The University of Liverpool


THE UNIVERSITY
of LIVERPOOL





SUMMER 2000 EXAMINATIONS

Bachelor of Science: Year 1

Bachelor of Science: Year 2

Master of Physics: Year 1

Master of Physics: Year 2

ASTRONOMY FUNDAMENTALS

 

 

TIME ALLOWED: 1 hour 15 minutes


INSTRUCTION TO CANDIDATES

Answer both questions.

The questions carry equal marks.


The marks allocated to each part of a question are indicated in square brackets.

In the event of a student answering both parts of the either/or question and not clearly crossing out one answer, only the answer to part (a) of the question will be marked.

1. Answer all parts of this question:

 

  1. Describe, with the aid of a sketch, the equatorial co-ordinate system. What defines the Ecliptic? [5]

    2.  

  2. The La Palma Observatory in the Canaries lies at a latitude of 280 North. A star is observed to have an Hour Angle of 2h 10m when the Local Sidereal Time is 7h 50m. When it transited the Meridian, its altitude was observed to be 400. Calculate the RA and dec of the star. [5]

    3.  

  3. Briefly describe how energy is generated and transported in the Sun. [5]

     

  4. A Population I Cepheid variable in an external galaxy is observed to have a period of 25.5 days and a mean apparent visual magnitude of 20.2. If the period-luminosity relation for these stars is given by:

    5. <MV> = -2.8 log10 P - 1.4

    hence find the distance to this galaxy in Megaparsecs.

    State why the original use of Cepheid variables led to an error in the estimation of the distance to M31. [5]

     

  5. Briefly describe why it is currently believed from direct observational evidence that there is a significant amount of "dark matter" in the Universe. What is the importance of this hypothesis to cosmological models? [5]

2. Answer either (a) or (b):

  1. Briefly describe the currently favoured theory of the formation of the Solar System. How does this account for some of the major physical features of today’s Solar System? [12]

    What are the Oort Cloud and Kuiper Belt? What is the evidence for their existence? [6]

    State Kepler’s Laws of planetary motion. Jupiter has an orbital period of 11.86 years. Calculate the value of the semi-major axis of its orbit around the Sun in Astronomical Units. [7]

     

     

    2. Or:

     

     

  2. Describe the post-main-sequence evolution of a star like the Sun. Include in your answer some details of the stages of nuclear burning and a sketch of the HR diagram with the most important phases of evolution of such a star clearly marked. [15]

    A cluster observed to lie in the Galactic Bulge contains 105 stars. The most luminous stars still on the main sequence have a luminosity L=1.5Lsun. What is the approximate mass of these stars in solar masses? Estimate the age of the cluster in terms of the main sequence lifetime of the Sun. Briefly describe the two types of star cluster found in our Galaxy and state, with reasons, which type of cluster this is most likely to be. [10]

     

    3. End