Astronomy 114 Exam 2 Review sheet PDF

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Cheat sheet exam 2. Contains information about the sun adn stars...

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The Sun -powered by Nuclear energy (E=mc ) -Nuclear -luminosity- total energy radiated by the sun; Calculated from the fraction of that energy that reaches Earth -Solar constant- amount of sun’s energy reaching earth is About 1400 W/m^2 -Total luminosity- is about 4 x 10^26 W- the equivalent of 10 billion 1-megaton nuclear bombs per second -Radius- 6.9 x 10^8 (109 x Earth) -Mass- 1.99 x 10^30 kg (300000 earths) -Sun is stable because weight of upper layers compresses lower layers -in equilibrium, inward gravitational force must be balanced by outward pressure -energy balance- rate at which fusion releases energy in sun’s core and the rate at which sun’s surface radiates energy into space -solar wind- flow of charged particles from the surface of the sun -corona- outermost layer of solar atmosphere (1 mil K) -chromosphere- middle layer of solar atmosphere (10^4-10^5 K) -photosphere- visible surface of sun (6000 K) -convection zone- energy transported upward by rising hot gas (opaque) -radiation zone- energy transported upward by photons (transparent) -core- energy generated by nuclear fusion (15 mil K) -fission- big nucleus splits into smaller pieces (nuclear power plants) -fusion- small nuclei stick to form bigger one (Sun & stars) - high temps enable nuclear fusion to happen in core -sun releases energy by fusing four H nuclei into 1 He nucleus (proton-proton chain) total mass is .7% lower -energy gradually leaks out of radiation zone in randomly bouncing photons -convection (rising hot gas) brings energy to surface (bright blobs on photosphere) Solar atmosphere -core,radiative zone, convection zone, photosphere,chromosphere, corona -photosphere- visible surface of sun 6k K, highly opaque (H- ions) -sunspots- are cooler regions of photosphere, strong magnetic fields

-solar prominences- gas trapped under giant loops -zeeman effect- measure mag fields w spectral lines -solar flares- caused by mag activity send bursts of x rays in to space -corona- appears bright (mag fields trap gas), high temp, outermost, low density -solar cycle- 11 years before N/S switch(sunspots rise and fall) -maunder minimum- quiet phase of sun 1650-1700 Stars -parallax- the apparent shift in position of nearby object in background of more distant objects -measure stellar distance w trigonometric parallax (depends on dist.) d=1/p -1 parsec= 3.26 light years -barnard’s star has largest proper motion of any star (actual shift in motion of star in sky) -doppler shift only tells motion away or toward -measuring velocity -star brightness depends on both distance and luminosity -luminosity- amt of power a star radiates (energy per sec =watts) -apparent brightness- amt of starlight that reaches Earth (energy per second per square meter) -two stars that appear equally bright may be a closer, dimmer star and a farther, brighter one -luminosity = 4π (distance)^2 x (brightness) -most luminous stars: 10^6 Lsun -least: 10^-4 Lsun -apparent magnitude- how bright a star appears in the sky (smaller mag=brighter star), depends on distance from earth and luminosity {(2.521)^m2-m1 ratio of apparent brightness intensity} -absolute magnitude- brightness measured at 10 parsecs from the Earth - Msun= 4.83 -luminosity=n^(4.83-M) used to compare other stars to the sun -distance modulus- m-M -binary star systems- contain two stars -visual binary star- both stars can be seen directly (and observed) -spectroscopic binary systems- identify through Doppler shifts in spectral lines (toward blue shift, away red shift) -eclipsing binary- orbit in our line of sight. When neither is eclipsed we see both lights. When one eclipses brightness drops because other is covered...