Astronomy exam 3
The star 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 it's really warm, those planets must be made of heavier elements. So heavier elements must have formed before the time this star formed.
Which of the following types of stars will spend the longest time (the greatest number of years) on the main sequence?
K
Which law do astronomers use to determine the masses of the stars in a spectroscopic binary system?
Kepler's Third Law
In the model that astronomers have developed for pulsars, why do they suggest that there must be two beams of energy coming from the pulsar?
because neutron star beams come out of the north and south poles of a magnetic field
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.
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
The first (living) star other than our own Sun found to have more than one planet orbiting it is called
Upsilon Andromedae
The first astronomer to show that spiral nebulae (today called spiral galaxies) have large Doppler shifts was
Vesto Slipher
Which of the following statements about dark matter in the Galaxy is FALSE?
While the dark matter cannot be observed with our present day instruments, we still have a pretty good idea what it consist of
Although centuries ago, astronomers thought that a nova was a new star, appearing for the first time in the heavens, today we know that it is:
a binary star system in which one star is a white dwarf and mass is being transferred to it
About two thirds of the nearby spiral galaxies (which we can study in more detail) don't have a round central bulge, but instead show
a central bulge with a bar of stars in the middle
In a supernova like SN1987A, once the crisis of iron fusion has begun, roughly how long does it take the star's core to collapse?
a few tenths of a second
Where does the energy come from that allows the Crab Nebula to keep shining almost a 1000 years after the star exploded? (Who ultimately "pays the energy bill"?)
a neutron star is slowing down (losing rotation energy)
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
Which of the following has the smallest mass?
a planet
Astronomers call a ball of matter that is contracting to become a star
a protostar
Astronomers observe the Small Magellanic Cloud (SMC), a not very dense, rather small galaxy near us. They notice that even those stars that formed recently have relatively few heavier elements (when compared to such recent stars in our Milky Way.) What is the likely explanation for this deficiency?
because the SMC is small and its stars are widely spaced, the rate of star formation (and star death) is much slower there
Because white dwarfs are small, as their name implies, they are hard to see. What is a way astronomers have to find white dwarfs that distinguishes them from main sequence stars?
because white dwarfs get really hot, we can search for their ultraviolet radiation
Two stars that are physically associated (move together through space) are called
binary stars
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
Factoring in everything we currently know about the history of the universe, our best estimate for the age of the universe is
about 13.8 billion years
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?
after a white dwarf cools off it becomes too cold and dark to emit visible light
Which of the following stages will our own Sun go through in the future:
all of the above
Which of the following stages will the Sun definitely go through as it gets older?
all the above
The event in the life of a star that begins its expansion into a giant is
almost all the hydrogen in its core that was hot enough for fusion has been turned into helium
In an H-R diagram, where can you see the spectral type of a star (whether it is an O type star or a G type star, for example)?
along the bottom (the horizontal axis)
One of your good friends who is on a diet asks you to point out the stars with the smallest mass on an H-R diagram that you are studying. Where are you sure to find the stars with the lowest mass on any H-R diagram?
among the stars at the bottom right of the main sequence
Which of the following statements about spectroscopic binary stars is FALSE?
an analysis of the ways the lines in the spectrum change allows us to calculate the star's distance directly
If an astronomer wants to find and identify as many stars as possible in a star cluster that has recently formed near the surface of a giant molecular cloud (such as the Trapezium cluster in the Orion Nebula), what instrument would be best for her to use?
an infra-red telescope (and camera)
Planets in the habitable zone of their stars:
are at a temperature where water can exist as a liquid
According to the models of the universe we discussed in this course, why do the galaxies move apart (why do we have Hubble's law)?
as a result of the Big Bang, space itself is stretching and this stretching carries the galaxies away from each other
Which of the following statements about the early universe (as envisioned by the standard model of cosmology) is FALSE?
at the very beginning, the energies were so great that the universe was actually contracting for a while
For what type of star can astronomers measure the diameter with relative ease?
eclipsing binary stars
Why did Einstein introduce the cosmological constant into the equations of his General Theory of Relativity when describing the universe?
einstein's equations required the universe to expand or contract; he could not imagine or accept it doing either one, so he put a factor in to stop it from moving
Which type of galaxy is observed to contain mostly older stars?
elliptical
Where in space did the expansion of the universe begin?
everywhere at once
After the core of a massive star becomes a neutron star, the rest of the star's material
explodes outward as a supernova
One of the main projects being carried out by the Hubble Space Telescope is to measure the distances of galaxies located in groups dozens of millions of lightyears away. What method do astronomers use with the Hubble to find such distances?
finding Cepheid variables and measuring their periods
Astronomers have noticed that the visible filaments in the Crab Nebula are moving toward us at great speed. How can they know about motions like this?
from the Doppler shift in the line radiation from the nebula
Astronomers identify the main sequence on the H-R diagram with what activity in the course of a star's life?
