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Lecture 26.docx

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Biology 1002B
Denis Maxwell

Lecture 26: The Drake Equation 1. All of the terms (and the rationale underlying their suggested values) of the Drake Equation.  N = N s f p n ×ef × fl i × fc× L  N = Number of advanced civilizations in our galaxy  N = Number of stars = 100 billion s  p = the fraction of those stars that have planets = 0.5 (observational data support)  ne= number of planets that can potentially support life = 2  f = the fraction of those planets that develop life = 1 l  i = the fraction of planets that develop intelligent life = 0.1  c = the fraction of planets willing and able to communicate = 0.1  L = average lifetime of a civilization (hard to achieve) 2. Mechanism by which the “transit method” detects extrasolar planets  To determine what fraction of stars have planetary systems  Ground base, telescope, hubber  Kepler mission o Detect presence of planets around distant stars  Detect sensitive changes in apparent of a star o Giant mirror that gathers light on bottom o Photometer that sits in the middle  42 CCD  Photons of star light convert to electrical current o Heliocentral orbit – orbiting sun and not Earth o Fixed and not scanning the sky o Looking at 100 000 stars o Do those stars have planets around them?  Transit method o The graph will oscillate  Rhythmic oscillating in apparent star brightness as orbiting planets move between kepler and star o When a planet transits/moves in front of a star  Dim the light  Measure at least 3 times (proof) – takes few years to be sure transit is a planet o Orbital time (distance)  Planets closer to the centre has a shorter orbital time  Can calculate the distance from the parent star o Transiting time  Calculate the orbital distance  Important to life o Radius of planet and star o Ligh
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