Number of galaxies in observable universe

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Number of Galaxies in the Observable Universe

Estimations of Galaxy Numbers

The observable universe is vast, containing an immense number of galaxies. Current observational evidence suggests that there are approximately 100 billion galaxies in the observable universe, each containing around 100 billion stars on average . This estimation is supported by various studies that have attempted to quantify the number of galaxies through different observational techniques and models .

Evolution and Density of Galaxies

The number density of galaxies has evolved over time. Research indicates that the total number of galaxies in the universe up to a redshift of z = 8 is about 2 trillion, which is significantly higher than what is observed in deep sky surveys like the Hubble Ultra-Deep Field . This discrepancy is due to the limitations of current observational technologies, which cannot detect the faintest galaxies.

Challenges in Counting Galaxies

Counting the exact number of galaxies is a complex problem due to biases and incompleteness in astronomical surveys. It is easier to detect brighter and closer galaxies, while many faint and distant galaxies remain undetected . This leads to underestimations in the total count of galaxies.

Implications for Galaxy Evolution and Cosmology

Understanding the number and distribution of galaxies has significant implications for galaxy evolution and cosmology. The evolution of galaxy number density helps in understanding the formation and growth of galaxies over cosmic time . Additionally, the cosmic background light in the optical and near-infrared likely arises from these unobserved faint galaxies, providing insights into the overall energy output of the universe .

Conclusion

In summary, while the observable universe is estimated to contain around 100 billion galaxies, more detailed studies suggest that the actual number could be as high as 2 trillion. This highlights the limitations of current observational methods and the need for more advanced technologies to fully understand the vastness of the universe. The study of galaxy numbers not only helps in mapping the universe but also provides crucial insights into the processes of galaxy formation and evolution.

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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.

2011·

59citations

·C. Sivaram et al.

arXiv: General Physics·

DOI

THE EVOLUTION OF GALAXY NUMBER DENSITY AT z < 8 AND ITS IMPLICATIONS

The total number of galaxies in the universe up to z = 8 is (2 trillion), a factor of 10 higher than would be seen in an all sky survey at Hubble Ultra-Deep Field depth, and this result resolves the Olbers' paradox.

2016·

148citations

·C. Conselice et al.

The Astrophysical Journal·

DOI

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.

2016·

2citations

·Keith T. Smith

Science·

DOI

Our Universe

Our universe contains about two billion galaxies and 88 constellations, with Virgo being the second largest constellation in size and easily observed in the sky by humans.

2017·

53citations

·R. Petrescu et al.

DOI

Submillimetre galaxies in a hierarchical universe: number counts, redshift distribution, and implications for the IMF

Our model predicts well-matched observations of high-redshift submillimetre galaxies, suggesting that the difficulty in explaining SMG counts is likely due to more general problems rather than specific to the SMG population.

2012·

168citations

·C. Hayward et al.

Monthly Notices of the Royal Astronomical Society·

DOI

HerMES: SPIRE galaxy number counts at 250, 350, and 500 μm

HerMES has determined galaxy number counts down to 20 mJy, providing a more precise benchmark for galaxy population evolution models and testing pre-existing models of galaxies.

2010·

138citations

·S. Oliver et al.

Astronomy and Astrophysics·

DOI

The 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.

2012·

379citations

·B. Reid et al.

Monthly Notices of the Royal Astronomical Society·

DOI

The 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.

2003·

931citations

·S. Shen et al.

Monthly Notices of the Royal Astronomical Society·

DOI

Galaxy number counts. - I. Photographic observations to B=23.5 mag.

COSMOS machine measurements of Anglo-American Telescope photographs provide accurate galaxy number-magnitude counts and color distributions for faint galaxies up to B=23.5 mag.

1991·

75citations

·L. Jones et al.

Monthly Notices of the Royal Astronomical Society·

DOI

Galaxies as Gravitational Lenses

Gravitational lenses can produce distorted and amplified images of distant galaxies, allowing us to study their morphological configurations.

1968·

20citations

·J. Barnothy et al.

Science·

DOI

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