NGC 5617 is an open cluster in the Southern constellation Centaurus and was discovered by James Dunlop in 1826. NCG 5617 forms a binary open cluster with Trumpler 22. Its age is estimated to be 82 million years old, classifying it as an intermediate age cluster. The cluster has a concentration of heavy stars in the center and fewer, less massive stars at the perimeter.  

James Dunlop found this cluster to be 4’ or 5’, however in a study performed by John Herschel (Southern Gems) it was found to be 15’ so, due to the limited field of view of our telescopes, the edges of the cluster may be missing. He also described the shape of the cluster to be ‘irregularly round’ 

In order to study NGC 5617 and investigate the relationships between the colours, brightnesses, and the age and chemical composition of the cluster as a whole, I collected 15 total images, 5 in each of the filters B, V, and R with telescopes PROMPT-MO-1, Prompt2, Prompt5, with total exposure durations of 60, 30 and 20 seconds in B, V, and R filters respectively, with other imaging parameters, using Skynet. I used Afterglow and Cluster Pro Plus for their purposes and I found these basic results: 

Distance: 2.15 kpc ± 30% 

Proper Motion: RA: -5.688 ± 0.281 mas/yr 

DEC: -3.172 ± 0.15 mas/yr 

Log(age): 8.12 log(yr) 

Metallicity: -0.32 solar 

E(B-V): 0.57 mag 

More parameters

A study published in 2015 by G.M. De Silva et al (NGC 5617) found the parameters to be as follows: 

Distance: 2.1 ± 0.3 kpc 

Age: 70 ± 10 million years 

Log(age): 7.85 

E(B-V): a range with an average around 0.4 

I had to adjust the metallicity to help fit the isochrone model using their parameters: 

 

Images

Using afterglow I layered the images taken in their filters to process a coloured image of the cluster 

Processed image 

 

Dereddened using estimate of E(B-V) 

 

 Conclusion

I really enjoyed collecting images of this cluster and processing them to see the images come to life in colour. The differences between the original image and the image adjusted for the reddening is fascinating to me and a clear example of how interstellar medium alters the appearance of farther away objects. 

In comparison to the parameters collected in the 2015 study, the age and distance I determined were close to theirs. However our E(B-V) values differ. When I plotted their data, the turn off point does not quite fit the top of the main sequence. I think my model has a good fit and I feel confident about my results.