Hertzsprung

Figure 1.2 The Hertzsprung-Russell diagram for stars with known luminosities and spectra.

Fig. 5.7. Evolutionary tracks for Z = 0.02 (near solar metallicity) stars with different masses in the HR diagram. (Luminosities are in solar units.) Points labelled 1 define the ZAMS and points labelled 2 the terminal main sequence (TAMS), the point where central hydrogen is exhausted. The Schonberg-Chandrasekhar limit may be reached either before or after this (for M > 1.4 Af0). Points marked 3 show the onset of shell hydrogen-burning. Few stars are found in the Hertzsprung gap between point 4 and point 5 , where the surface convection zone has grown deep enough to bring nuclear processed material to the surface in the first dredge-up. Adapted from Iben (1967).

Fig. 3.3. Theoretical Hertzsprung-Russell diagram. The right-hand scale shows in absolute bolometric magnitude what the left-hand scale expresses as the logarithm of the intrinsic luminosity in units of the solar intrinsic luminosity (Lq = 4 x 10 erg s ). On the horizontal axis, the logarithm of the effective temperature, i.e. the temperature of the equivalent blackbody, is put into correspondence with the spectral type of the star, as determined by the observer. This temperature-luminosity diagram shows the lifelines of the stars as strands combed out like hair across the graph. With a suitable interpretation, i.e. viewed through the explanatory machinery of nuclear physics, it opens the way to an understanding of stellar evolution and its twin science of nucleosynthesis. (Courtesy of Andre Maeder and co-workers.)...

Fig. 3.4. Observed Hertzsprung-Russell diagram. Luminosity is given in absolute magnitude (about +5 for the Sun). The point marked Sanduleak is the progenitor star of the 1987A supernova as it was observed before the cataclysm. On the horizontal axis, the spectral type is given instead of temperature. (After Kaler 1997.)...

For a whole range of stellar masses between 1 and 100 times the mass of the Sun, evolutionary tracks are traced out in the temperature-luminosity plane, also known as the Hertzsprung-Russell diagram, so frequently referred to by astronomers. 

Figure 1 Mass loss over the Hertzsprung-Russell diagram. The numbers give values of -log ( M) for individual stars, to one decimal. The lines are interpolation lines according to a formula given by De Jager et al. (1987).

The uppermost part of the Hertzsprung-Russell diagram is of particular interest since the stars in that area are apparently close to their limit of existence, which is shown by their stochastic variability, pulsations, large rate of mass loss and occasional episodic mass loss. The curve above which no stars appear to exist is called the Humphreys-Davidson limit (Humphreys and Davidson 1979 De Jager, 1980) cf. Figure 2. Stars close to that limit exhibit many of the properties listed above. In that area one also finds the Luminous Blue Variables, which are stars that erratically expell a large amount of mass. At some distance from the star the gas condenses into dust particles and thus the star becomes reddened. Sometimes the expelled gas is optically... 

Figure 4 Proposed solar wind mechanisms in the Hertzsprung-Russell diagram. R = radiation driven winds W = wave-(turbulence-) driven D = dust-driven T = thermal (coronal) winds.

Fig. 1 - Hertzsprung-Russell diagram for stars of 15 and 20 M and composition appropriate to the LMC (Z /4) (solid lines) and to the sun (dashed lines) evolved through hydrogen, helium, and carbon burning. The location of the presupernova stars are indicated. The four-pointed star indicates the best estimated properties of SK-202-69. 

The Danish astronomer Ejnar Hertzsprung and the American astronomer Henry Norris Russell independently observed a very well defined correlation between the luminosity and surface temperature of stars. That correlation is shown in Figure 12.7 and is called a Hertzsprung-Russell, or H-R, diagram. Most stars, such as our sun, fall in a narrow band on this diagram called the main sequence. Stars in this main sequence have luminosities L that are approximately proportional to 7 s5u3face, or in terms of their mass, M, L °c M3 5. How long a star stays on the main sequence will depend on its mass, which, in ton, is related to the reaction rates in its interior. 

Figure 12.7 Schematic representation of a Hertzsprung-Russell diagram. (From C. E. Rolfs and W. S. Rodney, Cauldrons in the Cosmos, Chicago University Press, Chicago, 1988.)...

Hertzsprung-Russell, Mass-Luminosity Relations, and Binary Stars... 

Figure 5.1 Hertzsprung-Russell (H-R) diagram. About 90 percent of all stars lie in a diagonal band called the Main Sequence.

Quoted in Dieter B. Herrmann, The History of Astronomy from Herschel to Hertzsprung (Cambridge Cambridge University Press, 1973), p. 69. 

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