Messier 5 and 5 Serpentis

May 11, 2023

The M5 globular cluster in the constellation Serpens (NGC 5904) might be the oldest globular cluster in our galaxy, somewhere around 13 billion years old, with the Milky Way itself almost as old as the universe at 13.61 billion years, forming just a few hundred million years after the Big Bang. M5 is about 27,000 lightyears away in the galactic halo, and is one of the largest clusters, with a diameter of about 165 lightyears. Imaging notes: 60 x 60-second subs with the ZWO ASI071MC cooled to -10C and the 800mm FL newtonian scope. 

Take a closer look at the variable double star, 5 Serpentis, lower right with the diffraction spikes (the spikes are an artifact of some reflector telescopes, like the Hubble Space Telescope). If you look closely, you can see both stars, 5 Serpentis A is the larger of the two, with 5 Serpentis B just visible at the lower left of the main star. The main star (5 Serpentis A) is a large F-type main-sequence star, that has been fusing hydrogen like mad, has used most of it up, and is headed toward a red giant phase. Its companion, 5 Serpentis B, much smaller, has recently been estimated to have an orbital period of 3,371 years.