Nasa has released an incredibly beautiful close-up shot of Messier 5 (M5), an ancient cluster of over 100,000 stars captured by the Hubble Space Telescope which has been fascinating astronomers for the last 400 years.

Hubble captured a close-up view of M5 that spans about 20 light-years near its central region. Even close to its dense core at the left, the cluster's aging red and blue giant stars and rejuvenated blue stragglers stand out in yellow and blue hues in the sharp colour image.

Estimated to be about 13 billion years old, M5 is believed to be one of the oldest globular star clusters in existence. In the 18th century, astronomer Charles Messier thought that M5 was a nebula, which is a cloud of space dust and gas. In his extensive catalogue of star clusters, he wrote about the fifth cluster he found: "Beautiful Nebula discovered between the Balance [Libra] & the Serpent [Serpens] ..."

"Though it appeared to Messier to be fuzzy and round and without stars, Messier 5 (M5) is now known to be a globular star cluster, 100,000 stars or more, bound by gravity and packed into a region around 165 light-years in diameter," says Nasa.

Globular star clusters are ancient members of the Milky Way and M5 is located 25,000 light-years away from Earth.

Yesterday, the Hubble Space Telescope celebrated its 24th year in low Earth orbit – it was deployed into space on 25 April, 1990.