Download Star Types

Classificagtion of Stars:
The H-R diagram
“The stars are distant and
unobtrusive, but bright and
enduring as our fairest and most
memorable experiences.”
Henry David Thoreau (1849)
Are Stars similar to our Sun?
How far away are they?
Where did they come from?
What do they do?
Do they live forever?
Reading Assignment
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All Chapter 9
Discussion Question
How can I understand the performance of CARS
P = P(Weight; Power; Overall Built)
Make a plot that shows the general relationship
between Weight and Horsepower of cars.
-now add to your plot sports cars…
-… racing cars…
-… and economy models
This kind of plots summarizes in a powerful way
general features of most cars
Classification of Stars
1) Collect information on
a large sample of stars.
2) Measure their
luminosities
(need the distance!)
3) Measure their surface
temperatures
(need their spectra)
The Hertzsprung-Russell Diagram
The Hertzsprung-Russell Diagram
The Hertzsprung-Russell Diagram
The Main Sequence
- all main sequence
stars fuse H into He
in their cores
- this is the defining
characteristic of a
main sequence star.
The Hertzsprung-Russell Diagram
Red Giants
- Red Giant stars
are very large, cool
and quite bright.
Ex. Betelgeuse is
100,000 times more
luminous than the Sun
but is only 3,500K on
the surface. It’s radius
is 1,000 times that of the
Sun.
The Hertzsprung-Russell Diagram
The Hertzsprung-Russell Diagram
White Dwarfs
- White Dwarfs
are hot but since
they are so small,
they are not very
luminous.
The Hertzsprung-Russell Diagram
More mass,
more fuel,
very fast burning.
Shorter
Lifetime
of Star
Less mass,
less fuel,
slow, steady burning.
Think
SUV vs a Honda Civic
Longer
How do we know the age of a star?
The H-R diagram
O
What is the order of stellar evolution of
a star like the Sun?
Which is the faintest? the
sun, an O star, a white dwarf,
or a red giant?
Which of these star is the
hottest?
What are Sun-like stars (0.4
Msun < M < 8 Msun) in
common?
What about red dwarfs (0.08
Msun < M < 0.4 Msun) ?
Where do stars spend most
of their time?
L=4πR2 σT4
To calculate a star's radius, you must
know its
1) temperature and luminosity.
2) chemical composition and temperature.
3) color and chemical composition.
4) luminosity and surface gravity.
L=4πR2 σT4
If a star is half as hot as our Sun, but has
the same luminosity, how large is its radius
compared to the Sun?
1) ½ times as large
2) ¼ times as large
3) 4 times larger
4) the same
What is burning in stars?
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Gasoline
Nuclear fission
Nuclear fusion
Natural gas