ASTRONOMY 162 TEST 2 E = mc^2 c = 300,000 km/sec E/A =sigT^4 r = 1/p" v = f*lambda wavelength(max) = 3000/T multiple choice. 3 points each. 1. A white dwarf is * a) hot, but not producing any new energy b) hot because it produces energy in its core c) small but gradually getting larger d) a smaller version of a neutron star 2. What would happen if mass is continuously added to a 1.4 solar mass neutron star? a) the star would erupt as a supernova * b) The star would eventually become a black hole c) the star would become a white dwraf d) the star's radius would increase 3. Two stars have the same radius but star X's surface temperature is 20,000 degrees K whereas star Y's is 5,000 degrees K. The luminosity of star X is a) 4 times brighter than star Y b) the same as star Y c) 8 times brighter than star Y * d) 256 times brighter than star Y 4. Which of the following in NOT correct? Stars in a single cluster * a) have the same mass b) are of about the same age c) have the same initial chemical composition d) are all at about the same distance 5. The observed parallax of relatively nearby stars is caused by a) Earth's rotation on its axis b) the Doppler shift of light from the stars * c) the Earth's revolution about the Sun d) motion of the stars across our line of sight 6. Pulsars are a) vibrating brown dwarves * b) rapidly rotating neutron stars c) rapidly pulsing white dwarves d) rapidly spinning black holes 7. The uniquely important feature of binary stars is that they enable us to determine stellar a) temperature b) pressure c) compositions * d) masses 8. Suspected black holes can be detected a) because they block out views of objects behind them b) from their blackbody radiation c) by x-rays emitted from the black hole's dense central region * d) by x-rays emitted from material falling into the black hole 9. Interstellar gas is composed mainly of * a) hydrogen and helium b) carbon c) silicate dust particles d) hydrogen and carbon 10. What is the critical temperature at which hydrogen can begin to fuse into helium in the core of a star a) 10,000 degrees K b) 500,000 degrees K * c) 10 million degrees K d) 200 million degrees K 11. Compared to a red star, a blue star always has a) more mass b) smaller radius * c) hotter surface temperatue d) all of the above 12. Helium fusion to heavier elements such as Carbon a) occurs in neutron stars b) does not release any energy * c) requires a higher temperature than hydrogen fusion into Helium d) all of the above 13. What is the size of a typical white dwarf? a) 30 km b) 500 km * c) 10,000 km d) 1,000,000 km 14. What happens when an interstellar cloud fragment shrinks? a) the density rises b) the temperature rises c) the pressure increases * d) all of the above 15. A high-mass star dies more violently than a low-mass star because a) it cannot fuse elements heavier than carbon * b) its core eventually collapses c) gravity is weakened by its high luminosity d) it is most often found as part of a binary system 16. What characteristic of a star cluster is used to determine its age? a) the total number of main sequence stars b) the faintest stars seen in the cluster c) the number of red giants * d) the luminosity of the brightest stars still on the main sequence 17. The heaviest nucleii of all (like lead) are formed * a) during a supernova explosion b) during carbon burning in Red Giants c) during all stages of stellar evolution d) through the p-p cycle 18. After a star like the Sun has used up all the hydrogen in its core it a) explodes and becomes a neutron star * b) expands and becomes a red giant c) blends into the interstellar medium d) becomes a planet Section 2: Answer the following questions about the H-R plot. 2 pts each like HR diagrams in Chapter 8 and 9 19. Which star has the smallest radius? ____________ 20. Which star has the largest radius? ____________ 21. In which star(s) is helium burning occuring? ____________ 22. The radius of star F is about how much larger than ____________ the radius of star C? 23. Which star will live the longest? ____________ 24. Which star is most similar to one that star C ____________ will eventually evolve into? 25. Which main sequence star will probably end ____________ up as a white dwarf? 26. Which star(s) will probably become a supernova? ____________ 27. Which stars are red giants? ____________ 28. Which star has the hottest surface temperature? ____________ 29. Which star has the hottest core temperature? ____________ 30. Which main sequence star will probably not become ____________ a red giant? 31. What are the steps from Red Giant formation to a supernova explosion to whatever is left afterward? 10 pts 32. What are the steps leading to the formation of a main sequence star like our Sun? Plot the steps on a HR diagram. 12 points