ASTR 121|113 Final Exam Quiz Questions Correctly Answered|2024
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Course
ASTR 121
Institution
ASTR 121
about 91% (by number) of the atoms in the sun are the element - ️️hydrogen
Age of the Universe - ️️13.7 billion years
all the energy of the sun is generated in the - ️️core
alpha particle - ️️A cluster of 2 protons and 2 neutrons emitted from a nucleus in one type of radioactivit...
about 91% (by number) of the atoms in the sun are the element - ✔ ✔ hydrogen
Age of the Universe - ✔ ✔ 13.7 billion years
all the energy of the sun is generated in the - ✔ ✔ core
alpha particle - ✔ ✔ A cluster of 2 protons and 2 neutrons emitted from a nucleus in one type of
radioactivity
an astronomer discovers a new star and wants to measure its temperate. she could do this by: - ✔ ✔
take a spectrum of the star and determine the spectral type
Astronomers did star counts in all directions in the Milky Way and determined that we were near the
center of the Milky Way. Why does this method not work, since we are NOT near the center? OE - ✔
✔ star counts show equal numbers of stars in all directions because you can't see very far due to gas
and dust
at the beginning of a star's life on the main sequence, the core will be mostly - ✔ ✔ hydrogen
black holes OE - ✔ ✔ look for x-rays or binary stars with unseen companions (use physics to find
mass)
Chandrasekhar limit - ✔ ✔ the maximum mass of a white dwarf above which it collapses; 1.4 solar
masses
classification scheme for ellipticals - ✔ ✔ classified by degree of flattening as E0, E1, E2,..., E7; E0
galaxies are spherical and round & E7 are highly elongated; stars in elliptical galaxies highly elliptical
plunging orbits rather than circular disk stars in spiral galaxies; dwarf elliptical galaxies most common
type of galaxy (contain several million stars)
Compare and contrast Population I stars and Population II stars (age, location in galaxy, metals, orbits)
OE - ✔ ✔ population I: young, in disk, high metal content, circular
population II: old, in halo and central bulge, low metal content, spherical distribution
core helium fusion - ✔ ✔ the fusion of helium to form carbon and oxygen at the center of a star
core hydrogen fusion - ✔ ✔ The thermonuclear fusion of hydrogen at the center of a star.
, Cosmic microwave background-why is it important, what is its origin? - ✔ ✔ CMB is faint cosmic
radiation filling all space; oldest electromagnetic radiation in universe; evidence of Big Bang
Cosmological principle (homogeneity, isotropy) - ✔ ✔ Einstein; infinite static universe was unstable
and gravity can cause collage; must be repulsive force (cosmological constant) that balances gravity;
"biggest blunder of my life"
Cosmological principle homogeneity - ✔ ✔ average density of matter is same in all places in
universe; no special place in universe
Cosmological principle isotropy - ✔ ✔ no special directions to universe; uniformity of properties
degenerate-electron pressure - ✔ ✔ the pressure exerted by degenerate electrons
Describe an open, closed, and flat universe. Which do astronomers think we live in? OE - ✔ ✔ open:
not enough mass to stop the expansion; universe is infinite in time and space
closed: there is enough matter to stop expansion universe collapses on itself; time and space are finite
flat: universe slows to 0 speed in an infinite amount of times; this is the universe we live in
describe how astronomers use spectra to determine composition of stars - ✔ ✔ they take the
spectrum and match the absorption lines of all the elements
Describe how Shapley determined the distance to the center of the Milky Way Galaxy. OE - ✔ ✔ he
found the center of the globular cluster distribution and reasoned it was the center of the milky way
describe the spectral classification system both classes and subclasses - ✔ ✔ the classification is from
hot to cold. it is classified by "OBAFGKML." It then has subclasses 0-9.
E=mc^2 says that: - ✔ ✔ mass is a type of energy
Einstein theory of gravity - ✔ ✔ mass can warp, bend, push, pull time; gravity natural outcome of
mass's existence in space
evidence for big bang - ✔ ✔ universe homogeneous and isotropic; universe expanding; matter is
about 75% hydrogen and 25% helium; universe filled with electromagnetic radiation with black body
temperature of 2.7 K
evolutionary track - ✔ ✔ a representation of the changes in color and luminosity of an evolving star;
depend on initial mass of protostar
explain three reasons star formation is difficult to study - ✔ ✔ 1. too dark in giant molecular clouds
2. too small and can't be seen in telescope
3. too fast and too quick to catch
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