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Physics > Topic D - Astrophysics > Flashcards

Topic D - Astrophysics Flashcards

I am the harbinger of entropy, the masterstroke of Armageddon

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1
Q

nebular hypothesis

A

long after big band gas and dust starts to gather gas and dust in a pinpoint location in space

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2
Q

what is : a main sequence star

A

if H -> He

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3
Q

what is : Hydrostatic Equilibrium

A

radiation pressure from center vs gravitational forces are balanced

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4
Q

what is : an asteroid

A

a rocky body

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5
Q

what is : a comet

A

irregular object that have vapor trails and orbit a sun

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6
Q

what is : a binary star system

A

solar system with 2 central stars

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7
Q

what is : a stellar cluster

A

a group of stars gravitationally connected (young)

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8
Q

what is : a globular cluster

A

a group of stars gravitationally connected (old)

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9
Q

what is : a galaxy

A

a system of stars gravitationally connected
spiral, eliptical, or irregular

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10
Q

what is : a cepheid variable

A

cepheid variable = standard candle = supernova Ia

Luminocity changes due to growing and shrinking size of a star off the main sequence

outer layers contract and expand periodically

cepheid variables come in a couple different types, each type with a known luminocity and period, based on that distance can be calculated

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11
Q

what is : a parsec (plus limitation)

A

distance when a star has a parallax angle of 1 arcsec

Limit : due to gravitational lensing and light bouncing in atmosphere
100 parsec
0.01 arces

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12
Q

how is : parallax angle measured

A

usually opposite sides of earth or opposite sides of earths orbit

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13
Q

Luminosity + Mass + age relation

A

More massive, shorter lifespan
More luminous, faster energy production

L proportional to M^3.5

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14
Q

Types of stars (and star outcomes)

A
  • Supergiants
  • Red Giants
  • MS
  • White Dwarfs
  • Neutron Stars
  • Black Holes
  • Supernova
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15
Q

Fate/Steps of MS Stars

A
  • When H is depleted, no more fusion
  • Core collapses as hydrostatic equilibrium is disrupted
  • Gravitational Contraction : kinda like standard candle
    • pulls H into core
  • More H + He pulled from shell to core
  • He Flash : rapid temp spike (5.5*10^3 hotter than sun core)
    • FAST fushion
    • outer layer is blown away with heavier elements (due to He in core)
    • electron degeneracy pressure : e- force stops star from collapsing more
    • white dwarf is born
    • over billions of years, cools into a rock + dust
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16
Q

Fate/Steps of Red Giants

A
  • Large luminosity due to size, slightly colder
  • When H runs out, gravitational contraction happens
    • now C, O, etc. also become fused almost immediately because bigger and heavier elements
  • they become super red giants
  • super hot core fuses into iron
  • the sun forms layers with different elements
  • The Chandrasekhar (C) limit
    • if M < 1.4M(solar) -> White dwarf
    • if M > 1.4M(solar) -> supernova
  • neutron degeneracy pressure : further gravitational collapse
    • oppenheimer-vakhoff limit
    • if 1.5-3 M(solar) -> DENSE Neutron Star
    • if M > 3M(solar) -> Black Hole
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17
Q

Black Holes (facts)

A

Neutron pressure is insignificant so a whole in the universe is formed

no proof but :
- x-rays emitted from things spiraling inside it
- strong gravitational field/lensing
- giant jets of matter emitted from galaxy center

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18
Q

what is : red shift

A

things appear more red because they are receding

(Andromeda is blue shifted because it is the only thing we see coming towards us)

related to the doppler effect

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19
Q

the red shift constant (z)

A

or as Hubbles law, z=(Ho*d)/c

d = (c*z)/Ho

z < or = 0.2

20
Q

big bang model

A
  • everything came from an infinitesimally small point (possibly the other side of a black hole)
  • guess is 10^32 Kelvin (10^-44 seconds after birth of space)
  • all matter and energy at one point in space
21
Q

How to : Age of Universe

A

(equals are proportionalities)
v = Hod
c = HocT
T=1/Ho
T=1.410^10 years (age of the universe)

22
Q

What is : scale of universe

A

d = R∆x
R = scale factor of universe
d = real distance between two points
∆x = arbitrary unit difference between two points

23
Q

what is : cosmic background radiation (CBR)

