International Journal of Physics
ISSN (Print): 2333-4568 ISSN (Online): 2333-4576 Website: Editor-in-chief: B.D. Indu
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International Journal of Physics. 2019, 7(2), 44-49
DOI: 10.12691/ijp-7-2-2
Open AccessArticle

The Flat Rotation Curve of the Spiral Galaxies may be the Result of the Perfect Combination of the Fluid Mechanics and the Gravitational Mechanics

Hongjun Pan1,

1The Department of Chemistry, University of North Texas, Denton, TX 76203, USA

Pub. Date: July 17, 2019

Cite this paper:
Hongjun Pan. The Flat Rotation Curve of the Spiral Galaxies may be the Result of the Perfect Combination of the Fluid Mechanics and the Gravitational Mechanics. International Journal of Physics. 2019; 7(2):44-49. doi: 10.12691/ijp-7-2-2


A new hypothesis is proposed to explain the flat rotation curve of the spiral galaxies. The spiral galaxies can be treated as ideal fluid systems. For Milky Way, the mass density is constant within the radius of 0.65 kpc in the central portion of the bugle and results the linear relationship between the rotation velocity and the distance to the galactic center. The rotation of the spiral galaxies is driven by the central galactic bars and follows both fluid mechanics and gravitational mechanics, the flat rotation curve of the spiral galaxies is the result of the perfect combination of the fluid mechanics and the gravitational mechanics, the nature has balanced itself very well, the mass density distribution indirectly extracted from NASA’s near-infrared image of the Milky Way seems matching the hypothesis. Therefore, the “dark matter” could be unnecessary for the purpose of adding additional gravitational matter, but this does not deny the possible existence of the proposed dark matter in the universe. The feature of the flat rotation curve could be established during the formation of the galaxies from vast clouds of gas and dust, then, is maintained by gravitational force among those celestial objects, gases and interstellar medium, and such gravitational force acts as a binding force and fluid viscosity. After galactic merging, the combination of the fluid mechanics and gravitational mechanics is the only way to restore the galaxies into nice symmetric disk-like morphology with flat feature of the rotation curve after enough evolution time. The super black holes in the centers of the galaxies could be the rotation engines for whole rotation of galaxies. This model may not be perfect and could be improved in the future.

rotation curve spiral galaxies fluid mechanics gravitational mechanics

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[1]  Lequeux, J. Structure and Evolution of Galaxies, pp 27. Gordon and Breach science publishers. 1969.
[2]  Chemin, L., Renaud F., & Soubiran, C. “The incorrect rotation curve of the Milky Way”, Astron Astrophys. 578, A14, 2015.
[3]  Corbelli, E., Salucci, P. “The extended rotation curve and the dark matter halo of M33”, MNRAS, 311 (2), pp 441-447, 2000.
[4]  Massimo Persic Paolo Salucci Fulvio Stel. The universal rotation curve of spiral galaxies — I. The dark matter connection MNRAS, 281 (1), pp 26-47, 1996.
[5]  Karukes, E, Salucci, P. The universal rotation curve of dwarf disc galaxies, MNRAS 465, 4703-4722. (2017).
[6]  Koupelis, T., Kuhn, K. In Quest of the Universe. pp. 492, Figure 16-13, Jones & Bartlett Publishers, 2007.
[7]  Jones, M., Lambourne, R. & Adams, D. An Introduction to Galaxies and Cosmology, pp 21, Figure 1.13, Cambridge University Press, 2004.
[8]  Mroz, P., Udalski, A., Skowron, D. et al. “Rotation curve of the Milky Way from Classical Cepheids”. ApJL, 870:L10, 2018.
[9]  Dwek, E., Arendt, R., Hauser, M., et. al., “Morphology, Near-infrared Luminosity, and Mass of the Galactic Bugle from COBE DIRBE Observation”, ApJ., 445, pp 716-730, 1995.
[10]  Cao, L., Mao, S., Tataf, D., Rattenbury, N., “A New Photometric Model of the Galactic Bar Using Red Clump Giants”, MNRAS 434, pp 595-605, 2013.
[11]  Portail, M., Wegg, C., Gerhard, O., Martinez-Valpuesta, I., “Made-to Measure Models of the Galactic Box/Peanut Bugle: Stellar and Total Mass in the Bugle Region”, MNRAS 448, pp 713-731, 2015.
[12]  [Online]. Available: [Accessed July 12, 2019].
[13]  Farnes, J. “A Unifying Theory of Dark Energy and Dark Matter: Negative Masses and Matter Creation within a Modified ΛCDM Framework”, A & A 620, A92. 2018.
[14]  Arbey, A., “Is It Possible to Consider Dark Energy and Dark Matter as a Same and Unique Dark Fluid?”, arXiv:astro-ph/0506732, 2005.
[15]  Arbey, A., "Dark Fluid: a Complex Scalar Field to Unify Dark Energy and Dark Matter". Phys. Rev. D., 74 (4): 043516, 2006.
[16]  Pan, H., “‎Application of Fluid Mechanics to Dark Matter”, Int. J. Mod. Phys. 20(14), 3135-3137. 2005.
[17]  Pan. H., “The Redshift and Geometrical Aspect of Photons”, arXiv:0704. 1044, 2007.
[18]  Ghez, A., Salim, S., Weiberg, N. et. al. “Measuring Distance and Properties of the Milky Way's Central Supermassive Black Hole with Stellar Orbits”, ApJ. 689, pp 1044-1062, 2008.
[19]  Abuter, R., Amorim, R., Baubock, M. et al. (2019), “A Geometric Distance Measurement to the Galactic Center Black Hole with 0.3% Uncertainty”, Astron. Astrophys. 625, L10, 2019.
[20]  Conselice, C., Wilkinson, A., Duncan, K., Mortlock, A., “The Evolution of Galaxy Number Density at z < 8 and Its Implications”, ApJ, 830:83, 2016.
[21]  Kruijssen, J., Pfeffer, J., Reina-Campos, M., Crain, R., Bastian, N., “The Formation and Assembly History of the Milky Way Revealed by Its Globular Cluster Population”, MNRAS 486, pp 3180-3202, 2019.
[22]  [Online] Available: [Accessed July 12, 2019].