Introduction to Cosmology

1. Introduction to Cosmology Multiple Choice Questions

2. Test Question Does this quiz work? A. Yes B. No

3. Introduction to Cosmology 1. Why is the sky dark at night? A. Stars have finite lifetimes and can’t shine forever. B. The speed of light is finite so only stars within a finite distance can be observed. C. The Universe has a finite age. D. All of the above. y

4. Introduction to Cosmology • 2. The distance modulus formula: m – M = 5logr – 5, can be rearranged for r. What is this new arrangement? • r = 105(m – M + 5). • r = 100.2(m – M + 5). Y • r = (m – M) / 5log(-5). • r = -2.5logM – 5m.

5. Introduction to Cosmology • 3. How does the Milky Way rotate? • Rigidly. • Differentially. • Both rigidly and differentially depending on radius. y

6. Introduction to Cosmology • 4. Which of the following statements about the spiral arms of the milky way is true? • The arms are populated by a large number of O and B type stars and they are sites of recent and ongoing star formation. Y • The arms are populated by a large number of K and M type stars and they are sites of recent and ongoing star formation. • The arms are populated by a large number of O and B type stars and they are sites of many of the oldest stars in the galaxy. • The arms are populated by a large number of K and M type stars and they are sites of many of the oldest stars in the galaxy.

7. Introduction to Cosmology • 5. In order to plot a galactic rotation curve, the gravitational potential energy (GMm / r2) must be equated to the kinetic energy (mv2 / r) of the circular motion about the centre. If this equation is the rearranged for v2, how will v2 be proportional to r? • Directly proportional to r2. • Inversely proportional to r. y • Directly proportional to r2. • Inversely proportional to r.

8. Introduction to Cosmology • 6. Thinking about the observed rotation curve of a spiral galaxy and the predicted one, how do the velocities differ in these two rotation curves? • They match closer to the galactic centre but the predicted velocity is higher than the observed one further away from the centre. • They match further away from the galactic centre but the predicted velocity is higher than the observed one closer to the centre. • They match further away from the galactic centre but the predicted velocity is lower than the observed one closer to the centre. • They match closer to the galactic centre but the predicted velocity is lower than the observed one further away from the galactic centre. y

9. Introduction to Cosmology • 7. Which of the following is not a type of galaxy? • Barred irregular. y • Dwarf elliptical. • Lenticular. • Barred spiral.

10. Introduction to Cosmology • 8. If a galaxy cluster is virialised this means it has reached a state of balance between its… • Kinetic energy and potential energy. • Luminous matter and dark matter. • C. Mass and radius. • D. Size and temperature.

11. Introduction to Cosmology • 9. What is the Hubble tuning fork diagram? • A classification system for different types of galaxies based on their differences in visual appearance. y • A classification system for different types of galaxies based on their differences in rotation speeds. • An evolutionary sequence for different types of galaxies moving from elliptical to spiral. • An evolutionary sequence for different types of galaxies moving from spiral to elliptical.

12. Introduction to Cosmology • 10. Which of the following properties of radio galaxies is incorrect? • They are normally spiral galaxies. y • Compact sources often vary on time scales of days, implying that the size of the emitting region is no more than a few light-days across. • The radio source spectrum is usually synchrotron radiation. • Ratio of radio to optical luminosity is normally in the range 0.1 – 10.

13. Introduction to Cosmology • 11. Seyfert galaxies are spiral galaxies with unusually luminous red nuclei, true or false? • True. • False. y

14. Introduction to Cosmology • 12. Which of the following properties of quasars is incorrect? • They are at very large distances from us. • They are very close to the end of their lifetime. y • Their optical luminosities are up to 10 – 100 times that of a normal galaxy. • All of the above are true.

15. Introduction to Cosmology • 13. Hubble’s law is vrecessional = H0d. What are the units of Hubble’s constant? • Km s-1 Mpc. • m s-1 Mpc-1. • Km s-1 km-1. • Km s-1 Mpc-1. y

16. Introduction to Cosmology • 14. Hubble’s law indicates that… • The universe is expanding. • Nearly all other galaxies are moving away from us. • The universe must have had a beginning. • All of the above. y

17. Introduction to Cosmology • 15. In red-shift surveys looking at the universe on very large scale, the universe begins to look… • Homogeneous. • It stops beginning to look inhomogeneous and begins to isotropic. y • Isotropic. • Neither homogeneous nor isotropic.

18. Introduction to Cosmology • 16. What is the present best estimate of Hubble’s constant? • ~ 50 km/s/Mpc. • ~ 70 km/s/Mpc. Y • ~ 100 km/s/Mpc. • ~ 72 m/s/Mpc.

19. Introduction to Cosmology • 17. What type of distance indicator is the Tully-Fisher relation and why? • A primary indicator because it does not rely on any other data than the period luminosity relationship. • A primary indicator because it does not require to be calibrated using primary distance indicators. • A secondary indicator because it does not rely on any other data than the period luminosity relationship. • A secondary indicator because it does not require to be calibrated using primary distance indicators. y

20. Introduction to Cosmology • 18. Read the following statements: “Isotropic universe = Universe looks the same not matter where you are in it.” “Homogeneous universe = Universe looks the same no matter what direction you look in. Which of these statements are true? • Both are true. • Both are wrong. y • The first is true but the second isn’t. • The second is true but the first isn’t.

21. Introduction to Cosmology 19. If the Universe has less than the critical matter density (and assuming the cosmological constant is zero) then… A. It has a closed geometry, and expands indefinitely. B. It has a closed geometry, expands and then recollapses. C. It has an open geometry, and expands indefinitely. y D. It has an open geometry, expands and then recollapses.

22. Introduction to Cosmology • What kind of curvature does a saddle shaped surface have? • Positive curvature. • Negative curvature. Y • Both positive and negative curvature depending on the position. • Neither positive or negative curvature.

23. Introduction to Cosmology • 21. The critical density of the universe ‘ρcrit’ is the density required to just close the Universe, on what variables does it depend? • Hubble’s constant and the cosmological constant. • The cosmological constant and the gravitational constant. • Hubble’s constant and the gravitational constant. y • The cosmological constant only.

24. Introduction to Cosmology • 22. The density parameter ‘Ω’ can be used to indicate whether the universe is closed open or flat, true or false? • True. y • False.

25. Introduction to Cosmology • 23. Below is listed four dark matter candidates. Which of these is non-baryonic? • Gas clumps in galaxy halos and clusters. • Weakly interacting massive particles (WIMPS) such as massive neutrinos. Y • Massive compact halo objects (MACHOs), such as failed stars. • Low surface brightness galaxies.

26. Introduction to Cosmology • 24. About 10% of the white noise in an analogue T.V signal (when not picking up a channel) is made op of the cosmic microwave background radiation, true or false? • False. • False, its actually 5 %. • True. y

27. Introduction to Cosmology • BONUS QUESTION: Who wrote the following scientific paper in October 2008: “Peculiar velocities into the next generation: cosmological parameters from large surveys without bias from non-linear structure”? • Dr Martin Hendry only. • Dr Luis Teodoro only. • Einstein. • Newton. • Dr Hendry and Dr Teodoro. y