Messier 5 or M5 (also designated NGC 5904) is a globular cluster in the constellation Serpens.
Spanning 165 light-years in diameter, M5 is one of the largest known globular clusters. The gravitational sphere of influence of M5, (i.e. the volume of space in which stars are gravitationally bound to it rather than being torn away by the Milky Way's gravitational pull) has a radius of some 200 light-years.
At 13 billion years old, M5 is also one of the eldest globular clusters in the Milky Way Galaxy. Its distance is about 24,500 light-years from Earth, and it contains more than 100,000 stars, as many as 500,000 according to some estimates