Phys 1070

 

Astronomy

                         Example Final Exam questions taken from previous exams

        The format and the kind of questions as well as the questions themselves will differ from year to year

 

 

 

Read all questions and instructions VERY carefully.  Write neatly: if I cannot read your answers, it will be very difficult to award any marks.  Please write answers in PEN, preferably a medium to dark texture (pencil is fine for diagrams).  Calculators are permitted.  Your answers are your work: cheating will result in a zero mark on the exam and/or expulsion from the course.  Good luck!

 

 

Part 1: Answer ANY 10.  Brief answers 2 or 3 sentences (generally) at most.  Use diagrams where appropriate.  3 marks each.

 

1.    What direction (be as specific as you can) did the Sun rise today and when (here in Toronto)?  What was its altitude at that time?

2.    State Kepler’s second law and what is its implication on the length of the Earth's day?

3.    Draw the light path followed by light for a Coude telescope.  What advantages does this design of telescope have over a refracting telescope?

4.    If a star rises tonight at 11:00 PM (local time), when will it rise (from the same location on Earth) three weeks earlier?

5.    A star is classified as K5V.  What is its approximate surface temperature, luminosity and visual appearance (colour)?

6.    What phase is the Moon currently at?  What is libration?

7.    What is an eclipsing binary star?  Draw and label a typical light curve.

8.    For the planet Saturn, state (and compare) 4 physical features that are distinctly different from the Earth.

9.    What would the type of spectrum for a A3 I star?  Identify the lines present and comment on the physical appearance of the lines.

10. A star has a parallax of 0.1 arc seconds.  What is its distance from Earth?

11. Energy can be transported by three mechanisms.  What are they?

12. Describe how an aurora is generated.

13. What is a minor planet?  Describe the difference (in location) between a Trojan asteroid and an Apollo asteroid.

14. Describe (with diagrams) how tides are generated on Earth.  Which bodies have the greatest (most significant) tidal force on our planet?

 

 

Part 2: Answer ANY 1.  Write sentences on every other line, to a maximum of 2 pages.  Be clear and concise in your commentary.  Diagrams encouraged.  (15 marks each.)

 

1.    Describe the anatomy of the Sun.  Be sure to include a discussion of the power generation mechanism for our star as well as examples of features to be found in the various layers of the Sun’s atmosphere.

 

2.    Draw the Hertzsprung-Russell diagram.  Be sure to label all axes as completely as you can and highlight the different regions (luminosity classes) to be found within the diagram.  Discuss the differences between differing luminosity classes.  Be sure to place our Sun on this diagram.

 

 

Part 3: Answer all parts thoroughly.  Use diagrams where possible to enhance your answers.  Show all numerical solutions in detail.  20 marks.

 

As an observer from Earth, you are monitoring a nearby open star cluster (yes, it is very beautiful).

 

1. You focus on one particular star in this cluster.  What is the (maximum) aberration angle you can observe for the star? (3 marks)
2. A spectrum of this same star reveals that the star is approaching Earth at 80 km/s.  For a spectral line (at rest) of wavelength 550 nm, what is its observed wavelength in the stellar spectrum? (3 marks)
3. The stellar spectrum reveals that it is single line spectroscopic binary star system.   The orbital period of the stars is 0.15 years and the separation of the stars is .45 AU.  What is the combined mass of the binary system? (3 marks)
4. If one of the stars is a twin to our Sun, what is the mass of its companion in the binary star system? (1 mark)
5. There are 20 stars in the cluster of apparent magnitude 3 and 700 stars in the cluster of apparent magnitude 8.  What is the integrated apparent magnitude for the cluster? (4 marks)
6. This cluster is at a distance of 175 parsecs.  What is its integrated absolute magnitude? (2 marks)
7. How long would it take a radio signal from Earth to reach this star cluster? (2 marks)
8. What is the clusters parallax in radians and arc seconds?  (2 marks)

 

 

THE END.                    TOTAL MARKS: 65

 

 

PHYS 1070

Astrophysics I

Useful Equations and constants

Constants

G = 6.6726x 10^-11 N-m² / kg²                      s = 5.6705 x 10^-8 W m^-2 K^-4

c = 3 x 10⁸ m-sec                                         g = 9.8 m-sec^-2

1 A.U.= 150 x 10⁶ km                                  h = 6.626 x 10^-34 J – sec

Earth Radius = 6371 km                            Earth Mass = 5.974 x 10²⁴ kg

1 parsec = 3.26 light years                                    Sun Mass = 1.989 x 10³⁰ kg

Sun Radius = 6.96 x 10⁵ km                      Sun luminosity = 3.85 x 10²⁶ watts

 

Equations

F = m x a                                                                    F = G x m₁ x m₂ / d²

P² = k x a³                                                                                                   P² = (4 x p²) x a³/ G x (m₁ + m₂)

(m₁ + m₂) = a³ / P²                                                                               Area (ellipse) = p x a x b                           

Perihelion = a x (1 – e)                                           Aphelion = a x (1 + e)

Dl / l₀ = v / c                                                             Dl = l - l₀

1 / S = 1 / P – 1 / E                                                   1 / S = 1 / E - 1 / P

 q = v / c                                                                      D = a x d

d = 206,265 / p                                                         d = 1 / p

g = G x M_earth / R²_earth                                                v² / (2 x g) = R_earth

q = 10⁵ x l / D

l_max = 0.0029 / T                                                      E = h x f

F = s x T⁴                                                                                        L = F x A

Circumference (circle) = 2 x p x R                                    Area (sphere) = 4 x p x R²

L = 4 x p x R² x s x T⁴                                                                      b = L / 4 x p x d²

m - M = -5 + 5 x log (d)                                            m₂ - m₁ = 2.5 x log (l₁/l₂)