Can you Sketch a Hertzprung Russel diagram detailing the evolutionary path of a solar mass star from inception to death
Starts out as main sequence then red giant then yellow giant the red super giant then planetary nebula then white dwarf
Can you describe the energy sources at each stage of a star's life?
protostar- Gravity, pre-mainsequence-gravitational contraction, main-sequence-P-P in core, Red Giant- P-P in shell plus gravitational contraction of core, Yellow Giant- buring helium in core, Red super giant- helium flash, planetary nebula- core star cools, white dwarf- star cools
What is the Helium Flash?
happens when helium begins burnin in the degenerate core and temp increase is not moderated by change in pressure
What does ZAMS stand for?
Zero age main sequence.. (the band that main sequence stars start at is a lower boundary of main sequence bad)
What is it about nuclear reactions inside yellow giants stars that leads to variability in luminosity?
Core concentration heats up the surrounding shell and He burning can take place. Temperature sensitivity of triple alpha process leads to instabiity in star's size/temp/luminosity
What i the de Broglie wavelength? Write a formula defining it in tersm of particles momentum
deBroglie showed that particles demonstrate wave like behavior.. and the wavelength associated with that is deBroglie's wavelength =h/p
What is the Pauli exclusion principle ?
for fermions no two electrons or neutrons can be in the same quantum state
What is the Heisenberg uncertainty principle? Write formula as it applies to momentum and position
We dont know everything about particle on quantum scales so the principle places a value on the minimum uncertainty we must have when measuring an electrons position and momentum.. ApAx>= h/4pi
What is a degenerate gas
gases composed of fermions that have high densities
How is degeneracy pressure related to density? How is the diff from ideal gas?
P proportional to (denstity)^(5/3)
in ideal gas..
P proportional to Density
What is a white dwarf? What types of stars form these/
-remnants of a star..
-main sequence stars with mass >= 1.44solar masses
What is a neutron star? Under what conditions are these formed?
remnants of a star made of mostly neutrons formed when M>1.44 Solar masses
what is a planetary nebula?
when helium burning exhausted the core will start to contract again.. thermal pulses eject mass and exposes inner regions..
planetary nebula is where the ejected material reacts with the UV photons from exposed shell. ionizing material and making it glow
What is the Chandrasekhar mass?
degeneracy pressure can only support a certain mass which is 1.44 solar masses
What is the Schwarzschild radius? What is the formula relating the Schwarzschild radius to a blackhole's mass?
the radius at which gravitational force is so large even light cannot escape.
What is Jean's mass?
This is the minimum mass in a gravitationally bound object.. 4piR^3(rho)/3
Why do some gas clouds form disks rather than compact spheres when they collapse?
contraction perpendicular to the rotation produces accretion disk
What population of stars are typically found in a globular cluster? an open cluster?
open clusters typically contain less than 1000 stars
globular clusters typically contain hundreds of thousands or even millions of stars
What are the major differences between globular and open flusters
open are smaller, associated with interstellar gas and dust and are mostly young stars have a high metallicity and found in disk of our galaxy... globular are opposite.. huge population no associated dust or gas, old stars.. low metallicity found in spherical part of galaxy
What is the point of convergence for a cluster and how do we calcuate distances using it?
if you extend the proper motion line of all the stars it is the point where the lines meet .
the angle of sight can be used to calculate the transverse velocity vt=vr*tan(theta) then D(km)=vt(km/s)/propermotion(rad/s) or D9pc)=Vt)km/s)/(4.74 propermotion (arcsec/year)
What is "Main Sequence Fitting" for a star cluster and how do we calculate distances using it?
When you slide main sequence onto a usual absolute magnitude for that spectra type until it fits then we can get apparent magnitudes to calculate distances
What is the turn off point for a star cluster, and how do we estimate age using it?
the point where no hotter main sequence stars are seen..
assuming that stars in a cluster were all formed at same time we can use the turn off point to tell relative ages of clusters or absolute age if we know how long stars of given spectral tpe stay on the main sequence
What population of stars are typically found in the galactic disk? the halo? the bulge?
Disk- population I stars.. clue reasonablye young
bulge- high density region of opp II stars red and very old
halo- low density of old stars
Can you sketch a diagram of our galaxy shoiwing its main features
halo bulge disk ..
What is the radius of our galaxy's disk? what about its height? How big is the galactic bulge
disk is 15 kpc in diameter
300 pc thick
the bulge is 1kpc by 6 kpc
Where are globular clusters usually found in the glaaxy ? an open cluster?
disk- open clusters
What is peculiar motion?
deviations from circular motion
What is differential rotation??
whens tars at different radii from the center move at different angular speeds this is known as differenntial rotation
How does the 21cm line help us probe the mass distribution of the galaxy
can use the doppler shift of emission wavelength to probe distance of cloud and can use the intensity of the emission line to probe density of cloud .. more dense greater the flux.. since spiral arms are regions of higher density material we can use the 21 cm line to help us
What is gravitational lensing?
when light from a distant bright source such as a quasar is bent around a massive object such as cluster or galaxies between the source object and the observer
what is an einstein ring?
the deformation of the light from something into a ring through gravitational lensing of the sources light
List the main properties of a spiral galaxy
flat disk, 5-50kpc in radius 10^9-10^12 solar masses Pop I and Pop II stars circiular stellar motions clue and red.. outside cluster.. example.. milky waydoes have dust and gas
List the main properties of a elliptical galaxy
shape round.. .1 kpc-100kpc in radius 10^5-10^13 solar masses little or no dust and gas.. pop II stars random stellar motions color is red location is within clusters example M 87
Could you tell what kind of galaxy one is from its classification ?
all classifications that start with S then no O is a spirla all that start with E are ellipticals and ones that start with SO or SBO are lenticular
How do galactic observations suggest there is dark matter?
there is a discrepancy between the amount of matter required to give this rotation curve and the amount of luminous matter we see.. theere must be other matter.. aka dark matter
Name two possible dark matter candidates
MACHOs- massive compact halo objects - small faint stars/stellar remnants
WIMPs- weakly interacting massive particles.. neutrinos or some undiscovered particle
What is a lenticular galaxy?
spiral galaxy without spiral (beween S and E)
What is a Seyfert galaxy
very similar to a normal distant spiral with a bright star superimposed on nucleus
what is a radio galaxy?
strong radio sources considered the radio loud analogs of seyferts but found in large ellipticals rather than spirals
what do we believe is the origin of Active Galactic Nuclei
believe to originate from the nuclear regions of the galaxy
What is the evidence for our galaxy having a supermassive black hole at its center
small size-inferred from variability timescales and unresolved components
large mass- inferred from large doppler broadening velocities in emission lines
What is Hubble Law?
all objects observed in deep space are found to have a doppler shift observable relative velocity to earth AND to each other
vr=Ho*d linear relationship between recessional velocity and sitance to nearby galaxies
What is the observed value of hubble's constant? including units
72 km-1 M pc-1 which is also s-1
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