What type of nebula is the Horsehead?
a. Primitive
b. Bright emission
c. Bright reflection
d. Dark
d
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The force that keeps your feet from sliding as you walk is
a. centripetal force b. weight c. kinetic friction d. static friction e. none of the above
Significant Figures: How many significant figures are in the number 0.0037010?
A. four B. five C. six D. seven E. eight
What is this a picture of?
A) a cluster of galaxies B) a globular cluster C) an elliptical galaxy D) the expanding universe
Which of the following statements about rich clusters of galaxies (those with thousands of galaxies) is not true?
A) They are sources of X-ray emission due to the presence of hot, intergalactic gas. B) There likely have been numerous collisions among the member galaxies at some time in the past. C) Galaxies in the central regions are predominantly spirals, while elliptical galaxies roam the outskirts. D) They often have a very large, central dominant galaxy near their center, perhaps formed by the merger of several individual galaxies. E) The speeds of the galaxies in the cluster indicate that most of the cluster mass is dark matter.