| 其他摘要 | Using the OPAL high temperature opacities and the new Wichita State low temperature opacities, we constructed the opacities matching well with Eggleton's code. Using Eggleton's code, we systematically calculate the normal stellar evolution, for both scaled-solar metal mixture and alpha-enhanced metal mixtures. In our calculations, the masses of stars range from 0.25 to 80.0 MsunThe values of metallicities Z are respectively as 0.0001, 0.0003, 0.001, 0.004, 0.01, 0.02, 0.03, 0.04, 0.06, 0.08 and 0.10. Through comparison, we find that alpha-enhancement can raise stellar effective temperatures by several thousand K, raise stellar luminosities by more than ten percent and reduce the evolutionary lifetime by more than ten percent. We make intermediate mass stars sharply lose envelope masses during the red giant branch phase, to construct a series of initial evolutionary models of hot subdwarfs. In our calculation, the metallicities of hot subdwarfs are 0.001, 0.004, 0.02 and 0.04, respectively. The core masses of hot subdwarfs are 0.400, 0.450, 0.475, 0.500 and 0.550 Msun, respectively. And the envelope masses of hot subdwarfs are 0.001, 0.005, 0.010, 0.015 and 0.020 Msun, respectively. Through calculation and comparison, it is found that alpha-enhancement can raise the effective temperatures by several thousand K, raise the gravity on the surface by dozens of percent, raise the luminosities by several percent and reduce the evolutionary lifetime by several percent, for hot subdwarfs. The higher values their metallicities are, the more obvious the alpha-enhanced effects are; and the thicker their envelopes are, the more obvious the \alpha-enhancement effects are. Using Eggleton’s code, we calculate the evolution of stars with metallicity 0.02 and with masses from 0.08 to 4.00 Msun. Then we newly fit the formulae of stellar luminosity and radius, the variable is stellar mass. Using the the boundary flux of habitable zones given by Jones in 2006, we calculate the habitable zones of host stars with masses 0.08-4.00 Msun. Using the distribution of semimajor axis and mass of planets given by Ida and Lin in 2005, we further achieve the probability distribution of terrestrial planets in habitable zones around host stars with masses 0.08-4.00Msun. Using the initial mass function of stars, we obtain the number of terrestrial planets in habitable zones of host stars in the Milky Way, just as 39.8 billion. And the number of terrestrial planets with lives in the Milky Way is about 3.74 billion. Using the boundary ultraviolet radiation of ultraviolet habitable zone given by Buccino et al. in 2006, we calculate the ultraviolet habitable zones of host stars with masses 0.08-4.00 Msun. A star will become brighter and brighter with stellar evolution, and the distance of its habitable zone will become larger and larger. Some planets outside the habitable zone of a host star during the main sequence phase may enter the habitable zone of the host star during other evolutionary phases. We calculate the habitable zone of our Solar system after the main sequence phase. It is found that the orbit of Saturn will enter the habitable zone of Solar during the horizontal branch phase for 137 million years. |
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