NASA has announced the discovery of seven exo-planets orbiting a star less than 40 light years from Earth. The most striking part of this discovery is that these exo-planets, about the size of Earth, could have water and an environment suitable for life sustenance.
Exo-planets are planets that orbit stars outside our solar system. Our solar system has Sun as our star around which Earth and other planets orbit. Similarly, TRAPPIST-1 is a star that is orbited by seven exo-planets that NASA has discovered. These exo-planets have not really been named but listed from b to h, wherein a is the star TRAPPIST-1 itself.
The first exo-planet was discovered about two decades ago. Since then, more than 3500 exo-planets have been discovered out of which about 600 have been confirmed.
Out of the seven exo-planets discovered, three lie in the habitable zone around TRAPPIST-1. A habitable zone is the range of orbital distance from a star that exhibits conditions most likely to support life form. The most crucial condition is existence of liquid water on the surface of a planet. This largely depends on the size of the star and its temperature. NASA hopes to discover these conditions on the TRAPPIST-1 exo-planets in the coming decade.