astronomy test over chapters 20-24
The first ordinary star (other than our own Sun) around which planets were definitely discovered was:
51 Pegasi
An astronomy class is so excited by the discovery of planets around other stars that they decide to do a library exhibit on the subject so that everyone in the school can learn about it. In this exhibit they want to pay tribute to both the astronomers of today who have done the work AND some of the scientists of the past whose work was essential to making the discoveries possible (and directly related to the techniques involved). Which of the following scientists of the past should definitely be included in the exhibit?
Christian Doppler
A rich donor to your college gets fascinated by gamma-ray bursts, and wants to give money to find out more about what produces them. Which of the following should her money go to fund?
a network of visible-light telescopes which can automatically swing to a location provided by an alert system at NASA
the big surprise about the first planet discovered around another regular star was that it
orbited so close to its star it took only 4 days to go around
When the mass of a star's core is greater than 1.4 times the mass of the Sun, degenerate electrons can't keep it stable as a white dwarf. Instead, it becomes:
a neutron star
a member of the college football team wants to weigh as much as possible. Assuming he could somehow survive on all of them, at the surface of which object would he weigh the most?
a neutron star
Why do all stars spend most of their lives on the main sequence?
because the fuel for energy production in this stage of the star's life if hydrogen; and that is an element every star has lots and lots of
which of the following descriptions of interstellar dust is FALSE?
interstellar dust must be at temperature equal to the outer layers of a star
the most stable (tightly bound) atomic nucleus in the universe is:
iron
which of the following about supernova 1987A is FALSE?
it exploded relatively close to us, in a spiral arm of the Milky Way Galaxy
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
how did observations the Compton Gramma-ray observatory show that gramma-ray bursts were not coming from the milky way galaxy?
the gramma-rays came from all over the sky, not just the plane of the galaxy
How did Supernova 1987A demonstrate that new elements are made in supernova explosions?
the light output was kept at high levels by the energy released from radioactive elements that decay very quickly; these must have been made by the supernova
Astronomers use the term interstellar matter to refer to:
Gas and dust that lies between stars
The star is now called Kepler-444 is 11 billion years old (much older than the sun) and has five planets orbiting close to it. What has this system taught astronomers about the history of star formation?
If such an old star has planets close to it, where its really warm, those planets must be made of heavier elements. So heavier elements must have formed before the time this star formed.
If you want to find stars that are just being born, where are the best places to search?
In giant molecular clouds
The astronomer who first worked out the mathematical description of blackhole event horizons was....
Karl Schwarzschild
which of the following can a black hole NOT "eat" (swallow) ?
another black hole
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
Biologists tell us that life on Earth took billions of years to evolve into astronomy students and other examples of intelligent life. If we want to search for planets with intelligent life-forms that evolved over the same period of time that we did, what sorts of stars should we NOT bother searching around?
O and B type stars
the astrophysicist who first calculated the highest mass that a dying star can have and still be a white dwarf was
S. Chandrasekhar
The first (living) star other than our own sun found to have more than one planet orbiting it is called
Upsilon Andromedae
When astronomers discuss a nebula, what are they talking about?
a giant cloud of gas and dust between or among the stars
a type of star cluster that contains mostly very old stars
a globular star cluster
according to the general theory of relativity, light and other radiation coming from a white dwarf or a neutron star should (and experiments show that it does) exhibit
a gravitational redshift
The Orion Nebula is
a large cloud of gas and dust illuminated by the light of newly formed stars within it
a graduate student is given the assignment to find stars with dusty disks around them. What kind of telescope would it be best for her to use for this purpose?
a large telescope that detects infrared radiation
The Messier Catalog is
a list of nebulae, star clusters, and galaxies that might be mistaken for a comet far from the Sun
The Local Bubble is
a region of low-density interstellar gas extending several hundred LY around the Sun
deep inside a back hole (and hidden from our view) is the compressed center, where all the "stuff" of the star goes. Astronomers call this central point
a singularity
which of these stars will take the shortest time to go from the earliest protostar stage to the main sequence?
a star ten times the mass of the sun
A group of graduate students, bored during a cloudy night at the observatory, begin to make bets about the time different stars will take to evolve. if they have a cluster of stars which were all born at roughly the same time, and want to know which star will become a red giant first, which of the following stars should they bet on?
a star that would type O on the main sequence star
Elements heavier than iron can be created during:
a supernova explosion
HII region is
a zone around a hot star where hydrogen atoms are ionized
which of the following stages will our sun go through in the future:
all of the above
why is it so difficult for astronomers to see new stars in the process of birth?
