Fourth-Fifth Test Flashcards
Harvard calculators
women who sat around in harvard and did math. famous: annie cannon and henrietta leavitt. both deaf math majors
Henry Draper
lived mid 19th century, interested in spectral lines but unsure what they were. had ability to make good spectra. on death wife gave money to harvard to study spectra, spectra discoveries there named after him.
star spectral types
Annie Cannon noticed similarities in different stars, designed an A-V sequence. When it was figured out what spectral lines are, cannon rearranged stars onto a scale from hot-cool, 30,000K to 3000K. O B A F G K M.
Draper Spectral Classification System
O B A F G K M. From hot to cool, 30,000K to 3000K. 0-9 subtypes. Oh, be a fine girl, kiss me!
division of temperature based on spectral lines.
HR Diagram
get apparent mag, get distance and temperature from spectral math filtering. get graph of line going top left to bottom right, hot left on X, bright high on Y. the line is the MAIN SEQUENCE. red giants in top right- low T high brightness, white dwarfs bottom left- opposite.
spectroscopic parallax
distance from star derived from spectrographs. astronomers call all distance spectrograph.
luminosity variance of stars
Henrietta Leavitt discovered that some stars vary in magnitude regularly, period measured in day. she checked if variation was related to anything useful- it was! luminosity… that is, the higher the period of of the star, the brighter it is.
cepheid star
UNCLEAR. a star that exhibits a certain kind of period-luminosity relationship. used as a standard candle to measure distances. including to distant galaxies, because 99% of the distance to a star is the distance to its galaxy.
two types of cepheid variables
Type I “classical”, type 2 “w viginis” viginis lower and lefter on graph.
stellar nurseries
gas clouds such as orion. gas and dust ejected from supernova, gas collapses, protostars blow gas around, disks form etc.
Messier catalog
1781, by messier. Lots of items have messier number.
NGC catalog
new general catalog. 1886, more stars.
solar system formation
cloud->disk->star-> planets
what happens to materials of dying star
5-10% imploded. 90-95% sent out and recycled.
making mathematical model of stars
make star into series of concentric circles. assumptions: star is spherical, layers made by concentric circles are same all around. measure Temperature, density, pressure, composition (T1, Ro1, Comp1, P1) of outermost layer with spectral stuff. Use physics to calculate it for each layer going in. Calculus removes the layers and can make it a continuous calculation.
once mathematical model exists
star can be evolved in the fourth dimension!
first stage of stellar evolution
Very big, low density cloud, density increasing, hot gas rises, cold sinks… strong convection. Temperature stays same, cloud gets smaller, thus smaller brightness.
second stage of stellar evolution
density continues to increase, convection gets harder, almost stops, keeps collapsing. temp keeps going up, still getting smaller = dimmer. moves left on graph.
third stage
gets hot enough that star IGNITES: hydrogen burns into helium, starts temperature chain reaction. equilibrium between temperature and gravitational pressure. is a star with disk around it that forms into planet
collapse of cloud into star
cloud has some natural tendency to rotate. as gravity shrinks it, spins faster to conserve angular momentum. Horizontal force towards center, vertical force towards equator of spin: causes disk with packed middle. spirals up or down.
other STAR formation fact.s
clouds of gas often form more than one star, many points of light. can form binary, tertiary stars, star clusters
once mathematical model exists
star can be evolved in the fourth dimension!
first stage of stellar evolution
Very big, low density cloud, density increasing, hot gas rises, cold sinks… strong convection. Temperature stays same, cloud gets smaller, thus smaller brightness.
second stage of stellar evolution
density continues to increase, convection gets harder, almost stops, keeps collapsing. temp keeps going up, still getting smaller = dimmer. moves left on graph.
gestation times of different stars
100 solar mass stars born in 10k yrs, solar mass one million, 10^8 years for much smaller. they also die in related amounts of time.
collapse of cloud into star
cloud has some natural tendency to rotate. as gravity shrinks it, spins faster to conserve angular momentum. Horizontal force towards center, vertical force towards equator of spin: causes disk with packed middle. spirals up or down.
other STAR formation fact.s
clouds of gas often form more than one star, many points of light. can form binary, tertiary stars, star clusters
accretion theory
one idea of how planets form. in cloud orbiting protostar, molecules stick together chemically. those then start sticking together gravitationally. kepler’s third say that each little orbiting body orbits at different velocities, tug and stick to each other
moon formation
maybe further accretion disks, maybe giant impact- he doesn’t like this
minimum mass for H fusion
1/12th solar mass
neutrino telescoping
would be able to see core of sun, as light takes 10^5 years of reabsorption and emission to get out. use perchrolo ethylene with helium bubbling at first, that cannot detect all kind of neutrino, now look for light flashes in a pool of water, can detect all three. blurry map of sun made. deep underground to remove noise from other solar particles.
solar neutrino flux problem
solar neutrinos detected did not match predictions not enough of them. Answered by neutrinos changing flavor as they travel, between electron, muon, and tao. before solution: sun’s core off? black hole at center w/ sun sustained by rotation around it?
hydrogen fusion process
2H fuse into He2, then one more H to become He3, etc, double chains, get the slide.
4H fusion equation
4H -> 1He4 + 2 gamma rays + 2 positrons + 2 neutrinos
neutrinos
“little neutral ones”. predicted 1930 when EM was not being conserved. Seen in 1942. Mass, not electric charge was missing, hence neutralness. almost impossible to detect, 10^13 through hand every second. half would survive ten lightyears of lead!
death of star
massive: red giant layers fall back in, process repeats of fusing heavier elements up to iron. iron is boundary between exothermic fusion and fission, no more fusing it. explodes in supernova maybe.
smaller: stops burning helium, becomes size of earth but one solar mass, radiative heat, fades eventually to black dwarf.
lifetimes of stars
10^0 - life of biggest star.
