Here's an interesting video on the Trappist-1 system.
Trappist-1 is a red dwarf star about 40 light-years away from Earth.
There are seven planets which orbit this star, all of their orbits are much closer than Mercury's but because the star is cool and a dwarf, several of these exoplanets inhabit the 'Goldilocks Zone', and so may harbour life.
Interesting …