Ast Final notes

Ast Final notes - Our Galaxy: spiral, about 7000 parsecs,...

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Our Galaxy: spiral, about 7000 parsecs, but we can only see 20 parsecs from the ground, but in space we can see 1000 parsec or .001” Stars: so far away, they appear like points of light making it hard to determine details Distance - comes from Dopplar shift; using that tells velocity and where there is star formation in galaxy - dust helps determine how far away something is in a not very accurate way, but okay if parallax can’t reach Parallax- use binocular vision to look though 1 “eye” then 6 months later look through the other; pictures determine the movement of star - π can stand for parallax; example: π=1” (“=arcsec) is at a distance of 1 parsec or 3 light years - 1” is about largest we can see, making it technically difficult when seeing is about 1” Temp - determines color of light object gives off - look at star through UV, Blue, and Visible filters, the brightness in each filter determines temp - Visible filter is needed for dust, to determine if star is red from being cool or dust in front of it; more red = more distance - better determined by details of atomic spectrum absorption lines; different elements are determ- ined by seeing very specific waves/frequencies of light, measured in angstroms Mass - determined well for stars in binary systems by using Kepler’s laws for viewing rotation around center of mass; about 50% of stars are in binary system Visual Binary- actually seeing 2 stars move around one another through images over a period of time. ..parallax; orbit can’t be determined if plane of sight is tilted Spectroscopic Binary- when 2 stars are determined to be there by seeing 2 different wavelengths, such as F and M wavelengths seen coming from the same star you know that can’t be true and is 2 stars Eclipsing Spectroscopic Binary- depends on Dopplar shift Lifetime - depends more on rate of hydrogen burning than mass Luminosity - (surface area)(black body radiation) or (4πr^2)(sigma x T^4); determined by dis- tance; luminosity can help determine size Luminosity class- roman numerals V-I represent stars’ stages in changing to a red giant and super giant Evolutionary Sequence - stars evolve towards end of life when they start losing hydrogen - determined by their luminosity vs others at the same temp; brighter = more surface area White Dwarf- low mass star that ages off of the main sequence; average density = 10^7 gm/cm^3; seen for about 10^6 years then cools and disappears, referred to as a He white dwarf or a star of about 5 solar masses cools to to a Carbon white dwarf; our Sun will be one of the two Planetary Nebula- low mass stars never get hot enough to convert He to C, causing ex-
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This note was uploaded on 03/18/2011 for the course AST 10G taught by Professor Lloydknox during the Spring '09 term at UC Davis.

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Ast Final notes - Our Galaxy: spiral, about 7000 parsecs,...

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