June 2022 - Picture of the Month
Globular Cluster IC 4499 in Apus
This month I wanted to head south because of the short nights in the northern hemisphere. I ended up as far south as any globular cluster in our galaxy would permit, with this image by Steve Crouch of IC 4499 in southern Apus.
This is a halo globular that lies about 65,000 light-years (20 kpc) from us, although high reddening in its direction make this measurement tricky. It's sparse for one of its kind, hence the Shapley–Sawyer classification of X–XI, and has a magnitude of 10.1V. Consequently Annals of the Deep Sky Vol. 1 claims that it's an easy object with a 12in telescope, although unimpressive due to the lack of a condensed core.
IC 4499 was thought to be unusual: the metallicity of an old globular cluster, but a surprisingly young age derived from a photometry study of its population of RR Lyrae stars. This caused speculation about the origins of this object, was it a recent capture?
However new photometric observations with the Hubble have demonstrated that IC 4499 has a much more conventional age for a galactic cluster of around 12 billion years. Hubble also produced another spectacular image of IC 4499 in the process.
James Whinfrey - Website Administrator.
