# February 2, 2012 In our study of Stars The students will be able to

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February 2, 2012 In our study of Stars The students will be able to
Determine color, temp., brightness and Size of a star And show what they learned by Interpreting the HR Diagram February 2, 2012

WARM-UP

Scientists classify stars based on their brightness (Luminosity)
HR DIAGRAM Hertzsprung-Russel Diagram Scientists classify stars based on their brightness (Luminosity) And Temperature

Classifying Stars Astronomers classify stars according to: size/mass,
temperature, color, and brightness.

How bright a star or galaxy shines is its brightness or luminosity
= Brightness How bright a star or galaxy shines is its brightness or luminosity

Draw this graph in your journal:
Luminosity (Brightness) Temperature

Notice what happens to the numbers as we move from Left to Right.
Now add your numbers Along the edge of the graph Notice what happens to the numbers as we move from Left to Right.

Increasing Temperature
Now add your numbers Along the edge of the graph Increasing Temperature

Now add your numbers Along the edge of the graph Hotter Colder

Now let’s look at Luminosity:
Luminosity (Brightness) Bright Stars Increasing Dim Stars Temperature

Now let’s begin placing our different types of stars

(Very stable in their life,
Now let’s begin placing our different types of stars Main Sequence Stars (Very stable in their life, Young to middle aged stars) White Dwarfs (Dim Stars)

White Dwarfs (Dim Stars)

White Dwarfs (Dim Stars)
Our Sun White Dwarfs (Dim Stars)

Star Temperatures Color of a star indicates its surface temperature Red stars are the ”coolest” while blue are the hottest Sun is a yellow star

Hertzsprung-Russell Diagram
17

27.2 The size of stars Stars come in a range of sizes and masses.
Our Sun is a medium-sized star. The largest stars, giant stars have a mass of about 60 times the mass of the Sun.

Which star is hottest supergiant?

What temperature is Sirius B?

Which star is the dimmest (least bright) on the chart?

Order these stars from hottest to coolest:
Procyon, Spica, Sirius B, and Pollux

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