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Qator 867:
| issue=5743 | pages=2027–2029 | doi= 10.1126/science.1117542
| pmid=16179471 | bibcode=2005Sci...309.2027B }}</ref>
==Termoyadroviy reaksiya yoʻllari==
{{Main|Yulduz nukleosintezi}}
{{Multiple image|direction=vertical|align=right|image1=FusionintheSun.svg|image2=CNO Cycle.svg|width=200|caption1=Overview of the proton-proton chain|caption2=The carbon-nitrogen-oxygen cycle}}
A variety of different nuclear fusion reactions take place inside the cores of stars, depending upon their mass and composition, as part of [[stellar nucleosynthesis]]. The net mass of the fused atomic nuclei is smaller than the sum of the constituents. This lost mass is released as electromagnetic energy, according to the [[mass-energy equivalence]] relationship ''E'' = ''mc''<sup>2</sup>.<ref name="sunshine" />
The hydrogen fusion process is temperature-sensitive, so a moderate increase in the core temperature will result in a significant increase in the fusion rate. As a result the core temperature of main sequence stars only varies from 4 million kelvin for a small M-class star to 40 million kelvin for a massive O-class star.<ref name="aps_mss">{{cite web
| date=February 16, 2005 | url=http://www.astrophysicsspectator.com/topics/stars/MainSequence.html
| title=Main Sequence Stars
| publisher=The Astrophysics Spectator
| accessdate=2006-10-10 }}</ref>
In the Sun, with a 10-million-kelvin core, hydrogen fuses to form helium in the [[proton-proton chain reaction]]:<ref name="synthesis">{{cite journal | display-authors=1 | last1=Wallerstein | first1=G. | last2=Iben Jr. | first2=I. | last3=Parker | first3=P. | last4=Boesgaard | first4=A. M. | last5=Hale | first5=G. M. | last6=Champagne | first6=A. E. | last7=Barnes | first7=C. A. | last8=KM-dppeler | first8=F. | last9=Smith | first9=V. V. | last10=Hoffman | first10=R. D. | last11=Timmes | first11=F. X. | last12=Sneden | first12=C. | last13=Boyd | first13=R. N. | last14=Meyer | first14=B. S. | last15=Lambert | first15=D. L. | title=Synthesis of the elements in stars: forty years of progress | journal=Reviews of Modern Physics | year=1999 | volume=69 | issue=4 | pages=995–1084 | url=http://authors.library.caltech.edu/10255/1/WALrmp97.pdf| format=PDF | accessdate=2006-08-04 | doi=10.1103/RevModPhys.69.995 | bibcode=1997RvMP...69..995W}}</ref>
:4[[Hydrogen-1|<sup>1</sup>H]] → 2[[deuterium|<sup>2</sup>H]] + 2[[positron|e<sup>+</sup>]] + 2[[neutrino|ν<sub>e</sub>]] (4.0 M[[electronvolt|eV]] + 1.0 MeV)
:2<sup>1</sup>H + 2<sup>2</sup>H → 2[[Helium-3|<sup>3</sup>He]] + 2[[photon|γ]] (5.5 MeV)
:2<sup>3</sup>He → [[Helium-4|<sup>4</sup>He]] + 2<sup>1</sup>H (12.9 MeV)
These reactions result in the overall reaction:
:4<sup>1</sup>H → <sup>4</sup>He + 2e<sup>+</sup> + 2γ + 2ν<sub>e</sub> (26.7 MeV)
where e<sup>+</sup> is a [[positron]], γ is a gamma ray photon, ν<sub>e</sub> is a [[neutrino]], and H and He are isotopes of hydrogen and helium, respectively. The energy released by this reaction is in millions of electron volts, which is actually only a tiny amount of energy. However enormous numbers of these reactions occur constantly, producing all the energy necessary to sustain the star's radiation output.
{| class="wikitable" style="float: left;"
|+ Minimum stellar mass required for fusion
|-
!Element
![[Solar mass|Solar<br />masses]]
|-
| Hydrogen ||style="text-align: center;"| 0.01
|-
| Helium ||style="text-align: center;"| 0.4
|-
| Carbon ||style="text-align: center;"| 5<ref>{{cite journal
| last1=Girardi | first1=L. | last2=Bressan | first2=A. | last3=Bertelli | first3=G. | last4=Chiosi | first4=C. | title=Evolutionary tracks and isochrones for low- and intermediate-mass stars: From 0.15 to 7 M<sub>sun</sub>, and from Z=0.0004 to 0.03
| journal=Astronomy and Astrophysics Supplement
| year=2000 | volume=141
| issue=3 | pages=371–383
| doi=10.1051/aas:2000126 |arxiv = astro-ph/9910164 |bibcode = 2000A&AS..141..371G }}</ref>
|-
| Neon ||style="text-align: center;"| 8
|}
In more massive stars, helium is produced in a cycle of reactions [[catalyst|catalyzed]] by carbon—the [[CNO cycle|carbon-nitrogen-oxygen cycle]].<ref name="synthesis" />
In evolved stars with cores at 100 million kelvin and masses between 0.5 and 10 solar masses, helium can be transformed into carbon in the [[triple-alpha process]] that uses the intermediate element [[beryllium]]:<ref name="synthesis" />
:<sup>4</sup>He + <sup>4</sup>He + 92 keV → [[Isotopes of beryllium|<sup>8*</sup>Be]]
:<sup>4</sup>He + <sup>8*</sup>Be + 67 keV → <sup>12*</sup>C
:<sup>12*</sup>C → [[Carbon-12|<sup>12</sup>C]] + γ + 7.4 MeV
For an overall reaction of:
:3<sup>4</sup>He → <sup>12</sup>C + γ + 7.2 MeV
In massive stars, heavier elements can also be burned in a contracting core through the [[neon burning process]] and [[oxygen burning process]]. The final stage in the stellar nucleosynthesis process is the [[silicon burning process]] that results in the production of the stable isotope iron-56. Fusion can not proceed any further except through an [[endothermic]] process, and so further energy can only be produced through gravitational collapse.<ref name="synthesis" />
The example below shows the amount of time required for a star of 20 solar masses to consume all of its nuclear fuel. As an O-class main sequence star, it would be 8 times the solar radius and 62,000 times the Sun's luminosity.<ref>{{cite journal | last1=Woosley | first1=S. E. | last2=Heger | first2=A. | last3=Weaver | first3=T. A. | title=The evolution and explosion of massive stars | journal=Reviews of Modern Physics | year=2002 | volume=74 | issue=4 | pages=1015–1071 | bibcode=2002RvMP...74.1015W | doi = 10.1103/RevModPhys.74.1015}}</ref>
{{-}}
{| class="wikitable" style="margin: 1em auto 1em auto;"
|-
!valign="bottom"| Fuel<br />material
!valign="bottom"| Temperature<br />(million kelvins)
!valign="bottom"| Density<br />(kg/cm<sup>3</sup>)
!valign="bottom"| Burn duration<br />(τ in years)
|- style="text-align:center;"
|| H
|| 37
|| 0.0045
|| 8.1 million
|- style="text-align:center;"
|| He
|| 188
|| 0.97
|| 1.2 million
|- style="text-align:center;"
|| C
|| 870
|| 170
|| 976
|- style="text-align:center;"
|| Ne
|| 1,570
|| 3,100
|| 0.6
|- style="text-align:center;"
|| O
|| 1,980
|| 5,550
|| 1.25
|- style="text-align:center;"
|| S/Si
|| 3,340
|| 33,400
|| 0.0315<ref>11.5 days is 0.0315 years.</ref>
|}
==Manbalar==
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