Astro final
How is radioactive dating used to determine the age of an object?
Both the amounts of radioactive and decay material are measured. Using these with the radioactive material's half-life, the age can be estimated.
The center of our galaxy lies in the direction of (but far beyond) the stars in the constellation of
Sagittarius.
How can the big bang still be visible? In what form has it been detected?
The big bang began as a single quantum space-time pulse of minimum size and duration. It expanded radially accelerating to the speed of light and it was at least 100 million years, when the first stars lit up that anything from the past would be detectable.
Why is the cosmic microwave background (CMB) so cold if the early universe was so hot?
The expansion of the universe has redshifted those photons to an effectively cooler temperature.
____ in other galaxies should contain luminous O and B stars if they are like the Milky Way.
The spiral arms
____ are produced when two galaxies pass near each other and pull large streamers of stars, gas, and dust away from the galaxies.
Tidal tails
The oldest rocks found on Earth are about ____ years old.
3.9 billion
___ can be used to determine the galaxy's mass if the galaxy is reasonably close, so that the Doppler shift of the galaxy disk material can be measured at several distances from the galaxy's center relative to the center.
A galaxy's rotation curve
What factors are important when trying to classify a spiral galaxy?
All of the above Amount of dust and gas in the galaxy Structure of the spiral arms Size of the central region
Astronomers now speculate that a galaxy's shape depends on all of the following except
All of these may be important in determining a galaxy's shape. the rate of star formation. the history of past collisions. the mass.
How do the motions of the sun and planets reflect the disk shape of the solar nebula?
All the planets orbit the Sun on planes that are just a few degrees from the plane of the Sun's equator.
How does the solar nebula theory explain the present densities and chemical compositions of the planets?
As the solar system was forming, the sun got most of the mass and has the greatest gravitational attraction. The heavier elements, due to having higher mass, were more strongly held by this gravity so the terrestrial planets are the solid, rocky planets closest to the sun. Meanwhile, the lighter atoms of various gases tended to drift farther out, forming the gas giant planets, which have very little rocky material in their cores. Some of it formed as their satellites, others became ring systems because a planet tried to form too close to the gravitational pull of the planet vs the sun and was pulled apart into an orbit around the gas giant like a miniature solar system.
Why are Cepheid variable stars important in our study of the Milky Way galaxy?
Because Cepheids are pulsating variable stars, their pulsation periods are directly related to their true luminosities. So we can use Cepheids as standard candles for distance measurements.
Why does the rotation of our galaxy suggest that it is more massive than previously thought?
Because its rotation pattern doesn't make gravitational sense. As in, the calculated gravitational force from known mass of the inner part of the galaxy doesn't make sense as being able to cause the required centripetal acceleration of the outer rim.
A newly formed planet or large asteroid becomes molten due to ______.
Both of the above
What is the fate of an open universe?
Can't be known without density information.
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?
Correct! Henrietta Leavitt
Why can't evolution go from elliptical to spiral to irregular?
Elliptical galaxies form into spiral galaxies because it's backwards evolution meaning, when a spiral galaxy merges with other spiral galaxies/irregular objects it forms an elliptical galaxy.
What evidence do we have that the universe is expanding?
First, distant objects are flying away from us in every direction, the further away they are, the faster they are moving away. Secondly, there is the size of the universe and the age of the universe. No object can travel faster than light, so the universe should be no more 26 billion lightyears in diameter (since it is 13 billion years old) if the expansion was simply objects moving away from eachother. Since it is much, much bigger than this, we know that space itself has to be expanding between the objects, since it isn't physically possible for them to simply be moving apart at several times the speed of light.
____ galaxies have a great many short spiral segments branching from the spiral arms.
Flocculent
What evidence do we have that large galaxies cannibalize small galaxies?
Galaxies grow by ingesting other star systems. While gigantic elliptical galaxies are believed to result when two or more massive precursor galaxies merge, spiral galaxies, such as our own Milky Way, grow by swallowing smaller dwarf galaxies.
