Background
NGC 3293, or also known as The Gem Cluster, is a young open star cluster found in the Constellation Carina. It was initially discovered by Nicolas-Louis de Lacaille in 1751 when he was observing parts of the southern hemisphere. Nicolas-Loius originally named the cluster “Fictor” which translated to “The Sculptor” in Latin, but the NGC designation is more commonly used these days in astronomical catalogues. This cluster is notable for its location near the Carina Nebula, a nearby region of active star formations.
The Gem Cluster is located at R.A. 10 35 24 and Dec. -58 13 48, therefore it is unfortunately not observable from Saskatoon. The best places to observe NGC 3293 is anywhere below around 10 degrees North. NGC 3293 has a visual magnitude of about 4.4, making it a relatively low brightness and more difficult to observe in light-polluted or urban areas.
Procedure and Results
To further understand the characteristics of The Gem Cluster, I captured 15 optical images using the University of North Carolina at Chapel Hill’s PROMPT5 telescope. For my analysis, I captured 5 images 9.76 seconds long in the B filter, 5 images 7.32 seconds long in the V filter, and 5 images 3.66 seconds long in the R filter. Using Skynet’s Photometry, I extracted 1650 stars from my images. Plotting each of these stars in Skynet’s Cluster Pro Plus, I was able to reduce my stars to 329, cutting out insignificant background stars.
Milky Way Star Clusters Catalogue
My Photometry Plotted Values
| MWSC | My Data | |
| PM in RA (mas/yr) | -7.667 ± 0.255 | -7.671 ± 0.125 |
| PM in Dec (mas/yr) | 3.406 ± 0.302 | 3.389 ± 0.195 |
| Distance (kpc) | 2.441 ± 30% | 3 ± 30 |
| log(Age) (log(yr)) | 6.75 | 7.06 |
| Metallicity (solar) | 0 | 0.57 |
| E(B-V) Extinction (mag) | 0.333 | 0.31 |
Breakdown and Conclusion
In addition to using 2MASS photometry data on Skynet, I also generated a graph using values found and provided by the Milky Way Star Clusters Catalogue. The proper motion values from MWSC were pretty close to the ones that I discovered. While using Cluster Pro Plus, I also found that the age of my cluster of 7.06 log(yr) is slightly older than the age found by MWSC. The largest difference, and the one that I believe had the most effect on the incorrect graph, was the metallicity value. MWSC did not have a solar metallicity value in their catalogue for NGC 3293. I suspect that is the reason why the second graph is so inaccurate mid-way through (you can clearly see a large hump in the isochrone model that does not follow the stars).
With the new E(B-V) extinction value determined using an isochrone model, I was able to de-redden my original image of NGC 3293. Using the extinction value on my image really brought out the blueness of the stars in my cluster. It shows just how young The Gem Cluster is, and it proves that interstellar dust scatters blue light waves. Having more accurate extinction and metallicity values helps astronomers better determine ages of stars. The Gem Cluster was very interesting to study and learn about. The most challenging part of analyzing this cluster was trying to match the isochrone lines. I could clearly tell based on the MWSC values that almost any change would be an improvement. Unfortunately, I encountered difficulty getting the BP-RP – M_RP and J-H – M_H graphs to both feature fitting isochrone lines. Consequently, I had to concentrate on the BP-M graph and hope that the J-M graph would somewhat coincide.
Despite the issues I was having, it was fascinating to see how I could create a very accurate colour image of a cluster by removing interstellar reddening. I was also fun to learn how to use Cluster Pro Plus to better determine the age of a star cluster.
Sources
https://en.wikipedia.org/wiki/NGC_3293