Starry Monday at Otterbein

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Starry Monday at Otterbein
Welcome to

• Astronomy Lecture Series
• -every first Monday of the month-
• May 5, 2008
• Dr. Uwe Trittmann

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Todays Topics

• How to find Life in the Universe
• The Night Sky in May

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On the Web

• To learn more about astronomy and physics at
  Otterbein, please visit
• http//www.otterbein.edu/dept/PHYS/weitkamp.asp
  (Observatory)
• http//www.otterbein.edu/dept/PHYS/ (Physics
  Dept.)

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How to find Life in the Universe

• What is Life?
• How to detect Life?
• Where to look for Life?
• Life vs. Intelligent Life

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What is Life?

• Has a metabolism
• Uses energy
• Reacts to changes in the environment
• Reproduces
• Transforms its environment
• Changes to environment hopefully observable

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What kind of Life?

• Focusing on carbon liquid water based life
• Carbon as a chemically unique element
• (Liquid) Water as a powerful solvent and reactant
• Assuming lower life-forms, we cannot expect life
  to actively produce signals
• Look for life on the surface of a rocky planet

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Water

• Phase diagram of water dictates temperature and
  pressure range for liquid

Minimal pressure 610 Pa
-18º C life on Earth exists
123º C life on Earth exists
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Where to look for Life?

• Where you can find (detect) it -)
• If carbon-liquid water based life exists on the
  surface of a planet
• Planet must have atmosphere for liquid water to
  exist
• Planet must receive enough energy from host star
  to liquify water
• ?Planet must be in the habitable zone (HZ) of its
  host star

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Definition of Habitable Zone

• Region around a star where stellar radiation
  maintains liquid water over a substantial part of
  the surface of a rocky planet
• Note planet must be big enough to hold on to its
  atmosphere, and possibly replenish it through
  outgassings from its interior.

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Extend of HZ depends on time

• Sun gets brighter as it ages
• Planets orbits change over time
• Planets rotational axis inclination changes
• Early Solar system
• Venus, Earth in HZ, Mars partially
• Now
• Earth, Mars in HZ

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Habitats beyond the HZ

• Temperature, pressure too low ? go to interior of
  planets/moons
• Earth 5km under surface liquid water can exist
• Tidal heating gravitational distortions will
  heat interior of (soft) moons
• Io ? Volcanism driven by Jupiter
• Europa ? liquid water under ice?
• Saturns Titan
• Methane/Nitrogen based geology/climate at -180C

Not on surface of Planet ? Hard to detect!
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Greenhouse Effect affects Climate

• Earth absorbs energy from the Sun and heats up
• Earth re-radiates the absorbed energy in the form
  of infrared radiation
• The infrared radiation is absorbed by carbon
  dioxide and water vapor in the atmosphere
• ?Typically happens and stabilizes climate on
  planet harboring life
• ?Good, because life takes at least a billion
  years to develop/ have effects on planet

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The biggest effect life had on Earth

• Shakespeare?
• Building the Great Wall of China?
• Explosion of the Hiroshima bomb?
• Transforming Carbondioxide into Oxygen!
• (Zero oxygen 3 billion years ago, now 21)

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Chances of detecting Life

• How far away is the nearest Earth-like planet? ?
  19 ly (if 3 of stars have ELPs)
• Is it habitable?
• Atmosphere
• Rocky
• Carbon/Water available
• shielded from heavy bombardment

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How to detect Life

• Life produces oxygen, methane
• Can detect ozone (made from O2), Methane via its
  characteristic infrared radiation
• Plants use photosynthesis chlorophyll rejects
  colors not utilized (utilizes visible
  frequencies)? IR red-edge
• TV Radio signals
• ? 1992 Galileo spacecraft detects life on Earth
  (and not on the Moon)!

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(Very) Intelligent Life

• Looking for extra-terrestrial intelligence, we
  can relax our assumptions (neither carbon nor
  water-base necessary)
• We are looking for signals of civilizations
  rather than signs of life

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Detecting Extraterrestrial Intelligence

• Detect radiation traveling from them to us
• detect their spacecraft/artifacts/them in our
  solar system
• Detect features of their planet/solar system
  revealing technological modifications

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Classification of Civilizations

• Type I uses energy sources of their planet
  including solar radiation arriving at their
  planet (us!)
• Type II uses a large part of the total radiation
  of their sun (shows up as reddening of the stars
  spectrum)
• Type III uses a large part of the energy
  production of their galaxy (might rearrange
  galaxy)

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Galactic Exploration

• John von Neumann build self-replicating space
  probe that builds many replicas of itself once it
  finds suitable conditions, send them on their way
• Can colonize galaxy in only 100 million years
  (less than 1 of lifespan)
• ONeill colonies

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Fermi Paradox

• If ETI exists it must be widespread
• If its widespread, why arent they among us?
• ETI must have had plenty time to occur
• Maybe they do not exist
• Maybe we didnt look hard/long enough?
• Maybe they are among us?

