1. How do we measure stellar luminosities?
Luminosity: Amount of power a star radiates (energy per
second = watts) Apparent brightness: Amount of starlight that reaches Earth (energy
per second per square meter)
2. How do we measure stellar temperatures?
Level of ionization also reveals a star’s temperature.
Hottest) O B A F G K M (Coolest) Remembering Spectral Types Oh, Be A Foolish
Ghoul, Kick Monsters
3. How do we measure stellar masses?
Visual binary, Eclipsing binary, Spectroscopic binary. We
can measure periodic eclipses. Exploring the Light Curve of an Eclipsing Binary
Star System
4. What is a Hertzsprung-Russel diagram?
An H–R diagram plots stars according to their surface
temperatures and luminosities.
5. What is the significance of the main sequence?
Any star lying on a diagonal band that extends from
hot stars of high luminosity to cool stars of low luminosity; any stars in the
Hertzsprung-Russell diagram from the upper left to the lower right of the
diagram;
6. What are giants, supergiants, and white dwarfs?
White dwarf stars exist after a star collapses, and they
slowly burn themselves out. Red and blue supergiants are huge stars that burn
their fuel much more quickly than main sequence stars. They are the ones that
have supernovas.
7. What are the two types of star clusters?
Open clusters contain up to several thousand stars and are
found in the disk of the galaxy. Globular clusters contain hundreds of
thousands of stars, all closely packed together. They are found mainly in the
halo of the galaxy.
8. How do we measure the age of a star cluster?
Massive blue stars die first, followed by white, yellow, orange,
and red stars. To determine accurate ages, we compare models of stellar evolution
to the cluster data. Detailed modeling of the oldest globular clusters reveals
that they are about 13 billion years old.
9. Do we know any cluster older than fourteen billion years?
No
10. How old is the Universe?
13.77 Billion Years
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