Multiple (Doppler) planet systems, ordered by host star mass (indicated at left with size proportional to M _⋆ , ranging from 0.31   M_⊙ for GJ 581 to 2.8   M_⊙ for BD +20 2457). Each planet in the system is shown to the right, with sizes proportional to log M_p (ranging from about 0.01−20   M_J). Horizontal bars through the planets indicate maximum and minimum star-planet distance based on their eccentricities.