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RV: can measure a planet’s minimum mass (from the amplitude of RV), but not its size. Transit method:can measure a planet’s size (from the amount of dimming of the star during transit), but not its mass. RV + transit: measure both mass & size! Follow-up RV on the Kepler planets: not easy. Most Kepler planets are far away & the host stars are dim → difficult to obtain the stars’ spectrum. photosphere:layer in solar atmosphere from which the sun’s visible light is emitted. opaque → cannot be anything below due to absorption of photons. solar granulation:granules form, disappear, reform for a few minute; 4m granules cover the solar surface. Solar energyearly ideas: chemical energy & coal (can only last 10,000 yrs) or gravitational contradiction → could last 10 m yrs. answer:antiparticleevery particle has a partner (e- → e+ & p → p-) when a particle meets an antiparticle, they annihilate each other & energy is released neutrino:a neutral weak particle; hard to detect & much smaller than electronenergy transport.photons scatter & diffuse out to surface in 10^5 yrs. not efficient, lot of heat loss. solar neutrinossolar interior can’t be observed due to opacity but neutrinos can penetrate huge amounts of material w/out being absorbed. theory was questioned → made 3 different neutrinos; nuclear fusion produces v^e. different neutrinos can spontaneously convert into one anothersolar wind:charged particles from the solar atmosphere flows away from the sun.coronal holes:largely from sparse regions of corona. active sun → sunspots, prominences, solar flares, coronal mass ejections.sunspots are magnetic, dark because they are cooler than the surrounding gas. number of sunspots on the sun varies w/ a period of about 11 yrs.sun's differential rotation→ solar activity. rotates faster at the equator than at high latitudes. magnetic field lines are twisted → sunspots form where kinks in magnetic field pop through the surface. 11 yr sunspot cycle = 22 yr magnetic cycle. prominences:magnetic looks can extend up into suns corona, gas from chromasphere can be trapped in the loops, cooler & denser than surround corona.how does solar activity affect humans:Bursts of charged particles from Sun can disrupt communications, satellites, & electrical power generation