from the capture of a free neutron (changing the isotope of the element) followed by a beta decay (a neutron decays into a proton and an electron, thus changing the element to one with a higher atomic number and an isotope with one less neutron).
Spectral lines also show Doppler shifts with respect to the rest velocity of the star, indicating that matter is streaming out from them.
www.shef.ac.uk /physics/people/pacrowther/spectral_classification.html   (1913 words)

  
 Almagest 2005 | The Constellations | Andromeda   (Site not responding. Last check: 2007-11-07)
The primary is a red giant (spectral type M2) with a magnitude which is thought to be variable between +4.76 and +4.93 Component ‘a’ (magnitude +16.0) is found 14.0″ south of the primary; A-B is a CPM pair with Component B (magnitude +13.0) found 7.6″ to the southeast.
Component B is a δ Scuti-type variable (spectral type A2) with a maximum magnitude of +8.7 It has an angular separation from the primary of 0.4″ and an orbital period of 76.6 years.
The primary (spectral type K1) has a magnitude of +6.02 and the secondary (spectral type K6) is +6.41 The pair have an angular separation (as of November 1983) of 0.68″ and orbit each other every 163.68 years.
www.almagest.pwp.blueyonder.co.uk /andromeda.htm   (4547 words)

  
 SARB Surface Map Explanation   (Site not responding. Last check: 2007-11-07)
The spectral albedo and emissivities are determined via a table lookup based on the scene type underlying the CERES footprint.
A table lookup determines spectral albedo (emissivity) for each scene type which are then weighted by the scene type percentages from the imager and integrated giving a spectral albedo (emissivity) curve for the entire footprint.
As the spectral intervals defined in literature do not match those required a set of weights were developed using MODTRAN surface insolation to interpolate (extrapolate) spectral albedos to the required limits.
snowdog.larc.nasa.gov /surf/pages/explan.html   (1552 words)

  
 Sky Publishing - The Spectral Types of Stars   (Site not responding. Last check: 2007-11-07)
Appended to the basic spectral type may be letters for chemical peculiarities, an extended atmosphere, unusual surface activity, fast rotation, or other special characteristics.
Spectral types on the blue end were called "early" and those on the red end "late." These terms are still used today, though the incorrect idea of stellar evolution they embody -- that stars simply cool with age -- has been obsolete for generations.
Type W or Wolf-Rayet stars are as hot and blue as the hottest O stars but show strong emission lines, either of nitrogen (WN), carbon and oxygen (WC), or neither (WR).
www.wwnorton.com /astro21/sandt/startypes.html   (2238 words)

  
 spectral type
From hottest to coolest they are: O, B, A, F, G, K, and M. Each class is characterized by the appearance of certain types of spectral lines and is further subdivided into 10 sub-classes numbered from 0 to 9.
The Sun, for example, is assigned the spectral class G2 in the modern Harvard classification, corresponding to a surface temperature of about 5,700°C.
Other spectral characteristics, such as the presence of emission lines, are indicated by an additional small letter placed after the spectral type (see Table 2).
www.daviddarling.info /encyclopedia/S/spectype.html   (277 words)

  
 Star Spectral Classification   (Site not responding. Last check: 2007-11-07)
Stars can be classified by their surface temperatures as determined from Wien's Displacement Law, but this poses practical difficulties for distant stars.
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.
Note the rise of the spectral curve toward the blue from the flbody radiation curve.
hyperphysics.phy-astr.gsu.edu /hbase/starlog/staspe.html   (409 words)

  
 Vspec - Wavelength calibration
This the tricky part of the Spectral processing as there is no automatic tool to immediately detect and tag the lines on every spectrum.
To know which spectral type is the star you are studying, use the "spectral type" function.
Up to 131 standard spectral type spectrum are provided, ranged from 1160 angstrom up to 10 590...
www.astrosurf.com /vdesnoux/howto01.html   (534 words)

  
 late star concept from the Astronomy knowledge base   (Site not responding. Last check: 2007-11-07)
G star (19 kinds, 195 facts) - Spectral type for yellow stars., Yellowish star in which the H and K lines of Ca II have become dominant and in which a tremendous profusion of spectral lines of both neutral and ionized metals, particularly iron, begins to show.
M star (12 kinds, 105 facts) - Spectral type for red stars, such as Betelgeuse, Antares, and Proxima Centauri., Star of spectral type M are cool red stars with surface temperatures of less than 3600 K whose spectra are dominated by molecular bands, especially those of TiO.
S star (1 kind, 8 facts) - Red-giant stars of spectral type S are similar to M stars except that the dominant oxides are those of the metals of the fifth period (Zr, Y, etc.) instead of the third (Ti, Sc, V).
www.site.uottawa.ca:4321 /astronomy/latestar.html   (911 words)

