We tend to see the large planets farthest away from their stars. So it is unlikely we will find any small planets close to their star similar to Mercury.
Uranus
They least resemble rocky planets like Venus Earth and Mars, particularly they least resemble planets that we would consider as possible life sustaining planets.
Most known extrasolar planets least resemble Earth, both in terms of size and distance from their parent stars. Gas giants, hot Jupiters, and super-Earths are more common than small, rocky planets like Earth among the exoplanets discovered so far.
Most known extrasolar planets least resemble Earth due to their extreme characteristics such as being extremely close to their parent star, having very short orbital periods, or being much larger than Jupiter. These differences make them fundamentally different from Earth in terms of habitability and physical properties.
Mars The inner planets such as Mars, Earth or Mercury. these are too small to identify in other systems and too close to the star.
Jupiter
Jupiter has at least 79 known moons, making it the planet with the most moons in our solar system.
Uranus has at least 27 moons. It is the seventh planet from the Sun and is known for its tilting axis which causes extreme seasons.
Earth is the inner planet that has at least one moon, known as the Moon.
Neptune is the most unknown since it's far away
It was not "found out" but a decision that was made by a panel of planetary experts to define what is a planet and what is not which "degraded" Pluto from planet status of "dwarf planet" on August 24, 2006.There are at least 44 dwarf planets known.
Mercury is the smallest and the least massive planet, out of the eight in our solar system.