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The HR Diagram

• What is the Hertzsprung-Russell (HR) diagram?
• What is the spectral class/type of a star?
• What is the luminosity class of a star?
• Which is hotter, a B2 star or a G3 star? A B5 star or a K2 star?
• What is the main sequence?
• What kind of star is Betelgeuse / Rigel / the Sun / Sirius / Sirius B?
• Sirius is an A1V star: What information does this give us about it?
• What kind of star is more common in our neighborhood?
• Is a main sequence O2 star more or less massive than the Sun?

Spectroscopic Parallax

• How would you find the distance to a star that is roughly 2,000 light years away?
• How can we use a star's spectrum to find its distance from us?
• What is spectroscopic parallax?
• For which stars can we use their spectrum to find their distance?

Star Lifetimes

• Which stars live longer (spend more time on the MS)?
• Does a main sequence O2 star live a longer or shorter time than the Sun?