A
  • isotropic signal from the skies
  • microwave region
  • black-body radiation (3Kelvin)
24
Q

what is : dark energy

A
  • the thing that is making the universe accelerate and accelerate faster
  • dark because we can’t measure or see it
  • kinda like anti-pressure of the universe
25
Q

how do : stars form

A
  • gas and dust in a region
  • a disturbance comes through (gravity starting)
  • enough temperature and density is required

Jeans Criterion

26
Q

what is : the Jeans Criterion

A
  • requirement for star formation
  • Mj = jeans mass
  • if Mj or KE too high, gas is unstable

No collapse when
* if low temp : low Ke
* if high mass : Large PE
* PE > KE

27
Q

what is : Fushion (and steps)

A
  • 4 hydrogens needed
  • He produced
  • Energy produced
  • H & C are both reactants and products
  • Energy comes from gamma radiation and B+ radiation
28
Q

Proton - Proton Fushion

A
29
Q

CNO Cycle

A

It does this on repeat and on loop

30
Q

Tripple alpha radiation

A

Red Giants fuse together three alpha particles, creating a new particle with six protons and six neutrons

31
Q

Nucleaosynthesis

A
  • a dying red giant
  • its the accordion reaction
  • triple alpha reaction
32
Q

neutron capture

A

Heavier Elements
* nucleus absorbs neutron
- becomes unstable

s-process (slow)
- slow-decay = captures more neutrons
- B+ decay
- stars : H->Fe
- s-process : Fe->further

r-process (rapid)
- many neutrons absorbed without decay
- then decay into HEAFTY elements

33
Q

Lifetime of a MS star

A
33
Q

what is : a Type 1 Supernova

A
  • absorption spectra - no Hydrogen
  • old
  • low mass
  • Ia, Ib, Ic …
34
Q

what is : a Type 2 Supernova

A
  • younger than type 1
  • with Hydrogen Spectra
35
Q

what is : an Ia supernova

A
  • often binary star system
  • often at least 1 white dwarf
  • predictable light emissions
  • M < 1.4M(solar)
  • produces larger elements
36
Q

what is : the shape/layout of the universe

A
  • isotropic
  • homogeneous
    • it looks the same everywhere from everywhere, no indistinguishable parts
    • because of this you can’t find the center
    • if universe turned into a cube puzzle, all pieces would be identical
37
Q

when did : the universe start to grow

A

right after the big bang

38
Q

what is : Cosmic Background Radiation (CMR)

A
  • small temperature fluctuations throughout the universe
    • do to slightly different temperatures in the universe during the big bang before expanding
  • now it looks like some non-isotropic regions
39
Q

what is : the relationship between velocity (v) and radius (r) inside an object vs outside it

A
  • inside a dense cloud : v ∝ r
  • outside (like on a frisbee) : v ∝ 1/r
40
Q

what does : the graph of v vs r look like for the stars in the universe

A
  • since it is ‘unexpected’ and is speeding up, we know that there is some force making it speed up
  • hence : dark matter
41
Q

what is : dark matter (possibilities)

A
  • MACHO’s (massive compact halo objects)
    • or cold non-radiating matter
    • we think its baryonic matter (from baryons)
  • we assume only 15% of matter is baryonic, so dark matter must have other forms
  • WIMP’s (weakly interacting massive particles (non-baryonic))
    • neutrinos
42
Q

what is : a Closed Universe

A
  • ρ(universe) > ρ(c)
  • Ωm > 1
  • the expansion will slow, then contract
  • if density is high, self gravity pulls universe back together
  • spherical geometry (parallel lines will converge)
43
Q

what is : an Open Universe

A
  • if ρ(universe) < ρ(c)
  • Ωm < 1
  • low density, self gravity won’t stop expansion
  • the expansion of universe and scale factor will continue forever
  • hyperbolic (pringle) geometry (parallel lines will diverge)
44
Q

what is : a Flat/Critical Universe

A
  • if ρ(universe) = ρ(c)
  • Ωm = 1
  • the expansion will stop expanding at infinity time way
  • Scale factor continues to decrease
  • flat geometry (parallel lines remain parallel)
  • currently universe is most likely flat
45
Q

how to : derive the critical density

A

m = mass
ρ(m) = mass of universe
ρ(c) = critical mass of universe
ρ(Λ) = density of universe
dark energy + dark mass = 1

46
Q

what is : universe with dark energy

A

the other three models don’t account for dark energy. with dark energy, universe will expand and scale factor will continue to increase

Physics (12 decks)

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