NGC 2323, also known as Messier 50 (M 50), is an intermediate, open cluster in the constellation Monoceros. It was discovered in 1772 by Charles Messier, but its sighting was also recorded before 1711 by G.D. Cassini. As it was often described as having a “heart-shaped figure“, NGC 2323 earned itself the nickname of Heart-Shaped Cluster.

NGC 2323 is roughly 2,900 ly away from Earth, has a core radius of 5.9 ly, and spans 17.8 ly. The cluster has 508 confirmed members.

A 2009 article by Jonathan Irwin et al in the Monthly Notices of the Royal Astronomical Society revealed promising research on the relationship of angular momentum and evolution of stars. The researchers chose to analyze stars in NGC 2323 as the cluster “represents an ideal target for such a study, having a large population over a relatively small area of sky, which can be observed very efficiently using the multiplex advantage afforded by a standard wide-field CCD mosaic” (Irwin et al, 2009). The study analysis focuses on rotation periods and spectral types of low mass stars to draw conclusions about stellar evolution, in reference to other clusters’ analysis. The study concluded that:

“The rotation period distribution as a function of mass was found to show a clear mass-dependent morphology, statistically indistinguishable from the distributions in the literature for M35 and NGC 2516 once the different mass ranges probed by the surveys are taken into account. Thus, the M50 results do not yet provide any indication of a dependence of rotation rates on cluster environment, or a ‘third parameter’ such as metallicity” (Irwin et al, 2009).

Overall, the 2009 study of NGC 2323 has helped to provide more evidence towards the relationship of a stars mass and rotation period, giving us a better understanding of stellar evolution.

In order to do my own study of NGC 2323 and investigate the relationships between the colour, brightness, age, and chemical composition of the cluster as a whole, I collected a total of 15 images using Skynet telescopes. Five 30 second images were taken with a B filter, five 15 second images were taken with a V filter, and five 15 second images were taken with an R filter. Once the images were collected, I used Afterglow and Cluster Astromancer to analyze my data as well as create HR diagrams, isochrome models, and colour images of the cluster.

I found these results in my analysis:

OPEN cluster
Star Count:1053
Mass: 9982 (solar)
Physical Radius: 11.64 (ly)
RA: 105.69°, 7h 2m 45.6s
Dec: -8.36°, 8° 21’ 36.0’’
Galactic Longitude: 41.659°, 41° 39’ 34.0’’
Galactic Latitude: -1.307°, 1° 18’ 26.3’’
Angular Radius: 0.202°, 0° 12’ 8.6’’
Proper Motion RA: -0.76 (mas/yr)
Proper Motion Dec: -0.62 (mas/yr)
Velocity Dispersion: 0.23 (mas/yr)
Distance: 1.01 (kpc)
Log Age: 7.9 log (yrs)
Age: 79.43 (Myrs)
Metallicity: -0.1 (solar)
E(B-V): 0.3 (mag)

 

HR Diagram

Isochrome Model (RP vs BP-RP)

Isochrome Model (R vs B-R)

Isochrome Model (V vs B-V)

Isochrome Model (H vs J-H)

Colour Image

 

This analysis was done in requirement for my Astronomy 113 class. The goal of the analysis was to obtain a better understanding of star evolution, as observed in clusters. My analysis results show a cluster with at least one red giant and some possible blue stragglers – as they fall behind the turn off point.

As part of our class, we compared our data to the Milky Way Star Clusters Catalog (MWSC). In my comparison with the MWSC, I found that my data largely confirms the data present in the MWSC. Both my model and the one proposed in the MWSC are very similar. I think the turn off point of the MWSC is a better fit then the one I estimated. This means that the catalogue likely has a better estimate on the age of the cluster. Reddening values for each are very similar (within 0.071 mag of each other). I don’t know if the value I have estimated has improved the value in the MWSC, but it has certainly confirmed that the value in that catalogue is fairly accurate. The distance and metallicity values have some interesting discrepancies. The MWSC uses a smaller distance value which moves the isochrome fit to be higher up along the photometry compared to my fit. No value was given for metallicity, so 0 had to be used. While I am no expert, I feel that the result of this data suggests that the MWSC should consider a higher distance value, or inputting a metallicity value somewhere between – 0.1 and 0. This change will result in an isochrome fit that is lower and more centered in the HR diagram. 

Overall, I think the values provided by the MWSC catalogue are fairly accurate and provide a good fit for the HR diagram of the cluster. My data, while very similar, may improve the MWSC catalogue data by suggesting improvements in the distance or an addition of a metallicity value.

After completing this background research and analysis of NGC 2323, I have gained a better understanding of stellar evolution. I have been able to analyze how stars evolve in clusters, and how the cluster I analyzed varies from other clusters analyzed in class. I’ve learned how to make colour images with photos taken with Skynet telescopes, and use tools like Cluster Astromancer to analyze cluster data.

Overall, I have found this class and cluster analysis project rewarding as it has bettered my understanding of stars and the universe.