The Planets

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The Planets

• by Dava Sobel

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Extrasolar Planets and the Possibility of Life
Beyond Our Solar System

• My old familiar solar system, once considered
  unique, now stands as merely the first known
  example of a popular genre. Dava Sobel, The
  Planets, pg 9

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Extrasolar Planets

• are bodies that orbit a star other than our Sun
• are bodies that are held together by their own
  gravity
• We have found 267 of these planets as of this
  November.
• 10 percent of Sun-like stars are found to have
  planets orbiting them.

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Infinite Monkey Theorem

• If an infinite amount of monkeys were to type on
  an infinite amount of typewriters, writing at
  random, sooner or later they would reproduce the
  complete works of Shakespeare an infinite amount
  of times.
• Same theory can be applied to the possibility
  that there is other life on extrasolar planets
  given an INFINITE universe

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• If the universe is infinite, there would be an
  infinite number of sun like stars, and an
  infinite number of extrasolar planetsalong with
  an infinite number of you and me, doing exactly
  what we are doing now.
• This would guarantee there is other life out
  there.

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However

• We do not know if the Universe is infinite
• We must rely on the observation of extrasolar
  planets
• Perhaps one day we can develop technology to
  flyby or land on these mysterious worlds

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• Extrasolar planets can be detected using indirect
  methods only since they are so far away
• This makes us unsure of their physical
  composition
• We do know that the planets found so far are very
  large, usually several times larger than Jupiter
• There are probably smaller extrasolar planets out
  there that are harder to detect

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Gliese 581 d

• Discovered by Stephane Udrys team of the Geneva
  Observatory in Switzerland
• Was found on a 3.6 m telescope in La Silla, Chile
• Was observed using the radial velocity
  technique

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Gliese 581

• Is a red dwarf star 20 ly from Earth
• Three planets orbit Gliese 581, Gliese 581 b, c,
  and d.
• Gliese 581 d is on the cusp of the Goldilocks
  Zone and within the Habitable Zone due to its
  distance from its star. (it is slightly too far
  away from the star to be in the Goldilocks Zone)
• Gliese 581 c is also in the Habitable Zone and is
  another a possibility of an extra large imitation
  of Earth. (it is slightly too close to the star
  to be in the Goldilocks Zone)

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Criticisms for the Possibility of Life on Gliese
c and d from Selsis and Kasting

• Water may not be available
• A high impact rate may prevent the emergence of
  life
• The thus far unknown minimum ingredients for
  lifes formation may not be present
• Gravity may be too low to retain a dense
  atmosphere
• The planet may have formed an atmosphere that
  keeps the surface pressure too high for water to
  remain liquid

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How Could the Atmospheres on These Planets Be
Important?

• If Gliese d (slightly too far from the star) had
  a thick atmosphere, it could retain heat
  generated in its core and be able to sustain the
  higher temperature needed for liquid water
  through the greenhouse effect.
• If Gliese c (slightly too close to the star) had
  a thick atmosphere, it could reflect away much of
  the damaging radiation and prevent a runaway
  greenhouse effect, which would make the planet
  too hot to sustain life.

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Rogue Planets

• Bodies that are held together by their own
  gravity but are not orbiting a star
• No consistent detection of a specific rogue
  planet but there are rumors of an Orion proximal
  cluster.
• They could have been ejected from their orbits
  around a star long ago and are now wandering
  aimlessly around in space.

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Why are Rogue Planets Interesting?According to
Stevenson

• They could have thick atmospheres that would not
  lose heat radiatively.
• Since they are far away from a star, there would
  be little ultraviolet radiation to wear away
  their initially thick atmospheres.
• Geothermal energy could rise from the core of the
  planet and be stuck in the atmosphere. This would
  raise the temperature of the surface enough to
  sustain liquid water.
• Since these planets would be heavily protected by
  their atmospheres, they would be geologically
  active for longer which could be a source of
  internal energy to support life.
• Moons that have been ejected with the planets
  could also create a source of energy with their
  tidal heating.

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As you can see

• The conditions for life on a planet seem
  complicated and improbable
• However, we know that this is possible because
• WE EXIST!

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Sources

• Slide 1 http//www.greatdreams.com/10-planets.jpg
  
• Slide 2 http//30gms.com/images/uploads/001_Plane
  ts.jpg
• Slide 3 http//upload.wikimedia.org/wikipedia/com
  mons/thumb/6/61/Extrasolar_planet_NASA3.jpg/800px-
  Extrasolar_planet_NASA3.jpg
• Slide 4 http//www.planet.nl/upload_mm/8/2/4/1998
  915409_1999998464_monkey_typewriter.jpg
• Slide 5 http//www.physicscentral.com/action/2002
  /images/planets-img1.jpg
• Slide 6 http//www.taborcommunications.com/hpcwir
  e/images/MareNostrumUniverse.jpg
• Slide 7 http//www.eso.org/public/outreach/press-
  rel/pr-2005/images/phot-14a-05-normal.jpg
• Slide 8 http//www.shatters.net/impulse/pictures
  /gliese581-d-tn.jpg
• Slide 9 http//forumst.free.fr/image.php?imageht
  tp//forumst.free.fr/home/Astronomie/Planetes/exoa
  planete-Gliese581.jpgadrhttp//images.google.com
  /imgres3fimgurlhttp//techno-science.net/illustr
  ation/Astronomie/Planetes/exoaplanete-Gliese581.jp
  g
• Slide 11 http//science.jpl.nasa.gov/images/orgs-
  6.jpg
• Slide 12 http//www.abc.net.au/science/news/img/z
  apatero.jpg
• Slide 14 http//apod.nasa.gov/apod/image/0501/ear
  th_apollo17.jpg
• General www.wikipedia.org www.nasa.gov