Yulduz: Versiyalar orasidagi farq
Kontent oʻchirildi Kontent qoʻshildi
Qator 752:
| title=Faintest Stars in Globular Cluster NGC 6397
| publisher=HubbleSite | accessdate=2006-06-08 }}</ref>
==Tasnifi==
{| class="wikitable" style="float: right; text-align: center; margin-left: 1em;"
|+ ''Turli sinf yulduzlar uchun<br />sirt harorati farqlari''<ref>{{cite web
| last=Smith | first=Gene | date=April 16, 1999
| url=http://casswww.ucsd.edu/public/tutorial/Stars.html
| title=Stellar Spectra
| publisher=University of California, San Diego
| accessdate=2006-10-12 }}</ref>
! Sinf
! Harorat
! Etalon yulduz
|- style="background: {{star-color|O}}"
| O
| 33 000 K yoki koʻp
| [[Zeta Ophiuchi]]
|- style="background: {{star-color|B}}"
| B
| 10 500–30 000 K
| [[Rigel]]
|- style="background: {{star-color|A}}"
| A
| 7 500–10 000 K
| [[Altair]]
|- style="background: {{star-color|F}}"
| F
| 6 000–7 200 K
| [[Procyon|Procyon A]]
|- style="background: {{star-color|G}}"
| G
| 5 500–6 000 K
| [[Quyosh]]
|- style="background: {{star-color|K}}"
| K
| 4 000–5 250 K
| [[Epsilon Indi]]
|- style="background: {{star-color|M}}"
| M
| 2 600–3 850 K
| [[Proxima Centauri]]
|}
{{Main|Yulduzlar tasnifi}}
The current stellar classification system originated in the early 20th century, when stars were classified from ''A'' to ''Q'' based on the strength of the [[hydrogen line]].<ref>{{cite journal
| last=Fowler | first=A.
| title=The Draper Catalogue of Stellar Spectra
| journal=Nature
| year=1891–2 | volume=45 | pages=427–8 | doi = 10.1038/045427a0 |bibcode = 1892Natur..45..427F }}</ref> It was not known at the time that the major influence on the line strength was temperature; the hydrogen line strength reaches a peak at over 9000 K, and is weaker at both hotter and cooler temperatures. When the classifications were reordered by temperature, it more closely resembled the modern scheme.<ref name=carlos>{{cite book
| first1=Carlos | last1=Jaschek | last2=Jaschek | first2=Mercedes
| year=1990 | title=The Classification of Stars
| publisher=Cambridge University Press | pages=31–48
| isbn=0-521-38996-8 }}</ref>
There are different single-letter classifications of stars according to their spectra, ranging from type ''O'', which are very hot, to ''M'', which are so cool that molecules may form in their atmospheres. The main classifications in order of decreasing surface temperature are: ''O, B, A, F, G, K'', and ''M''. A variety of rare spectral types have special classifications. The most common of these are types ''L'' and ''T'', which classify the coldest low-mass stars and brown dwarfs. Each letter has 10 sub-divisions, numbered from 0 to 9, in order of decreasing temperature. However, this system breaks down at extreme high temperatures: class ''O0'' and ''O1'' stars may not exist.<ref name="spectrum">{{cite web
| first=Alan M | last=MacRobert
| url =http://www.skyandtelescope.com/howto/basics/3305876.html
| title = The Spectral Types of Stars
| publisher = Sky and Telescope
| accessdate = 2006-07-19 }}</ref>
In addition, stars may be classified by the luminosity effects found in their spectral lines, which correspond to their spatial size and is determined by the surface gravity. These range from ''0'' ([[hypergiant]]s) through ''III'' ([[giant star|giant]]s) to ''V'' (main sequence dwarfs); some authors add ''VII'' (white dwarfs). Most stars belong to the [[main sequence]], which consists of ordinary [[hydrogen burning process|hydrogen-burning]] stars. These fall along a narrow, diagonal band when graphed according to their absolute magnitude and spectral type.<ref name="spectrum" /> The Sun is a main sequence ''G2V'' yellow dwarf, being of intermediate temperature and ordinary size.
Additional nomenclature, in the form of lower-case letters, can follow the spectral type to indicate peculiar features of the spectrum. For example, an "''e''" can indicate the presence of emission lines; "''m''" represents unusually strong levels of metals, and "''var''" can mean variations in the spectral type.<ref name="spectrum" />
White dwarf stars have their own class that begins with the letter ''D''. This is further sub-divided into the classes ''DA'', ''DB'', ''DC'', ''DO'', ''DZ'', and ''DQ'', depending on the types of prominent lines found in the spectrum. This is followed by a numerical value that indicates the temperature index.<ref>{{cite web
| url = http://web.archive.org/web/20091008115925/http://www.physics.uq.edu.au/people/ross/ph3080/whitey.htm
| title = White Dwarf (wd) Stars
| publisher = White Dwarf Research Corporation
| accessdate = 2006-07-19 }}</ref>
==Manbalar==
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