M5

Credits: Keith Turnecliff, Long Itchington

Discovered in 1702 by the German astronomer Gottfried Kirch, M5 is one of the oldest globular clusters in the Milky Way galaxy. With an apparent magnitude of 6.7 and a location 25,000 light-years away in the constellation Serpens, M5 appears as a patch of light with a pair of binoculars and is best viewed during July.
This image from Hubble captures M5 in stunning detail, resolving the patch of light into individual stars. A composite of exposures taken with visible and infrared cameras, this image features over 100,000 stars. A majority of M5’s stars formed more than 12 billion years ago, but there are some unexpected newcomers on the scene, adding some vitality to this aging population.
Stars in globular clusters are believed to form in the same stellar nursery and grow old together. The most massive stars age quickly, exhausting their fuel supply in less than a million years, and end their lives in spectacular supernova explosions. This process should have left the ancient cluster M5 with only old, low-mass stars.
Yet astronomers have spotted many young, blue stars amongst the ancient stars in this cluster. Astronomers think that these laggard youngsters, called blue stragglers, were created either by collisions between stars or other stellar interactions. Such events are easy to imagine in densely populated globular clusters, in which up to a few million stars are tightly packed together.

Facts about M5 by Keith Turnecliff

M5 is, under extremely good conditions, just visible to the naked eye as a faint "star" near the star 5 Serpentis. Binoculars or small telescopes will identify the object as non-stellar while larger telescopes will show some individual stars, of which the brightest are of apparent magnitude 12.2.
M5 was discovered by German astronomer Gottfried Kirch in 1702 when he was observing a comet. Charles Messier also noted it in 1764, but thought it was a nebula without any stars associated with it. William Herschel was the first to resolve individual stars in the cluster in 1791, counting roughly 200.