What do all the stars in the Orion Association have in common?
What will be an ideal response?
Like the stars in more compact open clusters, they are all born at about the same time, at the leading edge of the spiral arms, and thus have similar compositions. They tend to be very massive, collapsing rapidly, and very luminous as well.
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A force of 15.2 N directed along the positive x-axis combines with a second force to produce a total force vector of magnitude 17.9 N. What is the magnitude of the second vector?
A. Not enough information is given. B. 9.5 N C. 23.5 N D. 2.7 N
A gravitational lens occurs when
A) a massive object causes more distant objects to appear much larger than they should, and we can observe the distant objects with better resolution. B) a telescope lens is distorted by gravity. C) a massive object bends light beams that are passing nearby. D) dark matter builds up in a particular region of space, leading to a very dense region and an extremely high mass-to-light ratio.
What is in the box shown below? 
A. Positive charge B. Negative charge C. Zero charge D. One cannot determine the charge’s sign from this diagram.
Star A and star B have the same temperature, but star A is 5 times bigger than star B. Which statement below is correct?
A) Star A is redder and dimmer than star B. B) Star A is bluer and dimmer than star B. C) Star A is redder and brighter than star B. D) Star A is bluer and brighter than star B. E) Star A and star B have the same color, but star A is brighter.