ASTR 1102 exam 1 answers
what is the difference between brightness and luminosity?
Brightness is how much light we can see from a star; luminosity is how much light it emits
How is the distance to a star related to its parallax?
Distance is inversely proportional to parallax
Star A and Star B appear equally bright in the sky. Star A is twice as far away from the Earth as star B. How do their luminosities compare?
Star A is four times as luminous as star B
in the quantum mechanical view of the atom, electrons are often depicted as
a cloud that is centered on the nucleus
a spaceship is traveling toward the Earth while giving off a constant radio signal with a wavelength of 1 meter. what will the signal look like to people on Earth?
a signal with a wavelength less than one meter
what star would have the biggest redshift?
a star moving at high speed away from you
Earth is located approximately
about halfway out from the center of the milky way
a hypothesis may become a theory
after many repeated attempts to falsify it fail
if you observe a star you will see
an absorption spectrum
when you see a pattern in nature, it is usually evidence of
an underlying physical law
one of the central assumptions in astronomy is that the physical laws of nature
are the same everywhere in the universe
essentially all the elements heavier than iron in our Milky Way were formed
by supernovae
the interstellar medium is divided up into three different kinds of gas clouds, these are
cold gas at 100K, warm gas at 8000 K, and hot gas at about 1 million K
what is one way which high-mass stars differ from low-mass stars?
convection is important in their cores, which mixes up helium throughout the core
parallax is used to measure a star's
distance
for an object in hydrostatic equilibrium, if the temperature inside the object were to increase, the object would
expand
true or false: a scientific theory is an undisputed fact
false
we can identify only a fraction of all the radio pulsars that exist in our Galaxy because
few swing their beam of synchrotron emission in our direction
the source of the energy for a collapsing protostar comes from
gravitational potential energy
the collapse of the core in high-mass stars naturally explains all of the following neutron stars properties
high magnetic field, high density, small size, fast rotation
stars that have spectral type B are ______ in temperature compared with stars that have spectral type M.
hotter
a protostar's evolutionary "track" in the H-R diagram traces out
how the protostar's luminosity, temperature, and radius change with time
a red giant with the same mass as the Sun generates energy from
hydrogen burning to helium in a shell surrounding its core
On a typical H-R diagram, where are the white dwarfs located?
in the lower left corner
on a typical H-R diagram, where are the stars with the largest radii located?
in the upper right corner
if a main-sequence star's core temperature increased, fusion reaction rates would ______ because the protons would be moving ______
increase; faster
in the first stage of the protostar's evolution on the H-R diagram, the protostar's temperature _____ and luminosity _______
increases; increases
the most massive elements such as those that make up terrestrial planets like Earth were formed
inside stars and supernovae
what does it mean to say that an object is in the thermal equilibrium?
it is absorbing the same amount of energy that it is radiating
How does the speed of light traveling through a medium (such as air or gas) compare to the speed of light in a vacuum?
it is always less than the speed of light in a vacuum
what is the most likely explanation for a dark area in the night sky surrounded by a dense field of stars?
it is region with thick dust blocking the starlight from coming behind
the faster moving star in a binary is the
less massive star
the Hertzsprung-Russell diagram is a graph of ______ for stars
luminosity vs temperature
a nova is the result of which explosive situation?
mass transfer onto a white dwarf
the average density of the interstellar medium is
much less dense than the best vacuum on Earth
what critical event transforms a protostar into a normal main-sequence star?
nuclear fusion begins in the core
Albert Einstein is best known for his revolutionary theory of
relativity
massive stars explode when they
run out of nuclear fuel in their cores, and the cores collapse
type Ia (white dwarf) and type II (massive star) supernovae can be distinguished by what combination of observations
spectra and light curves
the dominate mechanism by which high-mass stars generate energy on the main-sequence is called
the CNO cylce
you observe a red star and a blue star and are able to determine that they are the same size. which star has a higher surface temperature and which star is more luminous?
the blue star has a higher surface temperature and luminosity
Why do some stars in the sky appear blue, whereas other stars appear red?
the blue stars have a higher surface temperatures than the red stars
the Milky Way is the name of
the galaxy in which we live
the following are directly measurable from the absorption lines of a star?
the identity of an atom producing a given absorption line, the surface temperature of the star, the ionizations stage of the atom producing a given absorption line
the local group os the environment around
the milky way that contains a few dozen galaxies
Binary star systems are extemely useful in studying stars because they allow us to determine
the stars' masses
Stars evolve primarily because
they use up the fuel in their cores
the following traits help slow or prevent the collapse of a gas cloud
turbulence, angular momentum, high temperature, magnetic fields
on the H-R diagram, where are the hottest stars located?
upper left corner
the sun eventually will become a
white dwarf
