You are studying a mystery companion to an evolved star, with mass transfer happening. Which of the following properties suggests that the companion is definitely a black hole?
A) The mystery companion has a mass of over 1.4 solar masses.
B) The mystery companion has a mass of over 3 solar masses.
C) The mystery companion has an X-ray emitting accretion disk.
D) The mystery companion gives off periodic X-ray bursts.
B
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Which of these hypothetical observations (none of them are real) would force us to reconsider our modern, Sun-centered view of the solar system?
a. We discover a small planet beyond Saturn that rises in the west and sets in the east each day. b. We find that we are unable to measure any parallax for a distant galaxy. c. We discover an Earth-sized planet orbiting the Sun beyond the orbit of Pluto. d. We discover that the universe is actually contracting, not expanding.
Structure 1 with member BC of length L/2 has force P1 applied at joint C. Structure 2 with member BC of length L has force P2 applied at C. Both structures have constant flexural rigidity EI. If the ratio of the applied forces P1/P2 5 5/2, the ratio of the joint B reactions RB1/RB2 is approximately:
(A) 1
(B) 5/4
(C) 3/2
(D) 2
Mass is a measure of
a. inertia. b. force. c. grams. d. weight. e. kilograms.
If the Sun's rotation carries two sunspots around the side out of sight, you might see them again in about
A. two weeks. B. a month. C. six months. D. twelve hours.