Search for Life in the Universe

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Search for Life in the Universe

• Chapter 1
• A Universe of Life?
• (Part 1)

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Announcement

• Astronomy Open Night talks to the public about
  astronomical topics of interest, followed by
  observing on the roof of the ESS Building,
  weather permitting
• Time and place First Friday of each month at
  730 PM in ESS 001 (big lecture hall)
• See the Fall 2005 Program

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Outline

• Is There Life Elsewhere?
• Life in the Solar System
• Nearby Stars
• Distant Stars in Our Galaxy
• Numbers of Stars
• Distances of Stars
• Communications and Travel
• Universal Astrophysics (Part 1)
• Expansion and Finite Lifetime of the Universe

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Is There Life Elsewhere?

• Hollywood picture ignores basic physics,
  chemistry, biology, and astronomy
• No credible UFO sighting (TBD in detail)
• Our task scientific search for life, based on
  physics, chemistry biology, and astronomy
• Science evolves we know today much more than we
  knew before
• But science is also always incomplete

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Life in the Solar System

• No civilization except ours, present or past
• Look for habitable worlds
• Evidence that Mars once had water
• Evidence for water under the ice of Europa
• Evidence for microbal life on Earth under harsh
  conditions
• Search for evidence of microbes
• Controversial Martian microbes

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Nearby Stars

• Many extrasolar giant planets (like Jupiter)
  discovered since 1995
• Detection by reflex motion of parent star
• A few transitions seen
• Terrestrial planets still below detection limit
• Giant extrasolar planets very prevalent in nearby
  stars
• No information, so far, on habitability

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Distant Stars in Our Galaxy

• Harder to detect microbal life
• Search for Extraterrestrial Intelligence SETI
• Main signature radio transmission

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Numbers of Stars

• The Solar System has just one star the Sun
• 1011 stars in our Milky Way galaxy
• 109 galaxies in the observable universe
• With planets so prevalent, shouldnt we expect
  life to exist elsewhere?
• Can we calculate the probability of life?
• Can we detect extraterrestrial life?
• Is it intelligent?

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Sizes to scale, distances not to scale
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Distances of Stars

• 1 astronomical unit (AU) Earth-Sun distance
  1.5 x 108 km (9.3 x 107 miles)
• Equals 500 light seconds (8 min. 20 sec.)
• Distance to nearest star, ? Cen 4 light years
• Distance to Galactic Center 2.5 x 104 light
  years
• Distance to the nearest big galaxy, Andromeda
  (M31) 2 x 106 light years

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Communications Travel

• Communication at the speed of light c
• 4 years to ? Cen
• 2.5 x 104 years to the Galactic Center
• 2 x 106 years to Andromeda
• Travel at 10-4x c
• 4 x 104 years to ? Cen
• 2.5 x 107 years to the Galactic Center
• 2 x 109 years to Andromeda

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Universal Astrophysics (Part 1)

• Universal laws of physics ultimately govern all
  processes
• Homogenous expansion of the universe ? similar
  physical development everywhere
• Gravity ? Galaxies, stars, and planets
• Nucleosynthesis ? abundances of elements
• Instabilities chaos ? different objects at
  different places (galaxies/stars/planets,
  intergalactic/stellar/planetary space)

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Expansion and Finite Lifetime of the Universe

• Hubble expansion v12 ? r12
• Finite age
• Early universe dense and hot
• Cosmic Microwave Background (CMB)
• Detected, present temperature 2.7 K
• Big-bang nucleosynthesis
• Correctly predicts primordial abundances of the
  light elements
• There is further nucleosynthesis in stars ?
  heavier elements
• Small-scale CMB anisotropies
• Detected primordial perturbations ? gravitational
  instabilities
• Deduced precise age of the universe (2003)
  13.70.2 x 109 yr

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