remarkably interesting, such as this one : (66391) 1999 KW 4 (also written (66391) 1999 KW4 ) is an Aten and Mercury-crosser asteroid discovered by LINEAR in 1999. 1999 KW 4 has a moon orbiting it. The moon, designated S/2001 (66391) 1 or '1999 KW4 Beta' is ~360 m in diameter,