Seven rocky planets of TRAPPIST-1 might be similar but they aren’t the same: Study

They have interest researchers since 2017 when it was discovered that three of the seven planets are located in the theoretical "habitable zone".

from http://www.firstpost.com/tech/science/seven-rocky-planets-of-trappist-1-might-be-similar-but-they-arent-the-same-study-9239551.html