PURPOSE: to discuss the energy production and structure of the Sun, as well as solar phenomena

MATERIALS: calculator, ruler, Sun images

INSTRUCTIONS: complete your prelab, print out these pages, and complete the activities below

2.1. (2 pts) In stars, which element is converted into which element via the proton-proton chain reactions?

2.2. (3 pts) Use the set of proton-proton chain reactions in your lab text to explain why the Sun is still 79%
hydrogen by mass even though it is constantly converting hydrogen into helium via fusion.

2.3. (3 pts) The mass difference between the initial hydrogen atoms and a resulting helium atom during fusion is
0.048 x 10^-27 kg. Use Einstein’s equation (with c = 3.0 x 10⁸ m/s) to find the amount of energy this produces.

This may seem like only a tiny amount of energy coming from the creation of one hydrogen atom. However, it is
in fact about 10 million times larger than the amount of energy released in a typical chemical reaction like ordinary
burning. The proton-proton chain reaction inside stars is about 99% efficient. In other words, for each kilogram of
hydrogen that goes into the reaction, only 0.993 kilograms of helium come out. Thus, this process explains just
how the Sun has been shining for billions of years and will likely shine for another 5 billion or so.

2.4. (3 pts) The Sun has a radius of R = 6.96 x 10⁸ m and a luminosity of L = 3.9 x 10 ²⁶ kg m² / s³. What is
the Sun’s surface temperature (in Kelvin) ?

2.5. (3 pts) Use the relationship, F = [ (9/5) (K – 273.15) ] + 32, to calculate the Sun’s temperature in °F.

2.6.   Use the data table and that the Sun’s luminosity is L = 4 x 10²⁶ W to answer the following questions:

3.1. (1 pt) List the three layers of the Sun's interior (starting with the innermost).

3.2. (1 pt) List the three layers of the Sun's atmosphere (starting with the innermost).

3.3. (6 pts) Match each of the layers of the Sun below with its corresponding temperature.

a) core    __________

**EXPERIMENT**
Examine images of the Sun to learn more about solar phenomena.

4.1. (3 pts) Look at this image of the Sun or the class Image #1. List and briefly describe (shape, color, size, etc.) at
least 3 different solar phenomena you see.

4.2.   Obtain class Image #2 (close-up of sunspot) from the TA.

a) (1 pt) Measure the width of the sunspot, excluding the outer dark orange region.     ________________ mm

b) (3 pts) In this image, 1 mm corresponds to 1470 km. How big is this sunspot in kilometers?

4.3. (3 pts) The typical size of a sunspot is 15,000 km, (= 9312 miles). The average width of Florida’s peninsula is
125 miles. How many Floridas could fit into a typical sunspot?

4.4.   Obtain class Image #3 (shows a solar flare) from the TA.

a) (2 pts) Measure the diameter of the Sun (in cm):

4.6. (4 pts) If we could watch long enough, a sunspot would appear to slowly move across the surface of the Sun. In a
matter of only minutes or hours, however, its movement is too small for you to see. Experiments indicate that a typical
sunspot at low to average solar latitude will move about 0.28° in 30 minutes. We can estimate the rate of solar rotation
for that solar latitude with the relationship, P = 360 ΔT / ΔL, where ΔL is the approx. degrees the sunspot moved, ΔT
is the time you watched the sunspot move, and P is the solar rotation rate at the latitude of the sunspot. Use all of this
information to calculate the period of solar rotation in days. (HINT: use the given equation to get the answer in minutes
and then convert to days)

-------------------------------------------------
**EXPERIMENT**
Now we will better understand the vast size of solar features.

Open this page with the images of a solar prominence over time. Once loaded, place the mouse cursor anywhere
on the image and watch the horizontal box at the bottom of your internet browser. Notice that after the webpage
address, there are two numbers (X,Y) that change as you move the mouse. This tells you the position of the mouse
cursor on the computer screen (in pixels). You will use this "mouse ruler" shortly.

NOTE: you can also use class Image #4 to answer question #4.7

4.7. (1 pt) How long (in hours) did it take the prominence to reach its full height (image 4 - image 1)? [Hint: first
find the time in hours and minutes separately, and then convert this to hours in the form of xx.xxx hours]

4.8.   Examine the first image of the whole Sun (labeled 01:18 UT).

a) (2 pts) Place your mouse cursor at the leftmost edge (i.e., a position of X,Y = 21,70) of this image. Then,
keeping Y = 70, place the mouse cursor at the rightmost edge of the Sun. Record the new X coordinate below
and calculate the difference:

left X = 21        right X = ______      diameter D(pix) = right - left = __________ pixels

b) (3 pts) Now find the image scale (S) by dividing the Sun's real diameter, D_SUN = 1.4 x 10⁶ km, by your
answer for D(pix) in part a) above. (Note: your result should have units of km / pixel)

4.9. (2 pts) Now look at the close-up image (picture just below the 01:18 UT label) of the prominence. The
height of the prominence here is 39.1 pixels. Multiply this by the image scale (S) you found in #4.8b to find the
minimum prominence height (in km).

4.10. (2 pts) Now look at the close-up picture just below the image labeled 16:07 UT. The height of the
prominence here is 58.6 pixels. Use the same method as in #4.9 to find the maximum prominence height (in km).

4.11. (1 pt) Find the growth of the prominence (in km) by subtracting the minimum height (#4.9) from the
maximum height (#4.10).

4.12.   A basic physics equation, v=d/t, can be used to find the velocity (v) of this prominence.

a) (3 pts) Use the time (t) from #4.7 and the growth (d) from #4.11 to find the prominence velocity (km/hr).







b) (2 pts) A typical car on the highway travels about 100 km/hr. How many times larger is the prominence
speed compared to this?

-------------------------------------------------
**EXPERIMENT**
In this experiment we will observe the Sun at the telescope (weather permitting).

At this point, your TA will direct the class to head outside. Print out a "Telescopic Solar Observing" sheet first.
Because of its harmful UV rays, the Sun must be observed through a telescope with a special filter. Make sure you
only observe the Sun after the lab manager and/or your TA says it is okay to do so. NEVER LOOK DIRECTLY
AT THE SUN WITH JUST YOUR NAKED EYE ... YOU CAN CAUSE PERMANENT DAMAGE.

4.13. (12 pts) Observe the Sun through the telescope and complete your "Telescope Solar Observing" sheet.
Be sure to turn in this page with the rest of your lab activities.





* TURN IN THESE ACTIVITIES PAGES TO YOUR TA*  

Astronomy Home                                    Physics Home

This web page created and maintained by Andrea Folcik