Kurzgesagt – In a Nutshell
Kurzgesagt – In a Nutshell
Embedded Files
Sources – Cosmic Voids
Sources – Cosmic Voids
We thank the following experts for their critical reading, feedback, and corrections:
Sofia Contarini
Postdoctoral Researcher, Max Planck Institute for Extraterrestrial Physics
Benjamin D. Wandelt
Physics & Astronomy Professor, Johns Hopkins University
Alice Pisani
Astrophysical Sciences Postdoctoral Researcher, Princeton University
—Today we know of over 8,000 voids and supervoids, and we keep discovering more.
We thank our expert Sofia Contarini for the following comment:
Quote: “Micheletti et al. (2014) identified 411 statistically significant underdensities in the range 0.55 < z < 0.9, with radii R > 10.5 h−1 Mpc (non-overlapping almost-empty spheres). [Since then, scientists have cataloged], 5952 voids in Hamaus et al. (2020) with BOSS data, and 8962 voids in Aubert et al. (2020) with eBOSS data. Both catalogs have purity cuts for applying reliable cosmological analyses.”
How many voids there are depends on what you count as a void. Currently, studies use different definitions of voids depending on what they want to study. Some define voids as spherical regions of space that are sufficiently empty. Some use a “watershed” definition of voids, defining voids as basins with a complex structure and borders defined by areas of higher density. The total number of voids also depends on how certain you want to be about a specific void candidate being a void.
Different definitions can also lead to different characteristics for a given void, and so, different numbers, like the radius of the void. The sources for each of the numbers given in this script are collected in this document and will depend on the definition of void and the level of certainty that the reference uses.
—Now we see the entire Milky Way with its 200 billion stars and dozens of dwarf galaxies zipping around it. 2.5 million light-years away on a collision course is giant Andromeda and its own swarm of satellite galaxies.
Nobody knows exactly how many stars are there in the Milky Way. We are using a relatively low estimate here to avoid exaggeration.
#Siegel, Ethan (2025): “Why we still don’t know how many stars are in the Milky Way”, BigThink
https://bigthink.com/starts-with-a-bang/how-many-stars-milky-way/
Quote: “Current estimates place the most likely number for “stars within the Milky Way” at between 200 billion and 400 billion.”
#Massetti, Magie (2015): “How Many Stars in the Milky Way?”, NASA Blueshift
https://asd.gsfc.nasa.gov/blueshift/index.php/2015/07/22/how-many-stars-in-the-milky-way/
Quote: “There are different models for estimating the number of stars in the Milky Way and the answers they give differ depending on what is used as the average mass of a star. The most common answer seems to be that there are 100 billion stars in the Milky Way on the low-end and 400 billion on the high end. But I’ve seen even higher numbers thrown around.”
#ESA (2021): “Dwarf galaxies around the Milky Way”
https://www.esa.int/ESA_Multimedia/Images/2021/11/Dwarf_galaxies_around_the_Milky_Way
Quote: “Our galaxy, the Milky Way, is surrounded by about fifty dwarf galaxies. Most of these galaxies are only identifiable through telescopes and have been named after the constellation in which they appear on the sky (for example, Draco, Sculptor or Leo). However, the two most obvious dwarf galaxies are called the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC), and these are easily visible to the unaided eye.”
#NASA (2025): “Messier 31”
#NASA Hubble Mission Team (2025): “NASA’s Hubble Provides Bird’s-Eye View of Andromeda Galaxy’s Ecosystem”
“Giant” here is used to distinguish Andromeda from the dwarf galaxies.
—We are now moving a million times faster than the speed of light, seeing the Local Group of over 50 galaxies woven together by gravity, rivers of gas, and invisible scaffolds of dark matter. This is our pocket of the universe, 10 million light years across, no human will ever leave it.
#Powell, Richard: “The Universe within 5 million Light Years, The Local Group of Galaxies” (retrieved 2025)
http://www.atlasoftheuniverse.com/localgr.html
#Powell, Richard: “The Galaxies of the Local Group” (retrieved 2025)
http://www.atlasoftheuniverse.com/galaxies.html
#NASA (2024): “Dark Matter”
https://science.nasa.gov/mission/hubble/science/science-behind-the-discoveries/hubble-dark-matter/
Quote: “Gravity is the glue that holds the universe together, collecting stars into galaxies, keeping planets on track around their stars, and drawing galaxies together into mergers across space. The more mass something has, the greater its gravity. But scientists have calculated that all the matter we can see in the universe doesn’t add up to enough gravity to keep galaxies from flying apart, or to allow them to form in the first place. Something else must be out there.
