ASTR 1010 Final Vanderbilt; Questions And
Answers
radioactive decay - answer -the process by which radioactive isotope breaks down
into a stable isotope of same/another element; each half-life leaves half of existing
population of radioactive isotope
star cluster + special properties - answer -gravitationally bound stars formed from
the same gas cloud; all about same dstnc from Earth, all about same age; open
clusters have countable stars, globular clusters have too many to count (stable for
like, ever with that much gravity)
main sequence fitting - answer -measuring the distance to a star cluster by
comparing the apparent brightness of the cluster's main sequence with that of the
standard main sequence
white dwarfs + special properties - answer -inert core of dead red giant; stable size
due to degeneracy pressr, DENSE (Earth size, Sun mass), can't generate new
energy, cool off, gradually grow fainter
period-luminosity diagram - answer -plots logarithmic relatnshp btwn cepheids'
varblty pd length and abs L; given abs L + apparent L, we can estimt dstnc to
cepheid + of obj in which it resides
cepheid variable stars - answer -variable star w/ irregular varblty trend, rapidly
brightening, fading progressively slower till 3/4 down, then rapidly
finishing/repeating; variatn related to intrinsic luminosity, i.e. their size/temp
changing
why we consider universe expanding rather than things just moving through it -
answer -cosmological principle; stuff would be moving away from the center, and
stuff is moving away from us, which would make us the center, which we know we
aren't
, Type I vs Type II cepheids/ who cares? - answer -Type I 4x brighter than Type II;
Type I found in SMC and spiral gxy arms; Type II found in globs & halos + nuclei
of spiral gxys
If one type is intrinsically dimmer than the other, P/L relationship yields a lower
curve/shorter dstnc, skews dstnc calcs if 2 types mixed together
early phases of Big Bang - answer -inflationary epoch: 10^-35 s, universe expands
beyond speed of light for reasons unknown
particle creation epoch: 5 s, T > 1,000 bil K, photons have so much energy that
they can turn into p/n/e's and back; higher energy = higher mass, but as univrs
expands, photon wvlngths stretch, losing energy & losing ability to convert to
particles at all
element creation epoch: 100 s, T < 6 bil K; n's too unstable to exist w/o fusing w/
p, so they either do that or fall apart into p/e's; protons have enough energy to
combine into H, 2H & He, even some Li/Be;
combination/recombination epoch: 380,000 y, T < 1 bil K, p/e's combine to form
H, e's absorb photons w/ enough energy to free them, H falls apart, univrs
expands/cools, H keeps reforming/falling apart with photons having less and less
energy to free to e's each time, until energy is too little and photons can't be
absorbed anymore
CBR release: 3000 K, freedom! no more absorption = photons can travel wherever,
gas now transparent and all that
large-scale structure problem + solution - answer -problem: total isotropy would
not allow for matter to collapse and form stars, gxys, clusters, etc.
solution part 1: COsmic Bckgrd Explorer (COBE) could measr temp dffrncs in 2
dffrnt plcs to millionths of a degree, but couldn't get a specific as a galaxy cluster
