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from an undefined
place,
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create (a place)
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— Viorica Hrincu
Sometimes when you stare at the void, the void sends you a poem.
Universe—Superclusters and Voids
The average density of the universe is about `10 \times 10^{-30} \text{ g/cm}^3` or about 6 protons per cubic meter. This should put some perspective in what we mean when we speak about voids as "underdense regions".
references
contents
Before you delve into the background material for the map, calm the nerves and awaken the imagination with these space-themed tunes.
Perfect to listen to while perusing the map ... or the terrain.
2 Wicky by Hooverphonic (Live at Koningin Elisabethzaal 2012)
Space walk by Lemon Jelly
Exploration by Karminsky Experience Inc.
100 Billion Stars by Lux
Journey through the Boötes Void by Scott Lawlor
Ok, now let's get to it.
The individual catalogues of objects (stars, clusters, superclusters, voids) shown on the map are available as a parsed single file.
n TYPE
----- ------------
2 quasar
1024 supercluster
2555 void
5250 abell
9096 hr
18707 zwicky
Each element is represented by a single line and all objects start with the same fields:
TYPE ID CONSTELLATION NAME radec RA DEC lb GALACTIC_LONG GALACTGIC_LAT sglb SUPERGALACTIC_LONG SUPERGALACTIC_LAT z REDSHIFT d DISTANCE(Mly)
For some objects the NAME is blank ("-").
In addition to these fields, each object type has additional information.
Abell cluters have the number of galaxies in them (N) and the IDs of the superclusters to which they belong listed.
abell ... count N mscc/sscc ID1,ID2,...
Superclusters have the number of galaxies in them (N), their size (SIZE) and the two constellation of the supercluster's Abell's clusters (same as CONSTELLATION if the supercluster's Abell clusters are all in the same constellation).
supercluster ... count N size SIZE(Mly) con_compound CON_COMPOUND
Voids have their size void ... size SIZE
The stars, taken from the Yale Catalogue of Bright Stars, do not have a distance or redshift but have a magnitude
hr ... mag MAGNITUDE
These are the individual catalogues from Vizier used in the map and to create the single parsed file above.
V/50 Bright Star Catalogue, 5th Revised Ed., Hoffleit+, 1991
VII/110A Rich Clusters of Galaxies, Abell+, 1989
VII/4A Abell and Zwicky Clusters of Galaxies, Abell+, 1974
VII/56 Redshifts for Abell Clusters, Sarazin+, 1982
J/APJ/365/66 Redshifts of a sample of distant Abell clusters, Huchra+, 1990
VII/165A Measured Redshifts of Abell Clusters of Galaxies, Andernach, 1991
VII/177 Redshifts and Velocity Dispersions for Abell Clusters, Struble+, 1991
J/APJS/96/343 Redshifts of rich clusters of galaxies, Quintana+, 1995
J/A+A/310/8 The ESO Nearby Abell Cluster Survey I., Katgert+, 1996
J/A+A/310/31 The ESO Nearby Abell Cluster Survey. II., Mazure+, 1996
J/APJS/126/1 Abell clusters photometry, Quintana+, 2000
J/AJ/126/119 Optical and radio data for rich Abell clusters, Rizza+, 2003
VII/190 Zwicky Galaxy Catalog, Zwicky+, 1968
J/PASP/111/438 Updated Zwicky catalog (UZC), Falco+, 1999
J/MNRAS/445/4073 Two catalogues of superclusters, Chow-Martinez+, 2014
J/APJ/744/82 Catalog of cosmic voids from the SDSS-DR7, Varela+, 2012
J/MNRAS/440/1248 SDSS DR7 voids and superclusters, Nadathur+, 2014
J/APJ/835/161 A cosmic void catalog of SDSS DR12 BOSS galaxies, Mao+, 2017
VI/42 Identification of a Constellation From Position, Roman, 1987
Good places to start your exploration of the Universe.
Hoffleit, D. & Warren, Jr., W.H. The Bright Star Catalog, 5th Revised Edition (Preliminary Version) (1991)
Roman N.G. Identification of a constellation from a position Publications of the Astronomical Society of the Pacific 99 695–699 (1987)
To determine constellation shapes, I originally started with a list by Marc van der Sluys
BSC (Yale Catalogue of Bright Stars) constellation edges by Marc van der Sluys
However, many of these constellations were not the asterisms sanctioned by the IAU. I therefore corrected all the constellation shapes by manually examining the IAU map and cross-referencing the stars to the Yale Catalogue of Bright Stars. Ugh.
IAU Constellation shapes as edges between BSC stars (Yale Catalogue of Bright Stars) by Martin Krzywinski
For more details about the constellations see my IAU Constellation Shape Resources.
