Stars Quiz

Which law do astronomers use to determine the masses of the stars in a spectroscopic binary system? a) Kepler's 3rd Law b) Stefan-Boltzmann Law c) Wien's Law d) Hubble's Law

a) Kepler's third Law

Studies of the spectra of stars have revealed that the element that makes up the majority of the stars (75% by mass) is a) hydrogen b) helium c) carbon d) stellarium

a) hydrogen

Which of the following characteristics of a single star (one that moves through space alone) is it difficult to measure directly? a) its mass b) its temperature c) its chemical composition d) its apparent brightness e) you can't fool me, all of these are quite easy to measure directly

a) its mass

An H-R Diagram plots the luminosity of stars against their: location in the sky a) surface temperature b) diameter c) mass d) age

a) surface temperature

Who was the astronomer who is the "H" in H-R diagram? a) Hubble b) Humason c) Hertzsprung d) Hoyle e) Huggins

c) Hertzsprung

A star that is quite hot and has a very small radius compared to most stars is called a) an M-type star b) a red giant c) a white dwarf d) a main-sequence star e) an O-type star

c) a white dwarf

Two stars that are physically associated (move together through space) are called a) brown dwarf stars b) first contact stars c) double stars d) binary stars e) main sequence stars

d) binary stars

Stars that do not have what it takes to succeed as a star (i.e. do not have enough mass to fuse hydrogen into helium at their centers) are called: a) red giants b) main sequence stars c) extras d) spectroscopic stars e) brown dwarfs

e) brown dwarfs

Some objects in space just don't have what it takes to be a star. Which of the following is a "failed star", an object with too little mass to qualify as a star? a) A brown dwarf b) any star with high proper motion c) An O-type star d) the Sun e) an M type dwarf

a) A brown dwarf

Which of the following looks the brightest in the sky? a) a star with magnitude -1 b) a star with magnitude 1 c) you can't fool me, all of the above look equally bright from Earth d) a star with magnitude 6 e) a star with magnitude 10

a) a star with magnitude -1

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)? a) along the bottom (the horizontal axis) b) only on the main sequence c) only in the red giant region d) H-R diagrams have nothing to say about spectral types e) along the right (vertical axis)

a) along the bottom (the horizontal axis)

At an astronomical conference, an astronomer gives a report on a star that interests astronomers because of hints that it may have a planet around it. In his report the astronomer gives the average speed with which this star is moving away from the Sun. How did the astronomer measure this speed? a) by looking at the Doppler shift in the lines of the star's spectrum b) by seeing how the luminosity of the star has been decreasing as it moves farther and farther away c) by seeing the whole star become much redder than it used to be d) by measuring the diameter of the star (which is easy to do) and noticing that it is getting smaller and smaller e) the astronomer must be making up stories to impress his colleagues; there is no way to measure the speed with which stars move away or toward us.

a) by looking at the Doppler shift in the lines of the star's spectrum

The most common kinds of stars in the Galaxy have enormous masses compared to the Sun a) low luminosity compared to the Sun b) a dozen or more stars in close orbit around them c) diameters thousands of times greater than the Sun's d) spectra that show they contain mostly carbon

a) low luminosity compared to the Sun

An exhausted-looking astronomer comes off the mountain where her observatory is located and tells you she has been doing photometry all night. What has she been up to? a) measuring the brightness of different stars b) measuring the positions of stars on photographic plates taken over many years c) putting the light of stars through a spectrograph to measure what elements are present d) counting the number of stars in different star clusters (groups) e) taking photos through bedroom windows in the valley below

a) measuring the brightness of different stars

Two stars have the same luminosity, but star B is three times farther away from us than star A. Compared to star A, star B will look a) nine times fainter b) nine times brighter c) three times fainter d) three times brighter e) just as bright as A

a) nine times fainter

Where on the H-R Diagram would we find stars that look red when seen through a telescope? a) only on the right side of the diagram and never on the left b) anywhere in the diagram c) only near the bottom of the diagram and never near the top d) only near the top of the diagram and never near the bottom e) only near the left side of the diagram and never near the right

