exam 3

older stars have ___ metallicity

older stars have ___ metallicity

less

newer stars have ___ metallicity

ex: Sun

more

parts of a black hole

escape velocity

singularity (mass in middle)

event horizon (size of black hole depending on mass)

acretion disk (plasma around hole)

jets (hot matter and x rays)

Schwarzschild radius (Rs)

radius of event horizon

shadow of a black hole

2.5 Rs

micro black hole

less than Ms (mass of sun)

stellar mass black hole

3-tens Ms

supermassive black hole

10,000 - billions Ms

intermediate black hole

not confirmed

first black hole discovered

cygnus x-1

how to find a black hole

1- stars orbiting something thats not there

2- bright x-rays from jets

3- take a picture

who discovered 1st supermassive black hole Sagittarius A*

genzel & ghez

photon sphere

inner edge where photons spiral out and warped that make it to our telescope

doppler beaming

increase luminosity due to matter moving towards you

• away → dimmer

tidal forces

squeeze from top to bottom

spaghettification (squeeze, stretch, push)

4 tests of general relativity

gravity redshift

gravitational time dilation

precision of perihelion

gravitational lensing

gravity redshift

closer you are to an object, the redder the object gets

ex: star close to black hole looks redder

gravitational time dilation

time runs slower the closer you are to massive objects

precision of perihelion

closest point in orbit to the sun

gravitational lensing

bending of light

1st test of general relativity

1919 solar eclipse - Arthur Eddington

hawking radiation

evaporation of black hole

• micro black hole evaporates quickly

• supermassive black hole evaporates slowly

anatomy of milky way

disc, center bulge, stellar halo

100,000 ly wide

10,000 ly length

disc stars

open clusters, young, blue, hot

center bulge stars

high luminosity, high number of stars

old, red stars

stellar halo

globular clusters, old, cool, red stars

star clusters

all stars in a cluster are same age and same distance to earth

open cluster

few thousand stars, young, hot, blue, dont last long due to low gravitational attraction, in disc

globular clusters

thousand to million stars, old, cool, red, last a long time, in stellar halo

thomas wright

1750

1st to describe shape of milky way

flat disc of stars and we are inside

immanuel kant

1755

solar system came from giant gas cloud (stellar nebula)

1st to suggest it rotates, held together by gravity

william herschel

1783

proposes 1st model of milky way

incorrectly puts sun at center of galaxy

fuzzy things = nebulae

great debate

1920

Smithsonian museum of natural history in DC

about nature of spiral nebulae and distances

heber curtis

1. nebulae = island universes (galaxies) TRUE

• 1917 nova in andromeda distance ~150,000 pc

2. why are there more nova in andromeda?

• should be evenly distributed if its a cloud in milky way

3. dust lanes in other “galaxies”

• milky way has dust lanes

4. cant use cepheid variables to measure distance

harlow shapley

• nebluae = cloud on outer edge of milky way

• if nebulae are galaxies, they would be millions of ly away

• 1885 nova outshined andromeda

  • nothing can outshine a galaxy

• cant visually measure rotation of galaxy in one’s lifetime (mistake using Maahen method)

• distance to andromeda = 100 Kpc

who won?

shapley had slight edge bc no one could imagine universe being so big like curtis said

edwin hubble

settles debate 1929

• use cepheids and leavitt’s law

• distance: 1.25 ly away

  • incorrect due to wrong calibration

• real distance: 2.5 million ly away

walter baade

• mount wilson observatory during ww2 (blackout)

• population 1, 2, 3 stars

population I stars

high metallicity, young, in disc

population II stars

low metallicity, in bulge and halo

population III stars

no metals, very 1st stars, hypothetical

spiral galaxies

60%

disc with arms

lots of star formation activity

barred

• bulge is cigar shaped

• SBa (tight arms) - SBc (loose arms)

• 2/3 of spirals

• milky way

ordinary

• circle bulge

• Sa (tight arms) - Sc (loose arms)

