Messier 71 is a globular cluster located around 13,000 light years from Earth. It is found in the constellation of Sagitta and is one of the smallest globular clusters in the Milky Way. It is not observable with the naked eye, but in good seeing conditions it can be seen with binoculars appearing as a fuzzy grey patch. The globular cluster was formed very recently in the scale of the Universe, approximately 9.5 billion years ago. It is possible to tell this by the cluster's metallicity content. It has 17% of the Sun’s metallicity and metals have been identified by spectroscopy in 89 of its stars. This is a very high metallicity content which shows its youth. As time goes by, so the abundance of metals increases.

M71 was first discovered in 1746 by Phillippe Loys de Cheseaux. It was catalogued by Charles Messier on 4th October 1780, having been found by Pierre Méchain on 28th June 1780.  Until 1970, it was not known whether M71 was an open or a globular cluster. In 1943 James Cuffey tried to prove it was a loose globular cluster, but his results were inconclusive. In 1970 astronomers began to examine the relationship between brightness and temperature of stars in a cluster and observed a trend characteristic only of globular clusters. They also identified the presence of a short 'horizontal branch', a stage in the evolution of stars that follows red giants, a characteristic of a globular cluster. Therefore, M71 is classified now as a very loosely concentrated globular cluster.

Messier 71 is best observed in June, July and August as it can be found inside the Summer Triangle asterism. It has around 20,000 stars, making it one of the smallest globular clusters; however, it is still quite bright with a magnitude of +8. M71 contains many unusual objects including millisecond pulsars and five X-ray sources inside the cluster core radius. There is an eclipsing binary millisecond pulsar in the centre of the cluster (MSP) PSR J1953+1846A. Messier 71 is a unique cluster that has mystified astronomers as to its exact nature for centuries and will doubtless hold secrets for many years to come.