largest moon in solar system, 2x mass of earth’s moon 50/50 rock/ice,2 terrains, dark, heavily cratered surface 30% → billions of yrs old, lighter, grooved terrain, richer in water ice 70% Callisto, cratered fireball, farthest moon from Jupiter, ancient surface → no recent geological activity, no substantial tidal heating (far from Jupiter) still bears scars of massive impact. Titan Saturn’s largest moon, thick atmosphere of 90% nitrogen, rest is argon, methane, ethane, hydrogen → atmosphere extends 10x more into space than earth’s. Enceladus 2 surfaces -> one is crater free, other has stripes possibly because of liquid that froze at the surface. Icy particles ejected from Enceladus may be continually coming out of the moon.may have subsurface liquid water Triton Neptunes moon, geologically active, surface is young (not many craters). captured Kuiper belt object in retrograde motion, dense. Jupiter Saturn: gas giants, 100-300x mass of earth, 10x radius of earth, atmosphere: 1000km thick, hydrogen & helium, ammonia clouds, liquid h & he interiors, metallic at very high pressure, core=rock, 10m x earth’s. Saturn :99.9% water ice. made up of countless particles 1cm-10m across. ring particles clump together. Gravitational effects of small moons sculpt Saturn’s rings.Prometheus & Pandora orbit outside & inside of Saturn’s F ring; prevent it from spreading Rings viewed from earth ring system = 3 Saturn diameters across; 10m thick; Disappears when you view edge on. Earth sees Saturn’s rings disappear at about every 15 yrs 1/2 of Saturn’s orbit when Saturn is at its equinox. Jovian Planet’ Rings all 4 have ring systems; fainter, smaller, darker. made of dark, dirty dust particles (not icy boulders) Ring Origins small rings dissipate over lifetime, about 1000yrs. need a source of new material to replenish the rings. small, close moons, impacts on moons can provide material. would provide dusty type material found in Jupiter’s rings, but not the larger icy boulders of Saturns rings. Exoplanet = planet orbits another star, help us study planet formation & other planetary systems. 2 techniques for finding them: tV & transit; planets don't emit light, only reflect star light. 1832 total exoplanets; 1145 planetary systems. signal > noise → wobble → planet detected. signal < noise → blue line is lost in random noise → planet not detected direct imaging planets light is overwhelmed by starlight. transit method: l ook for planets passing in front of a star → star appear dimmer. measuring amount of dimming gives us the size of the planet. measuring the orbital period gives us the planets distance from star. can only see when orbit is nearly edge on as seen from earth. not very likely, need to monitor many stars big planets = big wobbles&doppler shift & easier to detect close planets = fast wobbles. short period of doppler shift & less time to observe a full orbital period Hot Jupiters. there are jupiter sized planets less than .1AU away from. high radiation. Super Earth. 2-10x mass of earth. could be rocky core (earth) or ocean super earth (mini neptune) RV v Transit tV: can measure a planet’s minimum mass (from the amplitude of tV), but not its size.
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