Download Candidate`s registration number: Desk number: ………………….. Date

PHY111
DEPARTMENT OF PHYSICS AND ASTRONOMY
Autumn Semester 2014-2015
2 hours
OUR EVOLVING UNIVERSE
Answer ALL questions in Section A, and THREE questions in Section B.
You should spend roughly an hour on each section.
Answer Section A in the spaces provided on this paper, answer Section B in
an answer book.
At the end of the examination, tie this paper to your answer book for Section B
and hand them in together. Remember to fill in your registration number from
your UCard in the space below.
If you attempt additional questions in Section B, please indicate clearly on the
cover of your answer book which questions you wish to be examined on, and
cross out any work you do not wish to have assessed.
Candidate’s registration number:
Desk number: …………………..
PHY111
Date: …………………….
1
TURN OVER
PHY111
SECTION A
Answer ALL questions. 45 marks are available in this Section.
Write your answers in the spaces provided.
A1. Give TWO reasons why the mountains of the Atacama desert in Chile are
a good place to build large telescopes.
[2]
A2. In what part of the electromagnetic spectrum would it be best to observe
an M star? Briefly explain your choice.
[2]
A3. A star is observed to have lines of ionised helium in its spectrum. Could
this star be older than the Sun? Briefly justify your answer.
[3]
PHY111
2
CONTINUED
PHY111
A5. Make a careful drawing of a Hertzsprung-Russell diagram. Mark on it the
position of the main sequence and the Sun. Indicate the three giant branches
that the Sun will visit after the main sequence.
[8]
A6. A young star of a Solar mass has a dense disc around it. Give ONE way
in which this star will appear different from the Sun. Why are these discs of
great interest to astronomers?
[2]
PHY111
3
TURN OVER
PHY111
A7. In the context of star clusters, what is the turn-off mass and how can it be
used to age a cluster?
[4]
A8. A star doubles its temperature while its radius decreases by a factor of
four. By what factor does its luminosity change?
[1]
A9. What are the main elements found in a typical white dwarf?
[2]
A10. State any TWO properties of a globular cluster.
[2]
PHY111
4
CONTINUED
PHY111
A11. Make a careful drawing of the basic structure of the Milky Way galaxy
and indicate the main stellar components.
[4]
A12. Make a careful drawing of the rotation curve of a galaxy like the Milky
Way. Indicate how we would expect the rotation curve to look if the only
matter present was stars and gas.
[4]
PHY111
5
TURN OVER
PHY111
A13. Give a quick and simple observation that could distinguish between an
unresolved elliptical and spiral galaxy. Why would this observation distinguish
them?
[3]
A14. M82 and NGC1672 are both similar spiral galaxies with significant
amounts of star formation. M82 looks red, but NGC1672 looks blue. Give
ONE plausible reason for this difference.
[2]
A15. What are the units of the Hubble Constant? Why are they so strange?
[3]
A16. What is the cosmic microwave background? [1]
PHY111
6
CONTINUED
PHY111
A17. What were the main two elements formed after the big bang and in what
proportions?
[2]
END OF SECTION A
Turn over for Section B.
PHY111
7
TURN OVER
PHY111
SECTION B
Answer THREE questions. All questions are marked out of 15.
B1. Discuss blackbody (continuum) radiation, emission lines, and absorption
lines in astronomy. What are they, what produces each of them, and what
can they tell us?
[15]
B2. Discuss the death of stars and the origin of the chemical elements.
[15]
B3. Discuss in detail the structure and composition of the Milky Way.
[15]
B4. Compare and contrast spiral and elliptical galaxies.
[15]
B5. Briefly describe the Big Bang theory for the origin of the Universe.
[15]
END OF QUESTION PAPER
PHY111
8
CONTINUED