When a low mass star first runs short of hydrogen in its core, it becomes brighter because
A) its outer, cooler layers are shed, and we see the brighter central core.
B) it explodes as a nova.
C) the core contracts, raising the temperature and extending the hydrogen burning shell outward.
D) the helium flash increases the size of the star immensely.
E) helium fusion gives off more energy than does hydrogen.
C
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Why might astronomers someday establish an observatory on the Moon?
What will be an ideal response?
A body sliding on a table is observed to gradually slow down. The correct statement is that the body slows down because
A. no net force acts on the body. B. no force acts on the body. C. it is the nature of the body to slow down by itself. D. a net force acts on the body.
The mass of a galaxy's central black hole is proportional to the mass of its _______________
Fill in the blank(s) with correct word
If we observe one edge of a star to be redshifted and the opposite edge to be blueshifted, what can we conclude about the star?
A) The star is actually two bodies, one moving toward us, the other away from us. B) The star is in the process of falling apart. C) The star is in the process of formation. D) The star is rotating. E) The star's surface is very different from one side to the other.