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Oct.14 - 2B03.docx

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McMaster University
Laura Parker

Oct. 14 – 2B03 14/10/2011 9:34:00 AM Arrived 5 mins late. Transmit method. Velocity (Doppler) method – as a planet orbits around a star, it exerts a gravitational force on that star.  Larger planet (or close) , larger change in V. 3rd method – directly observing them (above 2 we just see the influence). Both transit and Doppler favour larger planets.  Vast majority found were massive, and close to parent stars. Observational bias, doesn’t mean all planets are large and live close to their stars.  In future, we want to concentrate on finding earth-sized planets. o Hard to find as a result of its small size. Planets don’t give off light, light comes from reflective light from parent star. Signs of life – looking for signatures that we know are important for certain molecules.  Not at this stage yet – we are still finding them. Closer to star, harder to find the planet. (Amidst the noise of the sun).  Farther orbits; easier to see. 2MASS Picture  Infrared telescope. o Planets become almost as bright as stars in the infrared. Disk picture  Disk material is the material from which planets form. There are others besides the 3 we discussed (we not going to discuss). How do Planetary Systems form?  When you take a big round object, with a bit of spin (angular momentum), it forms a disc.  Close to the forming star, you can make dust grains (particles with heavy elements [carbons, silicates], and come together to form chunks of rocks.  if you join enough of this material, you can create terrestrial planets. o Close to the star, you get the rocky stuff.  Outer planets made out of ices. Other molecules form ices, methane and ammonia. Close to the forming star, there is no frozen shit, just heavy elements. o Cores of ices that form at large radii o Jupiter and Saturn have cores of ices, and have hydrogen and helium gas around it.  Key points of slide: Key points - rocky, close to star. Ice and gas form at larger distances o Form far away, but move there over time -> planet formation and evolution.  Ices cant exist at small radii. o Rocky stuff out there at larger radii, but primarily ice. o Ice planets large, and rocky not too large. o Frost Line – beyond this radius, where ices can exit. Habitable Zone  Zone around any given star that is a favourable place for life to exist.  Life as we know it requires liquid water. We consider habitable zone those places where liquid water can exist.  Flawed concept – so many other factors that influence life. Atmosphere, migration are some of those factors. Gliese 581 picture.  2 planets that s
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