10^10 - life of sun
10^11 - life of bigs:moreth
solar neutrino flux problem
solar neutrinos detected did not match predictions not enough of them. Answered by neutrinos changing flavor as they travel, between electron, muon, and tao.
neutrino observatories
South Dakota goldmine, super kumioandi in japan, IceCube array in antarctica
serious star system
1844 serius B predicted from A wobbling, observed 1962, spec isolated 1915. problem: it was insanely dense!
serius b density properties
1 solar mass, size of earth. 150lb person becomes 75 billion tons, AA battery (1/20lbs) becomes 250 million tons. one teaspoon of white dwarf material is 20 tons on earth. 1 mil grams/cm^3
why white dwarfs are stable
Pauli Exclusion principle, heisenberg uncertainty principle. deltaX * deltaP > a constant. change in movement times change in momentum must remain greater than a certain constant. thus, as movement decreased, momentum increases, thus creating the quantum pressure needed to counter the force of gravity. “electron degenerate gas pressure”
lifetimes of stars
10^0 - life of biggest star.
10^10 - life of sun
10^11 -
white dwarfs general facts
white dwarf. what happens to them?
old vs new cluster of stars
old: clustered at bottom of HR, everything above has died. Lots of red giants shrinking to white dwarfs. in young cluster, lots of ones at top.
Sirius star system
1844 serius B predicted from A wobbling, observed 1862. 1915 observed with spectral lines.
Sirius b density properties
1 solar mass, size of earth. 150lb person becomes 75 billion tons, AA battery (1/20lbs) becomes 250 million tons. one teaspoon of white dwarf material is 20 tons on earth.
why white dwarfs are stable
Pauli Exclusion principle, heisenberg uncertainty principle. deltaX * deltaP > a constant. change in movement times change in momentum must remain greater than a certain constant. thus, as movement decreased, momentum increases, thus creating the quantum pressure needed to counter
Chandrasekar limit
1.4 solar masses. after that, degenerate electron motion gets relativistic- can’t hold up, no stability. developed 1930.
white dwarfs
<1.4 solar masses. takes 2x age of universe for leftover heat to radiate away, becoming black dwarves, none exist yet.
light leaving star
light (photos) made in core from energy of fusion. because of density of interior of star, takes 10^5 (10,000) years to get out of the star. mathematically: a random walk. imagine drunk person leaving bar and taking one equal step at a time home. Math says that you WILL get there eventually. this is the path light follows as it is absorbed and re-emitted repeatedly.
spectral line broadening
spectral lines from a star broadened by properties such as temperature, rotation/turbulence (producing red and blue shifts). Using a densitometer, see darkness of spectral line. Each broadening effect has a different signature, use mathematical curves to remove these bit by bit- getting data from each time.
what can get from spectral line curve analysis
Temp ±50° gas pressure+density chemical abundances rotational velocity mag field strength+direction expanding gas shell radial velocity from earth
red giant mass loss
can red giants lose enough mass to become white dwarves? big stars have to lose 98.6% of their mass. in casting off outer layers, stars lose a ton but losing 90% is rare. thus, they become SOMETHING MORE
light echo
light appears to be leaving a nebula faster than light, its not, just geometry and different angles??
Joclyn Bell
1967 PhD candidate under Anthony Hewish. Looking for an easy way to find quasars, which scintillate. Instead discovered radio pulses with regular period.
pulsar discovery process
Bell told to go back to quasars! At first thought that pulsars were man made, then they started varying sidereal (4 min off) meaning they were outside solar system.
how to discover pulsar
distance radio comes in as point source, narrow compared to cone-like planet. at the time, telescopes “integrate” radio signals, building them over time. This loses the pulsar data. Bell rented a field south of london built up-pointing antennas with 2x4s.
two early ideas for pulsars
Fastly rotating main sequence with a hotspot- with period of one sec, would fall apart. Two binaries working together- speed required would mean they’d merge. white dwarfs also would fall apart.
pulsar
rotating neutron star, left over after stellar explosion. size of burlington, 10km across. period of 1.3 millisecond to 10 seconds. .
synchrotron emissions discovery
a basic particle accelerator that synchronizes magnets with charged particles going around. researchers discovered that with a super-strong magnetic field, charged particles traveling at relativistic speeds emit blazes of light. a quantum effect, not a thermal emission
oppenheimer-volkoff
same as chand limit for white dwarves, but for neutron stars. limit is 1.4 (2 now) to five solar masses (upper limit). not sure how that bloody works! neutron stars only on small part of diagram.
how neutron stars form
collapsing stars >1.4 solar masses shrink past white dwarf density, pauli exclusion causes electrons and protons to fuse into neutrons. they find their own equilibrium like white dwarfs do = heisenberg delta x, delta p.
“nucleon degenerate gas pressure”
neutron star weight properties
150lbs Earth = 75 trillion trillion tons = 75*10^24 tons.
1/20lbs Earth = 25 billion trillion tons + 25*10^21
pulsar model
super spinning neutron star. magnetic axis off slightly. off axis and rotation speed taken down from orig star when star collapses. atmosphere around it, slimmish jet from pole.
“atmosphere” of pulsar
no pauli exclusion pressure on e- and p+ on outside of thing, they don’t form neutrons strong magnetic field + relativistic speeds = SYCHROTRON EMISSION!
as pulsar rotates, emitting part hits earth. width of emission cone is duration of pulse.
loss of spin for pulsars
angular momentum goes down, some energy is radiated out by the jet. loses .000005 seconds in four years, measured by mean julian year- exactly 24hrs.
