Easily visible with the naked eye as a diffuse patch against the background of the Milky Way, the open star cluster Messier 7 (NGC 6475) was known about over 2,000 years ago. It was written about by the Greco-Roman astronomer Claudius Ptolemy in 130 BCE and more recently by Charles Messier in 1764 who included it in his famous catalogue.
Messier 7 is around 200 million years old, which means the Milky Way galaxy hasn’t even had time to make one full rotation since this cluster was formed. The bright cluster of around 100 stars can be found 800 light years from Earth at the tail of the constellation Scorpius, in a group than spans around 25 light years in diameter. These stars formed around the same time, from the same dust cloud and have a similar chemical composition, which means they’re likely to end the same way at the same time. In fact, up to ten percent of Messier 7’s stars – the brightest in this image – will finish their days exploding in a massive supernova, which will be quite a sight for anyone who’s around to see it.
Image Credit: ESO