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MIDTERM 3 ASTRONOMY
MIDTERM 3 ASTRONOMY
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Which is NOT correct about the interstellar medium?
interstellar absorption lines and emission lines are indicators of the composition of the stars
A protostar is ____
a collapsing cloud of dust and gas that will son become a star
___ occurs when most of the material collapsing to form a protostar has fallen into a disk around the star, and a strong wind from the warm protostar ejects material from its poles
a bipolar outflow
Convection is important in stars b/c it
transports energy outward in the star and mixes the gases of the star
The H-R diagram main sequence of stars has a limit at the lower mass, or energy output end, because ____
there is a MINIMUM temp for hydrogen nuclear fusion
As a medium-mass main sequence star, like sun, exhausts hydrogen in its core, it next become
a red giant star
A star will experience a helium flash if ___
ALL THE ABOVE
which of the following is WRONG about helium fusion?
The helium fusion is easier to achieved than the hydrogen fusion because helium cores are heavier that attraction is stronger
A white dwarf is composed of
carbon and oxygen nuclei and degenerate electrons
A mass is transferred in a normal star in a binary system toward a white dwarf, the material forms a rapidly growing whirlpool of material known as
A Type I supernova is believed to occur when
a white dwarf exceeds the Chandrasekhar limit.
Synchrotron radiation is produced
in supernova remnants
How did Harlow Shapley use the period-luminosity relationship of RR Lyrae variables to determine the size of the Milky Way galaxy?
he found the distances to globular clusters distributed about the center of the galaxy
Which of the following is NOT a characteristic of the stars of the disk component of our galaxy?
ndomly inclined orbits
the galactic halo or corona is believed to contain mostly
___ galaxies have a great ay short spiral segments branching from the spiral arms
Population II stars ___
III & IV
(are primarily old low mass stars & are located in globular clusters)
who first determined that the energy/sec emitted by the luminosity of Cepheid variable stars is larger when the variation of their period is longer?
our galaxy is suspected to be surrounded by a galactic halo or corona because the disk of the galaxy
rotates faster than expected in its outer region
if the spiral density wave were the only thing producing spiral arms, it would be expected that
all galaxies would have only 2 smooth spirals
Pulsating variable stars are useful in determining
the distance to globular clusters
An elliptical (E) galaxy contains
mostly lower-main sequence stars and giants
How do astronomers know that hte luminous regions of active nuclei of active galaxies are very small?
The luminosity of the nuclei varies over short times
Which kind of active galaxy has been observed at the greatest distances from us?
standard Candles of choice for measuring the nature of the dark energy are
Type Ia Supernovae
the Cosmological Constant, A, was introcuced by Einstein to
make the universe static
We CANNOT see the center of our galaxy in which waveband?
The Cosmic Background Radiation:
(Was discovered by Penzias & Wilson @ Bell Labs, was emitted at a redshift of z - 1100, is nearly a perfect blackbody)
The observational evidence that the universe is flat (or very nearly so) is based on:
measuring the cosmic background radiation
The fact that the Cosmic Background Radiation has the same temp everywhere is explained by
the theory of inflation
From our studies of galactic rotation curves and galaxy clusters we know that most of the matter in the universe is
use the period-luminosity relation find distances to which variable stars?
the heavy elements in our bodies were formed:
in the interiors of stars
which of these stars is used in the most reliable method for measuring distances to nearby galaxies?
21-cm radiation is produced by:
cold hydrogen gas
The central engines of quasars are thought to be
accretion onto a supermassive black hole
Which is NOT TRUE about Population I stars in our Galaxy?
they are found in the halo
the metal content (metallicity) of the Galaxy
increased as the galaxy got older
in order to be a spiral galaxy, a galaxy must have
the most massive nucleus that can be produced in NORMAL stellar fusion is
a pulsar is bleived to be
a rotating neutron star
Observationally, gamma-ray burst (GRB) have been assoc. with
The bending of light rays around the sun is explained by:
Einsten's theory of general relativity
for a star cluster, the position of the "main sequence turnoff" tells us
the cluster age
the H-R diagram is
a plot of luminosity vs. temp for stars
Stars spend 90% of their lifes, where in the HR diagram?
When a black hole is formed the singularity is surrounded by
an event horizon
The most mass a neutron star can have is about
3 solar masses
Stars leave the main sequence bc
they have exhausted their hydrogen supply near the center
Type Ia supernovae are caused by
the thermonuclear explosion of a Chandrasekhar mass white dwarf
Which of these types of obects is NOT found in the halo of our galaxy?
The dust in our Galaxy makes stars seen through it appear
too faint and too red
SS 433 is our model for AGN and quasars. Which is NOT one of essential elements?
ALL OF THE ABOVE are elements of the microquasar model
Synchrotron Radiation is
produced by relativistic electrons in magnetic field
Pulsars are produced by
The r-process is responsible for producing
Why are hot stars better than cool stars at forming H II regions?
hot stars emit more ultraviolet radiation
Rotation curves of galaxies show us that
ALL THE ABOVE
OUr Galaxy is most like which of the following?
the Andromeda galaxy
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