If Galaxy A is found to have a recessional velocity four times greater than Galaxy B, what can you say about their relative distances from Earth?
Galaxy A is four times further away than Galaxy B.
How does the use of H II regions to find a galaxy's distance differ from the use of Cepheid variables?
H II regions are regions of ionized hydrogen and are luminous because they are regions where active star forming takes place in the galaxy. There is an empirical relation between a galaxy's absolute magnitude and the geometrical size of the brightest H II region. Tully-Fisher relation exist between the luminosity of galaxies and the rotational velocity of its H II regions. Cepheid variables are a class of bright stars that are variable and have the nice property that their period is related to their absolute luminosity. Once the latter is known the distance can be found by comparison with the apparent luminosity.
Who first used RR Lyrae variable stars to determine distances in the Milky Way?
Harlow Shapley
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.
What is the difference between homogeneity and isotropy?
Homogeneity is uniformity throughout in composition or structure, while isotropy is uniformity in all directions.
The orbits of population I stars I.are confined to disk of the galaxy.II.are very elliptical.III.are nearly circular.IV.are randomly inclined to the disk of the galaxy.
I & III
Population II stars I.are primarily found in the disk of the galaxy.II.contain more heavy metals than population I stars.III.are primarily old low mass stars.IV.are located in globular clusters.
III & IV
How might we tell whether the universe is open or closed?
If the universe were open it would have to be infinite and expand forever, a quantum universe can't be infinite and it is not possible for space to expand beyond a minimum density.
____ galaxies contain large clouds of gas and dust, both young and old stars, but have no obvious spiral arms or nucleus.
Irregular
Astronomers have found the center of the universe to be located at (in)
No center is thought to exist.
Where did the cosmic microwave background (CMB) come from?
Photons released when electrons and nuclei combined for the first time
In contrast to the outer solid mantle, parts of the central regions of Earth's interior are thought to be fluid because
S seismic waves cannot make it through those regions.
What observation has prompted astronomers to ponder the possible existence of dark energy?
Supernovae appear fainter than expected at large redshifts.
Why is volcanism associated with regions where one plate descends below another plate?
That is because volcanism is caused due to the subduction of plate. By plate tectonics, in the destructive boundaries of plates, the denser oceanic plate will subducts under the less dense continential plate under the sinking convection current of magma. During the process, cracks are formed due to pressure. The magma will then rise along the crack to cause fissure eruption and cools down. As the process of eruption and cooling repeat, a volcano will be formed, hence causing volcanic eruption.
Describe the four stages in the development of a terrestrial planet.
The first stage is differentiation that produces a dense core, thick mantle, and a thin crust and atmosphere. the second stage is cratering where the crust of the newly formed planet eventually cools, but the bombardment continues, and because the planet is no longer molten, the impacts form craters. Then there's flooding that while cratering is still occurring, the crust of a planet breaks and lava bursts through and flows over the land, smoothing the craters and filling them. Lastly, there's slow surface evolution where the face of the planet is slowly altered by the movement of tectonic plates and the effects of atmospheric movements and water. This collision pushes up mountains and shifts continents, while rain and wind slowly wear away the surface and remove all traces of early stages of planetary formation.
How do theories of the origin of the Milky Way explain its halo?
The globular clusters formed about the time the galaxy formed, and give an approximate age to the galaxy of about 10 billion years. Another source is the collision of galaxies which consumes the stellar matter and incorporates it into the disk, but the dark matter remains less affected, forming a dark matter halo that have only recently been detected
Describe four effects that helped to clear the solar nebula.
The gravitation of the individual planets that scoops up the dust and planetesimals, and lastly close encounters between planets and planetesimals, that eject the latter.
____ is (are) observed when light from a distant quasar travels past a massive galaxy between us and the quasar, and this light is focused to form two or more images of the same quasar.
The gravitational lens effect
Why does the average chemical composition of stars now forming differ from that of older stars?
The oldest stars had nothing but hydrogen and helium to form from; They fused the hydrogen and helium into heavier elements, and after they died, these heavier elements went to create newer stars and solar systems. As time moves on, there is less and less hydrogen in the universe, and more and more heavier elements - so newer stars will likely have components of these heavier elements in them.
