Astronomy

  1. An exoplanet was discovered to have a mass 0.4 times that of Jupiter and a radius 2.2 times that of Jupiter. The exoplanet orbits a star 1.6 times the mass of the Sun and has an orbital period 4.81 days. a. What is the exoplanet’s density? b. What is its semimajor axis distance to the star? 2. In daylight the Earth surface absorbs 400 Watts per square meter (400 W m-2). Earth’s internal radioactivity produces a total of 30 trillion watts that leak out through our planet’s entire surface. a. Calculate the amount of heat from radioactive decay that flows outward through each square meter (i.e., (W m-2) at Earth's surface. b. Compare quantitatively the heating from radioactive decay to the solar heating. 3. If a Mars-like extrasolar planet transited in front of star that is 1/5th the size of the Sun, by what percentage of the brightness of the star would dim during that transit? 4. Assuming a Galactic star formation rate R* = 20 stars/year, estimate and justify values for each of the terms in the Drake equation, and then combine these for an estimate of the number of intelligent civilizations in the Galaxy.