NGC 4833 is an old star cluster in the southern constellation of Musca. It was discovered by Abbe Lacaille in his 1751-1752 trip to South Africa and it was catalogued in 1755.

Caretta (2021) found the stars in this cluster had lots of potassium for a metal-poor cluster.

In order to study NGC 4833 and investigate the relationships between the colours, brightnesses, and the age and chemical composition of the cluster as a whole, I collected 15 images, 5 each in B, V, and R filters. I used Prompt 6 for all images with total exposure durations of 71.65s in the B filter and 48.03 in the V and R filters, using Skynet. I used Afterglow to process the images and Cluster Astromancer to fit my isochrone model.

Below is a table of results from my efforts:

Distance (kpc)	RA	Dec	Proper Motion RA (mas/yr)	Proper Motion Dec (mas/yr)	Age (Myrs)	Log Age	Metallicity (solar)	Reddening (mag)	# of stars	Solar masses
6.6	194.89	-70.84	-8.38	-0.98	12589.25	10.1	-1.45	0.22	1876	594114

And here is an image of the isochrone model that Astronomicon made:

 

Here’s one that I made:

As you can see (barely, sorry for bad quality), there’s a decent amount of stars in the horizontal branch, indicating many stars in the cluster are past their red giant phase. These stars are likely powered by helium fusion in their core, with a hydrogen-burning shell around the helium-burning core. There’s also a lot of stars in their red giant phase, heading towards the tip of the red giant branch to join their friends on the horizontal branch.

Kharchenko et all (2013) found the below results about NGC 4833:

Distance (kpc)	RA	Proper Motion Dec (mas/yr)	Log Age	Metallicity (solar)	Reddening (mag)
6.595	194.892	-70.877	10.1	-1.75	0.323

As you can see, I got pretty close!  The reddening and metallicity are the two values that I didn’t quite get right.

Having completed the analysis, I’m not sure if this project was the highlight of my life but I’m definitely annoying my friends with how much I’ve talked about it, so it’s up there. Overall, lots of fun and very interesting!