main-sequence phase of their lives?Because this is the longest-lasting phase in each star's lifeThe explosion of a supernova appears to leave behinda rapidly expanding shell of gas and a central neutron star or black hole.Why does the core of the Sun contain more helium and less hydrogen than the surface of the Sun?Thermonuclear reactions have converted much of the original hydrogen in the core into helium.Two stars, P and Q, can be seen in the same region of our sky with the same apparent brightness, but star Q is twice as far away as star P. What is the ratio of the intrinsic brightnesses (luminosities) of these stars (star P-to-star Q)?1-to-4The photosphere of the Sun isthe visible surface of the Sun.Two stars have the same luminosity. One star is spectral class B and the other is spectral class K. From this information, we know thatthe K-type star is larger than the B-type star.The temperature of the outer atmosphere of the Sunis very hot, about 106 K.Which of the following particles or types of radiation will provide the most direct information on the energy generation processes that are occurring at the present time in the solar core?NeutrinosHow does the number of sunspots on the Sun vary with time?They vary relatively regularly, with a period of about 11 years.The spectral class of the star Enif is K, while that of the Sun is G. Which of the following conclusions can be drawn about Enif from this information? It is cooler than the Sun.What process provides the power for the Sun?fusion ofhydrogen into heliumIn the Hertzsprung-Russell diagram below, which of the following is the correct sequence of stars in order of increasing luminosity?Barnard's Star, Sirius B, the Sun, DenebThe spectrum of sunlight, when spread out by a spectrograph, has what characteristic appearance?A continuous band of color, crossed by innumerable dark absorption linesThe centers of the granular cells on the surface of the Sun are brighter than the edges of the cells becausethe centers are hotter than the edges.If the surface temperatures of white dwarf stars are up to 4 times that of the Sun, why then are white dwarfs intrinsically so faint?Because they are very smallThe average time taken for energy generated in the center of the Sun toreach the surface layers and escape is calculated to bea few hundred thousand years.Where are the most massive stars to be found in the main sequence of a Hertzsprung-Russell diagram?The upper left endA particular star in a binary star system orbits the other in an elliptical orbit with a semimajor axis of 3 AU and a period of 5 years. What is the sum of the masses of the two stars in the system?: 1.1 MSunHow can we characterize the rotation of the Sun?Differential rotation, with the equator rotating faster than the polesThe central region of a sunspot is about 1500 K cooler than the surrounding solar photosphere. How will the light from the sunspot compare to the light from the rest of the photosphere?The light from the sunspot will be redder and dimmer.Spectral lines are of particular importance in astronomy becauseeach different element has a characteristic line spectrum.
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