Week 2 Classification & The Distance Ladder Flashcards
what are the two types of galaxy classification
Shape of Galaxy
Luminosity of Galaxy
briefly describe Hubble’s tuning fork
starts as elliptical section then branches into normal spiral and barred spiral
what is the problem with Hubble’s tuning fork
it only considered observable shape not evolutionary processes
how are elliptical galaxies classified according to hubble
En = 10(1-b/a)
a and b are the major and minor axis
how are lenticular galaxies classified according to hubble
split between S0(normal) and SB0(barred)
how are spiral galaxies subdivided
subdivided according to the tightness of winding
‘a’ is the tightest and ‘d’ is the least
what is the problem with luminosity classification systems
doesn’t correlate with well defined structures in a galaxy
what are the 3 methods for measuring within our Solar system
laser reflector on the Moon gives us accurate distance to Moon
Radar methods are used for inner solar system
Signal time delay from spacecraft gives distances for all visited objects in Solar system
define LSR (Local standard of rest)
fictitious star orbiting the Galactic centre in a perfect circle at the star’s mean galactocentric radius
what is true of peculiar motions
peculiar motions of stars are assumed to average to zero and to be random
define the components of motion of stars
tangential: motion in the sky plane
radial: motion in the line of sight
what is the peculiar motion parallax equation
πd = 4.74τrms/σr
what is the moving cluster parallax equation
πd = 4.74μ/(tan[l])
what is the expansion parallax equation
d = vr/θ*
what are the 6 different candles methods
1 Cepheid Variables 2 Tip of Red Giant Branch (TRGB) 3 Novae & Light Curves 4 Supernovae Type Ia 5 Assemblies of Globular Clusters 6 Planetary Nebulae
