In Kerbal Space Program, there are six planets, and these planets are orbited by moons or other objects. Each planet has it's own atmospheric differences, surface differences, gravity, and physics. These planets, in alphabetical order, are:
Moho is the closest planet to the sun. It is a analogue of Mercury, and has no moons. It has an orbital inclination of 7.0 degrees, and 1 mohoian year is 25 kerbin days, and 15.5 hours. It is impossible to achieve a geosynchronous orbit around Moho. Its equatorial radius is 250 Kilometers.
Eve can be considered a analogue of Venus, but it varies in some aspects. It has a strange purple color, but its landscape has plateaus, and what appear to be Maria in the dark purple spots. It has one natural satellite, named Gilly. Gilly has a highly elliptical orbit, and high orbital inclination, in a way that it’s hard to enter and get an entry.
Gilly is an small captured asteroid orbiting Eve in an highly elliptical orbit, and high orbital inclination. That combined with Gilly's small sphere of influence makes it very hard to get an flyby of.
Kerbin is the home planet of the kerbals. It is one of two water worlds in the kerbol system the other being Laythe. Kerbin has an high gravity and large sphere of influence, geostationary orbit can easily be achieved of this planet. Kerbin gives the least science from than any of the planets in the game. Kerbin has two natural satellites that being the Mun and Minmus.
The Mun Edit
The Mun is the Kerbal Space Program analog of the Moon. The Mun has similar gravity to it's real life counterpart, the Mun has no atmosphere making parachutes useless. Landing on the Mun requires a lot of Delta V, the Mun gives very little science compared to the other moons and planets of this game.
Minmus is an ice world and an very small asteroid sized moon orbiting kerbin not far away from escaping its sphere of influence getting an Minmus encounter can be tricky sometimes, it may be an more viable option than the Mun since creating orbit or landing there requires a lot less delta V.
Duna is a planet similar to Mars, but some noticeable features are the unusually large polar ice caps, and it has a relatively small diameter of 320 km. It has one moon named Ike. It is an large moon similar to the Mun in size.
Ike is the moon of Duna. It orbits in an near geostationary orbit around Duna making Ike in the dunatian sky seem like it goes slings to its sides. It has an large sphere of influence on Duna and getting an flyby of Ike is easy and can launch you out of Dunas sphere of influence this may or may not be a good thing.
Jool is the fifth planet from Kerbin. It is the largest planet in the Kerbol system, it has 5 moons: Laythe, Vall, Tylo, Bop and Pol. It is the only gas giant in the game and resembles Jupiter from real life.
Laythe is the first and closest moon of Jool. Laythe is a blue, watery planet with sandy islands on it. It also has a breathable atmosphere and the Kerbals can remove their helmets on the moon.
There is an easter egg on Laythe; The Sagan Sea, referring to Carl Sagan.
Vall is the second and second-closest moon of Jool. It is an ice planet that is an analogue of Europa, an ice planet.
There is an easter egg on Vall; The Vallhenge, a Stonehenge-like set of blocks. Some have wedges on them!
Tylo is a rocky moon that is supposed to be similar to the Mun. It is the largest moon in the game even larger than Kerbin. It is an analog of Ganymede.
In real life, Ganymede is only larger than Mercury.
PS: There's an easter egg on Tylo. A cave-like formation that between 0.2.1 and 1.0.5 [supposedly] that was hidden beneath the surface. I think it's still up there to see for your own eyes!
Bop is a captured asteroid that is the fourth and second-smallest moon of Jool. It is an asteroid that's supposedly an analog of any of the 59 minor moons of Jupiter [not one of them is similar, supposedly]. This asteroid moon is home to the Deep Space Kraken.
Pol, literally named after it's simularity to a grain of Pollen, is the fifth and smallest moon of the Jool system.
Dres and Eeloo Edit
Dres and Eeloo are dwarf planets. They are supposedly an analog of;
Dres: Eris, Sedna [confirmed both]
Eeloo: Pluto [supposedly, not final]
Kerbol is the star and NOT a planet/moon. Simular to Jool's gravity, Kerbol can pull things that go near it's surface.
- Laythe is nearly the size of Kerbin.