Gliese 581 c （格利澤581 c）ESI: 0.70

Gliese 581 c or Gl 581 c is a planet orbiting the red dwarf star Gliese 581.It is the second planet discovered in the system and the third in order from the star. With a mass at least 5.6 times that of the Earth, it is classified as a super-Earth (a planet of 1 to 10 Earth masses). (From Wikipedia)

Assuming that the planet's mass is close to the lower limit determined by radial velocity measurements (the true mass is unknown), it was the smallest known extrasolar planet around a main sequence star, but on April 21, 2009, another planet orbiting Gliese 581, Gliese 581 e, was announced with an approximate mass of 1.9 Earth masses, which is now the smallest known extrasolar planet around a main sequence star. (From Wikipedia)