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Instructor: Z. Kaymaz
Faculty: ITU, UUBF
Given :06/03/2017
Due :15/03/2017
(5)(a) Calculate the required time for each of the following to travel the Sun-Earth distance and compare them.
visible light produced in the photosphere (give your answer in minutes)
x-rays from a flare (give your answer in minutes)
Solar wind particles traveling at 400 km/s (give your answer in days)
A CME moving with a velocity of 1500 km/sec (give your answer in days)
A jet aircraft traveling at 220 m/s (give your answer in years)
(5) (b) It takes a photon produced at the center of the Sun to reach the surface about 2x105 years. How long does
it take this photon to travel the same distance in free space? Explain why these two differ by such a large factor.
(5) (c) A new red dwarf star system called TRAPPIST-1 was discovered in late 2015. It has 7 planets with the
possibility of holding water and habitable conditions. TRAPPIST-1 was found to be away from Earth about 40 light
years. Calculate:
(i) how long it will take for a jet plane with a velocity of 220 m/s to reach to the star system.
(ii) how long it will take for a radio light (signal) to arrive to the star system?
------------------------------------------------------------------------------------------------------------------------------Q.2. THE SUN (25 points)
(5) (a) How much mass is converted to energy in kg as a result of one fusion reaction in the core of the Sun? (ans.
4.84x10-29 kg per reaction to produce 1 Helium atom)
(5) (b) How much energy is produced from one fusion reaction in the core of the Sun? (ans: ~4.32x10-12 joule per
(5) (c) How many reactions would have to occur each second to produce the solar power output of 3.9x1026 Watts,
which is the total energy output of today’s Sun per second? (ans. 1x1038 reactions/sec). 1 Watt=1 Joule/sec.
(5) (d) Calculate the total mass which should be burned/lost in one second? (ans: 6.68x1011 kg/sec)
(5) (e) Assume that the present processes within the Sun will continue (not true) and the hydrogen is present only
within the core region. Estimate how long the Sun can last if it is losing mass at the rate you found in part (5) (d).
Assume that the density is distributed uniformly within the Sun. (ans.: ~1x109 years).
------------------------------------------------------------------------------------------------------------------------------Q.2. SOLAR WIND AND SOLAR ACTIVITY (30 points)
The mean distance from the Sun to Mercury, Venus, Earth, Mars and Jupiter are 0.39, 0.72, 1.0, 1.5, and 5.2 AU.
Assume that the density, solar wind speed, total magnetic field, and temperature at the base of the corona are
20x104 #/cc, 450 km/sec, 2,5x106 oK, radial (Br) component of magnetic field is 5 Gauss. Ignore the azimuthal
component of the Sun’s magnetic field and assume that the total magnetic field of the Sun is equal to radial
component. Using these values,
(a) Calculate the value of solar wind parameters shown in the Table below at each of these planets. Show all steps
in your calculations and also fill in the Table. Assume the base of corona is the surface of the Sun.
(b) Make a plot of total magnetic field (Btot), number density (n) and temperature (T) with distance (in AU) to show
how these parameters change with distance in space.
(c) Compare the Solar Wind Pressures (Pdyn, Pgas, Pmag) at the Earth’s orbit? Which pressure is dominant?
Speed (Vsw) (km/s)
Density (n) (#/cm3)
Btot (nT)
T (oK)
Pdyn (nPa)
Pgas (nPa)
Pmag (nPa)
-------------------------------------------------------------------------------------------------------------------------------------------------------Q.3. Search Question/Brain Storm:
a. What are Kuiper belt and Oort cloud?
b. What is the structure of a Comet? Can we say that comets have atmospheres? Why and how?
c. What are the differences between comets coming from Kuiper Belt and Oort Cloud and observed from Earth?
1. Homeworks returned after due date will not be accepted.
2. Homeworks are not accepted by e-mail.
3. Scanned homeworks are not accepted.
4. Use your handwriting. Do not use computer outputs unless it is specified.