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PHYS0003/PHYS1650 - Nature of the Universe

Assignment 3

Due date: 5:00pm, March 31, 2016Please submit to the assignment box in   first floor  of CYMP Buld.

Give answers and explanations for the following questions.

1. (10 marks) (a) If the Moon did not exist, would there still be tides onEarth?(b) If there were two moons, which were always on the opposite sidesof the Earth, would there still be tides on Earth?

2. (10 marks) The surface gravity of a planet is proportional to its mass,but inversely proportional to the square of its radius:

surface gravity = GM 

R2   (1)

where  G   is the gravitational constant. What are the ratios of surfacegravities of Mercury, Venus, Mars and Moon to that of the Earth?

3. (10 marks) Mars was at opposition on May 22, 2016. What is opposi-tion?

4. (10 marks) What would happen to the average surface temperature of the Earth if the Earth were moved to the Mars’ orbit?

5. (10 marks) Does Jupiter possess any magnetic field? How do you know?6. (10 marks) (a) When the probe Philae landed on comet 67P/C-G,

roughly how many A.U. was the comet away from the Sun?(b) What would happen to the probe if the comet was too far away?

7. (20 marks) Describe the sunspot cycle. Which year was the last solarmaximum, and which year will be the next?

8. (10 marks) (a) Look up the typical thickness and temperatures of thefollowing regions of the Sun: (i) chromosphere; (ii) core; (iii) photo-sphere. (b) How can we detect the differential rotation of the Sun?

9. (10 marks) Stars A, B and C are at the same distance to us. Star A’sapparent magnitude is 4.(a) If the luminosity of B is 500 times brighter than A, what is theapparent magnitude of B?(b) If Star C is 1400 times fainter than A, what is the apparent mag-nitude of C?

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10. (10 marks) The luminosity of star A is three times of star B, however,distance of star A from Earth is also three times larger than that of star B. Which one looks brighter when observed on Earth? What isthe difference in absolute magnitudes between the two stars?