science & techESA/Hubble

Messier 5 is about 13 billion years old yet contains young-looking blue stars

the gist

Messier 5 is a globular cluster of hundreds of thousands of stars, about 24,500 light-years away and close to 13 billion years old. Stars in such clusters are born together and age together, so the cluster should hold mainly old red giants and other ancient stars. Instead it contains blue stragglers, stars that look younger and hotter than their neighbours. These form when stars collide or when one strips material from a companion, which rejuvenates it. The cluster is a clear example of how interactions can override the usual script of stellar aging.

so what

Blue stragglers show that stars in dense clusters can be rebuilt through collisions and mergers, which changes how astronomers date old star systems and interpret their populations.

more on this

background

Messier 5 or M5 (also designated NGC 5904) is a globular cluster in the constellation Serpens. It was discovered by Gottfried Kirch in 1702.

From Wikipedia: Messier 5 (CC BY-SA 4.0) ↗

ESA/Hubble · CC BY 4.0

Image: ESA/Hubble & NASA