| Be familiar with the following material for the Final
Exam.
From the first half of the course:
What is a light year?
What is an astronomical unit?
What is a parsec?
Under what circumstances are the different
measurement systems used?
Magnitude is the measure of what about a star?
What's the difference between apparent and absolute
magnitude?
What element is most abundant in the universe?
What element is second most abundant in the universe?
Know the general features of an atom: nucleus,
protons, neutrons, electrons, ionization.
What are the three kinds of spectra?
What are the two most abundant elements in the Sun?
What process going on in Sun's core provides the
Sun's energy?
What are the spectral classes of stars?
What is the relationship between a star's color and
temperature.
Know that the H-R diagram plots luminosity and
temperature of stars, and that most stars are on the main sequence.
Know the mass-luminosity relationship of stars on
main sequence.
What is the interstellar medium and what is it
composed of? (75% H, 25% He, 1% dust)
What is a nebula? (cloud of gas and dust)
What are three kinds of nebulae? (dark, emission,
reflection)
What is a molecular cloud, and how is it different
from the interstellar medium? (cloud of gas and dust and molecules)
Where are stars born? (cold, dark molecular clouds or
giant molecular clouds)
Know about a protostar: what is it? is it fusing H to
He? is it on the main sequence?
Stars tend to form in groups rather than singly.
What is hydrostatic equilibrium (balance between
weight and pressure) and what does it appy to?
Brown dwarfs (0.08 solar mass) are not large enough
to get hot enough to fuse H to He and enter main sequence.
Red dwarfs are low-mass stars, but are large enough
to be on main sequence. They have the longest lifetimes of any other mass star.
The Sun is considered to be a medium-mass star.
White dwarfs are not on the main sequence; they are
stellar corpses, no fusion.
Average star spends 90% of its life on the main
sequence.
The more massive a star, the shorter its life (so an
O star would have shorter life than G star like sun).
The definition for degenerate matter: when gas is so
dense that its electrons are not free to change their energy levels. What kind of star is
composed of degenerate matter?
General path for medium-mass stars: most of life on
main sequence fusing H to He at core; turn into red giants (no longer on main sequence);
outer atmosphere expelled creating planetary nebula; end up as white dwarfs.
White dwarfs eventually radiate all their heat away,
turning into black dwarfs.
Massive stars (about 4 times mass of sun or larger)
do not turn into white dwarfs. They can experience supernova explosion, in which much of
their outer atmosphere can be expelled into space (supernova remnant), leaving behind a
neutron star (very dense) or pulsar. If the star is massive enough, it would turn into a
black hole instead of a neutron star or pulsar.
Neutron stars and pulsars are very dense, rotate
rapidly.
Understand escape velocity.
Know why black holes are dark (light can't reach
necessary escape velocity to leave surface of object)
Know speed of light as 186,000 miles per second.
What is a variable star?
Why are Cepheid variable stars important?
Know the period-luminosity relation of Cepheid
variables.
Open star clusters contain 100-1000 stars and exist
in the disk of our galaxy.
Globular clusters contain 100,000 - 1 million stars
and most are located around a point in the constellation Sagittarius.
Know where the center of the Milky Way is, and that
we are about 2/3 out from it in one of the spiral arms.
Know what kind of galaxy the Milky Way is.
Know main components of Milky Way: nuclear bulge,
disk, halo, globular clusters
Galaxy does not rotate as solid object, but exhibits
differential rotation.
What is a galaxy rotation curve?
Studies of galaxy rotation curves suggest the
presence of large amounts of dark matter, matter that must exist to result in the observed
rotation curve, but can't be seen.
Know what Sagittarius A* is.
What is the Hubble deep field?
Know the main catagories of galaxies, and generally
what they look like (spiral, barred spiral, elliptical, irregular).
Astronomers estimate that there are 100 billion
galaxies visible with existing telescopes.
Distance to galaxies are measured in mega parsecs (a
million parsecs).
One parsec equals 3.26 light years.
Know the term look-back time and what it means.
Galaxies differ in size, mass and luminosity.
Galaxies exist in clusters.
Rich galaxy clusters contain 1000 + galaxies, mostly
elliptical, in a spherical volume.
Poor galaxy clusters contain less than 1000 galaxies
which are irregularly distributed in an irregularly shaped volume.
What is the Local Group?
Do galaxies collide? Do the stars in them collide?
Know the average seperation between galaxies and
stars.
What is a starburst galaxy?
Know that elliptical galaxies appear to be products
of galaxy mergers.
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