  
 Spectral classification of late-type dwarfs
In practice, a spectral classification system is defined by a number of stars (or brown dwarfs) which are selected as fiducial standards, each representing a particular spectral class (M1, M2, M3, etc.).
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 /~inr/ldwarf.html   (2629 words)

  
 Spectral Type O Stars
In the solar vicinity, dwarf (luminosity class V) O type stars dominate the massive star population, leading to the conclusion that this is the most prolonged evolutionary phase in the lifetime of massive stars (Nota et al.
O is the earliest spectral type, radiating strongly at short wavelengths; thus their light appears bluish to the human eye.
This is the only main sequence spectral type in which ionised helium can be seen; only O stars are sufficiently hot to produce the 24ev required to ionise helium.
www.peripatus.gen.nz /Astronomy/SpeTypO.html   (1626 words)

  
 Catalogue: III/231   (Site not responding. Last check: 2007-11-07)
Note (1): This is the spectral type of the star, exactly as it appears in the original spectral type catalog.
Note (4): This is the distance in arcsec between the Tycho-2 object and the star from the spectral type catalog to which it was matched.
For example, if a spectral type was originally listed as K2/3 III, it will be K2 3, where K is the temperature class, 2 is the subclass, and 3 is the luminosity class.
cdsweb.u-strasbg.fr /cgi-bin/Cat?III/231   (795 words)

  
 Stellar classification - Wikipedia, the free encyclopedia
Type P objects are planetary nebulae and type Q objects are novae.
DA: a hydrogen-rich "atmosphere" or outer layer, indicated by strong Balmer hydrogen spectral lines.
All class D stars use the same sequence from 1 to 9, with 1 indicating a temperature above 37,500 K and 9 indicating a temperature below 5,500 K. edit]
en.wikipedia.org /wiki/Spectral_type   (2048 words)

  
 THE NEW NEARBY STAR SO025300.5+165258   (Site not responding. Last check: 2007-11-07)
Eight additional stars within 10 parsecs having spectral types M6.0V to M7.0V and BVRI photometry (14 individual sets of photometry) have been run through the same distance estimate code.
None of the eight stars has such a large disparity in the results, and the final estimated distances are more than 10% different from the true distances in only 3 cases of 14 (11.0%, 13.0% and 25.0%).
1994, 2002) to estimate a distance from the spectral type and the V magnitude.
www.chara.gsu.edu /RECONS/new.SO025300.5+165258.htm   (564 words)

  
 Star Classification - Zoom Astronomy
The Sun is a as a G2V type star, a yellow dwarf and a main sequence star.
The Hertzsprung -Russell (H-R) Diagram is a graph that plots stars color (spectral type or surface temperature) vs. its luminosity (intrinsic brightness or absolute magnitude).
X-ray binary stars are a special type of binary star in which one of the stars is a collapsed object such as a white dwarf, neutron star, or fl hole.
www.enchantedlearning.com /subjects/astronomy/stars/startypes.shtml   (1144 words)

  
 GCPD: The Lockwood photometric system   (Site not responding. Last check: 2007-11-07)
The Miras are shown to map out large loops in a diagram of molecular band strength as a function of color, and large differences of band strength can occur at a given color and phase in different stars or in the same stars during different cycles.
The Miras with periods less than 300d are warmer by several hundred degrees at a given spectral type than either the normal giants used for calibration or the Miras with periods longer than 300d.
The mean phase of earliest spectral type is ~0.03, while maximum light at 1.04 mu occurs at ~0.11.
obswww.unige.ch /gcpd/ph30.html   (247 words)

  
 Searchengine.net : Spectral Types
types are thought to correspond to an asteroid's surface...
types of light in the "pile of light" (the continuous spectrum) coming from the flbody.
spectral type, radiating strongly at short wavelengths; thus their light appears bluish to the...
msxml.infospace.com /_1_ZUUTFE03PMLJMT__info.snetuk/search/nextweb/Spectral%2BTypes/11/20/1/-/1/0/0/1/1/1/-/-/-/di2%253A1121563529196/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/999gpqjpj/10/0/10/-/-/-/1   (155 words)

  
 Spectral Type   (Site not responding. Last check: 2007-11-07)
For this purpose, several known objects with spectral type between M0.5 and L2 were observed, so that a correlation could be established between colour and spectral type in a (M915, M855-M915) colour-magnitude diagram.
In ChaI-5 the only object with clear Halpha emission is found to have a spectral type of M4-4.5 and it's most likely a low-mass star.
Three of them have later spectral types M7-9, while for the two faintest ones the same turning back as in ChaI-4 is observed.
www.tls-tautenburg.de /research/belen/jenam01/sptype.html   (248 words)

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