NGC 2287 – The Little Beehive Cluster

Posted on by MD Dilshad Hossain

Introduction

NGC 2287 or Messier 41 (M41) is an open star cluster in the constellation Canis Major in the southern celestial hemisphere. It is located almost exactly four degrees south of Sirius (the brightest star in the sky). According to Sky Catalogue 2000, it is estimated to be 190 million years old, classifying it as a young cluster. It is also known as the ‘Little Beehive Cluster’.

History

It was discovered by Giovanni Batista Hodierna, an Italian astronomer, in the early 1650s. However, in an article written by J.E. Gore, he mentions, “ancient Greek philosopher Aristotle reports in his Meteorologica (Aristotle, c. 325 B.C.), Book I, Chapter 6, that a star below [south of] Sirius was seen to have a faint tail, and that ‘if you looked hard at it the light used to become dim, but to less intent glance it was brighter.’” He argues that Aristotle may have observed M41 back in 325 BC. The name Messier comes from the French astronomer Charles Messier, who created the Catalogue des NĂ©buleuses et des Amas d’Étoiles (Catalogue of Nebulae and Star Clusters) categorizing 110 Messier objects including M41 in 1765.

Data Collection

This cluster observation was prepared using Skynet and their peripheral tools (Afterglow, Skynet Plotting). The observation was conducted using the Prompt5 Telescope in Cerro Tololo Observatory, Chile and PROMPT-MO-1 Telescope in Meckering Observatory, Australia. These telescopes consisted of lenses of aperture 0.4m and focal length of approximately 4600mm. The images ire taken with a 16-bit CCD with a flux range of 0 – 65353. The observational parameters ire taken from the study from Kharchenko et al (2013). Using the parameters, five images in the B Filter (blue), five in the V Filter (visible) and five in the R Filter (red).  I, then, used photometry in Afterglow to get an estimate of properties of my cluster and compare them to the MWSC (Milky Way Star Cluster) Catalog.

Figure 1: HR Diagram and Estimated Properties from My Observation of NGC 2287 (M41)

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Figure 2: HR Diagram and Estimated Properties from MWSC Observation of NGC 2287 (M41)

Observation Analysis

Figure 3: Comparison between my observation and archived image from ALADIN.

My Calibrated Observation (Stacked BVR Image) Archived Image (Aladin)

There are a few things to observe immediately. Both in my image and archive image, I can see quite a few bright blue stars. There are a few red giants include a bright red giant (HIP 32406) of spectral type K2 with a magnitude 6.9. I can see in my observation that the brightest stars have saturated the images to a degree. From the HR Diagram in Figure 1, I estimate that log(age) is around 7.9 log(yr). Which gives us the estimated age around 100 million years old. The HR Diagram shows that the cluster is still relatively young as we see blue stars just starting head towards giant branch. We do also see that, 2MASS shows some blue stragglers compared to GAIA data. Since it is a young cluster, it is not that metal rich (Metallicity : 0.04 solar mass). The star cluster is moving at an approximate velocity of 23.3 km/s away from us. (Kharchenko et al, 2013).

Since it is nearby cluster, it has been used in numerous studies on star behavior. One interesting study I found was by Weijia Sun et al (2019). In their study, they discussed effect of tidal locking in the members of NGC 2287. They found that some slow rotating stars may have been rapid rotating stars that have been slowed down due to tidal locking. They also noticed some splitting Main Sequence behavior in NGC 2287, which is something to study further.

Conclusion

Overall, this was an interesting research into stellar population. There was very little difficulty while going through the process of observing and taking measurements of the star cluster. I was able learn some of the applications of astrophysics while analyzing this star cluster. Hopefully, in the future, someone else may also observe this star cluster and analyze if any changes occurred. The project greatly enhanced my understanding of stars and clusters.

Reference

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