What have we learned about TRAPPIST-1 during this last year?

Just a year ago, on the 22 February 2017, at a press conference at NASA headquarters, an international team of researchers revealed the existence of a unique exoplanetary system, made up of seven planets orbiting a small nearby star. Known as TRAPPIST-1, this system created a hug buzz on the Web, in the media, and within the scientific community. Discovered a few months earlier by researchers from the University of Liège, led by the astronomer Michaël Gillon , TRAPPIST-1 quickly became a reference in the study of exoplanetary systems.  Review of a major scientific discovery.

Thirty years ago, the study of planets outside the solar system was restricted to science fiction writers. ...