Reference no: EM13583169

1. Summarize the evidence supporting the theory that the Cretaceous-Tertiary extinction, which includes the extinction of the dinosaurs, was precipitated to a significant degree by the impact of a meteorite.

2. What are the three primary ways in which a planet can have or acquire a Moon. What is the most probable origin of Earth's Moon? Given examples of moons that probably arose by the other two mechanisms

3. What is the Roche limit of a planet and its role in the formation of ring systems? What would happen to an astronaut who enters the Roche limit of a planet?

4. What are the defining properties of a dwarf planet? What extra condition must be satisfied in order for a dwarf planet to be a true planet?

5. Describe the position, layout and typical inhabitants of the Asteroid Belt, the Kuiper Belt and the Oort Cloud. What, in particular, are plutinos?

6. A comet often has two different tails. How are they created, of what do these tails consist and what determines their direction in space?

7. a) The dwarf planet, Ixion, has an orbit that ranges from 30.091AU out to 49.269 AU. Use Kepler's Laws of Planetary Motion to calculate the orbital period of Ixion.

b) Using the same technique, compute the maximum distance from the Sun of a long-period comet that has an orbital period of 1,500,000 years and a perihelion at 0.5 A.U. (Hint for a) and b): Remember that the semi-major axis is the average of the distance at perihelion and aphelion.)

8. What are the photosphere, chromosphere and corona of the Sun? Describe some typical phenomenon observed on or in each. What are the various emission and absorption line spectra associated with these layers of the Sun? What is the solar wind, and of what does it consist. How is it related to the corona and coronal holes? How is it related to aurorae on Earth?

9. What are sunspots and how are they related to the Sun's magnetic field? Is the magnetic field stronger weaker in sunspots? How does the temperature in a sunspot relate to the temperature in the rest of the photosphere? Describe the role of the Sun's differential rotation in the formation of sunspots. Describe (briefly) the 22 year solar cycle, stating its essential features.

10. At one time, the protostar that became our Sun had a surface temperature of about 3000K and a radius about 25 times that of the present-day Sun. How much more (or less) luminous, compared to today, was our Sun when it was a protostar? At what distance would you have to be from the protostar for it to have the same brightness as the Sun seen from Earth today?

11. What is the Solar Neutrino problem, and what are the possible resolutions of it? Which of these resolutions is now believed to be the most likely explanation?

12. What is the mass deficit in nuclear reactions? Where does the mass go? Which elements can fuse together to generate energy and why is iron considered to be the most stable element? Why do thermonuclear reactions occur only in the Sun's core, and not in the outer parts of the Sun? Why is it more difficult to fuse two helium nuclei than it is to fuse two hydrogen nuclei?

13. In the 19th century there was much discussion about what could be the energy source of the Sun. Why was it evident that the Sun could not be powered by chemical reactions? Kelvin and Helmholtz thought they had the answer. What was their idea and what 19th century evidence showed that they were wrong?

14. A red star and a blue star have the same size and are at the same distance from Earth. Which one looks brighter in the night sky? Why? (Ignore the interstellar reddening)

15. What is the fundamental explanation (in terms of atomic physics) of why hydrogen absorption lines are weak in O and M stars and strong in A stars. Why are molecular absorption lines strong in K and M stars but weak in O, B and A stars?

16. a) Sketch a Hertzsprung-Russell diagram: label the axes, marking off the scales. Indicate the regions on your diagram occupied by main sequence stars, red giants, supergiants, the Sun. Discuss how the one can determine the radius of a star from its position on the Hertzsprung-Russell diagram - you need not go into great mathematical detail, a short outline of the ideas will suffice.

17. a) Describe how we measure distance using parallax. What is the practical limitation of this technique, and what is the approximate distance (in parsecs) out to which this technique is useful.

b) Describe how we measure distance using "spectroscopic parallax". What is the practical limitation in using this technique, and what is the approximate distance (in parsecs) out to which this technique is useful.

c) How do we use the spectral class and the apparent color of a star to determine the amount of dust and gas (the "crud") that lies between us and the star.

18. Star A and star B have the same apparent magnitude, but star B is twelve times further away than star A. How much more luminous is star B than star A? Suppose that star B also only has half the surface temperature of star A, what is the energy flux from the surface of star B compared to star A? What is the ratio of the radius of star B over the radius of star A.

19. Describe how one can determine the mass of a star when it a) is part of a binary system b) when it is not part of a binary system. Mathematical details are not necessary - I only want you to briefly outline the methods.

20. Describe the complete life cycle of the Sun and plot it on an HR diagram. What is a planetary nebula? What process gives rise to such a nebula? What typically lies at the center of a planetary nebula?

21. The labels, "type I" and "type II," of different kinds of supernova come from observational astronomy and reflect a fundamental difference in their observed spectrum. What is that difference and, for type Ia and type II supernovae, how is it related to the evolution that leads to the supernova explosion? Why are type Ia supernovae so important to distance measurement in astronomy? What are the possible remnants of a type II supernova? Where and in what process were all the heavy metals and rare-earth elements, like gold, created?

22. What is the Chandrasekhar limit in the context of white dwarfs and neutron stars? Give a brief explanation of the result if the mass of the core of a star exceeds the Chandrasekhar limit. Is it possible that one could find a black hole or a neutron star of one (1) solar mass? Is it possible that one could find a black hole or a neutron star of ten (10) solar masses? What happens if you keep adding mass to a white dwarf (be careful here, the answer is not obvious from the context of this question)?

What happens if you keep adding mass to a neutron star?