Mass Segregation in Open Clusters

Authors

  • Mikhail Rudomanov Moscow Institute of Physics and Technology
  • Igor Bulygin Astro Space Center of Lebedev Physical Institute

Keywords:

student research, stellar dynamics, open clusters, mass segregation, minimum spanning tree

Abstract

This paper presents a student research project in astrophysics completed by a Grade 10 student. It demonstrates the feasibility of advanced research project work for upper secondary students and identifies communication tools and principles for structuring a student's work. The research component focuses on assessing mass segregation in 12 open clusters using data from the SAI Open Clusters Catalog. Segregation is quantified using the minimum spanning tree (MST) method, which compares the MST length for a sample of the most massive stars with the distribution of MST lengths for random subsamples of the same size. Stellar masses are estimated from photometric data using an approximate mass–luminosity relation, while a simple model of changes in the number of stars is based on the initial mass function. A characteristic relaxation time is also estimated for each cluster using formulas from stellar dynamics. The results indicate a possible relationship between the dynamical age of a cluster and the value of ΛMSR; however, because of the small sample, approximate mass estimates, and simplified cluster membership selection, the conclusions should be regarded as qualitative estimates obtained within a student research project.

Author Biographies

Mikhail Rudomanov, Moscow Institute of Physics and Technology

Student, Moscow Institute of Physics and Technology (National Research University); Graduate, Comprehensive School of the Center for Teacher Excellence, Moscow

Igor Bulygin, Astro Space Center of Lebedev Physical Institute

Highly qualified Junior Researcher at the Astro Space Center, P.N. Lebedev Physical Institute of the Russian Academy of Sciences

References

Automated search for star clusters in large multiband surveys. II. Discovery and investigation of open clusters in the Galactic plane / E. V. Glushkova [и др.] // Astronomy Letters. 2010. Т. 36, № 2. С. 75—85. DOI: 10.1134/S1063773710020015. arXiv: 0910.1330 [astro-ph.GA].

Sternberg Astronomical Institute Open Clusters Catalog (SAI OCL) / E. V. Glushkova [и др.]. 2009. URL: https://cdsarc.cds.unistra.fr/viz-bin/cat/V/132 ; SAI OCL website: http://ocl.sai.msu.ru/catalog/. VizieR Online Data Catalog, V/132.

Global survey of star clusters in the Milky Way. II. The catalogue of basic parameters / N. V. Kharchenko [и др.] // Astronomy & Astrophysics. 2013. Т. 558. A53. DOI: 10.1051/0004-6361/201322302. arXiv: 1308.5822 [astro-ph.GA].

Using the minimum spanning tree to trace mass segregation / R. J. Allison [и др.] // Monthly Notices of the Royal Astronomical Society. 2009. Т. 395, № 3. С. 1449—1454. DOI: 10.1111/j.1365-2966.2009.14508.x. arXiv: 0901.2047 [astro-ph.GA].

Introduction to Algorithms / T. H. Cormen [и др.]. 3-е изд. Cambridge, MA : MIT Press, 2009.

Duric N. Advanced Astrophysics. Cambridge University Press, 2004.

Kroupa P. On the variation of the initial mass function // Monthly Notices of the Royal Astronomical Society. 2001. Т. 322, № 2. С. 231—246. DOI: 10.1046/j.1365-8711.2001.04022.x.

Kroupa P., Jerabkova T. The Salpeter IMF and its descendants // Nature Astronomy. 2019. Т. 3. С. 482—484. DOI: 10.1038/s41550-019-0793-0. arXiv: 1910.01126 [astro-ph.SR].

Chandrasekhar S. Principles of Stellar Dynamics. University of Chicago Press, 1942.

Spitzer Jr. L., Hart M. H. Random Gravitational Encounters and the Evolution of Spherical Systems. I. Method // The Astrophysical Journal. 1971. Т. 164. С. 399—409. DOI: 10.1086/150855.

Binney J., Tremaine S. Galactic Dynamics. 2-е изд. Princeton University Press, 2008.

Spitzer Jr. L., Hart M. H. Random Gravitational Encounters and the Evolution of Spherical Systems. II. Models // The Astrophysical Journal. 1971. Т. 166. С. 483—511. DOI: 10.1086/150977.

Spitzer Jr. L. Equipartition and the Formation of Compact Nuclei in Spherical Stellar Systems // The Astrophysical Journal Letters. 1969. Т. 158. С. L139. DOI: 10.1086/180451.

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Published

2026-08-12

How to Cite

[1]
Rudomanov, M. and Bulygin, I. 2026. Mass Segregation in Open Clusters. Astronomy Education. 1, 2 (Aug. 2026), 26–34.

Issue

No. 2 (2026)

Section

Student Research Activity

License

Copyright (c) 2026 Mikhail Rudomanov, Igor Bulygin

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