5. Which of the following techniques can be used to estimate the density of an extrasolar planet? A. radial velocity method b. astrometric method c. transit method 6. What is the major physical process that should cause the material around young stars to form a disk, rather than, say, a sphere? A. powerful winds from the newly formed star b. gravity c. collisions between particles d. rotation 7. What has been a major surprise from recent searches for extrasolar planets? A. Most solar-type stars don”t have planets. B. Terrestrial-sized planets have not been found. C. Many of the planets discovered have very eccentric orbits.