The physical quantities of stars, the determinants of stellar structure and evolution.The most fundamental and reliable method to determine the stellar mass is to use the orbital motion of binary stars.The lower limit of star mass is 0.08 solar mass.A smaller star can form, but its central temperature is not high, so it can not start nuclear reaction, and can only rely on gravitational contraction to release energy. No main sequence star with a mass lower than 0.08 solar mass has been found.
As for the theoretical upper limit of stellar mass, it is very uncertain, and some calculations give 60~100 solar masses.However, infrared and visible light surveys show that there are many evidences of stars with a mass of about 200 sun. Such stars may not pass throughRed GiantPhase.There is also evidence that R136a, a super massive star in Large Magellan, contains about 3000 solar masses. Although most astronomers regard it as dozens or hundreds of O-shaped clusters, other astronomers believe it is a single super massive star based on the data of the International Ultraviolet Exploration Satellite and ground optical observations.
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Quality isfixed starOne of the most important physical parameters is star structure and star evolution (seeFormation and evolution of stars）The decisive factor of.The most basic way to calculate the mass of stars is to use the orbital motion of physical binaries.The mass obtained by this method is called dynamic mass.
Specific methods
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Method 1
① Such asVisual binaryThere are reliableparallax, can be appliedKepler's third lawThe sum of the mass of the two sub stars is calculated from the true length of the semi major axis of the orbit and the orbital period, and then the mass ratio of the two sub stars is obtained from the ratio of the distance between the two sub stars and the common center of mass, and then the mass of each sub star is calculated.For example, theSiriusThe masses of A and B are 2.143 and 1.053 solar masses respectively.
② Such as bispectrumSpectroscopic binaryIt has scored light breakdown, and this pair of stars isEclipsing binaryThe mass of the two sub stars can be obtained by knowing the orbital inclination in the photometric solution.Using this method, the masses of the eclipsing binary star Daling Wujia and B are 3.7 and 0.81 solar masses respectively.
③ Such asBispectral spectroscopic binaryThe mass of the two sub stars can be obtained if the binary stars have been divided into photolysis, and they are interference binary stars and their orbital inclination angles are known.Calculated by this methodCornucopiaThe masses of A and B are 10.9 and 6.8 solar masses respectively.
④ The mass of the two sub stars can also be obtained by the splitting of the double spectral light splitting stars and the orbital inclination angle obtained from the polarization observation. For example, the mass of Plaskett star (HD47129=HR2422, a sixth class star in the constellation Kirin) is calculated in this way.
Method 2
Other methods for calculating star mass mainly include:White dwarfOfGravitational redshiftMeasure the mass of the white dwarf;According to true radius and surfaceGravitational accelerationCalculate the mass of the star (i.e. spectral mass or atmospheric mass);According to the statistical relationship between the mass and luminosity of stars（Mass light relation）, estimate the mass from the luminosity;Using stars inHerotuEstimating the stellar mass (called "evolutionary mass") from the theoretical evolution trajectories on;For known true radiusPulsating variable star, the average density can be estimated from the pulsation period to obtain the mass (called "pulsation mass").But these methods are not as reliable as the dynamic mass method.
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The mass data of many stars are still very unreliable or low in accuracy, includingarcturus, the elderlyVega 、Hegu II、Betelgeuse、Antares Isobright stars.A lot of work needs to be done to compile an accurate stellar mass table of considerable scale.
The stellar mass ranges from a few percent of the solar mass (such as some red dwarfs, especially the children of physical binaries) to 120 solar masses, sometimes more, but the mass of most stars ranges from 0.1 to 10 solar masses.1978~1979X-ray binaryAccording to the data ofneutron starThe average mass is 1.6 ± 0.3 solar mass.The mass range of a star is much smaller than the luminosity and diameter range.
The mass of a star changes with time.In addition to thermonuclear reactions, which constantly convert mass into radiant energy, many stars also lose mass due to the expansion of the atmosphere or the ejection of matter.Nova、SupernovaThe mass is thrown out when the star shines, and the mass may be greatly reduced after the supernova explodes.Close binarySometimes the mass of one sub star will gradually transfer to another (seeQuality communication)。
