Astronomy Assignment: Planet Formation and Earth's Core - Spring 2009, Lab Reports of Astronomy

Download Astronomy Assignment: Planet Formation and Earth's Core - Spring 2009 and more Lab Reports Astronomy in PDF only on Docsity! PTYS/ASTR 206 – Section 1 – Spring 2009 Activity #8: 2/24/09 NAME:_________________________________________________________________ #1. (a) Early in their formation, the dominant forms of energy that heated the planets were accretion and chemical differentiation. Both of these involve the conversion of gravitational energy into thermal energy. Based on this, which planet at the right would you expect to have the highest internal temperature shortly after formation? Planet A – it has the largest gravitational energy (which then is converted to kinetic, and then thermal energy) (b) Which of the two planets would you expect to cool the most rapidly? Why? Planet B – it is the smallest, so it will cool the fastest (c) The third energy source discussed in class is through the decay of radioactive elements within the planet. The amount of heating depends on how much material there is. Assuming that the two planets above have the same composition, which one will have the highest heating rate. Planet A – it has the largest mass, hence more radioactive material, hence more heating. (d) Finally, what is the most important factor in determining how active a planet’s interior is likely to be, and how long it is likely to stay active? (Circle one) A) The object’s distance from the Sun. B) The object’s composition. C) The object’s size #2. Why are scientists so certain that part of Earth’s core is liquid? They have analyzed seismic waves, particularly the seconday wave (or S wave, or shear wave). They have found a region on the opposite side of the Earth from the origin of each earthquake where the S-waves are not seen – this is the so-called shadow zone. They know that S-waves cannot move through liquid, and hence, are able to tell that Earth’s interior is partially liquid, and can even tell how big this region is.