NGC 2477, also known as Caldwell 71, is an open cluster located in the constellation of Puppis. This celestial treasure, discovered by Abbé Lacaille in 1751, is home to approximately 300 stars and spans almost as extensively across the sky as the full moon. Its age is estimated to be around 700 million years, making it an intermediate-aged cluster that offers a unique window into the evolutionary processes of stellar populations. NGC 2477 stands out as “one of the top open clusters in the sky,” comparable in its visual splendor to a globular cluster yet without the dense center that characterizes such clusters. Its richness and compactness surpass even that of M46, another open cluster in Puppis, showcasing a massive variety of stars that has fascinated astronomers and observers alike.
Observation data from the J2000 epoch pinpoint its right ascension at 07h 52m 09.8s and its declination at −38° 32′ 00″. Positioned roughly 3600 light-years away from Earth, NGC 2477 shines with an apparent magnitude of 5.8 and spans an apparent diameter of 27 arcminutes (Wikipedia). These characteristics underscore the cluster’s prominence and beauty.
In order to study NGC 2477 and investigate the relationships between the colours, brightnesses, and the age and chemical composition of the cluster as a whole, I collected 15 images in B, V and R filters with the Skynet Robotic Telescope Network’s Prompt6 telescope at Cerro Tololo Inter-American Observatory in Chile, with total exposure durations of 91, 41 and 21 seconds in these filters, with other imaging parameters. I used Afterglow and Cluster Astromancer for proper stellar analysis. I found the following results for NGC 2477’s distance, proper motion and other characteristics:
- Mass: 12970.9482
- Physical Radius: 13.61758 (ly)
- Right Ascension (RA): 118.05°
- Declination (Dec): -38.54°
- Galactic Lognitude: 73.5765°
- Galactic Latitude: -5.8372°
- Angular Radius: 0.164979
- Distance: 1.45
- Proper Motion (RA): -2.43
- Proper Motion (Dec):Â 0.9
- Velocity Dispersion: 0.16817
The exploration of NGC 2477 was driven by my curiosity regarding stellar objects and the aim to meaningfully contribute insights into its stellar evolution and science in general. This deep dive into the cluster’s attributes using Gaia data and measurements, HR diagrams and isochrone fitting techniques revealed several interesting findings. What emerged from this exploration were fascinating insights into its stellar population. Notably, the cluster was found to host several red giants, their luminous nature apparent in the pictures captured below. Among these ancient stars, a few blue stragglers also made their presence known, defying the usual stellar lifecycle by appearing younger and hotter than their counterparts. These discoveries highlight the dynamic and evolving nature of NGC 2477, showcasing the diversity and complexity of stellar evolution processes within this stunning star cluster.
NGC 2477 was studied by Friel et al. in 2002 (https://iopscience.iop.org/article/10.1086/344161/pdf), who found parameters E(B-V) and metallicity for the 28 starts analyzed in their study. Their results showed higher E(B-V) values and lower metallicity values, 0.29 and approximately -0.145, respectively. When I plotted the Gaia data with these parameters, I found that the isochrone diagram failed to achieve an appropriate model fit.
Measured Parameters from the Isochrone Gaia HR Diagram:
- Distance: 1.45
- Log Age: 9
- Metallicity: 0.25
- E(B-V): 0.25
Isochrone Gaia HR Diagram:
Stacked Colour Image of NGC 2477:
Having completed my analysis against the backdrop of Friel et al.’s (2002) foundational research on NGC 2477, I encountered intriguing differences between our findings, particularly in metallicity and E(B-V) values. Their work, which provided detailed spectroscopic data, contrasted with my observations derived from Gaia data, highlighting the evolving nature of astrophysical research. The identification of red giants and blue stragglers within the cluster underscored the dynamic and complex processes of stellar evolution at play.
This project not only allowed me to engage deeply with the intricacies of NGC 2477 but also to connect historical studies with contemporary astrometric observations, once again, illustrating the dynamic and evolving nature of stellar astronomy and the cosmos in general.
Overall, my analysis of NGC 2477 has been an incredibly rewarding journey, marking the highlight of my astronomical explorations thus far. The process of both collecting and analyzing my data, comparing methodologies, and uncovering the secrets of a celestial marvel like NGC 2477 has been a long, but fulfilling journey. This project not only expanded my understanding of the cosmos but also deepened my appreciation for the collaborative and ever-evolving nature of scientific discovery. As I reflect on my cosmic journey, it underscores the profound impact that studying the stars can have, affirming my passion for astronomy and my commitment to contributing to our collective quest to understand the universe.
Thank you for reading this blog post. I learned a lot throughout this whole process, and if you made this far, I hope you know a bit more too.
My revision and submission for NGC 2477 to Astronomicon can be found at Astronomicon.