The 7 Planets of TRAPPIST-1 Have Surprisingly Similar Properties

Astronomers are getting very good at hunting for exoplanets with a little help from powerful ground and space-based telescopes. We're no longer finding one planet here and there -- we're discovering entire solar systems. TRAPPIST-1 has been of particular interest with its system of seven planets, discovered in 2016 and 2017. A new study has confirmed that all these planets are small and rocky like Earth, and they're all surprisingly similar to each other.