Topic D - Astrophysics Flashcards
I am the harbinger of entropy, the masterstroke of Armageddon
nebular hypothesis
long after big band gas and dust starts to gather gas and dust in a pinpoint location in space
what is : a main sequence star
if H -> He
what is : Hydrostatic Equilibrium
radiation pressure from center vs gravitational forces are balanced
what is : an asteroid
a rocky body
what is : a comet
irregular object that have vapor trails and orbit a sun
what is : a binary star system
solar system with 2 central stars
what is : a stellar cluster
a group of stars gravitationally connected (young)
what is : a globular cluster
a group of stars gravitationally connected (old)
what is : a galaxy
a system of stars gravitationally connected
spiral, eliptical, or irregular
what is : a cepheid variable
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
what is : a parsec (plus limitation)
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
how is : parallax angle measured
usually opposite sides of earth or opposite sides of earths orbit
Luminosity + Mass + age relation
More massive, shorter lifespan
More luminous, faster energy production
L proportional to M^3.5
Types of stars (and star outcomes)
- Supergiants
- Red Giants
- MS
- White Dwarfs
- Neutron Stars
- Black Holes
- Supernova
Fate/Steps of MS Stars
- 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
Fate/Steps of Red Giants
- 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
Black Holes (facts)
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
what is : red shift
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
the red shift constant (z)
or as Hubbles law, z=(Ho*d)/c
d = (c*z)/Ho
z < or = 0.2
big bang model
- 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
How to : Age of Universe
(equals are proportionalities)
v = Hod
c = HocT
T=1/Ho
T=1.410^10 years (age of the universe)
What is : scale of universe
d = R∆x
R = scale factor of universe
d = real distance between two points
∆x = arbitrary unit difference between two points
what is : cosmic background radiation (CBR)
- isotropic signal from the skies
- microwave region
- black-body radiation (3Kelvin)
what is : dark energy
- 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
how do : stars form
- gas and dust in a region
- a disturbance comes through (gravity starting)
- enough temperature and density is required
Jeans Criterion
what is : the Jeans Criterion
- 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
what is : Fushion (and steps)
- 4 hydrogens needed
- He produced
- Energy produced
- H & C are both reactants and products
- Energy comes from gamma radiation and B+ radiation
Proton - Proton Fushion
CNO Cycle
It does this on repeat and on loop
Tripple alpha radiation
Red Giants fuse together three alpha particles, creating a new particle with six protons and six neutrons
Nucleaosynthesis
- a dying red giant
- its the accordion reaction
- triple alpha reaction
neutron capture
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
Lifetime of a MS star
what is : a Type 1 Supernova
- absorption spectra - no Hydrogen
- old
- low mass
- Ia, Ib, Ic …
what is : a Type 2 Supernova
- younger than type 1
- with Hydrogen Spectra
what is : an Ia supernova
- often binary star system
- often at least 1 white dwarf
- predictable light emissions
- M < 1.4M(solar)
- produces larger elements
what is : the shape/layout of the universe
- 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
when did : the universe start to grow
right after the big bang
what is : Cosmic Background Radiation (CMR)
- 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
what is : the relationship between velocity (v) and radius (r) inside an object vs outside it
- inside a dense cloud : v ∝ r
- outside (like on a frisbee) : v ∝ 1/r
what does : the graph of v vs r look like for the stars in the universe
- since it is ‘unexpected’ and is speeding up, we know that there is some force making it speed up
- hence : dark matter
what is : dark matter (possibilities)
- 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
what is : a Closed Universe
- 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)
what is : an Open Universe
- 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)
what is : a Flat/Critical Universe
- 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
how to : derive the critical density
m = mass
ρ(m) = mass of universe
ρ(c) = critical mass of universe
ρ(Λ) = density of universe
dark energy + dark mass = 1
what is : universe with dark energy
the other three models don’t account for dark energy. with dark energy, universe will expand and scale factor will continue to increase
