Milky Way and Galaxies

Question 1

main parts of milky way

Answer 1

disk - spiral arm and interstellar matter, stars with heavy elements.

halo - shape detrmined from globular clusters, no dust, reffer, stars with few heavy elements.

bulge

Question 2

milky way size, thickness, etc.

Answer 2

100,000 ly diameter, from sun to center is 26,000 ly, thickness varies but approx. 1000 ly here.

Question 3

formation of milky way

Answer 3

merger of previous big clouds, flattening from rotation (like solar system).

Question 4

dwarf/sattelite galaxies

Answer 4

large and small magellanic clouds (irregular galaxies 160-200 kly)

closest ones are canis major (discovered 2003), ursa major, sagittarius dwarfs.

Question 5

local group

Answer 5

andromeda galaxy (2.5 million ly) and its satellites

more than 50 galaxies in local group

Question 6

galaxy types

Answer 6

spirals, ellipticals, irregulars

Question 7

spiral galaxies

Answer 7

most common (60%)

disk, white/blue spital arms (from star formation and gas/dust), bulge, and halo

varied like barred spirals

classified by Sa (large bulge, tight spiral) to Sc (small bulge, loose spiral).

Question 8

elliptical/ellipsoidal galaxies

Answer 8

no disk, all halo

mainly old stars in random motions, no gas/dust, 1 trillion giant stars and 100 million dwarfs

classified by E0 (perfect circle) to E0 (extremely elliptical)

Question 9

irregular galaxies

Answer 9

nothing like other galaxies, less common

stars form, gas/dust

magellanic clouds

no classification