Briefly describe Sagittarius A*
What will be an ideal response?
Observations show that Sagittarius A* (abbreviated as Sgr A*) is only a few astronomical units in diameter but is a powerful source of radio energy. The tremendous amount of infrared radiation coming from the central area appears to be produced by crowded stars and by dust warmed by those stars.Since the middle 1990s, astronomers have been able to use large infrared telescopes and adaptive optics to follow the motions of stars orbiting around Sgr A*. The size and period of the orbit allows astronomers to calculate the mass of Sgr A* using Kepler's third law. The orbital period of the star SO-2, for example, is 15.2 years, and the semimajor axis of its orbit is 950 AU. The combined motions of the observed stars suggest that Sgr A* has a mass of 4 million solar masses.At its closest, SO-2 comes within 17 light-hours of Sgr A*. The available evidence eliminates alternate hypotheses that Sgr A* is a large cluster of normal stars or neutron stars or stellar-mass black holes. Only a single black hole could contain so much mass in so small a region.
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In Diagram 6-1, which of the transitions would absorb a photon with the greatest energy?
An empty coal-car (mass 20,000.kg) of a train coasts along at 10.m/s. An unfortunate 3000. kg elephant falls from a bridge and drops vertically into the car. Determine the speed of the car immediately after the elephant is added to its contents
What will be an ideal response?
Three couples of equal magnitude (M0 5 100 N?m) are applied as shown. A single couple (in N?m) that is statically equivalent to the three couples is:
(A) 83.2i 2 89.4j
(B) 283.2i 1 89.4j
(C) 93.2i 1 79.4j
(D) 83.2i 1 89.4j
The frequency of induced voltage in a wire coil depends on
A) the frequency of current producing it. B) how frequently a magnet dips in and out of the coil. C) the number of loops in the coil.