Then it warms the gas in the convective zone of the Sun and that hot gas bubbles up to the photosphere, producing granules°Thermal RadiationHot objects naturally give off light (more intensity)The color of that light depends on the temperature of the object (hotter=shorter wavelength of max output)The Sun and other stars light comes from this thermal radiation (r>white>b = cooler>hotter)Sun acts like blackbody object°NeutrinosThe fusion in the Sun’s core produces neutrinosNeutrinos are VERY hard to detect, but we have telescopes that can detect a fewThrough neutrino observations, we can take a direct image of the core of the Sun!Part 21:What is solar activity?Periodic disruptions in the Sun’s surface and atmosphere Sunspots: cooler regions of the Sun’s surface, lots of E, due to “kinks” in magnetic field (cuz spin diff)Flares: violent explosions in the Sun's atmosphere above sunspotsProminences: loops of gas trapped above sunspots
Coronal Mass Ejections: huge bubbles of gas ejected from the Sun, can be dangerous to Earth (bo, sat)All are related to magnetic fields °How does solar activity vary with time?Activity rises and falls with an 11-year period (spots)Solar max/min during that time°What causes solar activity?Stretching and twisting of magnetic field lines near the Sun’s surface causes solar activity°How does solar activity affect humans?Bursts of charged particles from the Sun can disrupt communications, satellites, and electrical power generationPart 22:°How do we measure stellar distances?Parallax tells distances to the nearest stars (big P=close)Compare position of object to background twice/1yr°How do we measure stellar luminosities? M=xLsun Lum=M3.5If we measure a star’s apparent brightness and distance, we can compute its luminosity with the inverse square law for light; distance double> bright v by 4°How do we measure stellar masses?Newton’s version of Kepler’s third law tells us the total mass of a binary system, if we can measure the orbital period in yrs (p) and average orbital separation of the system (a) P2= a3/M1+M2 M1/M2=r2/r1Part 23:°What are the three basic types of spectra? (fingeprints)Continuous spectrum (all)high density hot matter, emission line spectrum (lines) from hot gas, absorption line spectrum (missing lines) light through cold gas°How does the Sun’s spectrum tell us about its composition?Each element has a unique spectrum line “fingerprint”
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