Test 3 Flashcards
RR Lyraes stars
Round a 1/2 day period. Old stars Low mass Low metallicity Usually found in globular clusters
Instability strips
Region on the HR diagram where variable stars are found.
Cepheid variable stars
1-100 day period Young stars High metallicity High mass Found in open clusters or disk
Constellation at middle of Milky Way galaxy
Sagittarius
Shapely
He found RR Lyrae stars in globular clusters and determined we are not at the center of the galaxy
Edwin Hubble
Used the hooker telescope and found cepheid variable stars in andromeda galaxy proving it was a whole nother galaxy not just a star forming region within our galaxy
Used to map the spiral arms of the Milky Way galaxy
Hydrogen spin-flip transition
Halo
No gas and dust Old stars Metal poor Population II stars Globular clusters
Disk
Gas and dust Young stars Emission nebulas Star formation, GMCs Open clusters Population I stars Metal rich Sun
Bulge
Contains population I and II stars
Forming spiral arms
1) star formation propagation
2) density wave theory
Milky Way rotation
Use Doppler effect
V = 230 km/sec
Galactic year
The time it takes to go around the center of the galaxy.
One galactic year for the sun: t= 200,000,000 - 250,000,000 years
So sun is about 22 galactic years old
Mass of Milky Way
m = 9.4 * 10^10 solar masses
Number of stars in the Milky Way.
200,000,000,000 stars
Dark matter
For the outside of the galaxy to be goin as fast as the center of the galaxy there must be more mass that can’t be seen.
Missing mass.
The effects of it’s gravity can be seen but not what’s causing it.
WIMP: Google
Center of Milky Way
Super massive black hole.
Sgr A: 3,000,000 solar masses
There’s that much mass in a spot smaller than the solar system
Spiral galaxies
Gas and dust Orbits with a plane Young O&B stars Open and globular clusters Blue Metal-rich
Elliptical galaxies
Very little gas and dust Random orbits Old stars Globular clusters Red Metal poor
Poor clusters
About 30 galaxies in a group
Local group: MW, andromeda, etc (about 25)
Rich clusters
1000s of galaxies
Giant ellipticals usual found at center
Super clusters
Clusters of galaxy clusters
Large scale structure of the universe
Voids: regions without galaxies
Galaxies cluster together in long filaments
What type of galaxy cluster is the Milky Way apart of?
Poor