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Bellwork 11/10 Please turn in your bellwork sheet from last week
1. Choose a star name out of the beaker: 2. Using a computer or your device, look up: Temperature Luminosity Color Size (Dwarf, giant, super giant, ect) 3. Then, cut out a circle for each of your stars. 4. Write the information on the star & shade the circle with the star’s color
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What can stars tell us about the universe?
Properties of Stars What can stars tell us about the universe?
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*Side note: Stellar = relating to a star…
Not the way we use it in common language
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Stellar Brightness Brightness when viewed from Earth
There are 2 ways we can talk about “brightness” of a star… 1. Apparent brightness Brightness when viewed from Earth Decreases with distance
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2. Absolute brightness "True" or intrinsic brightness of a star
Does not depend on distance Can also be measured in “luminosity” amount of radiation leaving a star Both of these terms are “intrinsic” or “real” quantities
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Canis Major (Great Dog) Constellation
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How do scientists figure out this intrinsic value?
The distance will always be 10pc when measuring absolute brightness Where do the “5’s” come from?
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Color & Temperature of Stars
Color and temperature Hot star Temperature above 30,000 K Emits short-wavelength light Appears blue Cool star Temperature less than 3000 K Emits longer-wavelength light Appears red Between 5000 and 6000 K Stars appear yellow e.g., Sun
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Hertzsprung-Russell diagram
Shows the relation between stellar Brightness (absolute brightness) and Temperature Diagram is made by plotting (graphing) each star's Luminosity ( or absolute brightness) and
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What observations can you make about the HR Diagram?
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Let’s “dissect” the HR Diagram a little bit more
HR Diagram Lab End Goals: 1. Understand how to read/interpret the HR Diagram 2. Infer how the HR Diagram helps scientists make predictions
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Hertzsprung-Russell diagram
Parts of an H-R diagram Main-sequence stars Most stars are on the main sequence Band through the center of the H-R diagram Giants (or red giants) Very luminous Large Upper-right on the H-R diagram
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Hertzsprung-Russell diagram
Parts of an H-R diagram Super Giants Very large giants are called supergiants Only a few percent of all stars White dwarfs Fainter than main-sequence stars Small (approximate the size of Earth) Lower-central area on the H-R diagram Perhaps 10% of all stars
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Spectral Class
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What else does the Hertzprung-Russell diagram show us?
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Properties of stars Binary stars Two stars orbiting one another
Stars are held together by mutual gravitation Both orbit around a common center of mass More than 50% of the stars in the universe are binary stars Why are Binary stars important or worth talking about??
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Properties of stars Stellar mass
Determined using binary stars – the center of mass is closest to the most massive star
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Binary stars orbit each other around their common center of mass
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