Galaxy Types Flashcards
What are the 3 galaxy types?
•spiral-disc like with arms and central bulges
•elliptical-sphéroïdal blobs with less structure
•irregular-amorphous shapes
Describe spiral galaxies
•discs contain hot gas, cold gas, dust, stars of mixed ages, heavy metal
•dust blocks light, producing patchy effect
•mostly blue indicating younger stars
How does bulge correlate with tightness of arms?
Brighter bulge=tighter arms
Describe elliptical galaxies
•smooth and spherodial
•vary in roughness from spherical to highly elliptical
•no disc or spiral arms
•all gas is very hot
•older stars so very red
What is a lenticular galaxy?
Part way between bulge and disc. Like a disc without spiral arms but with bulge
What colour are lenticular galaxies?
Red as little gas and low star formation
Describe irregular galaxies
•mostly smaller
•lots of cold gas, new stars
•very blue
•many knots of star formation
How are spiral galaxies classified by tuning fork?
•a=tightest arms, brightest bulge
•c=spread arms, faintest bulge
•also classified by whether they have bars across bulge(B)
How are elliptical galaxies classified using tuning fork?
•ordered by ellipticity
•0=roundest
•7=most elongated
What are distant galaxies more likely to be?
•more irregular
•smaller
•bluer
•still growing via star formation
What might affect eventual galaxy type?
Proto-galaxy cloud rotation
•fast rotation, quick collapse to disc, collapses before cooling, stars formed after collapse, spiral
•slow rotation, slow collapse, cooling before collapse, stars formed before collapse, elliptical
What other property of proto-galaxy cloud might affect eventual type?
Density
•low density, long time to cool, collapses before cooling, stars formed after collapse, spiral
•high density, fast cooling, cooling before collapse, stars formed before collapse, elliptical