a) only on the right side of the diagram and never on the left

An astronomer whose secret hobby is riding merry-go-rounds has dedicated his career to finding the stars that rotate the most rapidly. But the stars are all very far away, so none of them can be seen to spin even when he looks through the largest telescopes. How then can he identify the stars that rotate rapidly? a) stars that rotate have much wider lines in their spectra than stars that do not b) stars that rotate bring the light atoms (like hydrogen) spinning up to their surfaces; so they can be identified by the elements they contain c) stars that rotate have a significantly lower luminosity than stars that do not rotate d) all stars that rotate show a huge Doppler shift toward the blue end of the spectrum e) this astronomer better spend some more time enjoying his hobby, because he is not doing well at his job; there is no way we know about today to identify stars that rotate

a) stars that rotate have much wider lines in their spectra than stars that do not

Which of the following has the smallest mass? the sun a) a brown dwarf b) a planet c) the smallest mass star that can still have fusion of hydrogen to helium in its core d) you can't fool me, all the above have roughly the same mass

b) a planet

Some "superstars" give off more than 50,000 times the energy of the Sun. Why are there no such stars among the stars that are close to the Sun? a) because such superstars only give off a lot of energy for a year or so, before they die b) because such very luminous stars are extremely rare, and thus any small neighborhood in the Galaxy is unlikely to contain one of them c) because such superstars are really several hundred stars blending their light together (but so far away we can't distinguish individual stars); nearby stars are easy to separate d) because all stars in the vicinity of the Sun have planets, and planets rob a star of its brightness e) because conditions in the "neighborhood" of the Sun only permit low-mass (low luminosity) stars to form

b) because such very luminous stars are extremely rare, and thus any small neighborhood in the Galaxy is unlikely to contain one of them

One key difference that astronomers use to distinguish between brown dwarfs and high-mass planets is that: a) brown dwarfs are all much larger in diameter than any planets b) brown dwarfs are able to do deuterium fusion in their cores, while planets can't c) brown dwarfs shine quite brightly in visible light, while planets are only visible from the light they reflect d) brown dwarfs have a much lower luminosity than any planets e) brown dwarfs are much lower in mass than planets like Jupiter

b) brown dwarfs are able to do deuterium fusion in their cores, while planets can't

Stars on the main sequence obey a mass-luminosity relation. According to this relation, a) if you double the mass, you get double the luminosity b) luminosity is proportional to mass to the fourth power (luminosity increases strongly with mass) c) the lower the mass, the higher the luminosity d) the brightest stars are made of such light materials they hardly have any mass at all e) bright stars have more mass around them in the form of planets, comets, and asteroids

b) luminosity is proportional to mass to the fourth power (luminosity increases strongly with mass)

I am measuring the spectrum of the stars in a spectroscopic binary system. When one of the stars is moving toward the Earth in its orbit, we observe a) that the lines in its spectrum merge with the lines of the other star b) that the lines in its spectrum show a blue-shift c) that it is no longer possible to learn what elements are in the star d) that the lines in its spectrum get brighter e) none of the above

b) that the lines in its spectrum show a blue-shift

When an astronomer measures a color index for a star, what is she measuring? (be careful here, this question is tricky) a) the amount of hydrogen in the atmosphere of the star b) the difference between how bright a star looks at two different wavelength regions c) how the color of the star is changed when its light passes through the Earth's atmosphere d) what color the human eye sees when people look at that star e) the total luminosity of the star in all parts of the electromagnetic spectrum

b) the difference between how bright a star looks at two different wavelength regions

Ninety percent of all stars (if plotted on an H-R diagram) would fall into a region astronomers call: a) the visual region b) the main sequence c) the twilight zone d) the supergiant region e) the white dwarf region

b) the main sequence

Which of the following can astronomers NOT learn from studying the spectrum of a star? a) its motion toward or away from us b) you can't fool me, all of the above can be learned from studying the spectrum c) whether it is a star the size of the Sun or a giant star d) its surface temperature e) whether it is rotating slow or fast

b) you can't fool me, all of the above can be learned from studying the spectrum

The first astronomer who did photometry in a systematic way (even though he did not have a telescope) was a) Galileo b) Ptolemy c) Hipparchus d) Kepler e) Hubble

