It's important to clarify that you're asking about a planet similar to Luna, which is another name for the Moon. There are no planets exactly like our Moon, but there are some celestial bodies that share certain similarities.

Here are a few options depending on what aspects of the Moon you are interested in:

* Other Moons: Many moons in our solar system share similar characteristics with our Moon, like being rocky, airless, and cratered. Examples include:

* Europa (Jupiter's moon): While larger than our Moon, Europa is also covered in ice and may have a subsurface ocean, suggesting potential for life.

* Ganymede (Jupiter's moon): The largest moon in our solar system, Ganymede is also very heavily cratered and has a thin atmosphere.

* Callisto (Jupiter's moon): A heavily cratered, geologically inactive moon with a very thin atmosphere.

* Titan (Saturn's moon): Titan is unique because it has a thick atmosphere and is the only moon in our solar system known to have stable bodies of liquid on its surface (methane lakes).

* Asteroids: Some asteroids, particularly the larger ones, can share similarities with our Moon in terms of size, composition, and surface features. For example:

* Ceres: The largest asteroid, Ceres, is considered a dwarf planet and has a rocky surface with signs of possible water ice.

Ultimately, the "most similar" celestial body to our Moon depends on which aspects you are focusing on. Do you care about size, composition, geological history, or something else?

Let me know what aspects you're most interested in, and I can provide a more specific answer!