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Glossary of Astronomy Test 3

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Main sequence life starts where?
The ZAMS line
Characteristics of Main sequence stars
Hydrostatic Equilibrium
Hydrogen Fusion
Hydrogen Core Fusion-2 kinds
P-P-temp<10MK
CNO-temp>15MK
Main Sequence Lifetime depends on...
amount of fuel (mass)/rate of fuel consumption (luminosity)
Lifetime at the top of the main sequence is ______ than life at the bottom
shorter
Which is more abundant, upper or lower MS stars?
Lower
If a star has a high mass, it's death will be...
Complex
Death of a low mass star
H fusion ends because all H has been converted to He. Star contracts and shrinks to a white dwarf
Death of a medium mass star
H fusion ends because all H has been converted to He. As the star contracts, the internal temp rises to 100MK and the He is converted into Carbon. It then becomes a giant. When fusion ends, it becomes either a white dwarf or neutron star. It's ejected layer becomes a planetary nebula
Mass of a white dwarf vs. a neutron star
>1.4solar masses vs. <1.4solar masses
Death of a high mass star
H fusion ends and eventually the core turns to iron. Star collapses and material bounces off the core and the star tears apart to become a supernova. The remaining core collapses to form a neutron star or black hole
Neutron Star vs. Black Hole
<2.5-3 solar masses vs >2.5-3 solar masses
Pulsar
a neutron star's beam of radiation
Chandrasekhar Limit
White dwarf<1.4 solar masses
Put in order of diameter size, smallest to largest: white dwarf, neuton star, black hole
NS, WD, BH
Degeneracy of a white dwarf
Electron Degeneracy Pressure
Degeneracy of a neutron star
neutron degeneracy pressure
Singularity, Event Horizon, and Schwarschild radius for black holes
0 diameter, the place where events can be seen before entering the black hole. Rsch is proportional to the mass of the black hole
Naked Eye View of the Milky Way
hazy band of light around the celestial sphere
Galileo
discovered that the milky way is made up of thousands of stars
Herschels
concluded that the sun is near the center of the milky way by counting stars in bright regions
Shapley
finds that the sun is not at the center of the milky way
Leavitt
studied cepheid variables (pulsars) in the two magellanic clouds and discovered a period-luminosity relationship
Shapley 2
Studies RR lyrae variables in globular clusters and finds the distance to the clusters and that they are centered around a point 50,000 ly away
Globular Cluster
100,000-2 million stars in a ball located in and around sagittarius
Trumpler
Finds that dust dims starlight and that the center of the milky way is only 26,000 ly away
Structure of the Milky Way galaxy
Central bulge with a disk and halo
Open Cluster
10's-1000's of stars with little symmetry located along the milky way
Sun's orbit around central bulge
takes 225 million years
Method to find the mass of the milky way
mass of star=a au cubed/p years squared
Mass of the Milky Way
One trillion solar masses
What percentage of the Milky way is dark matter?
90%
What is dark matter?
Matter indicated by gravity but not seen at any wavelength
Method to find the age of the milky way
Look at the stars turnoff point on an HR diagram
If a star has a lower turn off point it is...?
Older
Age of the Milky Way
13 billion years
Nucleus of the Milky way
Sag A at radio
Sag A* at x-ray
Orbit of S2 around A* at infared
Mass of black hole at center?
2.6 million solar masses
Messier Catalog
Messier listed fuzzy, non moving objects M1-M110
New General Catalog
Dreyer listed 1000's of fuzzy objects
The Great Debate
Shapley vs. Curtis
Spiral Neb part of MW vs. Spiral Neb other galaxies
Hubble and Humason
Observed cepheid variables in M31, it was too far away to be part of the milky way
Baade
Discovers two types of cepheid variables
Total number of galaxies
100 billion
Local Group
40 galaxies within 5 million ly of the MW
Galaxy Cluster
group of galaxies
Supercluster
group of galaxy clusters
3D map of galaxies
bubbles surrounded by sheets of galaxies
Slipher
finds that all spiral nebulae have a red shift in spectral lines
Hubble
Recessional speed is proportional to distance (further away=greater speed away)
Hubble's Law
Recessional Speed=Hubble Constant * distance
Einstein
therory of relativity; spacetime is curved by matter
Friedman
finds that universe is either expanding or contracting
Open Universe
keeps expanding with a rate >0 as time goes to infinity
Closed Universe
expansion stops due to gravity, then contracts
Flat Universe
expansion is forever, buy expansion=0 as time reaches infinity

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