ASTR 1010 FINAL VANDERBILT
universe age from star clusters - ANSWERS-globular clusters have so many stars
they can hold together forever, oldest ones we have; isochrones map H-R positns
of stars of every possible mass at a certain point in time; turn-off point of
isochrone's m-s shows oldest living star in the bunch; comparison of
hypotheticals' turn-off points to star cluster's turn-off point yields age estimate
for the cluster; universe must be older than oldest (lowest turning point)
observed clusters, 13-14 BY
universe age from expanding universe - ANSWERS-v = HD; given redshifting speed
of galaxy + distance to galaxy, we can get H, which yields time for which universe
has been expanding assuming it has been happening at a consistent speed (which
it isn't); space dust makes stuff look fainter and redder and closer, and different
cepheid types are now known to exist; distinguished cepheids + better dstnc
measrmts = 13.1-14.0 BY
universe age from CBR - ANSWERS-discover it, map fluctuations (COBE + WMAP;
hot and cold spots), calculate power spectrum (spatial frequencies of hot and cold
spots), use Hubble constant to get expansion rate of universe use amounts of
dark energy and dark matter to determine 'flatness' of universe, w = -1 equation
yields answer between 13.5 and 14 BY
parallax - ANSWERS-P = 1/d; inverse of dstnc (pc) = parallax in s of arc
inverse square law for light - ANSWERS-dffrnc in brightness = distance squared
(helps w/ H-R star placemt)
, inverse square law for gravity - ANSWERS-pwr increases proportionally to product
of objs' masses, decreases w/ dstnc squared btwn 2 objs
Wien's law - ANSWERS-T = 0.29 cm K/lambda[sub:max] (cm); temperature
decreases as wavelength increases (helps w/ H-R star placemt)
Stefan-Boltzmann law - ANSWERS-L = 4 [pi] R^2 [sigma] T^4; luminosity increases
with star's size & (more so) temp
mass-energy equivalence - ANSWERS-E = mc^2; energy is contained in mass; more
mass = more energy contained within, more energy for light to convert to matter
wavelength-energy equivalence - ANSWERS-E = hc/lambda; energy decreases as
wavelength increases
Doppler shift - ANSWERS-v/c= (lambda[sub:observed] - lambda[sub:rest]) /
lambda[sub:rest] ; wavelength of obsrvd object increases with speed of the object
Hubble's law - ANSWERS-v = HD; as dstnc to an obj, univrs expands it away faster
also relevant: 1/H= t[sub:H] (Mpc/km/s) = Hbl time; assumes univrs expands @
constant v (it doesn't)
universe age from star clusters - ANSWERS-globular clusters have so many stars
they can hold together forever, oldest ones we have; isochrones map H-R positns
of stars of every possible mass at a certain point in time; turn-off point of
isochrone's m-s shows oldest living star in the bunch; comparison of
hypotheticals' turn-off points to star cluster's turn-off point yields age estimate
for the cluster; universe must be older than oldest (lowest turning point)
observed clusters, 13-14 BY
universe age from expanding universe - ANSWERS-v = HD; given redshifting speed
of galaxy + distance to galaxy, we can get H, which yields time for which universe
has been expanding assuming it has been happening at a consistent speed (which
it isn't); space dust makes stuff look fainter and redder and closer, and different
cepheid types are now known to exist; distinguished cepheids + better dstnc
measrmts = 13.1-14.0 BY
universe age from CBR - ANSWERS-discover it, map fluctuations (COBE + WMAP;
hot and cold spots), calculate power spectrum (spatial frequencies of hot and cold
spots), use Hubble constant to get expansion rate of universe use amounts of
dark energy and dark matter to determine 'flatness' of universe, w = -1 equation
yields answer between 13.5 and 14 BY
parallax - ANSWERS-P = 1/d; inverse of dstnc (pc) = parallax in s of arc
inverse square law for light - ANSWERS-dffrnc in brightness = distance squared
(helps w/ H-R star placemt)
, inverse square law for gravity - ANSWERS-pwr increases proportionally to product
of objs' masses, decreases w/ dstnc squared btwn 2 objs
Wien's law - ANSWERS-T = 0.29 cm K/lambda[sub:max] (cm); temperature
decreases as wavelength increases (helps w/ H-R star placemt)
Stefan-Boltzmann law - ANSWERS-L = 4 [pi] R^2 [sigma] T^4; luminosity increases
with star's size & (more so) temp
mass-energy equivalence - ANSWERS-E = mc^2; energy is contained in mass; more
mass = more energy contained within, more energy for light to convert to matter
wavelength-energy equivalence - ANSWERS-E = hc/lambda; energy decreases as
wavelength increases
Doppler shift - ANSWERS-v/c= (lambda[sub:observed] - lambda[sub:rest]) /
lambda[sub:rest] ; wavelength of obsrvd object increases with speed of the object
Hubble's law - ANSWERS-v = HD; as dstnc to an obj, univrs expands it away faster
also relevant: 1/H= t[sub:H] (Mpc/km/s) = Hbl time; assumes univrs expands @
constant v (it doesn't)
