Life of the Sun

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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?

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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

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Russell Diagram
first HR Diagram from Russell (1914) spectral
types used white dwarf is 40 Eri B
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Super HR Diagram
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Star Colors
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RECONS HR Diagram
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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
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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
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HR Diagram Famous Stars
range 108
L R2 T4 keep T constant 108 R2 104 R
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Star Genetics
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
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Suns Composition
99.9
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The Stellar Struggle
A STAR is a gas ball gravity pulling in,
radiation pressure pushing out
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