all of the above
What type of main sequence star is most likely to become a black hole?
an O-type star
Astronomers have concluded that growing supermassive black holes(which have millions of times the Sun's mass or more) is pretty unlikely at our location in the Milky Way Galaxy. Where do they think is the most likely place in the Milky Way for such a supermassive black hole?
at the center of the Milky Way Galaxy, where matter is more crowded.
what happens in the process of fluorescence?
atoms absorb ultraviolet rays and convert them to visible light as their electrons cascade to lower energy levels
Why can a star with a mass like our Sun not fuse (produce) further elements beyond carbon and oxygen?
because they just cannot get hot enough for the fusion of heavier nuclei
When astronomers carefully examine the planets found by Kepler and draw conclusions from the Kepler sample, what do they conclude about planets the size of earth?
earth size planets are common, but so are planets somewhat bigger than Earth
our solar system has 8 planets orbiting the sun. Based on the discoveries of exoplanets so far, what can we say about a star with 8 planets?
even though planets were only discovered starting in 1995, so we can't yet find planets that take centuries to go around their star, we already know other stars with 8 planets and we are likely to find more.
What is a key reason that gravitational waves are so much harder to detect than electro-magnetic (e-m) waves?
gravitational waves are much weaker than e-m waves, and therefore require very, very precise equipment to detect.
A handsome, rich, but vain movie star notices that he is starting to age, and consults you as his astronomy expert, to see if you can find an astronomical way to slow down his aging. Putting aside practical considerations (such as the fact that we cannot travel to other stars), which of the following strategies would IN THEORY allow him to age more slowly than the rest of humanity.
he should be in orbit around the earth, and expose himself to as many cosmic rays as possible
Cosmic rays are
high-speed atomic nuclei, electrons, and positrons
The red color we see on a lot of photographs of nebulae comes from which element?
hydrogen
which of the following is NOT a place where astronomers believe interstellar dust grains can form?
in HII regions
which of the following statements about the Crab Nebula is FALSE?
inside, there are a number of newly formed massive stars (O and B type stars)
The closest star to the sun, Proxima Centauri, was recently found to have a planet in its habitable zone. Proxima Centauri is a main sequence star with spectral type M. How would its habitable zone differ from the habitable zone of our sun?
it would be significantly closer to Proxima Centauri than ours is to the sun
How long a main sequence star remains on the main sequence in the H-R diagram depends most strongly on
its mass
Given the presence of dust throughout the disk of the Milky Way Galaxy, what is the best technique for learning about more distant regions of our galaxy's disk.
look for radiation at long wavelengths, for example, in the infrared region of the spectrum
which of the following statements about the main sequence stage in the life of a star is FALSE?
main sequence stars are rare in the galaxy, so we are lucky to be living around one
To predict whether a star will ultimately become a black hole, what is the key property of the star we should look at?
mass
what technique did astronomers use to make the first confirmed discovery of a planet around another star like the sun?
measure the doppler shift of the lines in the star's spectrum and look for periodic changes in this shift due to the pull of the planet as it orbits the star
The largest types of clouds found in interstellar space are
molecular clouds with supplies of dust and molecules
Wearing a very accurate watch, you volunteer to go on a mission to a blackhole in a spaceship that has powerful rockets. You are able to orbit the blackhole and stay a little distance outside of the event horizon. Compared to watches on Earth, your watch near the black hole will run:
more slowly
How are globular clusters distributed in our Milky Way Galaxy?
mostly in a large spherical halo (or cloud) surrounding the flat disk of the galaxy
Cosmic rays differ from other forms of interstellar matter by
moving much faster, at typical speeds of 90% the speed of light
Astronomers were surprised to find so many Jupiter-mass planets so close to their stars. According to their best theories and models, such "hot Jupiters"
must have formed further out from the star and must have "migrated inward" early on
Some years after college (and after you recover from your astronomy class,) you get married and exchange gold rings with your sweetheart. What connection is there between the gold in those rings and recent observations of gravitational waves?
our new understanding is that significant amounts of gold in the universe are produced in the mergers of neutron stars, which can be detected with gravitational waves
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
An astronomy student, for her PhD, really needs to estimate the age of a cluster of stars. Which of the following would be part of the process she would follow?
plot an H-R diagram for the stars in the cluster
If an astronomer wanted to find some relatively complex molecules in space, what technique should she use?
point a radio telescope into regions in the galaxy where there is a lot of dust
which of the following is the largest (in diameter)?
red giant
why is it easier for red giants to lose mass than main sequence stars?