We call this substance dark matter, an invisible form of matter that doesn’t emit, absorb or reflect light, or interact with normal matter. It’s theorized to make up 85 percent of the universe’s total mass, or almost 30 percent of the universe’s combined mass-energy.
No one knows exactly what dark matter is, but theories posit that it consists of currently unknown particles that rarely interact with normal matter. [...]
Dark matter is thought to be the scaffolding that normal matter arranges itself around and upon, a web woven through the universe whose gravity attracts normal matter. Hubble has played a major role in helping map the presence of dark matter throughout the cosmos, including the creation of a three-dimensional map that offered the first look at the web-like large-scale distribution of dark matter in the universe.”
—the Local Void – a gigantic, empty bubble 200 million light-years across. If it was a bright thing and not absolute darkness, it would fill 40% of the night sky we see from Earth.
#Tully, R. Brent et al. (2019): “Cosmicflows-3: Cosmography of the Local Void”, The Astrophysical Journal, vol. 880, 1
https://iopscience.iop.org/article/10.3847/1538-4357/ab2597
Quote: “The average place in the universe is in a void. The Local Void (Tully & Fisher 1987) subtends 40% of the sky and begins 1 Mpc away, at the fringe of the Local Group. [...]The rough dimensions of the Local Void at the isodensity contour −0.7 is ΔSGX, SGY, SGZ = 5200, 3000, 4500 km s−1 = 69, 51, 60 Mpc, hence a volume of ∼2 × 105 Mpc3.”
The diameter of the void is around 60Mpc,or approximately 200 million light years.
—As we zoom away even faster we see the Virgo Supercluster, a colossal wall of more than 2,000 galaxies spread over roughly 100 million light-years.
#Powell, Richard: “The Universe within 100 million Light Years: The Virgo Supercluster” (retrieved 2025)
http://www.atlasoftheuniverse.com/virgo.html
#ESO Supernova Planetarium & Visitor Centre: “Virgo Supercluster” (retrieved 2025)
https://supernova.eso.org/exhibition/images/0106F_Virgu_Superlcuster/
#Klypin, Anatoly et al. (2003): “Constrained Simulations of the Real Universe: the Local Supercluster”, Astrophysical Journal, vol. 596, 1
https://arxiv.org/abs/astro-ph/0107104
Quote: “Einasto et al. (1984) applied a battery of tools to quantify the statistical properties of the galaxy distribution in the LSC [(Local, or Virgo Supercluster)] region and compared the results with quantitative and qualitative predictions of several cosmological models. In particular, they showed that the LSC is similar in structure and morphology to other known superclusters such as the Perseus-Pisces supercluster and is a part of the large-scale network of clusters, sheets, and filaments. More recent studies (Tully & Fisher 1987; Karachentsev & Makarov 1996; Lahav et al. 2000) showed that the main body of the LSC is a filamentary structure that extends over some 40h−1 Mpc and is roughly centered on the Virgo cluster. The whole region is dominated by several clusters (Virgo, Ursa Major, and Fornax are the most prominent), groups, and filaments, the latter bordering nearby voids (such as the Local Void). The LG [(Local Group)] is located in the outskirts of this region in a small filament extending from the Fornax cluster to the Virgo cluster (Karachentsev & Makarov 1996).”
We take the diameter of the Virgo supercluster to be around 40 Mpc, or 130 light years. The exact diameter of the Virgo supercluster is fuzzy, because it does not have exact limits. Rather, it is part of a larger structure: Laniakea.
The main cluster of the Virgo supercluster is the Virgo cluster, which has around 2,000 galaxies
#Powell, Richard: “The Virgo Cluster” (retrieved 2025)
http://atlasoftheuniverse.com/galgrps/vir.html
Quote:“The Virgo cluster is a massive cluster of galaxies which dominates the Virgo supercluster. There are roughly 2000 galaxies in this cluster (although ninety percent of them are dwarf galaxies).”
