Astronomers have discovered planets orbiting other stars; i.
, “extrasolar” planets.
Surprisingly, many of these planets resemble our Jupiter but orbit much closer to their Sun, ~0.
015 to 0.
In other words they orbit ~20x closer to their stars than Mercury does around our Sun.
The temperatures of these “Hot Jupiter” planets can reach 3000 K, whereas in Homework XVI you learned that Jupiter’s temperature is very cold, 150K.
Based on the graph below, would you expect these “Hot Jupiter” planets to retain their hydrogen and helium gases? Why or why not? [HINT: The temperature of 3000 K lies off the edge of this graph.
Using a ruler, you should “extrapolate” the dotted lines to the 3000 K temperature shown on the horizontal axis.
Planetary Surfaces and Atmospheres
Questions #4-5: Surprising Discoveries? Pretend we were to make the following discoveries about the terrestrial planets in our Solar System.
(These are not real discoveries.
) In light of your understanding of planetary geology, decide whether the discovery should be considered reasonable or surprising.
(In some cases, both views can be defended.
) Explain your answer carefully by tracing your logic back to that planet’s fundamental properties.
Such properties might include mass, radius, distance from the Sun, temperature, magnetic field, rotation rate, etc.
A spacecraft mission to Mercury detects vast fields of sand dunes on the surface.
[HINT: What are “sand dunes” and how are they produced?]
A Venus radar mapper discovers extensive regions of layered sedimentary rocks, similar to those found on the Earth.
[HINT: What is a “sedimentary” rock?]
Questions #6-7: Mystery Planet.
It's the year 2098, and you are designing a robotic mission to a newly discovered planet around a nearby star that is nearly identical to our Sun.
The planet is as large in radius as Venus, rotates with the same daily period as Mars (~24.
5 hours), and is located 1.
2 AU from its star.
Your spacecraft will orbit but not land on the planet.
Some of your colleagues believe that the planet has no metallic core.
HOW could you confirm or disprove their hypothesis? What experiment could you conduct while in orbit to infer that the planet has a metallic core? [HINT: What two properties must a planet have in order to make a compass point north?]
Other colleagues believe that the planet formed with few, if any, radioactive elements inside it.
HOW could images of features on the surface confirm or disprove their hypothesis? [HINT: What effects do radioactive elements have inside the planet that can affect the planet’s surface?
This graph shows the speeds of various gases versus temperature.
Round symbols represent the correct temperatures and escape velocities of the planets in our Solar System.