The Dawn of Destruction

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The Dawn of Destruction

• Distant future of the Sun and Earth revisited,
  K.-P. Schröder R.C. Smith, accepted in MNRAS,
  arXiv0801-4031
• Presenter Paul Edmon
• Journal Club
• 1-31-08

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• Since the dawn of time man has yearned to
  destroy the Sun.
• C. Montgomery Burns

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Outline

• The Sun and Earth
• Solar Evolution Model
• Fate of Sun and Earth

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The Sun

• Current Mass 2x1033 g
• Current Luminosity 4x1033 ergs/s
• Current Surface Temperature 5778 K
• Current Radius 7x1010 cm
• Current Age from ZAMS 4.6 Gyr
• Gravitational Binding Energy 2.3x1048 ergs

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The Earth

• Current Mass 6x1027 g
• Current Surface Temperature 287 K
• Current Radius 6.4x108 cm
• Current Orbital Radius 1.5x1013 cm
• Gravitational Binding Energy 2.3x1039 ergs
• If the Suns Luminosity could be focused on the
  Earth it would be destroyed in 600 ks or about
  6.5 days.
• 1.3x1018 g of antimatter or at normal rock
  density a cube of antimatter 6 km per side
• 55 ZettaTons (1021) of TNT or a sphere of TNT 30
  times the size of the Earth

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Simulation Goals

• Will the Earths orbit intersect the Sun when the
  Sun goes through the Red Giant Branch (RGB) or
  Asymptotic Giant Branch (AGB)?
• When does the Earth move out of the Habitable
  Zone (HZ)?
• If the Earth does fall into the Sun what initial
  radius will prevent this?
• How much mass is left over in the White Dwarf
  (WD) and Planetary Nebula (PN)?
• Do we expect to find planets around WDs and if so
  where would they be?

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Solar Evolution Model

• Used Eggleton (1973) evolution code with updated
  opacities and equation of state (Pols et al.
  1998)
• Self-Adapting 1D Mesh
• Mass Loss Applied as Boundary Condition
• Well tested against observed giants and
  supergiants
• Mass loss in cool giant phase uses a new formula
  for ordinary cool winds
• This has been checked against galactic giants and
  supergiants
• This mass loss rate does not apply for
  dust-driven winds
• The Sun will not reach the critical luminosity
  for a dust-driven wind, 4000 L? (Schröder et
  al. 1999)

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Solar Evolution
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Solar Radius
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Habitable Zone

• Habitable Zone (HZ) Water can be liquid
• HZ depends on
• Solar Luminosity
• Albedo
• Green House Effect
• Kasting, Whitmire Reynolds (1993) give a
  conservative estimate of 0.95 to 1.37 AU for the
  current Sun

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Habitable Zone

• HZ radius scales as L0.5
• ZAMS .8-1.15 AU
• MShottest 1.07-1.54 AU
• MSfinal 1.29-1.86 AU
• RGBtip 49.6-70.5 AU
• ZA-He 6.96-10 AU
• AGBtip 43.4-62.6 AU
• AGBtip-TP 61.3-87.2 AU
• According to this model the Earth will move out
  of the HZ in about 1 billion years or when the
  Solar Luminosity increases by another 11

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Tidal and Drag Effects

• Tidal Effects
• Solar Rotation Essentially Stops in RGB Phase
• Tidal Bulge Drag
• Drag Effects
• Halving the effect of tidal drag and reducing the
  mass loss rate by 10 does not prevent the
  destruction of the Earth

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Minimum Safe Radius

• R1.15 AU
• Villaver Livio (2007) 3 AU in order to avoid
  evaporation by stellar heating
• An 8 change in the angular momentum of the Earth
  would save it
• Korycansky et al. (2001) Encountering a body of
  large asteroids every 6000 years
• Jupiter and Saturn
• Possibility of collision with the asteroids
  and/or triggering an orbital instability

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Final Phase of Mass Loss

• During RGB the Sun loses 1/3 of its initial mass
• The lower shell mass going into the AGB phase
  (0.116 M?) and lower total mass reduces the mass
  loss rate to only 2x10-7 M?/yr
• The final circumstellar shell mass of the Sun is
  about 0.01 M? which is rather small and may
  produce a peculiar PN
• The final WD mass of the Sun will be 0.5405 M?

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The End (IC 2149)
Credit Young et al. MMT