FINAL EXAM - astronomy

astronomers today know a lot about the size and shape of the milky way galaxy. which of the following common objects most resembles the shape of the luminous part of our galaxy?

a CD or DVD

objects in the luminous disk orbiting around the center of the milky way obey kepler's 3rd law. this means that:

a cloud of gas or star that is further from the center will generally take more time to orbit

a type of star cluster that contains mostly very old stars is

a globular star cluster

what type of main sequence star is most likely to become a black hole?

an O-type star

which of the following is a characteristic of degenerate matter in a white dwarf star?

the electrons get as close to each other as possible and resist further compression

the region around a black hole where everything is trapped, and nothing can get out to interact with the rest of the universe, is called

the event horizon

a star whose temperature is increasing but whose luminosity is roughly constant moves in what direction on the H-R diagram?

to the right

when the outer layers of a star like the sun expand, and it becomes a giant, which way does it move on the H-R diagram?

toward the upper right

what have we learned from the work of harlow shapley and others about the location of the sun in the milky way galaxy?

we are in the disk of the galaxy, about 3/5 of the way from the center

the diagram illustrates velocities of galaxies for a hubble constant of 70 km/s per Mpc (megaparsec) as seen from the milky way. what would be the velocity of galaxy #2 as seen from galaxy #1?

700 km/s

the schwarzschild radius of a one solar mass black hole would be 3 km. thus, the schwarzschild radius of a three solar mass black hole must be

9 km

the venn diagram below categorizes characteristics of the components of the milky way galaxy. the characteristic "metal-rich (2%) stars" most appropriately belongs at position....

A (Disk)

in the venn diagram on supernova, the term "useful as a standard bulb" most appropriately belongs at the lettered location

A (Type la)

the evolutionary track of a low-mass star is shown on the HR diagram. which cut-away core diagram (A-D) correctly illustrates the source of fusion energy when the star is at the position indicated by the dot

B

which of these graphs correctly reflects the relationship between recessional velocity Vr and distance D for galaxies as expressed by hubble's law?

B

the venn diagram illustrates the characteristics of the three major types of galaxies. the characteristic Active Star Formation would most appropriately be categorized in position

B (both spiral and irregular)

the venn diagram illustrates the characteristics of the three major types of galaxies. the characteristic Lots of Gas would most appropriately be categorized in position

B (both spiral and irregular)

the venn diagram illustrates the characteristics of the three major types of galaxies. the characteristic Lots of Old, Small Stars would most appropriately be categorized in position

C (elliptical)

which region describes galaxies as Sb?

C (in the middle)

the block diagram summarizes the major stages of stars with masses similar to the sun. in which stage is the star the largest?

D

the evolutionary track of a low-mass star is shown on the HR diagram. which position (A-D) on the track corresponds to the cut-away core diagram shown (where an arrow indicates fusion)?

D

which region describes galaxies classified as Sc?

D (bottom left)

exoplanets discovered used the radial velocity technique are most likely to be found in which labeled region in the plot?

E

which of the following types of stars will spend the longest time (the greatest number of years) on the main sequence?

K

astronomers making observations in our galaxy have been able to rule out a number of suggestions for what the dark matter in the galaxy might be. which of the following have we NOT been able to rule out (which suggestion is still "in the running")?

a new kind of subatomic particle

the central region of our galaxy is not as flat as its main disk of stars. which of the following has roughly the same shape as our central region of stars?

a peanut

astronomers call a ball of matter that is contracting to become a star

a protostar

elements heavier than iron can be created during:

a supernova explosion

the population I stars in the milky way galaxy

all of the above

planets in the habitable zone of their stars:

are at a temperature where water can exist as a liquid

one of the most important observations in the history of astronomy was the one by edwin hubble that established that there are other galaxies, quite removed from the milky way. how did hubble show this?

by observing a cepheid variable in a nearby galaxy and using it to get the distance

according to the general theory of relativity, the presence of mass

causes a curvature (or warping) of spacetime

an electron is in the ground state of a hydrogen atom. the average distance between this electron and the proton in the nucleus is

constant

what objects did harlow shapley use as "signposts" to figure out the extent of the milky way galaxy and the location of its center?

globular clusters

a science fiction writer needs an environment for her latest story where stars are as crowded together as possible. which of the following would be a good place to locate her story?

in a globular cluster

if you want to find stars that are just being born, where are the best places to search?

