1	Forming Stars and Planets II & Our Solar System Lecture 14 Ay-1
2	Lecture 11: Summary all planets (terrestrial & Jovian) orbit Sun counterclockwise system extends to ~ 10,000 AU (Oort cloud) most orbits ~ circular & close to ecliptic plane planetary motions follow Kepler’s laws 1 AU = 1.5 x 10¹³ cm (or 149,597,870 km) solar system formed 4.6 Byrs ago in a rotating, circumstellar disk of gas and dust follow evolution by observing sources at different epochs
3	planet-forming disks in Orion stars £ 1 Myr
4	HR 4796: age ~ 10 Myrs A0 star ( 2 M_¤) at 67 pc dust ring width ~ 17 AU, radius 70 AU collisionally-produced debris?
5	b Pictoris ~ 20 Myrs
6	Vega : 350 Myrs
7	Epsilon Eridani : ~ 0.5 -1 Byr distance ~ 10 lyrs 850 mm dust emission ® ring, mass ~ 0.2 MÅ inner radius 35 AU ~ Neptune’s orbit outer radius 75 AU ~ Kuiper Belt
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9	CARMA Combined Array for Research in mm-wave Astronomy
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15	Condensation sequence :
16	Venus
17	Planetary radiative equilibrium Energy absorbed = Energy radiated (L/(4pd²))pr² = 4pr²sT⁴ T = 278 (L_¤/d²AU)^1/4 K Greenhouse effect : Earth’s atmosphere relatively transparent to solar radiation (heating) but re-radiation (cooling) in infrared is impeded (photons absorbed by CO₂, H₂O) For Venus, greenhouse effect is enormous due to CO₂, T = 600K (could happen at Earth)
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28	Saturn density 0.69 gm/cc belt zones like Jupiter but under a methane haze and less visible 24 moons - cause gaps in rings due to gravitational perturbations Titan largest ~ Mercury mass 1.5 x moon atmosphere; methane and nitrogen smog surface cold - ice (179K); reverse greenhouse effect - smog blocks sunlight
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