• 1/3 of spirals

lenticular galaxies

20%

disc with now arms

little star formation

S0 (ordinary) or SB0 (barred)

elliptical galaxy

10%

largest (giant elliptical)

minimal star formation

red, old, low mass stars

E0 (sphere) - E7 (elliptical/wide)

formed in 2 steps:

• protogalactic cloud collapse w no angular momentum

• collision of spirals

irregular galaxies

10%, no shape structure, random

ring galaxy

rare, know nothing

dwarf galaxy

orbit major (spiral, elliptical, lenticular) galaxies

milky way has ~20 dwarf galaxies = magellenic clouds

less than a billion stars in it

most common dwarf galaxy

dwarf spheroidal galaxy

hubble’s classification

• 1st to classify galaxies

• turning fork

• thought to be evolution diagram (wrong)

• 3 classifications: elliptical, spiral, lenticular

ordinary galaxy

• milky way

• light comes from stars → uniform

• central light bulge variation is minimal

active galaxies

10%

active = supermassive black hole accretes matter

• most luminosity from central bulge

• central bulge has a lot of variation

4 active galaxies

radio, seyfert, quasars, blazars

Active Galactic Nucleus (AGN)

accreting supermassive black hole

1- large bright accretion disk

2- large relativistic jets

radio galaxy

most elliptical, double radio lobes

seyfret galaxy

common active galaxy, spiral, low energy, can see host galaxy

quasars

quasar w/ lets pointed at earth

star system

one or more stars

solar system

galaxy

collection of star systems

milky way

group

~50 luminous galaxies

local group

cluster

100-1,000 luminous galaxies

supercluster

~10 clusters

virgo supercluster

laniakea supercluster

supercluster complex / galactic filament

largest structure in universe

pisces-cetus supercluster complex

dark matter

pushes stars and clumps together

fritz zwicky

1933

coma cluster: galaxies should be flying apart

dark matter holds it in

vera rubin

1963

measuring rotation rate of galaxies

dark matter → galaxies are moving faster due to something

80-90% of galaxy matter is dark matter

detected thru gravitational lensing

dark energy

pushes universe outward

einstein’s theory of relativity

• 1917: Adds a cosmological constant to equation through subtraction to prevent expanding universe

• 1913 Einstein removes cosmological constant

• 1998: constant re-added to equation thru addition = shows universe is expanding faster than they thought

hubbles law

1- most galaxies have redshift

2- further the galaxy, faster it is moving away

age of universe

13.8 billion years

z = redshift

z = 0

• no redshift

z < 0

• neg, blueshift

z > 0

• high redshift = far galaxy

cosmic laddar

• Parallax 100 pc

• RR lyrae 1Mpc

• Novae 20Mpc

• cepheids 20Mpc

• Type Ia 1,000Mpc

• Hubble’s law >10Mpc

vesto slipher

1912

1st redshift measurement

george lemaitre

primeval atom (where universe was contained b4 big bang)

1st suggestion of big bang

george gamow

1940

predicts 380,000 yrs for photons to cool

arno penzias & robert wilson

1964

build horn antenna

look 4 radio waves bouncing off satellites

discover CMBR

cosmic microwave background radiation (CMBR)

left over radiation from big bang that proves it happened

expansion of universe and inflation

• 93 billion ly across

• Horizon problem: universe is a uniform temperature

• Temp: should be hotter in some parts than others

• 1980’s: inflation, universe was thermodynamically connected early on to have a uniform temperature

electroweak era

• 10^-38 to 10^-10 seconds

• Have 4 forces of universe by end of era

• Farthest back that we understand

• Inflation occurs

• Universe is created = amounts of matter and antimatter

Nucleosynthesis Era

• .001 sec – 3 mins

• Fusion

  • Create 75% H and 25% He

nuclei era

• 5 mins – 380,000 years

• End when photons escape, give CMBR

big crunch

universe collapses back

big bounce

each collapse produces a new big bang

constant expansion of universe forever

• Eventually everything will freeze

• Big freeze / heat death of universe

• Current leading theory

dark energy continues to increase

rips everything apart