1) The mass of Jupiter. Use the period and semi-major axis of the orbit of Jupiter's moon, Io. See the chart of Io's orbit on the next page to get the data. Remember to convert kilometers into AU and days into years. (There are 150,000,000 km in one AU and 365.25 days in one year.) Data: a= =90,000 km == _AU) / ( _ yr) (0.0026 AU) /(0.075 yr) How many Earth masses is Jupiter's mass? AU P = 2 days Mass of Jupiter Mass of the Earth yr