Tucked away in the constellation of Serpens, M5 is  a vibrant globular cluster packed with hundreds of thousands of stars. As one of the oldest known globular clusters, M5 provides a rare snapshot of the ancient universe and serves as an exceptional laboratory for the study of stellar evolution and dynamics. 
Spanning about 165 light-years in diameter, M5 is one of the largest known globular clusters. Its tidal radius, the region beyond wich stars are no longer gravitationally bound to the cluster, is approximately 200 light-years. The core of M5 is densely populated with stars and has undergone a process known as core collapse, common in many globular clusters, resulting in a highly concentrated central region.
M5 is a stellar treasure trove, hosting roughly 500,000 stars. These stars are remarkably old, with an estimated age of about 13 billion years, indicating that they were formed when the universe was in its infancy. Consequently, the stars are predominantly metal-poor, consistend with the elemental abundance of the early universe. The majority of M5's  stars are red giants, though a significant population of blue stragglers and variable stars can also be found.
M5 is particularly renowned for its high concentration of variable stars, with over 100 RR Lyrae variables and numerous Cepheid variables. These stars pulsate periodically, and their luminosity is directly linked to their pulsation period, making them excellent cosmic yardsticks for measuring astronomical distances. The study of these variable stars offers valuable insights into stellar evolution, providing a better understanding of the life cycles of stars and the mechanisms underlying their various stages.
The scientific importance of M5 cannot be overstaded. Its diverse stellar population, age and structural properties make it a perfect astronomical laboratory. M5 allows researchers to study a plethora of astronomical phenomena , from the processes of stellar evolution and dynamics to the conditions prevalent in the early universe. Moreover, its relative proximmity to Earth and the large number of variable stars it hosts enable precise measurements, offering critical calibrations for distance and age determinations in cosmology.
M5 has an apparent magnitude of 5.6, making it almost visible to the naked eye under optimal observing conditions. The cluster resides about 24,500 light-years away from Earth. Its intrinsic brightness, combined with its relative proximity to our planet, makes M5 one of the most spectacular globular clusters in the night sky.