Binary galaxy

A binary galaxy is a system of two interacting galaxies where their distance is 5-10 times less than the distance of the nearest galaxies of comparable brightness and dimension.^[1] The orbital periods of theses galaxies are typically in the timescales of hundreds of millions of years.^[2] The Milky Way galaxy and the nearest galaxy, Andromeda Galaxy may be classed as a binary galaxy.^[3]

Milky Way and Andromeda galaxies are thought to be binary galaxies.

Binary galaxies, if spaced out a large distance, can be stable. However close pairs of galaxies can cause disruptions to their structures. They can also merge and become an interacting galaxy.^[2]

These pairs of galaxies are useful in the field of astronomy to determine the mass of galaxies.^[4]

References

1. Karachentsev, I. D. (1979-11-01). "Binary galaxies". Zemlya Vselennaya (in Russian) (6). ISSN 0044-3948.
2. "Binary galaxies: life together, not always harmonious…" (PDF). lilith.fisica.ufmg.br. Archived from the original (PDF) on 2024-03-19. Retrieved 2025-04-23.
3. "Binary galaxies". ned.ipac.caltech.edu. Retrieved 2025-04-23.
4. "Modern Cosmological Observations and Problems - G. Bothun". ned.ipac.caltech.edu. Retrieved 2025-04-23.