fusing hydrogen into helium in their cores
If stars with masses like our Sun's cannot make elements heavier than oxygen, where are heavier elements like silicon produced in the universe?
heavier elements are made in the cores of significantly more massive stars than the Sun, which can get hotter in the middle
In a distant galaxy, whose light is just arriving from 10 billion light years away, our spectroscope should reveal that the most common element is
hydrogen
Which of the following statements about the implications of Hubble's Law is FALSE?
if you were observing the universe from a distant galaxy, you would NOT see all the galaxies (except those in your own group) moving away from YOU
When the BeppoSAX satellite, together with telescopes on the ground, helped astronomers pinpoint the location of the first gamma-ray burst to be identified with something that gave off visible light, the burst's location turned out to be in
in a distant galaxy
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
Where would you look for the youngest stars in the Milky Way Galaxy?
in the disk
Imagine that powerful telescopes in the future give us a truly representative sampling of all the stars in the Sun's cosmic neighborhood. Where on the H-R diagram would most of the stars in our immediate vicinity lie?
in the lower right, among the least luminous main sequence stars
If a galaxy contains a great deal of dark matter, what will that do the galaxy's mass-to-light ratio?
increase quite a bit
A star with a mass like the Sun which will soon die is observed to be surrounded by a large amount of dust and gas -- all material it has expelled in the late stages of its life. If astronomers want to observe the radiation from such a giant star surrounded by its own debris, which of the following bands of the spectrum would be the best to use to observe it?
infrared
Which of the following statements about our best candidate for long-duration gamma-ray bursts is FALSE?
it involves the merger of two black holes
Measurements show a certain star has a very high luminosity (100,000 x the Sun's) while its temperature is quite cool (3500°K). How can this be?
it must be quite large in size
What was especially noteworthy about the Sagittarius Dwarf Galaxy when it was discovered among the small galaxies near the Milky Way?
it was on a collision course with the Milky Way and would be swallowed by it eventually
How long a main sequence star remains on the main sequence in the H-R diagram depends most strongly on
its mass
When a star settles down to a stable existence as a main-sequence star, what characteristics determines where on the main sequence in an H-R diagram the star will fall?
its mass
Astronomers believe that disks of material will form around protostars that are spinning. Which of the following observed phenomena is a good indication of the presence of a disk around a protostar?
jets and Herbig-Haro objects
If we include the effects of deceleration in our calculations of the age of the universe, the age we get is
less than the Hubble time
Based on many surveys of the average density of matter in the universe (regular matter and dark matter), astronomers now conclude that the average density of the universe is
less than the critical density
The most common kinds of stars in the Galaxy have
low luminosity compared to the Sun
In figuring out the evolutionary tracks on the H-R diagram, astronomers
make model stars on a computer and then follow how their characteristics will change with time
In describing the universe using his equations of general relativity, Einstein assumed that it was isotropic (the same in all directions.) What recent observations have confirmed that the universe is isotropic on the large scale?
measurements of the 3-degree cosmic background radiation
Radio astronomy has played a pivotal role in showing us the detailed structure of the Milky Way Galaxy. Which of the following techniques would a radio astronomer use as an essential part of an investigation of this structure?
measuring the Doppler shift of a line in a radio spectrum
In a collapsing star of high mass, when electrons and protons are squeezed together with enormous force, they turn into a neutron and a:
neutrino
Astronomers have long realized that supernovae -- when they explode -- give off an enormous amount of light. But observations of Supernova 1987A (in the Large Magellanic Cloud) revealed that the supernova gives off even more energy in another form? That form is:
neutrinos
Which of the following is the smallest?
neutron star
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
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
What kind of telescope did Jocelyn Bell use to discover pulsars in 1968?
radio
The very strong source of radio waves at the center of our Galaxy is called
sagittarius A
A white dwarf, compared to a main sequence star with the same mass, would always be:
smaller in diameter
Which of the following did NOT happen during the first few minutes after the Big Bang?
some very massive early stars formed
Compared to the mass of our own Milky Way Galaxy, the total mass we estimate for the Andromeda Galaxy is
somewhat bigger
Our Milky Way Galaxy is what type of galaxy?
spiral
The Tully-Fisher relation (looking at rotation speeds) only works for:
spiral galaxies
Why can astronomers not measure the diameters of stars directly?
stars are so far away, we cannot resolve (distinguish) their diameters
What is strongest known force in the universe?
strong nuclear force
Astronomers have discovered pulsars spinning 500 x per second or more. How do astronomers think pulsars got to be spinning so outrageously fast?
such fast spinning pulsars have companion stars near them, which dump material on the pulsar and that spins faster and faster
The new instrument that made it possible for Edwin Hubble to demonstrate the existence of other galaxies in the early 1920's was:
the 100-inch reflector on Mount Wilson
As a cluster of stars begins to age, which type of star in the cluster will move off the main sequence of the H-R diagram first?