Abell clusters [Wikipedia]
Abell, G.O. The distribution of rich clusters of galaxies. A catalog of 2712 rich clusters found on the National Geographic Society Palomar Observatory Sky Survey The Astrophysical Journal Supplement Series 3 211–88 (1958)
LC 1101: supergiant elliptical galaxy [Wikipedia]
Abell 2029 galaxy cluster [Wikipedia]
The universe within 2 billion light years. by Richard Powell
Finelli F. et al. Supervoids in the WISE–2MASS catalogue imprinting cold spots in the cosmic microwave background Monthly Notices of the Royal Astronomical Society 455 (2016)
Kopylov A.I. & Kopylova F.G. Search for streaming motion of galaxy clusters around the Giant Void Astronomy and Astrophysics 382 389–396 (2002)
Linder U. et al. The structure of supervoids. I. Void hierarchy in the Northern Local Supervoid. Astronomy and Astrophysics 329–347 (1995)
El-Ad H. & Piran T. Voids in the large-scale structure The Astrophysical Journal 491 421–435 (1997)
List of voids [Wikipedia]
Giant void [Wikipedia]
Boötes void [Wikipedia]
Northern local supervoid [Wikipedia]
Southern local supervoid [Wikipedia]
Eridanus supervoid (CMBR Cold spot) [Wikipedia]
J1120+0641 [Wikipedia]
Mortlock D.J. et al A luminous quasar at a redshift of z = 7.085 474 616–619 (2011)
Bañados E. et al An 800-million-solar-mass black hole in a significantly neutral universe at a redshift of 7.5 Nature 553 (2018)
J1342+0928 [Wikipedia]
Celestial coordinate system [Wikipedia]
NASA/IPAC Extragalactic Database: Coordinate Transformation & Galactic Extinction Calculator
RA DEC flexible converter by Jan Skowron
How far out in the universe can we see? by Harald Lang
Redshift and distance calculator by Edward Wright
Wright, E.L. The Publications of the Astronomical Society of the Pacific 118 1711–1715 (2006)
Loeb, A. Long-term future of extragalactic astronomy Physical Review D 65 047301.1–047301.4 (2002)
Bennett, C.L. et al The 1% Concordance Hubble Constant Astrophysical Journal 794 (2014)
Propensity score weighting
It is not certain that everything is uncertain. —Blaise Pascal
We have already explored how we can mitigate bias caused by confounding variables in observational studies using propensity score (PS) matching (PSM) and propensity score weighting (PSW). However, any statistical model is only as good as its assumptions and, if it is specified incorrectly, it can itself produce biased estimates of the treatment effect.
This month, we explore double robustness, a powerful statistical concept that provides a valuable “safety net” against the risk of an incorrect model. It offers two opportunities, instead of just one, to obtain a valid estimate of the treatment effect — making it possible to draw credible causal inferences from observational data without having to depend on a single set of modeling assumptions.
Kurz, C.F., Krzywinski, M. & Altman, N. (2026) Points of significance: Double Robustness. Nat. Methods 23:868–869.
Nature Biotechnology cover
My cover design on the 7 April 2026 Nature Biotechnology issue shows the dendrogram that represents a cluster of uniquely expressed (or downregulated) genes in human naive stem cells induced from such cells. Within each dendrogram block, the genomic barcode sequence (sampled from Supplementary Table 1) is depicted with a Code 39 barcode. The highlighted barcode is one of those used for cell isolation.
Ishiguro S. et al. A multi-kingdom genetic barcoding system for precise clone isolation (2026) Nature Biotechnology 44:616–629.
Browse my gallery of cover designs.
Happy 2026 π Day—
Art for the 5%
Celebrate π Day (March 14th) and enjoy the art — but only if you're part of the 5%.
Go ahead, see what you can't see.
Ishihara's Tests for Colour Deficiency
Authentic and accurate images of Ishihara's test plates photographed (and lovingly color-corrected) from the 38-plate Ishihara's Tests for Colour Deficiency.
I also provide the position, size, and color of each circle on each test plate.
Symmetric alternatives to the ordinary least squares regression
What immortal hand or eye, could frame thy fearful symmetry? — William Blake, "The Tyger"
This month, we look at symmetric regression, which, unlike simple linear regression, it is reversible — remaining unaltered when the variables are swapped.
Simple linear regression can summarize the linear relationship between two variables `X` and `Y` — for example, when `Y` is considered the response (dependent) and `X` the predictor (independent) variable.
However, there are times when we are not interested (or able) to distinguish between dependent and independent variables — either because they have the same importance or the same role. This is where symmetric regression can help.
Luca Greco, George Luta, Martin Krzywinski & Naomi Altman (2025) Points of significance: Symmetric alternatives to the ordinary least squares regression. Nat. Methods 22:1610–1612.
Beyond Belief Campaign BRCA Art
Fuelled by philanthropy, findings into the workings of BRCA1 and BRCA2 genes have led to groundbreaking research and lifesaving innovations to care for families facing cancer.
This set of 100 one-of-a-kind prints explore the structure of these genes. Each artwork is unique — if you put them all together, you get the full sequence of the BRCA1 and BRCA2 proteins.