What does the presence of vesicular basalts and breccias among the lunar rock samples tell us about the history of the moon? Your Answer: The presence of vesicular basalts and breccias among the lunar rock samples tell us that molten lava once flowed over the lunar surface.
The presence of vesicular basalts and breccias among the lunar rock samples tell us that molten lava once flowed over the lunar surface.
Why is the primordial background radiation visible in all directions?
The primordial background radiation is visible in all directions because the Big Bang occurred everywhere in the universe, not at some localized point.
Why is carbon dioxide important in maintaining a greenhouse effect?
The radiation from the Sun is mostly visible light. As the atmosphere is transparent to visible light, most of this is absorbed by the Earth's surface as heat. The Earth's surface radiates this energy back as infrared. Several gases in the atmosphere like CO2, methane and water are not transparent to infrared radiation so they absorb the heat. The heat is then passed to all gases in the atmosphere. So an increase in CO2 and other greenhouse gases like methane, will make this effect more efficient and more heat would be trapped in the atmosphere: the average temperature rises.
____ of the Milky Way contains mostly old (population II) stars and globular clusters.
The spherical halo component
There is radio noise from that direction and infrared images show lots of activity.
There is radio noise from that direction and infrared images show lots of activity.
How does the traditional theory of the formation of the galaxy explain the origin of globular clusters?
They formed early on during the free-fall collapse of the proto-galactic material.
Based on current observations, ____ has a heavy element core, and a very dense, deep atmosphere made mostly of hydrogen.
Uranus
How is Hubble's constant calculated?
Using the distance and recessional velocity of galaxies
What assumptions do we make when we use the Hubble constant to estimate the distance to a galaxy?
We assume that the farther away something is the faster it is moving away from us. Then we can use Doppler shift to determine how fast it is moving, then depending on it's speed we can estimate it's distance.
What observational evidence do we have that nebulae from which planets could form surround other stars?
We can see the protoplanetary disks forming in other Nebula. The Orion Nebula, for example, is a known heavy star forming region.
Explain why good distance indicators must be luminous objects. Why must they be unambiguously recognizable?
We cannot see what is not luminous. We determine distance by calculating what we see. If we cannot detect it we cannot measure it. So if it is utterly opaque, we cannot detect it or measure it's distance.
How do we know that the maria formed more recently than the highlands on the moon?
We know that the maria formed more recently than the highlands on the moon because there are far fewer craters on the Maria. Question 5Not yet graded / 1 pts What does the presence of vesicular basalts and breccias among the lunar rock samples tell us about the history of the moon? Your Answer: The presence of vesicular basalts and breccias among the lunar rock samples tell us that molten lava once flowed over the lunar surface.
How is the presence of space debris accounted for by solar system models?
a and b Space debris is left over material from the early solar system that never formed into a planet. Space debris was formed by the collision of objects after the planets formed.
What was the temperature of the universe when the recombination took place that produced the cosmic background radiation we observe today?
about 3000 K
After the first solid grains formed in our solar system, these particles could then grow by the process of ____, the collision and sticking of one particle with another to continue the formation of planetesimals. Each of these has many atoms or molecules.
accretion
If the spiral density wave were the only thing producing spiral arms, it would be expected that
all galaxies would have only two smooth spiral arms.
The central areas of our Milky Way Galaxy contain
all of the above a nuclear bulge of stars. a bar of stars. a radio wave emitting "whirlpool" of gas. a several million solar mass black hole.
The age of the solar system is believed to be approximately 4.6 billions years based on the data from
all of the above samples of lunar rocks. samples of Earth rocks. samples of meteorites.
If a star with a large peculiar proper motion and/or speed with respect a typical disk star is found, what other property would you expect it to have?
all of the above. low luminosity poor metal content compared to the Sun old age
The oxygen in Earth's atmosphere
all of these was manufactured inside stars. was added to the atmosphere by plant life. has grown more abundant since the origin of Earth.
