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Cosmological principle The universe is homogeneous and isotropic. Viewed on a sufficiently large scale the Universe appears the same to any observer at any location.
Homogeneous there is no preferred observing position in the universe
Isotropic there is no difference in the structure of the universe as you look in different directions
Hubble's Law v= Ho x d Ho is the Hubble Constant. Approximate value: 72km/s/Mpc. Every galaxy is moving away from every other galaxy. The space in between expands, like the dough in raisin bread.
Big Bang Evidence: Cosmic Microwave Background 1948–Residual evidence of the explosion should be visible as Blackbody radiation (George Gamow)1966–Observation of microwave background with horn antenna in Holmdel, NJ Robert Wilson & Arno Penzias find an excess of emission at T~3K
Nucleosynthesis In the first 1/2 hour,elements (Li, Be, B,H,He) were formed, but majority of mass in H (75%) & He (25%)
Types of Galaxies- Spiral Galaxies Disk Shape. Nuclear bulge. Spiral arms. Ordered rotational motion. Gas & dust between stars. New star formation. Very Luminous
Types of Galaxies- Barred Spirals Identical to Spirals except for the bulge. Center is stretched into a bar. 2/3 of all spirals are "barred"
Types of Galaxies- Elliptical Galaxies Elliptical/circular shape. No spiral structure. Random star motion. No gas or dust. No star formation. No hot, massive OB stars
Types of Galaxies-Irregular Galaxies Irregular Shapes. No spiral structure. No nuclear bulge. Chaotic mix of gas, dust, and stars. These, or dwarf ellipticals, are the most common types of galaxies
Evidence of Mergers-direct observation shows presence of molecular hydrogen (h2) clouds that have been stripped by tidal forces.
Evidence of Mergers-Ring Galaxies ring of debris around galaxy of material taken during merger
Evidence of Merger-Multiple Cores Some galaxies have evidence of multiple cores. False color images often allow cores to be visible.
Evidence of merger-Co-rotation Central regions stars rotate in the OPPOSITE direction from the outer sections
Sgr A* SUPERMASSIVE BLACK HOLE of the milky way galaxy. Kepler's law found mass to be 3.7mil solar masses. MUST be SMALL says Schwarzchild radius. a = 950 AU P = 15.2 yrs Closet Approach 17 light-hours = 7.2 AU Closer than Saturn’s orbit
Active Galactic Nuclei (AGNs) Luminosity is greater than sum of starlight. Small region of bright emission. Highly variable on short timescales. Bright in radio, UV, and X-rays All AGNs are the same, except for our point of view Radio Galaxies are the side view
Types of Active Galaxies- Seyfert Galaxies Off-center view of Black Hole’s accretion disk. Spiral galaxies with emission lines, highly ionized atoms, velocities of 10,000 km/s. 2% of ALL spirals. Type 1- broad lines, X-ray & UV bright. Type2- narrower lines, dimmer in X-rays & UV
Types of Active Galaxies- Radio Galaxies Side view Double-lobed radio emission Energy in lobe emission = 106 Mo * c2 SIDE FEW
Types of Active Galaxies- Blazars Looking down the jet (10,000 LMW) Looking down the barrel of the jet, variable over short timescales
Types of Active Galaxies- Quasars Quasi-stellar Objects (QSOs) Emission similar to radio galaxies, but looked like stars. Energy output~ Energy of over 100 average galaxies Luminosity changes over short time indicates small size
Rich Clusters Over 1000 members. Mostly Ellipticals. Within a volume 3 Mpc in radius. More crowded in center. 80-90% E&S0, few spirals. Example- Coma Cluster
Poor Clusters Less than 1000 members. Irregular shapes, NOT spherical. Small groupings of galaxies, NOT concentrated in center. 80-90% Spirals. Example, Hercules Cluster- Fewer than 100 members, no centrally dominate galaxy
Dark Matter Evidence- rotation curves flat rotation curves found in all spiral galaxies. Via Kepler's laws ASSUMPTION: Majority of mass is at center PREDICTION: Objects further from center move slower. Star rotation is affected by mass NOT at the center, Velocity is INCREASING with distance
Dark Matter Evidence- Cluster X-ray gas Coma Cluster Mass Dynamical Mass = 3 x 1015 Mo This is the mass calculated by observing the motion of galaxies within the cluster Mass in Galaxies = 5 x 1013 Mo Mass in X-ray gas = 3 x 1014 Mo Where is the other 90% ? -> DARK MATTER
Dark Matter Evidence- Gravitational Lensing We can calculate mass from the lensing, and we again find MORE MASS than we can see
Milky Way Structure Main Components- Disk, Bulge, Halo, Dark Matter Halo
Milky Way Structure- Disk Component Uncertain boundaries. OB stars along axis. Sun-like stars spread out further. Location of Spiral Arms. Location of Open Clusters. Order orbits in the same direction as the sun.
Layers/levels of Disk Extreme Disk – (100 pc) OB stars form here, short lifetimes so they don’t move off it Thin Disk – (1,000 pc) Sun-like stars Thick Disk – (~3,000 pc) Older stars
Milky Way Structure- Central Bulge radius 2,000 pc, mostly older stars. Hard to observe in visible light due to dust.
Milky Way Structure- Halo Globular clusters, are the oldest datable objects in the universe
Stellar Poplutions-Population I Extreme Location: Spiral Arms. Metallicity: 3%. Orbit: Circular. Age: <100 Myr.
Stellar Poplutions-Population I Intermediate Location: Disk. Metallicity: 1.6%. Orbit: Slightly Elliptical. Age: .2-10 Gyr.
Stellar Poplutions-Population II Extreme Location: Halo. Metallicity: .8%. Orbit: Highly Elliptical. Age: 10-14 Gyr
Stellar Poplutions-Population II Intermediate Location: Bulge. Metallicity: .8% Orbit: Elliptical. Age: 2-10 Gyr.
Stellar Population Overview/ population 3 PopI-sun-like stars 1.8% up to 3% metals PopII-Less than 1% metals.Big Bang created H and He, rest of elements created by stellar evolution. There MUST have been an initial generation of stars, POPIII-pure H and He, 0% metals, but have NEVER been observed
Possible Universes- Flat Expansion slows down, but doesn't stop until infinite time < 1
Possible Universes- Closed Expansion will stop, then reverse into the GNAB GIB = 1
Possible Universes- Open Universe expands forever, not enough mass to stop it > 1
Possible Universes- Accelerating None of the three universes it the data, the universe is __! Type Ia Supernova used as standard candles Supernova Cosmology Project-Berkeley Lab High-z Supernova Search Team – Led by Brian Schmidt
Created by: emilyclawson



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