Homework #3 - Peppy the Proton (Part 2)

due Monday July 29

When we last left Peppy the proton, she had been blown out into space as part of the supernova that ended the life of a large, massive star. However, the shock waves carrying Peppy out from the supernova compressed nearby gas in the Interstellar Medium, and started the gravitational collapse of some of this gas to form new stars. In this second star, however, Peppy was near the center of activity, and was fused together with her neighbors - first to a Helium nucleus, and then in a later stage this nucleus was fused with 2 others to make one Carbon nucleus. This massive star also went supernova, returning these new elements to the cold of interstellar space... Peppy had had enough. This cycle of fusion and explosion was getting to her - she wanted to find someplace nice to settle down for a while. So, as part of a carbon atom, she found a smaller group of friends that began collapsing in a cloud to make a low mass (long-lived) star. But something different happened this time - rather than ending up in the star, she ended up as part of a planet! There were two main types of planets orbiting around the star: small rocky ones and large gassy ones.

  1. What are the differences between these two types? Explain how astronomers think that these two types formed.

  2. Last October, the first planet orbiting a sun-like star was detected around the star 51 Pegasus. Since then, half a dozen other planet detections have been made. Astronomers are finally able to start testing their ideas about how planets form. The following are 3 examples of recently discovered planets (all around stars of ~1 solar mass). 

    Star name	Planet Mass(in MJupiter)	Planet Distance (in AU)
51 Pegasus		1.5 				0.05 
47 Ursa Major		2.3 				2.3 
70 Virgo		6.5 				0.43
    From the limited amount of information here, which type of planet do you expect each of these to be? Why? Comment on how this information agrees or disagrees with the theory you presented in question #1. If you think the theory is broken, speculate on how it might be fixed.
Peppy was trapped as part of a small rock, which accreted into the 3rd planet from the star (our Sun). Later, as more accretion occurred and the planet heated and differentiated, she was vented into the atmosphere as part of a molecule of carbon dioxide (CO2).
  1. Describe how the initial atmospheres of terrestrial planets form. Why do we expect that Venus, Earth, and Mars started with similar atmospheres?
Over time, the atmosphere in which Peppy resided changed. And when she communicated with carbon atoms on other planets, she found that the conditions there were wildly different from where she lived.
  1. Describe how the atmospheres of Venus, Earth, and Mars evolved into what they are today. Clearly explain any scientific theories you use in your description. (Hint: Think about the effects of distance from the sun, size, greenhouse effect, existence of water, existence of life, composition, etc...)
Peppy stayed in the atmosphere of the Earth for many years, until ... (to be continued)

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