Upgrade to remove ads
Only $2.99/month

Ch 20: The Hubble Age

Terms in this set (14)

white dwarfs, turnoff points of globular clusters, rate universe expanding (Hubble's law)
3 ways to now measure age of universe
fainter
1931: discrepancy where brightest cepheids in Andromeda were 1.5 magnitudes - than brightest milky way cepheids in globular clusters
Ockham's razor
14th century philosophy, critic of knowledge, what transcends experience can't be verified by rational logical arguments (fewer assumptions, keep it simple)
type I cepheids
classical cepheids, in spiral arms of galaxies, in SMC, not in globular clusters, bright, young stars from dying, massive stars, 4x brighter than other type
type II cepheids
in globular clusters, in halos of spiral galaxies, in elliptical galaxies, fainter, from lower mass stars, 4x fainter than other type
Walter baade
German native in US during WWII, Mt Wilson observatory, studied spiral galaxy where you can see disk and fuzzy halo, found lots of cepheids; designated population I and II of spiral galaxies
population II
globular clusters with faint cepheids; no O and B stars (correlated to type II cepheids)
population I
brighter cepheids in spiral arms; star clusters/ regions with lots of hot, luminous O and B stars; open clusters (correlated to type I cepheids)
II, I
Shapley's period luminosity diagram was of type - cepheids, but used by Hubble (whose cepheids were all type -) to calibrate distances to galaxies
fainter, closer, larger, smaller
because Hubble used Shapley's type II P-L diagram on type I cepheids:

assumed the cepheids were 4x - than they really are
concluded they were 2x -
so, H is 2x - than it should be
conclude the age of the universe is 2x - than it really is
interstellar dust
complication in measuring distance to galaxies, dark bands, blocks stars, makes stars appear fainter, "reddens" starlight
3x
baade, 1952, concluded distance to Andromeda is - larger than Hubble's measurement
error bar
as time goes on, with calculation of Hubble time, - - is shrinking even though the value is similar, progress has been made
70, 13-14
ballpark of the Hubble constant is -, so age of universe is between - billion years
THIS SET IS OFTEN IN FOLDERS WITH...