in the disks around massive stars that were just recently formed

if you trace back the history of a carbon atom in your little finger through all of cosmic history, where did this atom most likely originate?

it was fused from 3 helium nuclei in the core of a red giant star long before the sun existed

how long a main sequence star remains on the main sequence in the H-R diagram depends most strongly on

its mass

a charming friend of yours who has been reading a little bit about astronomy accompanies you to the campus observatory and asks to see the kind of star that our sun will ultimately become, long, long, after it has turned into a white dwarf. why is the astronomer on duty going to have a bit of a problem satisfying her request?

long after a white dwarf cools off it becomes too cold and dark to emit visible light

astronomers observe a young cluster of stars, where stars with three times the mass of the sun are still on the main sequence of the H-R diagram. yet the cluster contains two white dwarfs, each with a mass less than 1.4 times the mass of the sun. if we can show that the white dwarfs are definitely part of the cluster, how can their presence so soon in the life of the cluster be explained?

more massive stars can lose a lot of mass on their way to becoming white dwarfs; thus the white dwarfs could have started out as quite massive stars

which of the following is a reason that astronomers have not found giant planets with the orbit of neptune around other stars?

neptune takes 165 years to go around the sun; getting information about just one cycle of such a planet's orbit around another star would take astronomers 165 years

after it experiences a "helium flash" a star like the sun will have a brief period of stability, fusing helium into carbon (and sometimes oxygen). during this brief stable stage, the star

none of the above

if most stars are low-mass stars, and low-mass stars typically eject a planetary nebula, why then do astronomers see relatively few planetary nebulae in the sky?

planetary nebulae expand rapidly and soon become too faint to be visible

which of the following is the largest (in diameter)?

red giant

how is the behavior of galaxies in the local group different from what we observe for distant galaxies?

some are moving closer to us

our milky way galaxy is what type of galaxy?

spiral

spiral galaxies appear white because they contain

stars of all ages and colors

why was the kepler mission not able to find planets smaller than mars, even though it was in space (and had no earth atmosphere to deal with)?

such planets make dips in the light of the star that are too small for kepler to detect

when a star first begins the long path toward becoming a red giant, a layer of hydrogen around the core begins to undergo fusion. if this layer was too cold to do fusion throughout the main sequence stage, why is it suddenly warm enough?

the core is collapsing under its own weight and heating up from the compression; this heats the next layer up

what observations about disks of dusty material around young stars suggest that planets may be forming in such disks?

the disks show lanes that are empty of dust within them

an eccentric hollywood movie producer, vacationing in australia, goes to an observatory and offers to make a big donation if they can show him a place in the milky way galaxy where there are more than a million stars seen together. which object would satisfy his extravagant tastes?

the globular cluster omega centauri

which of the following is NOT part of the growing chain of evidence that makes many astronomers suspect there is a black hole at the very center of the milky way galaxy?

the hubble space telescope has shown us a visible-light image of an accretion disk at the center of the galaxy

the telescope that allowed astronomers to discover most of the planets found with the transit method was called

the kepler mission

which of the following is NOT a result of supernova explosions?

the neutron star is disrupted and tears apart into many pieces

which of the following is evidence that the formation process of our galaxy may have included collisions with smaller neighbor galaxies?

the observation of long moving streams of stars that continue to orbit through our galaxy's halo

to measure how dense a planet is (to know whether it is made of rock or gas and liquid) they must be able to measure the planet's mass from the doppler shift and

the planet's radius using the transit method

according to einstein's general theory of relativity, the stronger a star's gravity,

the smaller the event horizon will be of the black hole it makes

when stars become giants, which of the following does NOT usually happen?

their mass grows significantly as they incorporate planets and interstellar matter near the star

how do astronomers measure the mass that the galaxy contains inside the orbit of the sun?

they measure the distance to the center of the galaxy and the period of the sun's orbit and then use kepler's third law

astronomers studying regions like the orion giant molecular cloud have observed that a wave of star formation can move through them over many millions of years. what sustains such a wave of star formation in a giant molecular cloud?

when massive stars form, their ultraviolet radiation and later their final explosions compress the gas in the cloud and cause a new group of stars to form

a herbig-haro (HH) object is

where a jet from a star in the process of being born collides with (and lights up) a nearby cloud of interstellar matter

when a single star with a mass equal to the sun dies, it will become a

white dwarf

which of the following stages can only occur in the life of a low-mass star (whose final mass is less than 1.4 times the mass of the sun)?

white dwarf