But it also includes other smaller clusters, in which only a few hundred more galaxies have been confirmed:
#Loni, Alessandro et al. (2021): “A blind ATCA HI survey of the Fornax galaxy cluster: properties of the HI detections”, Astronomy & Astrophysics, vol. 648, A31
https://arxiv.org/abs/2102.01185
Quote: “Fornax has roughly 200 spectroscopically confirmed galaxies within Rvir ∼700 kpc”
#Tully, R. Brent et al. (1996): “The Ursa Major Cluster of Galaxies. I. Cluster Definition and Photometric Data”, The Astronomical Journal, vol. 112
https://arxiv.org/abs/astro-ph/9608124
Quote: “Although the Ursa Major Cluster lacks concentration and lies in a confusing part of space, it is reasonably cleanly defined because it has such a small dispersion in velocity. We define the cluster by windows on the plane of the sky and in velocity in order to define a list of high-probability members. The 79 galaxies that are accepted lie within 7.5° of α = 11h 56.9m, δ = +49° 22′ and have measured velocities, Vhelio + 300 sinℓcosb, between 700 and 1210 km s−1”
— All around us are dozens of superclusters and gigantic voids filled with suffocating emptiness.
#NASA Universe (2013): “Earth's Location in the Universe”
https://www.flickr.com/photos/nasablueshift/9402301601/
#Scientific American (2024): “How Analyzing Cosmic Nothing Might Explain Everything”
https://www.scientificamerican.com/article/how-analyzing-cosmic-nothing-might-explain-everything/
—You are now traveling towards the greatest and emptiest nothing in existence – right into the center of the Boötes Supervoid. A cosmic desert around 300 million light-years wide. So gigantic it should contain thousands of galaxies.
There are high uncertainties on how empty and how big the Boötes Supervoid is, and different ways of characterizing it lead to different results. This means different forms of calculating size and density, or of determining the borders of a void may come with different notions of which void is the largest or emptiest. It also means that the figures mentioned are there for illustrative purposes. Regardless, the Boötes Supervoid is remarkably large and empty, with different calculations giving a diameter of 300-400 million light years, and approximate densities of only 10% of the average density of the Universe.
#Kirshner, Robert P. et al. (1987): “A Survey of the Bootes Void” Astrophysical Journal, v.314
https://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1987ApJ...314..493K
Quote:“In an earlier paper we inferred, from the distribution of galaxy redshifts in three small fields ~30° apart, the existence of a 10⁶ Mpc³ void in the distribution of galaxies in the constellation of Bootes. In this paper, we describe a redshift survey undertaken to test that hypothesis. Galaxies were selected by eye from 283 small fields distributed between the three original fields, and redshifts were measured for 239 of them. We confirm the existence of a large, roughly spherical void, of radius 62 Mpc, centered at α = 14ʰ50ᵐ, δ = +46°, v = 15,500 km s⁻¹.”
This study finds a radius of 62 Mpc, and therefore a diameter of 124 Mpc, approximately 400 million light years. Other more recent studies find radii of around 45 Mpc, which gives a diameter of around 90 Mpc or 300 million light years.
#Wegner, Gary A. et al. (2019): “Metal Abundances and Star Formation Rates of Emission-line Galaxies in and around the Boötes Void”, The Astrophysical Journal, vol. 883, 1
https://iopscience.iop.org/article/10.3847/1538-4357/ab3a3c/meta
Quote:“We utilize our own density analysis to define the boundaries of the Boötes Void used of this study. Historically, the void has been determined to be located at a redshift of ∼15,000 km s−1, with a radius of ∼3100 km s−1 (∼44 Mpc), and an approximate center of R.A. = 14h48m and decl. = 47° (Kirshner et al. 1983). [...] Our final void center was very close to the canonical values listed above. We adopt a velocity = 15,000 km s−1 and R.A. = 14h50m. The final radius of the void was set at 3200 km s−1 (45.7 Mpc), slightly larger than what is typically used.
[...]
The mean density of the Boötes Void galaxies given in Table 2 (log(ρ) = −2.14 galaxies/Mpc−3) corresponds to an underdensity δv of −0.91 if we adopt the median density of the SDSS+UZC galaxies from Section 3 for the global average density.”
