Mass-luminosity relationship
A mass-luminosity relationship represents a connection between the mass of an object , for example a star , and its luminosity . This relationship can be used to estimate the mass of a star solely from observing its luminosity.
As an alternative to the luminosity, the effective temperature or the spectral type of a star can be used, which are usually easier to determine.
Main sequence stars
For main sequence stars which is empirically determined mass-luminosity relation well known. It was first described in 1926 in the book " The Internal Constitution of Stars " by Sir Arthur Stanley Eddington :
The relationship only applies to main sequence stars and can not simply be transferred to giant stars or brown dwarfs .
The mass-luminosity relationship specifically means that a star with twice the solar mass has 11.3 times the luminosity of the sun ; a star with 4 solar masses is already 128 times as bright as the sun. This strong dependency means that massive stars have a much shorter dwell time (“lifetime”) on the main sequence than low-mass stars, since their nuclear fuel is used up much faster.
The exponent of the mass-luminosity relationship (here the value 3.5) results from adapting the relationship to measurement data . With the help of the basic equations of the star structure , a mass-luminosity relationship can also be derived; this gives a value of 3 for the exponent.
The relation obtained in this way does not, however, represent an exact solution of the equations, but only an estimate and, in view of this, agrees quite well with the observed mass-luminosity relationship. The derivation of the relationship from the basic equations of the star structure (basically only mean values are considered) presupposes a certain similarity ( homology ) of the structure of stars with different masses. The confirmation of the relationship through observations allows certain conclusions to be drawn about the interior of the stars.
See also
literature
- Alfred Weigert , Heinrich Johannes Wendker : Astronomy and Astrophysics. A basic course. 3rd revised edition. VCH, Weinheim et al. 1996, ISBN 3-527-29394-9 .
- Arthur Stanley Eddington : The Internal Constitution of Stars. Cambridge University Press, Cambridge 1926 (Reissued: ibid. 1988, ISBN 0-521-33708-9 ( Cambridge science classics )).