The traditional "top-down" theory of the formation of our galaxy cannot explain why
all the above not all globular clusters are the same age. the youngest globular clusters are in the outer halo. the oldest stars are metal poor but not completely metal free. streams and rings of scattered stars are in the halo.
The traditional "top-down" theory states that the galaxy formed
as a large spherical cloud of gas that was rotating very slowly.
"Seeds" around which galaxies, clusters, and walls grew may have been _____ before inlation and recombination.
caused by initially tiny quantum mechanical fluctuations in space-time
Part of the current atmosphere of Earth is believed to be
composed of gases that were outgassed from the heated rocks sometime after the planet formed.
The first small solid grains or flakes formed in our solar system by the process of ____, the addition of material to an object an atom or molecule at a time.
condensation
Whether the universe is open, closed, or flat depends on the ____ of the universe.
density
The density of the universe is
equal to the critical density if the universe is flat
Which of the following is NOT one of the four stages in the development of a terrestrial planet?
fusion of hydrogen to helium
The first stars to form in our galaxy
had highly elongated elliptical orbits.
That Earth ____ , evidence that Earth differentiated.
has an average density that is higher than the density of the crust
Current observations indicate that the amount of baryonic matter and dark matter in the universe
implies that the universe is open.
The uncompressed density of a planet in our solar system
is greatest for the planets closest to the sun.
According to Hubble's Law, a large recessional velocity may imply that the galaxy
is moving faster than a galaxy closer to the Earth
If the universe is closed, then its age will be
less than two-thirds of 1/H.
Which one of the following IS NOT a characteristic of terrestrial planets?
low average density
Which one of the following IS a characteristic of Jovian planets?
low average density
The cluster method (motions of galaxies in a cluster of galaxies) can be used to determine the cluster's mass
mass.
The total mass of galaxies in a cluster of galaxies dvided by the number of galaxies in the cluster can be used to determine a typical galaxy's
mass.
The condensation sequence suggests that ____ should condense as solids closest to the sun.
metals and metal oxides
A(n) ____ is a solar system object that enters Earth's atmosphere and becomes very hot due to friction between the object and Earth's atmosphere. It does not survive to reach the surface.
meteor
If the universe is closed and finite, then
none of the above the universe will expand forever. the universe has a center. the universe has an edge.
The age of the Milky Way galaxy has been estimated to be at least 13 billion years based on
observations of globular clusters.
Earth possesses few visible craters, and the moon possesses many. This is because
only b and c the moon doesn't have an atmosphere that could burn up many of the meteorites before impacting. erosion and plate tectonics have slowly removed evidence of past cratering on Earth.
The Galilean satellites
orbit the planet Jupiter.
The most important effect in clearing the solar nebula of gas and dust was
radiation pressure.
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.
Which view of the universe states that the universe is eternal and unchanging?
static
In the late 1990s, it was discovered from distances of ______ in distant galaxies that the expansion of the universe is ___________.
supernovae; accelerating
The best determination of the Hubble constant using Cepheid variables found in distant galaxies by the Hubble telescope suggests
that the Hubble constant is about 70 km/sec/Mpc.
Accretion is
the adding of material to an object by collection of solid particles.
Space-time will be flat if
the average density of the universe is equal to the critical density.
Pulsating variable stars are useful in determining
the distance to globular clusters.
Radio maps of our galaxy show spiral arms because
the gas in spiral arms is denser.
The central regions of Earth's core are solid because
the pressure at the center raises the melting point.
Outgassing is
the release of gas from rocks as they are heated.
The mass of a single galaxy might be found by
the rotation curve method.
The assumption of isotropy states that
the universe looks the same in all directions over sufficiently great distances
The large planetesimals would have grown faster than the smaller planetesimals because
their stronger gravity would pull in more material.
If the terrestrial planets were formed by homogeneous accretion, then
they were initially collections of solid particles which melted then differentiated into a high density iron metal core and low density silicate crust.
The cosmic background radiation comes from a time after the origin of the universe
when electrons began to recombine with nuclei to form atoms.
