How many galaxies are there in the observable universe
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Number of Galaxies in the Observable Universe
Estimations of Galaxy Count
Hundred Billion Galaxies
Current observational evidence suggests that there are approximately 100 billion galaxies in the observable universe. This estimation is based on various astronomical surveys and observations, which have provided a broad understanding of the universe's structure and composition1 3.
Challenges in Counting Galaxies
Counting the exact number of galaxies is a complex task due to biases and limitations in astronomical surveys. These surveys often miss faint and distant galaxies, leading to an underestimation of the total number. Deep observations of the distant universe reveal a much higher density of galaxies than what is observed locally, indicating that many galaxies remain undetected2 5.
Variability in Estimates
Different studies and methods can lead to varying estimates of the number of galaxies. For instance, some sources suggest there could be as many as two billion galaxies, highlighting the challenges and uncertainties in making precise counts4. This variability underscores the need for continuous advancements in observational technologies and methodologies.
Implications of Galaxy Count
Formation and Structure
The large number of galaxies is thought to result from the primordial conditions of the universe. Theories suggest that non-irrotational hydrodynamic flows and primordial rotations could have led to the formation of numerous galactic structures, each containing a vast number of stars1.
Hidden Galaxies
There is increasing evidence that many galaxies are hidden from our current observational capabilities. The spectra of distant quasars, for example, show more absorption-line features than can be accounted for by the local galaxy population, suggesting the presence of many more galaxies than we can currently detect5.
Conclusion
In summary, while the exact number of galaxies in the observable universe remains uncertain, current estimates suggest there are about 100 billion galaxies. This number is likely an underestimation due to observational biases and limitations. Continuous advancements in astronomical technologies and methodologies are essential for refining these estimates and enhancing our understanding of the universe's vast and complex structure.
Sources and full results
Most relevant research papers on this topic
Hydrodynamics, Vortices and Angular Momenta of Celestial Objects
Non-irrotational hydrodynamic flow in the universe can explain the formation of large numbers of galaxies and stars, indicating a primordial rotation broken up into vortex line structures.
How many galaxies are in the universe?
Galaxy in the Milky Way than in the Virgo cluster, and surveys are biased towards the Milky Way, making it harder to detect distant galaxies.
Gamma-Ray Emission of Active Galaxies
The observable universe consists of billions of galaxies, many of them containing 100 billion or more stars, like our “Milky Way” for example. On a morphological basis these galaxies are grouped into three main categories: spirals, ellipticals, and irregulars.
A common mass scale for satellite galaxies of the Milky Way
The Milky Way's satellite galaxies have a common mass of about 107 within their central 300 parsecs, indicating they are the most dark-matter-dominated galaxies known.
Highly CitedThe clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: measurements of the growth of structure and expansion rate at z = 0.57 from anisotropic clustering
The anisotropic clustering of massive galaxies in the SDSS-III BOSS data release 9 sample suggests a cosmological expansion rate of 0.74 0.016 at z = 0.57, independent of the Universe's evolution at z 0.57.
Highly CitedOn the true shapes of galaxies
The APM Bright Galaxy Survey provides accurate measurements of image characteristics, enabling us to infer the true shapes of galaxies using oblate, prolate, and triaxial models.
Highly CitedThe size distribution of galaxies in the Sloan Digital Sky Survey
The size distribution of galaxies is well-defined by a log-normal function, with median being the median size for each type of galaxy.
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