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Search for Life in the Universe: 

Search for Life in the Universe Chapter 1 A Universe of Life? (Part 1)

Announcement: 

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 7:30 PM in ESS 001 (big lecture hall) See the Fall 2005 Program

Outline: 

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

Is There Life Elsewhere?: 

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

Life in the Solar System: 

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

Nearby Stars: 

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

Distant Stars in Our Galaxy: 

Distant Stars in Our Galaxy Harder to detect microbal life Search for Extraterrestrial Intelligence: SETI Main signature: radio transmission

Numbers of Stars: 

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, shouldn’t 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: 

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

Communications & Travel: 

Communications andamp; 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

Universal Astrophysics (Part 1): 

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 andamp; chaos  different objects at different places (galaxies/stars/planets, intergalactic/stellar/planetary space)

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Expansion and Finite Lifetime of the Universe: 

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): 13.7±0.2 x 109 yr

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