a ____ is a collection of hundreds and billions of stars.
the light year is a unit of ____
rotation is the term used to describe the motion of a body around some ____
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 ____
the apparent path of the sun across the sky is known as the ____
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 ____
an arc second is ____ ( give the fraction ) of an arc minute.
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.
as seen from earth, the sun and the moon have roughly the same ____
to measure distances to nearby stars by parallax, a baseline equal to earth's ____ is used.
the size of an object can be determined, if we know its distance, by measuring its ____
the radius of ____ was first measure by Eratothenes in 200BC
Stonehenge was used as a ____ by the people in the stone age
accurate records of comets and "guest" stars were kept over many centuries by ____ astrologers.
the astronomical knowledge of ancient Greece was kept alive and augmented by ____ astronomers
the apparent " backwards" ( westward motion ) of the planets Mars, Jupiter, or Saturn in the sky relative to the stars is known as ____ motion
observation, theory, and testing are the cornerstones of the ____
the heliocentric model was reinvented by ____
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.
Kepler's laws were based on the observational data obtained by ____
Kepler discovered that the shape of an orbit is and ____ not a ____ as it had previously been believed
Kepler's third law relates to the ____ of the orbital period to the ____ of the semi major axis
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.
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 ____
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.
A ____ is a glass wedge that disperses light into a spectrum.
blackbody radiation is an example of a ____ spectrum
Fraunhofer discovered absorption lines in the ____
a continuous spectrum can be produced by a luminous solid, liquid, or ____ gas.
an absorption spectrum is produced when a ____ gas lies in front of a source of continuous radiation.
light behaves both as a wave and as a ____
the experiment that demonstrated as the ____ caused Einstein to realize that light does not always behave like a wave.
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 ____
when an electron moves to a higher energy level in an atom it ____ a photon of a specific energy.
when an electron moves to a lower energy level in an atom it ____a photon of a specific energy.
the "specific energy" of the photon is exactly equal to the energy ____ between the energy levels involved.
changes in a particular molecular vibration states produce spectral features in the ____ part of the electromagnetic spectrum
changes in the molecular rotational states produce spectral features in the ____ part of the electromagnetic spectrum
high temperature, rotation, and magnetic fields all tend to ____ spectral lines.
a telescope that uses a lens to focus light is called a ____ telescope.
a telescope that uses a mirror to focus light is called a ____ telescope
all large modern telescopes are of the ____ type.
the light gathering power of a telescope is determined by the ____ of its mirror or lens.
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.
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.
Active optics and adaptive optics are both being used to improve the ____ of ground based optical telescopes.
all radio telescopes are of the ____ design
an ____ is two or more telescopes used in tandem to observe the same object, in order to improve angular resolution.
____ , ____ , 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.
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.
gamma ray telescopes are unable to form ____ of their fields of view
the ____ of a wave is the distance between any two adjacent wave crests
the ____ of a wave is measured in units of hertz (Hz)
____ is the ability of a wave to "bend around corners."
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
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 ____
the lowest possible temperature is ____ K .
water freezes at ____ K
because the sun emits its peak amount of radiation at about 480 nm its temperature must be about ____ K.
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 ?
if an astronomical object is observed to emit x -rays , it is reasonable to assume that its temperature is very ____
when an observer and / or object emitting radiation move toward each other, the observer sees the radiation shifted to ____ wavelengths
the ____ are bodies that orbit the sun between the orbits of Mars and Jupiter
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
the outer planets jupiter, saturn, uranus and neptune are known a s the ____ planets
the largest and most massive planet in the solar system is ____
asteroids and meteoroids have a ____ composition, in contrast with comets, which have an ____ composition.
rocky ; icy
asteroids are similar in composition to the ____ planets
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 ____
the viking 1 and viking 2 missions sent orbiters and landers to the planet ____
Jupiter was first visited by the U.S. spacecraft ____
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
pencil - beam surveys suggest that the largest structures in space are no larger than ____ Mpc in size.
homogeneous means " the same ____ "
isotropic means " the same in all ____"
together, the assumptions of cosmic homogeneity and isotropy are known as the ____
if the universe had an edge, this would violate the assumption of ____
if the universe had a center, this would violate the assumption of ____
a hubble constant of 65 km/s/Mpc gives a maximum age for the universe of ____ billion years
____ is slowing the expansion of the universe
the ____ of the universe determines whether the universe will expand forever
a ____ value for hubble's constant yields an age for the universe incompatible with the oldest globular clusters
luminous matter makes up about ____ percent of the critical density
by observing distant galaxies, astronomers have determined that the universe was expanding ____ long ago than it is today
the surface of a sphere is a two dimensional example of a ____ curved universe
an open universe has a density ____ the critical value
the temperature of the universe, as measured by the cosmic microwave background, is ____ K
comparing the mass density of radiation and matter , we find that, at the present time, ____ dominates
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 ____
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
elements heavier than helium were not formed primordially because, as time passed, the density and temperature of the universe____
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 ____
the cosmic microwave background radiation lat interacted with matter when the universe was about____ times its present size
if the theory of inflation is correct, then dark matter must make up about ____ percent of all matter in the universe.
which had density fluctuations first, normal matter or 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.
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
____ 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