Answer Happy

3) So far, things look promising for our new planet. Next, we want to determine if this planet is a gas giant or a terrestrial planet. We can determine the composition of the planet if we know its density, since planets like Jupiter and Saturn are less dense than planets like Earth. To determine the density of the planet, we need its mass (which we have from the previous step) and its radius. We can determine the radius of the planet using the Transit technique. Figure 2 shows the brightness of HD20945 versus time. When our planet moves in front of HD20945 it blocks some of its light, leading to a dip in brightness. The fraction of light blocked depends on the size of the planet and is given by the following equation: 2 fp (Rplanet Rstar

K-type stars are typically 100 times the size of the Earth (Rstar = 100 REarth). Measure the fraction of light blocked in Figure 2 and use the above equation to determine the radius of the planet, Rplanet, in units of Earth radii, REarth- Figure 2 1.0 0.9999 Brightness 0.9998 0.9997 0.9996 Time