Messier 23 (also known as NGC 6494) is an open cluster in the constellation Sagittarius. It was discovered by Charles Messier on June 20, 1764.

M23 is at a distance of about 2,150 light-years away from Earth, its radius is around 15-20 light years. There are some 150 identified members in this cluster, the brightest being of magnitude 9.2. M23 can be found with a modestly sized telescope in the rich starfields of the Sagittarius Milky Way.

The Moon (Latin: Luna) is the Earth’s only natural satellite. Although not the largest natural satellite in the Solar System, it is, among the satellites of major planets, the largest relative to the size of the object it orbits (its primary)  and, after Jupiter’s satelliteIo, it is the second most dense satellite among those whose densities are known.