Multiple choice questions
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| What two energy transport mechanisms, in order from outside the core to the surface, are found in the Sun? | radiative diffusion, convection
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| The outward pressure of hot gas in the Sun | is balanced by the inward gravitational pressure
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| The solar winds blow outward from | coronal holes
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| Suppose a large flare is detected optically. How long until radio interference arrives? | simultaneously
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| What natural barrier tries to prevent two protons from combining? | Electromagnetic repulsion
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| The critical temperature to initiate the proton-proton cycle in the cores of stars is | 10 million K
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| In the proton-proton cycle, the helium atom and neutrino have less mass than the original hydrogen. What happened to the "lost" mass? | It is converted to energy
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| Which is the net result of the proton-proton chain? | 4 protons = 1 helium4 + 2 neutrinos + gamma rays
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| Our best stellar parallax measurements to date from | the Hipparcos satellite
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| The Hipparcos data give us | parallaxes as small as 0.005"
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| A star has a parallax of 0.01 arc seconds. Its distance is | 100 parsecs.
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| A star is 10 parsecs from Earth. Which statement is true? | The star is about 33 ly away
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| Rigel has an apparent magnitude of +0.18 and Betelgeuse an apparent magnitude of +0.45. What can you conclude from this? | Rigel is brighter than Betelgeuse
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| Two stars both have parallaxes of 0.023", but star A has apparent magnitude +2.3, while star B is magnitude +7.3. Which statement is true. | Star A is both 100x brighter and more luminous than star B.
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| What physical property of a star does the spectral type measure? | temperature
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| The star's color index is a quick way of determining its: | temperature
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| The H-R diagram can plot | temperature versus luminocity
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| In the H-R diagram, what are the two most important types of data plotted? | spectral classes and absolute magnitudes
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| Stellar masses are measured directly by observations of the motions of | All of the above can give us their masses.
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| Interstellar gas is composed of | 90% hydrogen, 9% helium by weight
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| What effect does even thin clouds of dust have on light passing through them? | It dims and reddens the light of all more distant stars.
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| Which statement about dark dust clouds is true? | They can be penetrated only with longer wavelengths such as radio and infrared.
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| Some regions along the plane of the Milky Way appear dark becuase | stars in that region are hidden by dark dust particles
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| Due to absorption of shorter wavelengths by interstellar dust clouds, distant stars appear | redder
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| What is the primary visible color of an emission nebula? | red due to ionized hydrogen atoms
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| Emission nebulae like M42 occur only near stars that emit large amounts of | ultraviolet radiation
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| A large cloud in the interstellar medium that contains several type O and B stars would appear to us as | an emission nebula
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| A newly formed protostar will radiate primarily at which wavelength? | infrared
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| The single most important determinant of the temperature, density, radius, luminosity, and pace of evolution of a protostar is its | mass
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| A cloud fragment too small to collapse into a main sequence star becomes a | brown dwarf
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| All globular clusters in our Milky Way are about how old? | around 10 billion years old
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| Which is a characteristic of globular star clusters? | old age and hundreds of thousands of stars, only about 30 ly wide
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| Why are star clusters ideal "laboratories" for stellar evolution? | Their stars are all about the same age, compostion, and distance from us
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| A star (no matter what its mass) spends most of its life: | as a main sequence star
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| When a star's inward gravity and outward pressure are balanced, the star is said to be | in hydrostatic equilibrium
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| What temperature is needed to fuse helium into carbon? | 100 million K
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| When a low mass star first runs short of hydrogen in its core, it becomes brighter because | the core contracts, raising the temperature and hydrogen burning shell outward
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| The helium flash converts helium nuclei into | carbon
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| A solar mass star will evolve off the main sequence when | it builds up a core of inert helium
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| Which of these is true of planetary nebulae? | They are ejected envelopes surrounding a highly evolved low-mass star
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| Which of these evolutionary paths is the fate of our Sun? | planetary nebula
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| An iron core cannot support a star because | iron cannot fuse with other nuclei to produce energy
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| A 20 solar mass will stay on the main sequence for 10 million years, yet its iron core can exist for only a | day
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| The Chandrasekhar limit is | the upper mass limit for a white dwarf
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| The brightest stars of a young open cluster will be | massive blue main sequence stars
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| What is the typical age for a globular cluster associated with our Milky Way? | 10-12 billion years
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| Which is used observationally to determine the age of a star cluster? | the luminosity of the main-sequence turn-off point
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| What made supernova 1987a so useful to study? | All of the above are correct
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| A neutron star is about the same size as | a U.S. city
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| The best place to search for black holes is in a region of space that | has strong X-ray emission
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| If the Sun were magically to turn into a black hole of the same mass | Earth's orbit would remain unchanged
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| In a neutron star, the core is | made of compressed neutrons in contact with each other
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| Two important properties of young neutron stars are | extremely rapid rotation and a strong magnetic field
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| An object more massive than the Sun, but roughly the size of a city, is a | neutron star
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| The mass range for neutron stars is | 1.4 to 3 solar masses
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| What makes the Crab Nebula pulsar unusual among other pulsars? | It is relatively bright in shorter wavelengths, like visible and X-rays
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| The supernova of 1054 AD produced: | a pulsar with a period of 33 milliseconds, visible optically
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| In a hypernova, a very energetic supernova creates a | black hole
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| The Schwartzchild radius for a 12 solar mass star is | 36 km
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| As a spaceship's velocity gets closer to the speed of light | its length will decrease and its clock will run more slowly
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| If light from a distant star passes close to a massive body, the light beam will | bend towards the star due to gravity
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| What can we detect from matter that has crossed an event horizon? | Nothing
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| If the Sun were replaced with by one solar mass black hole | we would still orbit it in a period of one year
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| What is Cygnus X-1? | the leading candidate for an observable black hole binary system
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| In structure, our Milky Way is most similar to | M-31, the Andromeda Galaxy
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| All RR Lyrae stars have about about the same | luminosity of about 100 Suns
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| The first attempt to map the Galaxy via star counts was done by: | William Herschel in the late eighteenth century
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| For finding the distances to globular clusters, Harlow Shapley used | RR Lyrae variables
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| Why was Herschel's strategy for mapping our Galaxy flawed? | He relied on visual wavelengths, which are obscured by dust
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| Which is the correct description of the Sun's location within the Milky Way? | in the disc and about one-half a galactic radius from the center
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| What is one of the differences between Cepheids and RR Lyrae variables? | The RR Lyrae stars have much shorter periods than Cepheids
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| Harlow Shapley found the Milky Way was | much larger than previously expected
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| What is true about the stellar populations in the Galaxy? | Only old stars are found in the halo
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| Between us and the Galactic Center, the Milky Way has a mass of | 100 billion suns.
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| Which of these is not typical of the Galaxy's spiral arms? | Population II giants like orange Arcturus
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| What use are 21 cm radio waves to galactic astronomers? | Their Doppler shifts let us map the motions and locations of gas in the spiral arms.
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| According to Figure 14.6 (Period-Luminosity Relationship) in the textbook, a Cepheid variable star with luminosity 1000 times that of the Sun has a pulsation period of roughly | 3 days
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