When astronomers found the first giant planets with orbits of only a few days, they did not know whether those planets were gaseous and liquid like jupiter or rocky like mercury. the observations of hd 209458 settled this question because observations of the transit of the star by this planet made it possible to determine the radius of the planet. use the data given in the text to estimate the density of this planet, and then use that information to explain why it must be a gas giant.