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Astronomy Multiple 2

Multiple choice questions

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
Created by: dfw90