AS101 - Assignment 9 PDF

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Assignment 9 with answers...

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Wilfrid Laurier University AS101a Assignment # 9 Instructor: Dr. Ioannis Haranas 1. What is the term for a collection of 105 to 106 old stars in a region 30 to 100 light-years in diameter? a. Herbig-Haro object *b. globular cluster c. open cluster d. giant cluster 2. What is the defining characteristic of stars within a cluster that are at the turnoff point? *a. They are just leaving the main sequence. b. They are just becoming white dwarfs. c. They are just entering the main sequence. d. They are about to explode in supernovae. Cluster

3. What is the approximate age of the star cluster in the H-R diagram? (Hint: Main sequence stars of spectral types O and B have a core supply of hydrogen that is sufficient to last about 250 million years; types A and F, about 2 billion years; type G about 10 billion years; types K and M about 30 billion years. The apparent magnitude scale means that larger numbers are toward the bottom of the vertical axis.) a. 200 million years b. 2 billion years *c. 10 billion years d. 30 billion years 4. Refer to the H-R diagram. How would the H-R diagram of a more distant star cluster look different? *a. The points would shift down, because all of the stars would have larger apparent magnitudes. b. The points would shift to the right, because all of the stars would appear to be cooler. c. The points would shift up, because all of the stars would have smaller apparent magnitudes. d. The points would shift to the left, because all of the stars would appear to be hotter. 5. Which nuclear fuels does a one solar mass star use over the course of its entire lifespan? a. hydrogen *b. hydrogen and helium c. hydrogen, helium, and carbon d. hydrogen, helium, carbon, and oxygen

6. What is the ultimate fate of our Sun? a. It will become a neutron star. b. It will explode in a supernova. *c. It will become a white dwarf. d. It will explode in a nova. 7. Which of the following is the most important factor that determines a life cycle of a star (for example, why some stars have a short life span)? *a. mass b. temperature c. luminosity d. radius 8. What principle explains why matter flowing from one star in a binary system to its companion forms an accretion disk? a. conservation of tidal forces b. conservation of temperature *c. conservation of angular momentum d. conservation of energy 9. Suppose you discover a binary star system with a 0.7 solar mass giant star and a 2 solar mass main sequence star. Why is this surprising? a. 0.7 solar mass stars are not expected to become giants. b. All 2 solar mass stars should have left the main sequence. c. Giant stars are expected to destroy their companions, so the 2 solar mass star shouldn’t exist. *d. The 2 solar mass star should have become a giant before the 0.7 solar mass star.

10. When material expanding away from a star in a binary system reaches the edge of its Roche lobe, what happens? a. The material will start to fall back toward the star. b. All of the material will accrete on to the companion. *c. The material will no longer be gravitationally bound to the star. d. The material will increase in temperature and eventually undergo thermonuclear fusion. 11. When mass is transferred toward a white dwarf in a binary system, the material forms a rapidly growing whirlpool of material. What is that whirlpool called? *a. an accretion disk b. an Algol paradox c. a planetary nebula d. a supernova remnant 12. Under what conditions are Type Ia supernovae believed to occur? a. when the core of a massive star collapses *b. when a white dwarf exceeds the Chandrasekhar-Landau limit c. when hydrogen detonation occurs d. when neutrinos in a massive star form a shock wave that explodes the star 13. Which of the following is almost always associated with a nova? a. a very massive star b. a star undergoing helium burning

c. *d.

a white dwarf in a close binary system a solar-like star that has exhausted its hydrogen and helium

14. Why can’t massive stars generate energy through iron fusion? a. because iron fusion requires very high density b. because no star can get hot enough for iron fusion *c. because both fusion and fission of iron nuclei absorb energy d. because massive stars go supernova before they create an iron core 15. If the hypothesis that novae occur in close binary systems is correct, then which of the following should novae do? a. They should produce synchrotron radiation. b. They should occur in regions of star formation. c. They should all be visual binaries. *d. They should repeat after some interval. 16. Why is the material that accretes onto a neutron star or black hole expected to emit X-rays? a. The material contains magnetic fields that will produce synchrotron radiation. b. Hydrogen nuclei begin to fuse and emit high energy photons. *c. The material will become hot enough that it will radiate most strongly at X-ray wavelengths. d. As the material slows down it converts thermal energy to gravitational potential energy. 17. What is the term for the form of electromagnetic radiation produced by rapidly moving electrons spiralling through magnetic fields? a. Lagrangian radiation b. ultraviolet radiation *c. synchrotron radiation d. infrared radiation 18. What type of object is the Crab nebula? a. a planetary nebula b. an open cluster c. an absorption nebula *d. a supernova remnant 19. In the year 1054 CE, Chinese astronomers observed the appearance of a new star. What occupies that location now? a. a molecular cloud b. a planetary nebula with a white dwarf in the centre *c. a supernova remnant with a pulsar in the centre d. nothing 20. What produces synchrotron radiation? a. objects with temperatures below 10,000 K *b. high-velocity electrons moving through a magnetic field c. cold hydrogen atoms in space d. helium burning in a massive star 21. Where is synchrotron radiation produced? a. in planetary nebulae b. in the outer layers of red dwarfs

c. *d.

in the collapsing iron cores of massive stars in supernova remnants

22. What does the explosion of a type II supernova typically leave behind? a. It leaves behind a planetary nebula. b. It leaves behind a shell of hot, expanding gas with a white dwarf at the centre. *c. It leaves behind a shell of hot, expanding gas with a pulsar at the centre. d. Nothing is ever left behind. 23. Which of the following offered support for the theory that the collapse of a massive star’s iron core produces neutrinos? *a. the detection of neutrinos from the supernova of 1987 b. the brightening of supernovae a few days after they are first visible c. underground counts of solar neutrinos d. laboratory measurements of the mass of the neutrino 24. If you were to land on a neutron star, how would your mass change compared to your mass on the Earth? a. It would increase a lot. b. It would decrease a lot. c. It would increase a little. *d. It would remain the same. Good Luck!!...