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| Bootes Void | |
|---|---|
| Name | Bootes Void |
| Type | Void |
| Constellation | Boötes |
| Discovered | 1981 |
| Discoverer | Robert Kirshner |
| Distance | ~700 million light-years |
| Diameter | ~330 million light-years |
| Other names | Great Nothing, Boötes Bubble |
Bootes Void
The Bootes Void is one of the largest known cosmic voids, a vast underdense region in the large-scale distribution of galaxies located in the direction of the constellation Boötes. Discovered in 1981 by astronomer Robert P. Kirshner and colleagues during redshift survey work, the Void became notable for its extreme size and sparsity, attracting attention from observers using facilities such as the Palomar Observatory and the Cerro Tololo Inter-American Observatory. The feature lies at a comoving distance near 200–250 megaparsecs and has been discussed in the context of surveys like the Center for Astrophysics Redshift Survey and the Sloan Digital Sky Survey.
The initial identification of the Void emerged from redshift mapping efforts associated with projects led by Robert P. Kirshner and collaborators at the Harvard-Smithsonian Center for Astrophysics, using spectroscopic instruments on telescopes at Kitt Peak National Observatory and Palomar Observatory. Follow-up studies employed radio telescopes including the Arecibo Observatory and optical campaigns from the Cerro Tololo Inter-American Observatory to search for faint galaxies, active nuclei such as Seyfert galaxies, and emission-line objects. Later wide-field surveys—most notably the Two-degree Field Galaxy Redshift Survey and the Sloan Digital Sky Survey—mapped surrounding filaments, walls, and nodes, clarifying the Void’s boundaries and prompting comparison with structures cataloged by the CfA Redshift Survey and the 2MASS Redshift Survey.
The Bootes Void is approximately 200–330 million light-years (60–100 megaparsecs) in radius depending on measurement criteria, producing an effective diameter often quoted near ~330 million light-years. Its central redshift places it roughly at z ≈ 0.05–0.06, situating it within the local supercluster frame that includes the Virgo Supercluster and structures traced by the Local Group. The Void’s underdensity is quantified relative to mean cosmic density estimates from observations by missions and collaborations such as Planck and the Wilkinson Microwave Anisotropy Probe that constrain cosmological parameters. Measurements of galaxy counts, luminosity functions, and peculiar velocities within and at the edges of the Void have been used to estimate its density contrast and to test predictions from models employing the Lambda-CDM model.
In the standard hierarchical framework exemplified by the Lambda-CDM model, large-scale voids like the Bootes Void arise from the growth of primordial underdensities under cosmic expansion, amplified by gravitational instability as overdense regions collapse into filaments and clusters such as those found in the Coma Cluster and the Shapley Supercluster. Numerical simulations performed with codes and collaborations like the Millennium Simulation and the Illustris Project reproduce void statistics comparable to observed surveys, linking void sizes to the power spectrum constrained by experiments such as WMAP and Planck. Alternative theories, including variants of modified gravity explored by groups at institutions like Perimeter Institute and Institute for Advanced Study, have also used void properties including the Integrated Sachs–Wolfe effect measured with WMAP to probe cosmological parameters and dark energy models.
Although once described as nearly empty, the Bootes Void contains several dozen galaxies identified by targeted searches, including dwarf systems, low-surface-brightness galaxies studied at Palomar Observatory and candidate Seyfert or LINER nuclei found in spectroscopic follow-ups from teams at Harvard-Smithsonian Center for Astrophysics and Max Planck Institute for Astronomy. Some reports highlighted an isolated galaxy chain spanning parts of the Void, prompting comparisons with structures mapped in the CfA Redshift Survey and the 2dFGRS. Environmental studies involving galaxy morphology-density relations traced by observers at the European Southern Observatory and the National Optical Astronomy Observatory examine star formation rates and metallicities of Void galaxies relative to counterparts in filaments and clusters such as Perseus Cluster.
The Bootes Void has served as a striking illustrative example in discussions of the cosmic web described by theorists at institutions like Princeton University and Cambridge University and in observational programs including the Sloan Digital Sky Survey. Its size, shape, and galaxy content inform statistical measures such as the void probability function, two-point correlation function used by teams at the Max Planck Institute for Astrophysics, and topology analyses employing Minkowski functionals developed by researchers at University of Chicago. Studies of peculiar velocities around the Void feed into reconstructions of the local velocity field by groups using data from the CosmicFlows project and inform mass-mapping via weak gravitational lensing observed by surveys like the Dark Energy Survey.
The Bootes Void is often compared with other notable underdense regions such as the Giant Void, the voids cataloged in the Sloan Great Wall environs, and the emptier centers identified in the Local Void. Comparative analyses contrast the Bootes feature with superstructures including the Great Attractor region, the Sloan Great Wall, and prominent clusters like the Coma Cluster to contextualize its role in the cosmic web. Observational programs that mapped these neighboring structures—such as the CfA Redshift Survey, 2MASS, and SDSS—provide the baseline against which the Bootes Void’s properties are measured.
Category:Cosmic voids