The Great Debate Flashcards
charles messier
1730-1817
-discovered his first comet at 14
William Herschel
discovered Uranus in 1781
The General Catalog of Nebulae and Star Clusters
herschel and his son discovered over 5000 nebulae and star clusters
William Parsons
built largest telescope of 19th century
Island Universes
Lord Rosse
-distinct spiral pattern
who was the Great Debate between?
Heber Curtis & Harlow Shapley
what was Great debate about?
nature of the spiral nubulae
How big did Shapley think the MWG was and why?
100,000 pc across and Sun 30,000 pc from center
-measured distribution of globular clusters
How big did Curtis think the MWG was and why?
Much less than 30,000 pc across and Sun was center
-found separate galaxy
what did Curtis determine based on the Doppler shift?
the spiral nebulae were moving very rapidly (diff from most nebulae)
who won the debate
draw
-neither was totally right nor totally wrong
correct size of MWG
Shapley was correct, sun well off from center…size was too large
Correct nature of the spiral nebulae
Curtis won hands down…spiral nebulae lie outside the Milky Way
how could we prove that these really are distant “island universes”. What do we need to measure?
determining the distance to these spiral nebulae
What did Edwin Hubble discover?
1924
-discoverde Cepheid variable stars in the Great Spiral Nebula in Andromeda using 100 in telescope
What did Henrietta Leavitt discover in 1912?
the period-luminosity relation for Ceppheid variable stars
what did Hubble measure in Andromeda?
brightness and period of pulsation
what does the period provide?
luminosity, which combined with brightness gave Hubble distance to his stars
where were the stars Hubble dealt with?
great spiral nebula
size of today’s biggest telescopes?
10 m, or about 34 feet
what are the 2 major types of galaxies?
spiral galaxies and elliptical galaxies
what are barred spiral galaxies?
spiral galaxies w/ central bars
-spiral arms begin at end of these bars
in spiral galaxies, disks and spirals have a substantial amount of what two things?
gas and dust
new star formation in spiral arms come from?
hot gas
properties of spiral galaxies?
disk & spheroid
- spheroid has old stars and little gas/dust
- disk has gas/dust, young
properties of elliptical galaxies?
- only has spheroid component
- mostly old stars
- almost no gas/dust
in which galaxy type can new stars form?
spiral galaxies like the MWG
properties of irregular galaxies
- contain stars/gas/dust
- no spheroid
- star formation continuing
size range of galaxies?
dwarf to giant
galaxy clusters
when galaxies cluster together
-not uniformly distributed in space
Poor clusters
- few cluster members
- irregular shape
Rich clusters
- contains hundreds to thousands of galaxies
- spherical distribution
What type of galaxies are in poor clusters?
dwarf irregular/elliptical
what type of galaxies are in rich clusters?
elliptical and S0 galaxies
Local Group
poor cluster contains MWG and two other spiral galaxies
What are the remaining 40 galaxies?
all dwarf galaxies
-size=1 Mpc
what size cluster is common?
poor galaxy clusters, or small galaxy groups
what type of galaxy is common in rich clusters?
elliptical galaxies
Abel 1689
- rich cluster
- one of the largest galaxy clusters known
- giant elliptical galaxies
superclusters
clusters of galaxies are also clustered themselves
