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Boötes Void

The Boötes Void is a large, roughly spherical cosmic void in the direction of the constellation Boötes.

By Ethan Anderson| Reviewed by Olivia Bennett, Standards & Fact-Checking Lead| Updated July 26, 2026|2 min read| Fact-checked

The Boötes Void is a large, roughly spherical cosmic void in the direction of the constellation Boötes. It contains far fewer galaxies than expected for a region of its size and is often called the "Great Nothing." It is one of the best-known large voids in the observable universe.

Discovery

The void was identified in 1981 by Robert Kirshner and colleagues during a galaxy redshift survey. A later paper confirmed the existence of a large, roughly spherical void in the constellation Boötes.

Size and location

The Boötes Void is typically described as about 330 million light-years across, with a radius of 62 megaparsecs. Its center is reported near right ascension 14h 50m and declination +46°, about 700 million light-years from Earth.

Galaxies and structure

Although called a void, it is not completely empty. Sources report around 60 galaxies in the region, concentrated in a tube-like arrangement through the middle rather than spread uniformly throughout the volume.

Scientific significance

The Boötes Void is notable as one of the largest known voids in the visible universe. Its low density has been discussed as an important example of large-scale structure in the cosmos.

Key facts

  • It is a low-density region of space with very few galaxies compared with typical regions of similar size.
  • A 1987 redshift survey confirmed a large, roughly spherical void centered near right ascension 14h 50m and declination +46°.
  • Its diameter is commonly given as about 330 million light-years, though some popular sources vary slightly.
  • The void is often described as a supervoid because of its large size.
  • The region contains some galaxies, but far fewer than expected from large-scale structure models.

Frequently asked questions

What is the Boötes Void?
It is a large, low-density region of space in the direction of the constellation Boötes, containing far fewer galaxies than expected.
Why is it called the Great Nothing?
That nickname reflects its extremely low galaxy density and the impression of emptiness compared with surrounding space.
How big is the Boötes Void?
It is commonly described as about 330 million light-years across, or about 62 megaparsecs in radius.
How many galaxies are in it?
Sources commonly report about 60 galaxies, though the exact number depends on the survey and classification used.
Who discovered it?
Robert Kirshner and colleagues identified the void in 1981 during a redshift survey.
Is it completely empty?
No. It contains galaxies, but far fewer than expected for a region of its size.

References

  1. NASA ADS / The Astrophysical Journal — https://ui.adsabs.harvard.edu/abs/1987ApJ...314..493K/abstract
    Supports: Confirms the void as a large, roughly spherical region; gives radius 62 Mpc, center coordinates, and notes its low density.
  2. Wikipedia — https://en.wikipedia.org/wiki/Bo%C3%B6tes_Void
    Supports: Provides commonly cited figures for diameter, galaxy count, nickname, and general description.
  3. Astronomy Magazine — https://www.astronomy.com/observing/secret-sky-into-the-void/
    Supports: States that Robert Kirshner and colleagues discovered the void in 1981 and describes it as one of the largest known voids.
  4. BBC Sky at Night Magazine — https://www.skyatnightmagazine.com/space-science/bootes-void
    Supports: Describes the void’s location in Boötes, approximate size, and very low galaxy count.