c) Hipparchus

After a lot of work, a group of graduate students has finally measured the wavelengths of many dozens of lines in the spectrum of a distant star. If a number of the lines come from molecules such as titanium oxide, the star is likely to be which spectral type: (Hint: see table 17.2 in textbook) a) O b) we need more information; lines from molecules can be found in stars of every spectral type c) M d) A e) B

c) M

Which of the following types of star is the coolest (has the lowest surface temperature)? a) A b) F c) M d) G e) O

c) M

In recent decades, astronomers discovered stars even cooler than the traditional spectral type M stars recently. Astronomers gave these cool stars a new spectral type, L. If you wanted to go out and find more such type L stars, what kind of instrument would it be smart to use? a) an x-ray telescope, in orbit above the Earth's atmosphere b) a CCD camera attached to an ultra-violet telescope c) a sensitive infra-red telescope d) a swimming-pool size vat of commercial cleaning fluid, deep in an abandoned mine e) a small visible-light telescope (something even an amateur astronomer or small college might have)

c) a sensitive infra-red telescope

Why are astronomers much more interested in the luminosity of a star than its apparent brightness? a) because luminosity can tell us how bright it is inside the star's core, while apparent brightness only tells us about its outside layers b) you can't fool me, there is no difference between luminosity and apparent brightness; they are merely different terms for the same property of a star c) because the luminosity tells us how bright a star really is, while apparent brightness only tells us how bright it happens to look from Earth d) because luminosity can be measured exactly, but apparent brightness can only be roughly estimated e) because the luminosity also tells us what elements the star is made of, while apparent brightness cannot tell us a star's chemical make-up

c) because the luminosity tells us how bright a star really is, while apparent brightness only tells us how bright it happens to look from Earth

Which color star is likely to be the hottest? a) green b) yellow c) blue-violet d) oranges e) red

c) blue-violet

Astronomers identify the main sequence on the H-R diagram with what activity in the course of a star's life? a) letting go of a huge outer layer b) forming from a reservoir of cosmic material c) fusing hydrogen into helium in their cores d) you can't fool me; so many stars are on the main sequence that there is no special stage in a star's life that can be identified with it e) dying

c) fusing hydrogen into helium in their cores

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? a) in the lower left, among the white dwarfs b) in the upper left, among the bright main sequence stars c) in the lower right, among the least luminous main sequence stars d) in the upper right, among the supergiants e) in the middle of the main sequence, roughly where the Sun is

c) in the lower right, among the least luminous main sequence stars

Using a good pair of binoculars, you observe a section of the sky where there are stars of many different apparent brightnesses. You find one star that appears especially dim. This star looks dim because it is: a) radiating most of its energy in the infrared region of the spectrum b) partly obscured by a cloud c) it could be more than one of the above; there is no way to tell which answer is right by just looking at the star d) very far away e) very low luminosity

c) it could be more than one of the above; there is no way to tell which answer is right by just looking at the star

Stars that lie in different places on the main sequence of the H-R diagram differ from each other mainly by having different: a) internal structure b) compositions c) masses d) ways that they formed e) radial velocities

c) masses

A graduate student has done a careful analysis of the spectrum of a star. While she has found lines from many elements, there was not a trace of the element helium in the spectra she has been analyzing. From this she can now conclude: a) there is most likely no helium anywhere in the star b) all the helium must be in the core of the star; there is none of it in the outer regions c) since helium shows lines only in hot stars, this star must be relatively cool d) since helium is the kind of element that quickly bonds with others, all the helium in this star must be in the form of molecules e) the student was not surprised, because NO star ever shows any lines of helium

c) since helium shows lines only in hot stars, this star must be relatively cool

Why can astronomers not measure the diameters of stars directly? a) you can't fool me; measuring the diameter of any star is a relatively easy process b) stars are all in binary systems, and we can only see the combined diameter of both stars c) stars are so far away, we cannot resolve (distinguish) their diameters d) stars are so bright, their light burns out all the delicate instruments we would use to measure their diameters e) all stars change their diameters regularly, growing alternately larger and smaller

c) stars are so far away, we cannot resolve (distinguish) their diameters

A team of astronomers takes spectra of thousands of different stars in different parts of the sky. The spectra show significant differences. The main reason the spectra of the stars do not all look alike is that the stars a) sometimes have atmospheres and sometimes do not b) change their spectra as they age, and so young stars have very different spectra from older ones c) are located in many different regions of the Milky Way d) are made of significantly different elements e) have different temperatures

