Before the discovery of Gliese 581, these planets were the smallest extrasolar planets yet detected and the first of a new class of rocky terrestrial planets.

The planet orbiting Gliese 876 has a minimum mass of 5.9 Earths and is 7.5 times Earth’s size. The super-Earth orbits 2 million miles from its star - or 18 times closer than mercury orbits our Sun - and completes an orbit every 1.94 days. This super Earth’s surface temperature is probably between 400 and 750 Fahrenheit (200 and 400 Celsius)

It is intermediate between a true terrestrial planet like the Earth and a hot version of the ice giants Uranus and Neptune.

This planet is also important in relation to the alternate formation concept outlined in the later sections of this website.