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Astronomy Midterm

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a ____ is a collection of hundreds and billions of stars.
galaxy
the light year is a unit of ____
distance
rotation is the term used to describe the motion of a body around some ____
axis
to explain the daily and yearly motions of the heavens, ancient astronomers imagined that the sun, moon, and stars, and planets were attached to a rotating ____
celestial sphere /ring
the solar day is measured relative to the sun; the sidereal day is measured relative to the ____
moon
the apparent path of the sun across the sky is known as the ____
ecliptic
on December 21, known as the ____, the sun is at its ____ point on the celestial sphere.
winter solstice / southernmost
declination measures the position of an object north or south of the ____
celestial equator
an arc second is ____ ( give the fraction ) of an arc minute.
1/60th
when the sun, earth, and moon are positioned to form a right angle at earth, the moon is seen in the ____ phase.
waxing / waning gibbous
a ____ eclipse can be seen by about half the earth at once.
lunar
as seen from earth, the sun and the moon have roughly the same ____
size
to measure distances to nearby stars by parallax, a baseline equal to earth's ____ is used.
XXX
the size of an object can be determined, if we know its distance, by measuring its ____
XXX
the radius of ____ was first measure by Eratothenes in 200BC
Earth's
Stonehenge was used as a ____ by the people in the stone age
calendar
accurate records of comets and "guest" stars were kept over many centuries by ____ astrologers.
ancient
the astronomical knowledge of ancient Greece was kept alive and augmented by ____ astronomers
modern
the apparent " backwards" ( westward motion ) of the planets Mars, Jupiter, or Saturn in the sky relative to the stars is known as ____ motion
retrograde
observation, theory, and testing are the cornerstones of the ____
scientific method
the heliocentric model was reinvented by ____
Copernicus
central to the heliocentric model is the assertion that the observed motions of the planets and the sun are the result of ____ motion around he sun.
planetary
Kepler's laws were based on the observational data obtained by ____
research
Kepler discovered that the shape of an orbit is and ____ not a ____ as it had previously been believed
ellipse, circle
Kepler's third law relates to the ____ of the orbital period to the ____ of the semi major axis
XXX
Galileo discovered ____ orbiting Jupiter, the ____ of venus, and the sun's rotation from observation of ____
moon ; atmosphere ; the stars
the modern method of measuring the astronomical unit uses ____ measurements of a planet or asteroid.
AU
Newton's first law states that a moving object will continue to move in a straight line with constant speed unless acted upon by a ____
force
Newton's law of gravity states that the gravitational force between two objects depends on the ____ of their masses and inversely on the ____ of their separation.
sum ; distance
Newton discovered that, in Kepler's third law, the orbital period depends on the semi major axis and on the sum of the ____ of the two objects involved.
masses
A ____ is a glass wedge that disperses light into a spectrum.
prism
blackbody radiation is an example of a ____ spectrum
continuous
Fraunhofer discovered absorption lines in the ____
emission
a continuous spectrum can be produced by a luminous solid, liquid, or ____ gas.
super heated
an absorption spectrum is produced when a ____ gas lies in front of a source of continuous radiation.
emited
light behaves both as a wave and as a ____
particle
the experiment that demonstrated as the ____ caused Einstein to realize that light does not always behave like a wave.
gold foil
protons carry a ____ charge; electrons carry a ____ charge.
positive ; negative
when one or more electrons are stripped from the atom, the atom is said to be ____
ionized
when an electron moves to a higher energy level in an atom it ____ a photon of a specific energy.
absorbs
when an electron moves to a lower energy level in an atom it ____a photon of a specific energy.
expels
the "specific energy" of the photon is exactly equal to the energy ____ between the energy levels involved.
exchanged
changes in a particular molecular vibration states produce spectral features in the ____ part of the electromagnetic spectrum
microwave
changes in the molecular rotational states produce spectral features in the ____ part of the electromagnetic spectrum
visible
high temperature, rotation, and magnetic fields all tend to ____ spectral lines.
distort
a telescope that uses a lens to focus light is called a ____ telescope.
refracting
a telescope that uses a mirror to focus light is called a ____ telescope
reflecting
all large modern telescopes are of the ____ type.
refracting
the light gathering power of a telescope is determined by the ____ of its mirror or lens.
diameter
the angular resolution of a telescope is limited by the ____ of the telescope and the ____ of the radiation being observed
diameter ; amount
the angular resolution of ground based optical telescopes is more seriously limited by earth's ____ than by diffraction.
atmosphere
optical telescope on earth can see angular detail down to about ____ arc second
less than 1
CCDs produce images in ____ form that can be easily transmitted , stored and later processed by computers.
data bytes
Active optics and adaptive optics are both being used to improve the ____ of ground based optical telescopes.
clarity
all radio telescopes are of the ____ design
array
an ____ is two or more telescopes used in tandem to observe the same object, in order to improve angular resolution.
infra-meter
____ , ____ , and ____ astronomy can be done only from above earth;s atmosphere
x - ray, gamma, and ultraviolet
an object with a temperature of 300K would be best observed with an ____ telescope.
infrared
the mirrors in x-ray telescopes are different in design from those in optical instruments because x - rays tend to be ____ , rather than reflected, by solid surfaces.
