ASTR 1102 exam 1 answers

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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


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