According to NASA, the Kepler space telescope has discovered the smallest exoplanet ever observed in the constellation Lyra - which lies about 210 light-years from Earth. Dubbed as Kepler-37b, the little planet is slightly larger than the Moon, and you can check out a comparison of its size relative to other known planets in the illustration below.
According to the space agency's scientists, the planet is tiny and it’s discovery was a real challenge. It has one-third the size of Earth and is smaller than Mercury, and this is the first time that a planet smaller than those that exist in our solar system is found. In addition, although orbiting around a star resembling the Sun, the researchers believe that it is a planetary system very different from ours.
The researchers believe that Kepler-37b is a rocky planet and probably not habitable. As the little planet orbits very close to its star, it probably has no atmosphere or water, and high temperatures on its surface - estimated at over 400°C making it completely barren.