the O and B type stars
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 planet's orbit is tilted relative to us
Scientists speculate that the properties (laws) of the universe must be the way they are bc if they were significantly different, we would not be here to think about them. This idea is called
the anthropic principle
Which of the following statements about the nuclear bulge of our Galaxy is FALSE?
the best way to learn more about it is to observe higher energy radiation, such as ultraviolet and x-rays
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
Which of the following are the small regions that are the embryos of stars (where individual stars are most likely to be born)?
the cores within the clumps of molecular clouds
Astronomers believe that the many supernova explosions that happened in the Milky Way Galaxy could have played a role in the evolution of life over billions of years. How would they have influenced the development of life on Earth?
the cosmic rays produced by supernova explosions would have contributed to the rate of mutations over many generations
According to the most recent data from satellites making precise measurements of the properties of the cosmic background radiation (CBR)
the dark energy makes up just a little less than 70% of the density of the universe, making it the most significant constituent of the mass-energy
After the Big Bang, in order for the universe to become transparent to light and other electro-magnetic radiation, what had to happen?
the density of the universe had to decrease (to 1000 nuclei per cubic cm or less)
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
Astronomers have measured that there is more helium in the universe than can be explained by the fusion in stars over the last 13 billion years. How do they think the extra helium got into the universe?
the extra helium was made during the first few minutes of the Big Bang, when the entire universe was hot enough for fusion to occur briefly
What incident in a massive star's life sets off (begins) the very quick chain of events that leads to a supernova explosion?
the fusion of iron
Ninety percent of all stars (if plotted on an H-R diagram) would fall into a region astronomers call
the main sequence
Recent observations that the universe is expanding faster today than it was a few billion years ago (that, in other words, the expansion of the universe is accelerating.) What kind of observations have led astronomers to this surprising conclusion?
the measurement of galaxy distances using Type la supernovae
Which of the following is NOT a result of supernova explosions?
the neutron star is disrupted and tears apart into many pieces
What leads astronomers to conclude that the proto-galactic cloud (the cloud from which our Galaxy formed) was roughly spherical?
the oldest stars in the Galaxy (Population II stars, globular clusters) form a spherical halo around the Galaxy; they outline the original shape of the cloud that gave the Galaxy birth
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
Some of the energy produced in the event we call Supernova 1987A was used to blow the star apart. Out of the following places that the energy of this event could go, which absorbed by far the most energy?
the production of huge numbers of neutrinos
A 'galactic year' as defined by astronomers is:
the time it takes the Sun to revolve once around the center of the Milky Way Galaxy
In a Type Ia supernova, the cause of the violent outburst is:
the transfer of so much mass from a companion star that is a white dwarf goes "over the limit" and collapses, causing an enormous amount of sudden fusion
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
Edwin Hubble developed a classification scheme for galaxies. By what characteristic did he classify galaxies?
their shape
Most of the really bright stars in our sky are NOT among the stars that are very close to us. Why then do they look so bright to us?
these stars are intrinsically so luminous, that they can easily be seen even across great distances
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
When the core of a star reaches a temperature of about 100 million degrees (K), something new happens in the core. What is this new event?
three helium nuclei begin fusing carbon (element number 6)
The standard bulbs (standard candles) that made it possible for astronomers to discover the acceleration in the expansion of the universe were
type la supernovae
Which of the following objects is considered useful to astronomers as a "standard bulb" for determining distances?
type la supernovae
In a planetary nebula, the shell of expelled material is glowing intensely. What is the main source of energy for this glow?
ultraviolet radiation from the collapsing hot star at the center
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
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
One of the things that our current "standard model" of the Big Bang Theory doesn't explain is
why the temperature of the cosmic microwave background is so uniform throughout all of space
Before you can use Hubble's Law to get the distance to a galaxy, what observation must you make of that galaxy?
you must take a spectrum of the galaxy and measure the red shift
The first ordinary star (other than our own Sun) around which planets were definitely discovered was:
51 Pegasi
According to our textbook, roughly what percent of the mass and energy contents of the universe is made up of dark matter plus dark energy?
95 percent
Which of the following statements about a Type II Supernova is true?
A Type II supernova occurs at the end of the life of a star with 10 times the mass of our Sun or more
The first satellite (spacecraft with instruments) to measure and confirm the cosmic microwave background was the:
COBE (COsmic Background Explorer)
The scientist who made the first telescopic survey of the Milky Way and discovered that it is composed of a huge number of individual stars was
Galileo Galilei
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?
NOT SAME, NOT 8%!!!! idk the answer to this one but it is not those 2
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
Which of the following is NOT one of the reasons planets around other stars are so difficult to detect?
Planets only form very late in the life of a star, just when it is ready to die, and thus last only a very short fraction of the star's life
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
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
Which of the following statements about the different types (shapes) of galaxies is correct?
collisions and mergers between galaxies can sometimes change a galaxy's type (shape)
Which of the following was not done by Edwin Hubble?
discovering the relationship between period and luminosity of a cepheid variable
Which type of galaxy is very difficult to see, but (astronomers recently realized) may be very common?
dwarf elliptical
