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1 Admin Please fill in course evaluation. Deadline * Today * Final Exam: Saturday 7 Feb PM. SHL 100 Example-problems and MC questions for parts covered after mid term * posted on course calendar webpage * Today and Tomorrow Review and Examples and calculations 2015 Pearson Education, Inc.

2 Last time The upshot is.. Big Bang standard model: Flat Universe Inflationary cosmology Dark matter Dark energy Worst order of magnitude estimate ever made :

3 Last time -- Accretion of Planetesimals Many smaller objects collected into just a few large ones à The Earth is formed!

4 Last time -- Kepler NASA's Kepler mission was launched in 2008 to begin looking for transiting planets. It is designed to measure the 0.008% decline in brightness when an Earth-mass planet eclipses a Sun-like star.

5 Orbits and sizes of extrasolar planets from Kepler Already NOT up-to-date. The list grows every day

6 Results from Kepler indicate that planets are very common, and that small planets outnumber large planets. NOTE: Remember also here the fast increase of planet-detections

7 So planets are very common.. But can we go there? So far, we've only sent out some signals Earth to globular cluster M13: Hoping we'll hear back in about 42,000 years!

8 Difficulties of Interstellar Travel Far more efficient engines are needed. Energy requirements are enormous. Ordinary interstellar particles become like cosmic rays. There are social complications of time dilation. (Recall earlier discussions)

9 Where are the aliens?

10 Fermi's Paradox Plausible arguments suggest that civilizations should be common. For example, even if only 1 in 1 million stars gets a civilization at some time 100,000 civilizations! So why haven't we detected them? 1. We are alone: life/civilizations much rarer than we might have guessed Our own planet/civilization looks all the more precious 2. Civilizations are common, but interstellar travel is not, perhaps because: interstellar travel is more difficult than we think. the desire to explore is rare. civilizations destroy themselves before achieving interstellar travel. These are all possibilities, but they are not very appealing. 3. There IS a galactic civilization they just don t care (yet).

11 HOME -- The Pale Blue Dot

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14 Some key concepts (and some equations) NOTE1 from the coach: This is * NOT * a complete list! NOTE2 from the coach: You will get a useful formalue and numbers sheet on the final (like on the mid term)

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16 Ch. 12 HR Diagram Ch. 13 Star birth in cold molecular clouds Properties of low-mass and highmass stars Life stages of low-mass and highmass stars Fusion in of low-mass and highmass stars Ch. 14 White Dwarf Neutron star and pulsar Black hole Time-dilation and other relativity effects Ch. 16 Cosmic Recycling Spiral vs. elliptical galaxies Distances to galaxies Hubble s Law Ch. 17 The Big bang Theory Eras of Universe The Cosmic Microwave Background radiation Inflation Olber s paradox Ch. 18 Dark matter Dark energy The fate of the Universe Ch. 19 Interstellar travel Fermi s paradox

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22 /Stellar Flux

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25 v 2 esc =2GM/r Escape speed