THE SOUTHWORTH PLANETARIUM
207-780-4249   www.usm.maine.edu/planet
70 Falmouth Street   Portland, Maine 04103
43.6667° N                   70.2667° W 
Altitude:  10 feet below sea level
Founded January 1970
Julian date: 2458759.5
2019-2020:  XXIV
                  "I have loved the stars too fondly to be fearful of the night."
                                     -Sarah Williams

THE DAILY ASTRONOMER
Friday, October 4, 2019
Quiz V: The Sun!

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Our "quiz-journey" through the solar system and then beyond continues.   
Quiz I pertained to the moon.  Quiz II was related to the inferior planets.  We then diverted course during the following two quizzes.   Now, at quiz V, we arrive at the Sun!   What can be said about Sol that hasn't been said?    The less said the better, of course, especially as any information contained within the introductory paragraph could provide immensely helpful material for anybody taking this quiz.

Today, as we enjoy a drizzly, dark and dreary day tucked away in the pancreas part of New England, we celebrate the Sun, wherever it may be.


1.  How many Earth-sized spheres could fit inside the Sun?
a.  230,000
b.  514,000
c.  1.2 million
d. 2.8 million

2. What is the Sun's rotation period?
a. 27.4 days
b. 28.9 days
c. 38 days at the equator; 24.5 days at the poles
d. 24.5 days at the equator; 38 days at the poles

3. The Sun formed with many other stars, perhaps more than a thousand.  They were all part of a galactic cluster that slowly dissipated. How many of these "sibling stars" have astronomers identified so far?
a. none
b. 1
c. 2
d. 4

4. The Sun -and its attendant bodies- revolve around the galaxy at about 143 miles per second.  How long (approximately) does the Sun require to complete one orbit around the Milky Way?
a.  140 million years
b.  187 million years
c.  225 million years
d. 410 million years

5. The Sun, like other stars, emits radiation along all the wavelengths of the electromagnetic spectrum.  Each star also has a "peak wavelength," at which the Sun produces its maximum amount of radiation.  Along which part of the EM spectrum is the Sun's peak wavelength?
a.  in blue-green section
b.  in the near ultra-violet
c.  in the yellow section
d.  in the infra-red 

6.  What is the name of the solar probe NASA launched in 2018 that will come closer to the solar surface than any other spacecraft?
a. Webb Solar Probe
b. Parker Solar Probe
c. Huygens Solar Probe
d.  Helios 4

7.  The Sun is currently fusing hydrogen into helium in its core.    Approximately how much hydrogen is fused each second?
a.  110 million tons
b.  222 million tons
c.  415 million tons
d.  647 million tons

8. How long will the Sun's core hydrogen supply last?
a. 450 million years
b. 2.3 billion years
c. 5 billion years
d. 10 billion years

9. When will the Sun explode as a supernova?
a.  5 billion years from now
b.  6.5 billion years from now
c.  10 billion years from now
d.  It never will. 

10.  How distant is the nearest "Sun-like" star?  (Here defined as being spectrally similar and without any stellar companion.)
a.  12 light years
b.  23 light years
c.  34 light years
d.  45 light years

ANSWERS

1. c.  1.2 million
The Sun is enormous.  It accounts for more than 99% of all the matter within the solar system.  The rest of the material, including the planets, are merely afterthoughts.     It is the furiously hot furnace imparting copious energies on its attendant worlds. 

2. d. 24.5 days at the equator; 38 days at the poles
The Sun isn't solid and therefore rotates differentially:  the rotation speed depends on latitude.  The Sun's gases are rapid movers along the equator, but are more lethargic at either pole.

3. c. 2
 HD 162826 in Hercules and HD 186302  in Pavo
Astronomers expect to find many more of the Sun's siblings by examining stars with similar chemical compositions and orbital trajectories.

4. c.  225 million years
A "galactic year" is the time the Sun requires to complete one orbit around the Milky Way Galaxy.   This precise duration is uncertain.  Astronomers estimate, however, that the galactic year is about 225 million years long.     By this standard, one could say that the non-avian dinosaurs were Earth's dominant life forms a year ago.    

5. a.  in blue-green section

wien.gif

Wein's displacement law relates a star's "effective" temperature and the wavelength of its peak emission.    The Sun's peak wavelength is around 500 nanometers, within the blue-green section of the EM spectrum.   NOTE:  The Sun isn't yellow!    If seen in space it would actually appear to be white.  The yellow coloring is a result of atmospheric light scattering.  

6. b. Parker Solar Probe
Launched in August 2018, this probe will make 26 perihelion passes during its mission.  At closest approach, it will come within 4.3 million miles of the solar core, almost nine times closer than Mercury's average distance.      

7. d.  647 million tons
The Sun fuses hydrogen into helium.    In the process, some of the original hydrogen is converted into energy.     

8. c. 5 billion years
This hydrogen depletion won't destroy the Sun. Instead, the Sun will be powered by core helium fusion reactions.    Long before the Sun exhausts its hydrogen reserves, it will become far too hot to sustain life on Earth. 

9. d.  It never will. 
The Sun is not nearly massive enough to explode as a Type II supernova. Only stars at least nine times as massive as the Sun will end their life cycles as supernovae.

10.  a.  12 light years
Although it is about 78% as large as the Sun, Tau Ceti is the nearest of the "Sun-like" stars, or those that have a similar chemical composition.      Five planets are known to be in orbit around Tau Ceti. Two of these worlds revolve within the star's habitable zone, making them of particular interest to alien-seeking astronomers

Compare_sun_tau_ceti.png
The Sun and Tau Ceti.  Our star is to the left and Tau Ceti is to the right.
In this artistic depiction, we can readily observe that Tau Ceti is the smaller of the two stars.


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