These are planets that exist outside our solar system and they
orbit another star (Sun) instead of our Sun. Thousands have been discovered in
the past two decades. The Kepler space telescope sent by NASA on March 7, 2009, has played an important role in these discoveries. These planetary worlds exist
in different sizes and orbits. Some of these are giant planets, which are very
close to the central star of their solar system, while others are icy or rocky.
NASA and other agencies are looking for a special type of planet the size of
Earth and orbiting a sun-like star in the habitable zone.
By the habitable zone is meant the distance from a star where
the temperature of the planet creates the liquid oceans that are most important
for life on the planet.
In August 2016, astronomers announced that they had discovered
one such planet. The planet called Proxima B is 1.3 times more massive than
Earth, which indicates that it is a rocky world. As of December 6, 2021, NASA's
Kepler telescope has discovered approximately 4,888 exoplanets.
