CEN 511: Recent Discoveries in Astronomy

1. Prepare a table in which you list the period $P$ and semi-major axis $a$ for each planet. The semi-major axis is the mean distance from the planet to the Sun, and the period is the length of the planet's year. Use units for the period in terms of Earth-years, and semi-major axes in Astronomical Units. In a third column in your table, calculate the ratio of the cube of the semi-major axis to the square of the period, in other words the quantity $a^3/P^2$. You should find that this ratio is almost the same for each planet. What is this telling you?
2. What was Newton's major contribution in terms of understanding the dynamics of the solar system, i.e., how the planets orbit?
3. Do a search to find out how Eratosthenes determined the size of the Earth. Be prepared to answer a question about his method.
4. Do a search to find out the extent of the Oort Comet cloud. About how many comets is it estimated to contain? About how much mass, compared to the Earth's mass, is it suspected to contain?
5. What is the difference between a Trojan asteroid and an Apollo asteroid? Which should be be more concerned about?
6. What solar system objects are connected to certain types of meteorites and are thought to be the birthplace of these meteorite types?
7. When the Moon was formed, it could have been as close as just outside the Roche limit of the Earth. If so, what was the strength of its tidal interaction with the Earth compared to today? I.E., how many times stronger were tides then compared to today?
8. How can the lack of iron-loving elements and the lack of water (and other volatile materials) on the Moon be explained?
9. How can the relatively large iron concentrations of the planet Mercury be explained?
10. Using a dime for Mercury and a quarter for the Sun, demonstrate to yourself how the length of one Mercury day is equal to two of its years. Remember that in the period that it takes Mercury to orbit the Sun once, it spins on its axis 1 1/2 times. First, you have to define what the term "day" means. What is this definition?