3 - dwarfs so the Sun is a “dwarf star” HR Diagram...

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1. Apparent Magnitude (m) – how bright a star appears 2. Absolute Magnitude (M) – how bright a star really is Organizing the Family of Stars - To understand the huge diversity of stars, we organize them according to their: 1. Temperature (T) 2. Luminosity (Lstar/Lsun) - How are these properties related? - To find out, each star is plotted as a point on a graph - The x-coord. Is Temperature (T) - The y-coord. Is Luminosity (Lstar) Hertzsprung-Russell (HR) Diagram Downward sloping line is called “main sequence” The H-R diagram is a graph on which stars luminosities are plotted vs. their temperatures. (….Sometimes absolute magnitudes are plotted vs. spectral type.) Every point is a star. HR Diagram L vs. T Most stars are found along the main sequence , including the Sun - Stars on the main sequence are called
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Unformatted text preview: dwarfs , so the Sun is a “dwarf star” HR Diagram Giant Stars have great luminosity. Supergiants are even more luminous. White Dwarfs are fainter and bluer. Proxima Centauri – The Nearest Star to the Sun is a faint M star on the Main Sequence Use of H-R Diagram-H-R Diagram are the astronomers “most useful tool”-They quickly tell us which kind of star (giant or dwarf)-They can also reveal the mass, age & lifespan of the star.-We can use them to determine the ultimate fate of a star… including the Sun. (The most important characteristics of a star is its MASS) Mass determines the fate of the star: whether or not it will explode. Mass is measured in units of – Msun For Main Sequence Stars: more massive stars are hotter and more luminous....
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