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