star Arcturus is a red giant that is easily visible in the night sky. Based on models of stellar evolution, what is happening to Arcturus as this stage of its life?
A) It is increasing in size, and hydrogen fusion reactions are occurring in a shell around the core.
B) It is stable in its size, and hydrogen fusion reactions are occurring in its core.
C) It is decreasing in size, and hydrogen fusion reactions are occurring in its core.
D) It is increasing in size, and hydrogen fusion reactions are occurring in its core.
E) It is decreasing in size, and hydrogen fusion reactions are occurring in a shell around the core.
F) It is stable in its size, and hydrogen fusion reactions are occurring in a shell around the core.
A) It is increasing in size, and hydrogen fusion reactions are occurring in a shell around the core.
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The ____ is responsible for binding the electrons to the nucleus
a. Kirchhoff's law b. ground state c. temperature d. Coulomb force e. Balmer series
Which of the following statements about brown dwarfs is not true?
A) Brown dwarfs eventually collapse to become white dwarfs. B) Brown dwarfs are supported against gravity by degeneracy pressure, which does not depend on the object's temperature. C) Brown dwarfs form like ordinary stars but are too small to sustain nuclear fusion in their cores. D) All brown dwarfs have masses less than about 8% that of our Sun.
What happens to the core of a star after a planetary nebula occurs?
A) It contracts from a protostar to a main-sequence star. B) It breaks apart in a violent explosion. C) It becomes a white dwarf. D) It becomes a neutron star. E) none of the above
How much energy is necessary to place three +2.0-µC point charges at the vertices of an equilateral triangle of side 2.0 cm if they started out extremely far away? (k = 1/4??0 = 9.0 × 109 N ? m2/C2 )
A) 4.5 J B) 5.4 J C) 6.7 J D) 7.6 J