1. Life of the Sun
When the Sun started shining as a star on the main sequence, what
was its luminosity compared to today?
What happens on the Earth in 1.1 billion years when the Sun reaches 1.1 LSun now?
3. What might prevent that disaster from happening?
Why might the Earth not get engulfed by the expanding Sun?
Name any future phase of the Sun other than red giant.
B. How long does the Sun last on the main sequence?

2. …………………………………………

3. Life of the Sun
When the Sun started shining as a star on the main sequence, what
was its luminosity compared to today?
0.7 LSun now
What happens on the Earth in 1.1 billion years when the Sun reaches 1.1 LSun now?
moist greenhouse effect
3. What might prevent that disaster from happening?
clouds
Why might the Earth not get engulfed by the expanding Sun?
mass loss
Name any future phase of the Sun other than red giant.
subgiant, [red giant], horizontal branch, asymptotic giant branch, pulsating AGB, planetary nebula, white dwarf, [black dwarf]
B. How long does the Sun last on the main sequence?
11 Gyr

4. Russell Diagram first HR Diagram from Russell (1914)
spectral types used
white dwarf is 40 Eri B

5. Super HR Diagram

6. Star Colors

7. RECONS HR Diagram

8. Sun Among Stars Average medium type
there are hotter/cooler stars, bigger/smaller stars
Sun is “average”
typical or common type
89% of stars are smaller, cooler than the Sun
Sun is NOT “average”

9. Hipparcos + HR Diagram Hipparcos: faint dots future SIM: blue
future Gaia: yellow
Supergiants: best guesses
O Stars: best guesses
PNe central stars: Harris
white dwarfs: Subasavage
blue regions are for SIM; yellow regions are for Gaia

10. HR Diagram: Famous Stars
range 108
L ~ R2 T4
keep T constant
108 ~ R2
104 ~ R

11. Star “Genetics” MASS IS (nearly) ALL ! Star Genetics mass
central temperature
fuel reactions … structure
 energy released … luminosity … absolute mag
radius
 surface temp … color … spectral type
evolution
lifetime
end state
MASS IS (nearly) ALL !
multiplicity … interactions
composition … slight tweaks

12. Sun’s Composition
99.9%

13. The Stellar Struggle
A STAR is a gas ball … gravity pulling in, radiation pressure pushing out

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