d) are made of significantly different elements

Imagine that a brilliant but quirky scientist in the biology department manages to put you in a deep freeze and you wake up in a million years. Which of the following statements about the sky you would see in that future time is correct? a) all the stars and constellations would look exactly the same as they do now b) all the stars we can see in the sky today will have died in a million years c) at the present time, astronomers do not know enough about the universe to say what the sky might be like in a million years d) because of proper motion, a number of the familiar constellations will look somewhat different in a million years e) if you could see them up close, almost all the stars in the sky today will have changed their color significantly in a million years

d) because of proper motion, a number of the familiar constellations will look somewhat different in a million years

When an astronomer rambles on and on about the luminosity of a star she is studying, she is talking about: a) what color the star is b) the star's apparent size (the size seen from Earth) c) the elements she can see in the star's spectrum d) how much energy the star gives off each second e) the total amount of mass in the star

d) how much energy the star gives off each second

Measurements show a certain star has a very high luminosity (100,000 x the Sun's) while its temperature is quite cool (3500o K). How can this be? a) this must be an error in observations; no such star can exist b) it must be brown dwarf and not a regular star c) it must be quite small in size d) it must be quite large in size e) it must be a main sequence star

d) it must be quite large in size

Which of the following is a method for measuring the diameter of a star? a) watching the body of the Moon go across the star c) getting the light curve of an eclipsing binary star d) more than one of the above e) comparing the color of a star seen high above our heads and then again when it's near the horizon

d) more than one of the above

Astronomers call the motion of a star across the sky (perpendicular to our line of sight) its a) light travel time b) radial velocity c) spectral type d) proper motion e) doppler shift

d) proper motion

A star moving toward the Sun will show: a) no change that can be measured with our present-day instruments b) more and more helium lines as it approaches us c) a significant increase in its apparent brightness (magnitude) d) a shift in the spectral lines toward the red end (as compared to the laboratory positions of these lines) e) a shift in the spectral lines toward the blue end (as compared to the laboratory positions of these lines)

e) a shift in the spectral lines toward the blue end (as compared to the laboratory positions of these lines)

One of your good friends 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? a) stars with low mass can be located anywhere at all in the H-R diagram b) among the stars at the top left of the main sequence c) among the white dwarfs d) among the supergiants e) among the stars at the bottom right of the main sequence

e) among the stars at the bottom right of the main sequence

Which of the following statements about spectroscopic binary stars is FALSE? a) we can use the spectrum to determine the sum of the masses of the two stars b) we can often use the changes in the positions of the spectral lines to measure the radial velocity of the stars in the system c) visually we can only see one star d) some of the lines in the spectrum are double, with the spacing changing over time e) an analysis of the ways the lines in the spectrum change allows us to calculate the star's distance directly

e) an analysis of the ways the lines in the spectrum change allows us to calculate the star's distance equally

Astronomers arrange the stars into groups called spectral classes (or types) according to the kinds of lines they find in their spectra. These spectral classes are arranged in order of: a) decreasing distance from us b) increasing amount of hydrogen c) you can't fool me, there is no order to the spectral types d) that's why the letters are not in alphabetical order) increasing mass e) decreasing surface temperature

e) decreasing surface temperature

A white dwarf, compared to a main sequence star with the same mass, would always be: a) less massive b) smaller in diameter c) the same size in diameter d) younger in age e) larger in diameter

e) larger in diameter

Two stars have the exact same luminosity, but star Y is four times dimmer looking that star X. This means that a) star Y is half as far away as star X b) star Y is four times as far away as star X c) we can't figure out the relative distance of the two stars from the information given d) star Y is 16 times as far away as star X e) star Y is twice as far away as star X

e) star Y is twice as far away as star X

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? a) these stars vary in brightness (flashing brighter and dimmer) and are thus easier to notice b) we see them in crowded regions of stars, which give us the impression that the stars there are brighter than they really are c) all the brightest stars are red, and red color is much easier to see against the black night sky d) ) actually, this is just an optical illusion; all stars are really the same brightness e) these stars are intrinsically so luminous, that they can easily be seen even across great distances

e) these stars are intrinsically so luminous, that they can easily be seen even across great distances