astrophysics test 3

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Milky way diameter
100,000 LY
how many stars in milky way
100-400 billlion stars
different naming of milky way
greeks galaxies kuklos (milky circle)
then romans named: via lactea (milky way)
distances by cepheid variable stars
henrietta leavitt 1912
vary in luminosity/time
determining size by open star clusters and globular clusters
open star clusters- location within milky way
globular clusters- up to 1 million stars in tight sphere- oldest original of our MW Galaxy
MW components: disk and spherical
disk component- all matter is confined to galaxy rotation, flattened, spiral arms 2 barred, and 3-5 arms
spherical component- matter confined to a sphere, nuclear buldge densest, 13,040 LY in diameter
Mass of Mw
Study the proper motion of stars
Vmw= 220 km/sec
Age of MW
13.21 Billion years
population 1 stars
stars within disk-> spiral arms
rich in metals
circular orbits
younger, hotter, bluer
population II stars
stars in nuclear buldge, halo
globular clusters
lean in metals- H, He
density wave theory
one spiral arm overtakes another
-gas, dust , density increases
unstable gas and dust create pillars
formation by the “traditional hypothesis”
1. spherical cloud gas, gravity pulls in cloud denser towards the center less dense out
2. gravity starts rotation
3. giant, supergiant stars are formed + globular clusters. Remain in nuclear buldge; remain in outer halo globular clusters
4. Giants + Supergiants-> supernovae
5. Gas + dust collect in disk, rich in metal
6. New hotter, bluer stars form in disk
Cosmology Definition
study of structure + evolution of the universe
Obler’s paradox- Edgar Allan Poe’s idea
Universe was created in one moment of time
further look back time, infinitely darker
Hubble law
big bang
-one moment in time where all baryonic matter was formed 10^-43 second
-point of singularity
Cosmic background microwave- started when?
13.8 BY
Big bang temp and density at beginning
Temp 0k
desnity 5*10^13 g km^3
Isotropy, homogeneity, cosmological principle
Isotropy- being uniformed in all directions
homogeneity- same in all locations
cosmological principle- universe is Isotropic+Homogenous
galaxies expanding or space?
galaxies are slow in velocity- virtually no redshift
all galaxies have redshifts
Space is expanding
-galaxies are along for the ride
-all galaxies move away from each other
3 theoretical shapes
1. finite- closed
-curves back onto itself
-“sphere” 2-D surface- expanding
2. infinite open universe
-“flat”- no curvature- no edge
3. Infinite- open universe
-negative curvature
-“saddle shaped”
Critical Density
-Critical density= 9*10^-30 g/cm^3
-Universe>critical density-> spherical sharp positively curved
-universe=critical density-> space time is flat
-universenegatively curved
percentage of baryonic and non baryonic matter
4% baryonic
95% non baryonic
Grand unified theory- four fundamental forces
Strong force- atomic bonding
weak force- radioactive decay
electro-magnetic force
gravitational force- gravity
current best model of our universe
flat model universe
-big rip
Multiverses definition
hypothetical set of finite and infinite universes including our universe
common terms (multiverse)
parallel universe
dimensional planes
alternative universe
other universes
physical evidence
2010- study of background, microwave radiation
-gravitational wave anomalies
suggest a collision with another universe
Max Tegmark “four levels”
Level 1- hubble volume, chaotic inflation, infinite
Level 2- different physical constraints variant of level chaotic, inflation stretch forever, large bubbles
Level 3- Many- worlds of quantum mechanics, variant of level 1, no prediction of events
Level 4- ultimate ensemble, all universes are equally real, all described by different mathematical models
Brian Greene “nine types”
1. quilted- infinite number of space
2. inflationary- “bubble universe” various pockets collapse
3. Brane Membrane – Gravity extends through them
4. Cyclic- multiple membranes
5. landscape- string theory, energy strings
6. quantum- many worlds- level 3, different quantum
7. holographic multiverse- simulated universe
8. simulation- computer modeling
9. ultimate ensemble- every mathematical possibility
black hole cosmologcial model
Black hole, galactic center, singularity, white hole opposite another galaxy+ universe
Categories: Astrophysics