red giants are so big, the gravity at their surface (that holds material to the star) is less
astronomers have concluded that pulsars are
rotating neutron stars
The amount of interstellar matter present in our galaxy is always changing. Which of the following processes is NOT a MAJOR contributor to the change?
some atoms of gas combine in dusty clouds to make more complex molecules
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?
some 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
The telescope that allowed astronomers to discover most of the planets found with transit method was called
the Kepler mission
from which of the following will a wave of light show the greatest gravitational redshift:
the Sun
With our current techniques, astronomers can typically only measure the minimum mass of a planet orbiting another star. To know the precise mass of the planet, they must also be able to determine
the angle at which the planets orbit is tilted relative to us
The first, indirect detection of gravitational waves in the 1970s involved...
the black hole in the Cygnus X-1 system.
A friend of yours who has not taken an astronomy class looks at your textbook and really likes the picture of the Pleiades, a cluster of stars surrounded by a blueish reflection nebula. She wants to know what causes that blue beautiful glow. To explain it to her, you want to compare the process that causes the blue glow to something that us un your friend's everyday experience. Which of the following terrestrial phenomena is the result of the same type of process that makes a reflection nebula in space?
the blue color of the earths sky
in 1959, Pound and Rebka did an experiment to test the prediction of Einstein's theory of general relativity about the relationship between the pace of time and the strength of gravity. When two identical atomic clocks, one on the ground floor and one on the top floor, were compared,
the clock on the top floor ran a tiny but slower
You are an astronomy graduate student and you are observing the big Orion Nebula from an airplane that has a good-sized infrared telescope built into it (there really is such a plane.) On an infrared image of the Nebula, what would particularly stand out?
the clouds of the nebula that have a lot of dust in them
If observations of supernovae in other galaxies show that such an explosion happens in a spiral galaxy like the Milky Way on average every 25 to 100 years, why have astronomers on Earth not seen a supernova explosion in our Galaxy since 1604?
the disk of our galaxy contains a great deal of dust, which tends to block the light of supernova explosions from more distant parts of our galaxy
The equivalence principle (principle of equivalence) says that
the effects of gravity are equivalent to the effects of acceleration
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
If we look back to the first generation of stars made when the Galaxy was first forming, how do they differ from stars being formed today?
the first generation stars contain little or no elements heavier than helium
In the far future, a starship becomes trapped inside the event horizon of a black hole. Although the crew discovers that their ship cannot out, they at least want to send a message to other ships in the area to stay away from the danger zone. If they send out a message in the form of a radio wave, what will be its fate?
the message will never emerge from the event horizon
a neutron star is as dense as:
the nucleus of an atom
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 planets mass from the Doppler shift and
the planets radius using the transit method
on an H-R diagram of a cluster of stars, which characteristic of the diagram do astronomers use as a good indicator of the cluster's age?
the point on the main sequence where stars begin to "turn off"-- to move toward the red giant region
which of the following is one reason we do not detect a pulsar in many remnants of supernova explosions?
the pulsar beam doesn't happen to point toward us in many cases
astronomers now have a good idea for explaining how the short-duration gamma-ray burst might come about. Which of the following is part of their explanation?
these bursts most likely come from the merger of two neutron stars
a type Ia supernova involves the transfer of mass from one star to a companion white dwarf? Yet, in some cases, astronomers cannot locate a star near where they see Type Ia explosions. How do they explain the absence of a companion star?
they suggest that some type Ia supernova are caused by the collision of two white dwarfs, both of which they explode.
which of the following statements about open clusters of stars is FALSE?
they typically contain more mass than any other type of cluster
Your sweetheart gives you a piece of gold jewelry as a present to celebrate your passing your astronomy class. Where did the gold atoms in that gift originally come from (where were they most likely made)?
they were built up from smaller nuclei during a supernova explosion
The dust in the dust clouds in interstellar space consists of
tiny solid grains
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
Some of the interstellar gas in our Galaxy has been heated to millions of degrees, a temperature that surprised astronomers when it was first discovered. How do we now think that gas between stars gets that hot?
very powerful shock waves from exploding stars heat the gas they come into contact with
When neutron stars were first predicted theoretically, no scientist expected to be able to detect one of them across interstellar distances. What enabled astronomers to find neutron stars in the late 1960's?
we found strongly magnetic neutron stars whose whirling beams of energy were detected as pulsars
Astronomers identify the "birth" of a real star (as opposed to the activities of a protostar) with what activity in the star?
