What is a galaxy's rotation curve? To which galaxies is it best applied, and what does it tell us about the distribution of dark matter?
What will be an ideal response?
The speed of rotation at various distances from the galaxies center is plotted for spiral galaxies whose rotation is more easily observed. The flat curve going out toward the edge shows us that there must be a dark halo, extending well beyond the visible one, and that dark matter may account for 90% of the total mass.
You might also like to view...
A car is making a 12-mile trip. It travels the first 6.0 miles at 30 miles per hour and the last 6.0 miles at 60 miles per hour. What is the car's average speed for the entire trip?
A) 20 mph B) 35 mph C) 40 mph D) 45 mph E) 50 mph
You discover a binary star system in which one member is a 15 solar mass main-sequence star and the other star is a 10 solar mass giant star. Why should you be surprised, at least at first?
A) The two stars should be the same age, so the more massive one should have become a giant first. B) The two stars in a binary system should both be at the same point in stellar evolution; that is, they should either both be main-sequence stars or both be giants. C) It doesn't make sense to find a giant in a binary star system. D) A star with a mass of 15 solar masses is too big to be a main-sequence star. E) The odds of ever finding two such massive stars in the same binary system are so small as to make it inconceivable.
The H-R diagram is a diagram plotting the stars according to their
A. luminosity and temperature. B. spectral type and temperature. C. mass and diameter. D. brightness and luminosity class. E. apparent brightness and temperature.
What is the distance between a -2.00 
C charge and a -3.00 
C charge if their potential energy is 0.491 J?
A. 25.0 cm B. 15.5 cm C. 11.0 cm D. 3.14 cm E. 0.911 cm