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Signals

• Probably electromagnetic waves
• Easy to generate
• not exceedingly absorbed by interstellar medium,
  planetary atmospheres
• Information can be imprinted on them with minimal
  energy cost
• Travels fast (but not fast enough?!)
• We are detectable since 12. December 1901

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Green Bank (or Drake) Equation

• Estimated number of technological civilizations
  present in the Milky Way galaxy is given by
• the average rate of star formation
• ? fraction of stars having planetary systems
• ? average number of planets within the
  habitable zone for various types of star and star
  system
• ? fraction of habitable planets that develop
  life
• ? fraction of life-bearing planets on which
  intelligence appears
• ? fraction of intelligent life forms that
  develop technology
• ? average lifetime of a technological
  civilization
• Could be 100 to 1 billion (?)

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Illustration of Drake Equation
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Time is of the Essence

• A lot of things can go wrong in cosmic
  instances like a few thousand years
• It is guesstimated that a technological
  civilization might last about 3000 years

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Extinction of the Dinosaurs

• Possibly caused by impact of
• a large meteorite
• Large amount of dust thrown into atmosphere,
  causing global cooling, disruption of the food
  chain
• Evidence
• Iridium layer found in fossil record at about
  time of extinction of dinosaurs
• Large numbers of species become extinct at about
  the same time
• Crater in Yucatan may be the one
• Are extinctions periodic?

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SETI

• If average lifetime is 1 million years, then the
  average distance between civilizations in the
  galaxy is 150 ly
• Thus 300 years for messages to go back and forth
• Communications via radio signal
• Earth has been broadcasting in RF range for most
  of this century
• Earth is brighter than the Sun in radio
• 1821 cm wavelength range good for interstellar
  communication
• SETI search is ongoing
• SETI_at_Home http//setiathome.ssl.berkeley.edu
• If they exist, should we contact them?

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SETI with Radio Telescopes

• Radio frequencies are used because
• Civilizations are likely to use these frequencies
• We can observe them from the ground
• Biggest radio telescope is in Arecibo, Puerto Rico

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CETI Talking to Aliens

• How can we communicate?
• Put up a big sign (?!)
• Send a (radio) signal
• Send a space probe with a message
• Should we try to communicate?

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Our Messages to the Aliens

• Golden plate with essential info on humans
• On board Pioneer 10 space probe
• Started in the 70s
• past solar system

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Our EM Message to the Aliens

• In 1974 sent radio signal from Arecibo to
  globular cluster M13 (300,000 stars, 21,000ly
  away)
• Brighter than the Sun
• The signal, transmitted at 2380 megahertz with a
  duration of 169 seconds, delivered an effective
  power of 3 trillion watts, the strongest man-made
  signal ever sent.

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The Night Sky in May

• Nights shorter and EDT gt later observing!
• Spring constellations are up Cancer, Leo, Big
  Dipper
• Mars, Saturn dominate early evening, Jupiter
  early morning.

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Moon Phases

• Today New Moon
• 5 / 11 (First quarter Moon)
• 5 / 19 (Full Moon)
• 5 / 27 (Last Quarter Moon)
• 6 / 3 (New Moon)

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Today at Noon

• Sun at meridian, i.e. exactly south

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10 PM

• Typical observing hour, early May
• Saturn

Mars
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Zenith

• Big Dipper points to the north pole

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South

• Saturn near Praesepe (M44), an open star cluster
• Oops, that was last year! Now Saturn is here!

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South

• Spring constellations
• Leo
• Hydra
• Crater
• Sextans

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East

• Canes Venatici
• M51
• Coma-Virgo Cluster
• Globular Star Clusters
• M3, M5

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East

• Virgo and
• Coma
• with the Virgo-Coma galaxy cluster

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Virgo-Coma Cluster

• Lots of galaxies within a few degrees

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M87, M88 and M91
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East

• Hercules
• Corona
• Borealis
• Bootes

• Globular Star
• Clusters
• M 3
• M 13
• M 92

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M13 Globular Cluster
These guys will know of our existance in 21,000
years!
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Mark your Calendars!

• Next Starry Monday June 2, 2008, 8 pm
• (this is a Monday
  )
• Observing at Prairie Oaks Metro Park
• Friday, May 9, 2008, 900 pm
• Web pages
• http//www.otterbein.edu/dept/PHYS/weitkamp.asp
  (Obs.)
• http//www.otterbein.edu/dept/PHYS/ (Physics
  Dept.)