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Astronomy
| Question | Answer |
|---|---|
| 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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