NGC 2539 is an intermediate age open star cluster discovered by astronomer Fredrick William Herschel in 1785. This cluster is located in the north edge of the Puppis Constellation.
What separates an open cluster from different types of clusters?
- Open clusters consist of stars roughly the same age due to formation from the same molecular cloud
- Open clusters often due not say together. The relatively loose gravitational attraction causing the cluster to disperse faster over time compared to the more massive clusters with stronger force of gravitational attraction(wiki).
Recent study on open clusters involving NGC 2539
As stated above open clusters are unique in their composition due to the many stars forming from the same molecular cloud. This Constraint on available matter can provide great insight to astronomers in galactic evolution (Amy E. Ray et al 2022). In a recent study, “The Open Cluster Chemical Abundances and Mapping Survey. V. Chemical Abundances of CTIO/Hydra Clusters Using The Cannon”(Amy E. Ray et al 2022) the chemical compositions of multiple open star clusters (including NGC 2539) were analyzed and documented to be compared to other mass surveys and studies done in the past.
My Investigation into NGC 2539
Similar (though not as complex) to the above mentioned study, I also chose study the chemical composition of NGC 2539 also along with the age, relationship between the different colour stars and the brightness. I collected 15 total exposures through Skynet optical observing using filters R,V,B. I then aligned stacked and colour matched the observations with their corresponding colour gradient in after glow to create a ISM-reddened image of NGC 2539(fig(1.1)). Then continuing to use afterglow I used the photometry tool to gather all possible light sources for data to be exported into Cluster Pro Plus for analysis(fig(2.1)).
fig(1.1) above is the stacked reddened image of NGC 2539
Cluster Pro Analysis
In fig(2.1) My data is plotted and compared to a custom isochrone model I fitted to the data which was able to display some common properties of NGC 2539.
fig(2.1) pictured above is the data collected from after glow with determined properties based on Isochrone model
Purpose of analysis
My main purpose for this analysis was to gather the E(B-V) value which I could decide use in Afterglow to deredden (fig(3.1)) my stacked image to get a more accurate colour image of the cluster. An interesting characteristic noticed from my observations was how barren the cluster looked in my images. I believe this was due to NGC 2539 being an open cluster thus having an overall lower gravitational attraction as well as the limited FOV of the optical observing telescopes of Skynet. My cluster did also display blue stragglers (which NGC 2539 is known for(wiki)) with no discernable nebula or giants.
My cluster was also indexed into the MWSC (Milky Way Star Clusters catalog) where the Gaia data was fit to a specific isochrone model(fig(3.2)). When the catalog log(age), metallicity and E(B-V) was compared to my estimated isochrone model I noticed that it fit better due my assumption that the 2MASS plot was inaccurate. This inaccuracy in my model made me decide that, in order to get a properly dereddened image I needed to use the more accurate MWSC model(fig(3.2)).
fig(3.1) final dereddened image for NGC 2539 using the MWSC E(B-V) value
fig(3.2) Gaia data transposed onto MWSC isochrone model
Conclusion
Picking and analyzing a cluster was very interesting to me because I got to understand the basic properties of the distant celestial bodies where star formation occurs. I found this assignment challenging and informative to further deepen my astronomy knowledge. If I was to repeat this assignment I think I would like to observe an older and larger cluster to get a more dense core with a better distribution of colours.