The evolution of hydrogen-helium stars
The evolution of hydrogen-helium stars
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氢氦星的演化
DOI：
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发表时间：
1971
期刊：
影响因子：
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通讯作者：
A. Cameron
中科院分区：
文献类型：
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作者：
D. Ezer;A. Cameron
根据杜伦和卡梅隆以及其他人在银河系化学演化方面的工作，银河系中的第一代恒星主要包含大质量天体。如果大爆炸核合成对氦的形成负责，那么第一代恒星将含有大约80%的氢和20%的氦，这与最近的太阳恒星演化研究中发现的大约22%的氦是一致的。本研究跟踪了5、10、20、30、100和200m⊙恒星的前主序演化和主序演化。在整个质量范围内的正常恒星通常通过主序上的CN循环将氢转化为氦。目前的5米和10米⊙的氢氦恒星必须达到更高的中心温度，才能通过质子-质子链将氢转化为氦。因此，恒星中的平均密度更大，表面温度也高于正常恒星。在20m⊙和更大的恒星中，当收缩产生接近108K的中心温度时，质子-质子链无法成功地提供恒星所需的光度。在这一点上，三重阿尔法反应产生少量的C12，然后在CN循环中充当催化剂，然后C12的速度受到循环中发生的β衰变的限制。在这些质量较大的恒星演化过程中，中心温度保持在108K附近，主序上的表面温度接近105K。200m⊙的恒星在其主序演化的后期通过辐射压力对表面质量损失变得不稳定，这些质量损失效应没有被遵循。包含这些大质量恒星的年轻星系将具有非常高的光度，但如果它们形成于宇宙现在年龄的十分之一或更晚，那么来自它们的光将主要存在于可见光或紫外线中，而不是像Partridge和Peeble所建议的那样，存在于红外中。
According to the work of Truran and Cameron, and of others, on the chemical evolution of the Galaxy, the first generation of stars in the Galaxy contained principally massive objects. If big-bang nucleosynthesis was responsible for the formation of helium, the first generation of stars would contain about 80% hydrogen and 20% helium, to be consistent with the approximately 22% helium found in recent stellar evolutionary studies of the Sun. The present investigation has followed the pre-main sequence evolution and the main sequence evolution of stars of 5, 10, 20, 30, 100, and 200M⊙. Normal stars in this entire mass range normally convert hydrogen into helium by the CN-cycle on the main sequence. the present hydrogen-helium stars of 5 and 10M⊙ must reach higher central temperatures in order to convert hydrogen to helium by the proton-proton chains. Consequently, the mean densities in the stars are greater, and the surface temperatures are higher than in normal stars. In the stars of 20M⊙ and larger, the proton-proton chains do not succed in supplying the necessary luminosity of the stars by the time the contraction has produced a central temperature near 108K. At that point triple-alpha reactions generate small amounts of C12, which then acts as a catalyst in the CN-cycle, the rate of which is then limited by the beta-decays occurring within the cycle. During the evolution of these more massive stars, the central temperature remains in the vicinity of 108 K, and the surface temperature on the main sequence approaches 105 K. The star of 200M⊙ becomes unstable against surface mass loss through radiation pressure in the later stages of its main sequence evolution, and these mass loss effects were not followed. Young galaxies containing these massive stars will have a very high luminosity, but if they have formed at one-tenth the present age of the universe or later, then the light from them will mainly reside in the visible or ultraviolet, rather than in the infrared as has been suggested by Partridge and Peebles.