absorbed
gamma ray telescopes are unable to form ____ of their fields of view
image
the ____ of a wave is the distance between any two adjacent wave crests
wavelength
the ____ of a wave is measured in units of hertz (Hz)
frequency
____ is the ability of a wave to "bend around corners."
diffraction
when a charged particle moves, information about this motion is transmitted through space by means of its changing ____ and____ fields.
positions ; electric
the visible spectrum ranges from ____ to ____ in wavelength
400 ; 700 nm
light with a wavelength of 700 nm is perceived to be ____ in color
red
earth's atmosphere has low opacity for three forms of electromagnetic radiation. they are ____ , ____ , and ____ .
infrared ; radio ; visible
the peak of an object's emitted radiation occurs at a frequency or wavelength determined by the object's ____
temperature
the lowest possible temperature is ____ K .
0
water freezes at ____ K
273
because the sun emits its peak amount of radiation at about 480 nm its temperature must be about ____ K.
6000
two identical objects have temperatures of 1000K and 1200K , respectively. it is observed that one of the objects emits twice as much radiation as the other. which one is it ?
1200K
if an astronomical object is observed to emit x -rays , it is reasonable to assume that its temperature is very ____
high
when an observer and / or object emitting radiation move toward each other, the observer sees the radiation shifted to ____ wavelengths
shorter
the ____ are bodies that orbit the sun between the orbits of Mars and Jupiter
asteroids
the two planets with the highest eccentricity and orbital tilts are ____ and ____
Pluto ; Uranus
the inner planets, mercury, Venus, earth, and mars are known as the ____ planets
inner/rocky
the outer planets jupiter, saturn, uranus and neptune are known a s the ____ planets
outer/gaseous/jovial
the largest and most massive planet in the solar system is ____
Jupiter
asteroids and meteoroids have a ____ composition, in contrast with comets, which have an ____ composition.
rocky ; icy
asteroids are similar in composition to the ____ planets
inner
comets have compositions similar to the ____ moons of the ____ planets
icy ; outer
the mariner 10 spacecraft was sent by ____ ( country ) to photograph the planet ____
USA ; mercury
the U.S. Magellan probe mapped the entire surface of Venus using ____
radar
the viking 1 and viking 2 missions sent orbiters and landers to the planet ____
mars
Jupiter was first visited by the U.S. spacecraft ____
pioneer 10
The U.S. spacecraft ____ is the only probe to have visited each of the giant outer planets.
voyager 2 or new horizon
spacecraft visiting one planet often use a ____ assist to visit another planet
gravity
pencil - beam surveys suggest that the largest structures in space are no larger than ____ Mpc in size.
200
homogeneous means " the same ____ "
throughout
isotropic means " the same in all ____"
directions
together, the assumptions of cosmic homogeneity and isotropy are known as the ____
cosmology
if the universe had an edge, this would violate the assumption of ____
dark matter
if the universe had a center, this would violate the assumption of ____
isotropic principle
a hubble constant of 65 km/s/Mpc gives a maximum age for the universe of ____ billion years
15
____ is slowing the expansion of the universe
gravity
the ____ of the universe determines whether the universe will expand forever
mass
a ____ value for hubble's constant yields an age for the universe incompatible with the oldest globular clusters
large
luminous matter makes up about ____ percent of the critical density
1
by observing distant galaxies, astronomers have determined that the universe was expanding ____ long ago than it is today
faster
the surface of a sphere is a two dimensional example of a ____ curved universe
positive
an open universe has a density ____ the critical value
less than
the temperature of the universe, as measured by the cosmic microwave background, is ____ K
3
comparing the mass density of radiation and matter , we find that, at the present time, ____ dominates
matter
energetically speaking, radiation and matter were equally important approximately ____ years after the big bang
a few thousand
in the process of pair production, two ____ interact to form a particle and an ____
photon ; antiparticle
the temperature necessary to form electrons and positron is about ____
10^9
the temperature necessary to form proton and ____ is about ____ K
neutrons ; 10^13
when the universe was a few minutes old, nuclear fusion produced ____ and ____
helium ; ditrium
after about a million years, ____ had formed in the universe
galaxies
elements heavier than helium were not formed primordially because, as time passed, the density and temperature of the universe____
decreased
the fact that the density of normal matter is so much less than the known density of matter in the universe implies that much of dark matter must be ____
veronic
the cosmic microwave background radiation lat interacted with matter when the universe was about____ times its present size
1150
if the theory of inflation is correct, then dark matter must make up about ____ percent of all matter in the universe.
97
which had density fluctuations first, normal matter or dark matter?
dark matter
we know that density fluctuations in the normal matter component of the early universe must have been very small because otherwise we would see their imprint on the____
cosmic microwave background
hot and cold dark matter differ in the masses of their particles. cold dark matter consists of ____ particles.
heavy
theory predicted tiny fluctuations in the ____ of the microwave background; the ____ satellite found them.
temperature ; koke
the volume surveyed through a long, thin ____ extending deep into space rather than a wide swath through the local universe
cross section
____ states not only that are we not central to the universe but that no one can be central, because the universe ____
isotropic theory ; is expanding