The Hertzsprung-Russell
Diagram

(Section Not Complete)



HR diagram for the globular cluster M5 in the constellation Serpens.

HR diagram for open clusters h and chi Persei.

Properties of Stars

Stellar Magnitudes

The Harvard Spectral Sequence
Spectral Class Distinguishing
Characteristics
Temperature (K) Example
O Ionized He and metals;
weak H
28,000 - 60,000 zeta Orionis
B Neutral He, ionized metals, stronger H 10,000 - 28,000 Rigel, Spica
A Balmer H dominant, singly-ionized metals 7500 - 10,000 Sirius, Deneb
F H weaker, neutral and singly-ionized metals 6000 - 7500 Procyon, Canopus
G Singly ionized Ca, H weaker, neutral metals 5000 - 6000 Sun, Capella
K Neutral Metals, molecular bands
begin to appear
3500 - 5000 Aldebaran, Arcturus
M Ti oxide molecular lines; neutral metals < 3500 Antares, Betelgeuse

DATABASE of GENEVA STELLAR EVOLUTION MODELS: "An extensive and homogenous database of stellar evolution models for masses between 0.8 and 120 solar masses at different metallicities is available. In general the models include evolutionary phases from the main sequence up to the end of carbon burning for massive stars. Horizontal branch and early asymptotic giant branch models are also provided. The metallicities covered are Z=0.001, 0.004, 0.008, 0.020 (=Z_solar), and Z=0.04.

In addition to the evolutionary grids we also provide Fortran codes for the calculation of isochrones and stellar population burst models.

Recent models now cover also pre-main sequence phases. Predictions regarding the spectral evolution of massive stars can be obtained from the so-called "combined stellar structure and atmosphere models" (CoStar)."

A (somewhat flaky) DOS program (StarClock) written in Pascal that implements graphic HR diagram evolution based on the above tables can be found at http://www.sci.muni.cz/~ondra/sclock/sclock.html.

Exercise:
Go to the Dome of the Sky. Select "Enter the Dome" and then select sky charts for a northern latitude (say New Orleans, at 30 degrees N). Select the sky chart for December 20 and locate the characteristic shape of the constellation Orion on the celestial equator to the left of center. Click on the brighter stars in Orion to display information about them (use the status bar at the bottom of the browser to help ensure that you are over the star when you click; for example, it should display "Betelgeuse" when the cursor is over that star). Use the HTML Tablemaker to make a table of the following information (if given) for the brightest stars in Orion: Name, Spectral Class, Color Index, Distance, Visual Magnitude. Put this table into your astronomy homepage if you are constructing one (see the instructions on the Tablemaker interface).


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