Censor.NET reports citing BBC.
The researchers say that all seven could potentially support liquid water on the surface, depending on the other properties of those planets.
Three of the Trappist-1 planets fall within the traditional habitable zone definition, where surface temperatures could support the presence of liquid water - given sufficient atmospheric pressure.
Lead author Michaël Gillon, from Belgium's University of Liège, said: "The planets are all close to each other and very close to the star, which is very reminiscent of the moons around Jupiter. Still, the star is so small and cold that the seven planets are temperate, which means that they could have some liquid water - and maybe life, by extension - on the surface."
The planets were detected using Nasa's Spitzer Space Telescope and several ground-based observatories.
Astronomers claim the planets are relatively close to the Earth, noting however a journey there on a jet plane would take about 40 million years.
Until now, scientists have discovered a few dozens of planets that are considered to be Earth's twins.
Meanwhile, no evidence of life on these planets has been revealed.