when nuclear fusion reactions begin inside its core
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 4.1 times the mass of the sun)?
white dwarf
Supposing we launched a very fast dart from the Space Shuttle, pointed in some direction away from any planet, so that it could travel beyond the solar system. What would it be MOST likely to hit first after traveling outward for a while?
an atom of interstellar gas
Planets in the habitable zone of their stars:
are at a temperature where water can exist as a liquid
which of the following statements about life of a star with a mass like the sun is correct?
as the star is dying, a considerable part of its mass will be lost into space
in a science fiction television show set in the far future, a starship finds itself approaching a stellar association. what types of objects would they be most likely to notice in such an association as they approach?
bright O and B type stars
which of following is NOT a way astronomers discover clouds of interstellar matter that have a large amount of dust in them?
by giving off x-rays from hot gas surrounding the dust cloud
When Einstein proposed his General Theory of Relativity, he suggested some pretty strange ideas about space, time, and gravity. How did scientists in 1919 show that Einstein's theory described the behavior of the real world and wasn't just a crazy hypothesis?
by observing starlight coming close to the sun during an eclipse
Really massive stars differ from stars with masses like the Sun in that they
can fuse elements beyond carbon and oxygen in their hot central regions
When one member of a binary star system is a black hole, and astronomers detect flickering x-rays coming from the system, where are these x-rays usually coming from?
from a disk of material around the black hole (material that has been pulled from the companion star and is falling toward the black hole).
As a star becomes a giant, its outer layers are expanding. Where does the energy for expanding these layers come from?
from the fusion of hydrogen into helium in a shell around the core
In order for a cold atom of hydrogen to emit a 21-cm wave, it must first be in a slightly higher energy state. What event usually "kicks" the hydrogen atom up to this higher state?
gas atoms within the cloud collides
the oldest structures in our galaxy turn out to be
globular clusters
You are an astronomer whose supervisor has just forbidden drinking alcoholic beverages near the observatory. In frustration, you undertake a search for alcohol molecules in space. Where would your search be most likely to succeed?
in an interstellar cloud of gas and dust
how did astronomers determine that the planet orbiting the star HD 209458 is a gas giant like Jupiter and not made mostly of rocks or metals?
it took more than one of the above measurements to figure out this problem
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
Far away from a black hole (at the distance of another star), which of the following is a possible way to detect it?
search for flickering x-rays being given off from an accretion disk around the black hole, as it "eats" part of a neighbor star.
if you wanted to discover the youngest stars you could find in some grouping of stars in the Galaxy, which type of star group would be the best to search?
steller associations
How do fragile structures like acetaldehyde (CH3CHO) molecules survive in the harsh environment of interstellar space? Why are they not destroyed by high-energy radiation from stars?
such molecules are found only in dense clouds that have a lot of dust; the dust keeps the radiation from hot stars from reaching the molecules
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 scientists say that "black holes have no hair", what do they mean?
that once a black hole forms, very little information can be extracted from it about the material that is now inside.
When astronauts aboard the International Space Station (ISS) in space let go of an orange, it just floats there. Why is that?
the ISS is falling around the earth, and in free fall, things feel no weight.
you are observing a binary star system and obtain a series of spectra of the light. from the two stars. In this spectrum, most of the absorption lines shift back and forth as expected from the doppler effect. A few lines, however, do not shift at all, but remain at the same wavelength. How can we explain the behavior of the non-shifting lines?
the lines come from interstellar matter between us and the star, not from the stars themselves
Once a black hole forms, the size of its event horizon is determined only by....
the mass inside the event horizon
In the first direct detection of gravitational waves by LIGO in 2015, the waves came from....
the merger of two black holes.
Astronomers use the term interstellar extinction to refer to:
the scattering and absorption of starlight by dust grains in space
Many names used by astronomers are misleading or outdated. A good example is the term planetary nebula, which astronomers use to refer to:
the shell let go by a dying slow mass star
The first time that astronomers observed both gravitational waves and electro-magnetic waves from the same event, what they were observing was:
the spiraling toward each other of two neutron stars.
When a star undergoes a nova explosion, it may return to its "quiet state" and later become a nova again. What would allow a nova explosion to happen to a star more than once?
the star that goes nova has a companion star near it, which dumps material onto the first star and continues to do so even after the first nova explosion
which of the following statements about the mass of the sun during its lifetime is correct?
the sun will lose a significant amount of mass during and after its red giant phase
which of the following statements about the way the mass of a white dwarf affects spacetime is correct?
the white dwarf mass will attract light, and pull it in a curved path; spacetime is not affected