Why do astronomers consider gamma-ray bursts to be one of the greatest mysteries in astronomy?

A) because they are so rare
B) because we know they come from pulsating variable stars but don't know how they are created
C) because the current evidence suggests that they are the most powerful bursts of energy that ever occur anywhere in the universe, but we don't know how they are produced
D) because current evidence suggests that they come from our own Milky Way, but we have no idea where in the Milky Way they occur
E) because current evidence suggests that they come from massive black holes in the centers of distant galaxies, adding to the mystery of black holes themselves


C
An advanced civilization lives on a planet orbiting a close binary star system that consists of a 15MSun red giant and a 10MSun black hole. Assume that the two stars are quite close together, so that an accretion disk surrounds the black hole. The planet on which the civilization lives orbits the binary star at a distance of 10 AU.

Physics & Space Science

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Series/Parallel Circuits: The lamps in a string of decorative lights are connected in parallel across a constant-voltage power source. What happens if one lamp burns out? (Assume negligible resistance in the wires leading to the lamps.)

A. The brightness of the lamps will not change appreciably. B. The other lamps get brighter equally. C. The other lamps get brighter, but some get brighter than others. D. The other lamps get dimmer equally. E. The other lamps get dimmer, but some get dimmer than others.

Physics & Space Science

A box is moved 10 m across by a floor a force of 25 N acting along the direction of motion. The work done by the force is

A. 25 J. B. 125 J. C. 35 J. D. 2.5 J. E. 250 J.

Physics & Space Science

The SI base units for the spring constant are which of the following?

a. Kg/s2 b. kg/m2 c. kg/s2 d. Kg/m2

Physics & Space Science

The Moon physically changes its shape throughout its orbit around the Earth giving us the phases of the Moon we see

a. True b. False Indicate whether the statement is true or false

Physics & Space Science