The Kepler team recently announced the detection of five stars, each with multiple transiting planets (Steffen et al, 2010). The left Figure below shows the Quarter 1 (Q1) light curve for the star SPH10102031 (Kepler ID 10723750) with two transit dips from two different planets. The transits do not repeat because the orbital periods are longer than the time baseline. The first transit dip is from a planet that is about the size of Jupiter. To highlight the typical boxy shape of a planet transit curve, we have zoomed in on the second transit event in the Figure below and on the right. The depth of the transit is about 0.25% and given the assumed radius of the star, the planet radius is about 7.6 times the radius of the Earth (larger than Neptune, but smaller than Jupiter).
Light curves for two other stars in the Steffen et al 2010 paper are shown below. The Figure on the left is the Q1 light curve for SPH10120491 (Kepler ID 8394721). This light curve contains transit dips from three different planets! One of these is very obvious and is caused by a planet that is 6.5 times the radius of Earth that only transits once during the 35-day light curve. However, there are two other transiting planets that are harder to see with radii of just a few times that of the Earth. One of these planets transits every 13.5 days and the other transits every 27.4 days.
The Figure above and to the right shows the light curve for SPH10017624 (Kepler 5972334). There are three transit dips from a Jupiter-sized planet that orbits every 15.4 days. In this Figure, it is virtually impossible to see the second planet, which has a radius just twice that of the Earth and transits every 2.4 days.
To get a better look and some practice (you won’t be able to save these), pull up these amazing light curves and use the zoom tool to identify the transits.