#NASA Blueshift (2013): “Next Stop: Voids”
https://asd.gsfc.nasa.gov/blueshift/index.php/2013/07/30/jasons-blog-next-stop-voids/
Quote:“Our next contender is the Boötes (boh-OH-teez) Void (or the Great Void, for the more dramatic), discovered in 1981 and located in the vicinity of the constellation of the same name. At 250 to 330 million light years across, the Boötes Void is one of the largest voids out there that we’ve discovered. So far 60 galaxies have been discovered in the Boötes Void and all of those are found in a tube shape running through the void. For a fun thought experiment consider the distance between us and our closest galactic neighbor, Andromeda. At about 2.5 million light years, this would only cover about 1% of the Boötes Void. If we are to use a rough estimate of about 1 galaxy every 10 million light years (4 times farther than Andromeda) there should be approximately 2,000 galaxies in the Boötes Void.”
#Winder, Jenny (2025): “There's an enormous void of nothingness in our Universe. And scientists found it by accident” BBC Sky at Night Magazine
https://www.skyatnightmagazine.com/space-science/bootes-void
Quote: “The Boötes void spans an area 330 million lightyears across but contains very few galaxies, making it the largest void in the known Universe.”
—You are surrounded by perfect darkness, the most absolute blackness the human mind can conceive. There is no up or down. No motion. Nothing to orient yourself. There is not a single sign that the outside universe even exists. It’s an inescapable prison. And this isn’t some exotic corner of the cosmos. This is how the vast majority of the universe feels to human eyes. Just silent blackness without any movement. Everywhere. Forever.
The radius of the observable Universe is around 45 billion light-years
#NASA’s Goddard Space Flight Center (2017): “Age & Size of the Universe Through the Years”(retrieved 2024)
https://imagine.gsfc.nasa.gov/educators/programs/cosmictimes/educators/guide/age_size.html
Quote: “The most distant objects in the Universe are 47 billion light years away, making the size of the observable Universe 94 billion light years across. How can the observable universe be larger than the time it takes light to travel over the age of the Universe? This is because the universe has been expanding during this time.”
and it has around 2 trillion galaxies.
#Conselice, Christopher J. et al. (2016): “The evolution of galaxy number density at z < 8 and its implications” The Astrophysical Journal, vol. 830, 83
https://iopscience.iop.org/article/10.3847/0004-637X/830/2/83
Quote: “Our major finding is that the number densities of galaxies decrease with time such that the number density fT(z) ∼ t−1, where t is the age of the universe. We further discuss the implications for this increase in the galaxy number density with look-back time for a host of astrophysical questions. Integrating the number densities fT, we calculate that there are (2.0 ± 0.7/0.6) galaxies in the universe up to z = 8, which in principle could be observed.”
The Boöotes Void has about 10% of the mean density of galaxies in the Universe.
#Wegner, Gary A. et al. (2019): “Metal Abundances and Star Formation Rates of Emission-line Galaxies in and around the Boötes Void”, The Astrophysical Journal, vol. 883, 1
https://iopscience.iop.org/article/10.3847/1538-4357/ab3a3c/meta
Quote:“The mean density of the Boötes Void galaxies given in Table 2 (log(ρ) = −2.14 galaxies/Mpc−3) corresponds to an underdensity δv of −0.91 if we adopt the median density of the SDSS+UZC galaxies from Section 3 for the global average density.”
This means that the galaxy density in the Boötes Void is of
0.1 × (2×1012) galaxies / (45×109 light-years) = 2.5 × 1021 galaxies/light-year
Or equivalently, that we expect to find the closest a galaxy around 8 million light years from a random point. Note that in reality, the center of the void is likely to be even less dense and have galaxies more spaced out.
Even taking the closest galaxy to be only 8 million light-years from the center, and assuming that it is a big galaxy like Andromeda (as we will see, galaxies in voids tend to be smaller), its apparent magnitude would be:
m= 3.6 -2.5 × log((2.5 million light-years/8 million light-years) 2) = 9.4 > 6
#COSMOS - The SAO Encyclopedia of Astronomy: “Andromeda galaxy” (retrieved 2025)
https://astronomy.swin.edu.au/cosmos/a/andromeda+galaxy
#NASA (2025): “Messier 31”
which is much less bright than human eyes can see. To review apparent magnitude calculations, you can use this tutorial:
#Dinerstein, Harriet (2014): “Brightness, Magnitudes, and Luminosity: A Tutorial”
https://www.as.utexas.edu/astronomy/education/fall15/wheeler/secure/MagnitudeTutorial.pdf
—Although there is something mysterious hiding in the dark – faint tendrils of dark matter, penetrating into the void like cosmic lichen. A miniature echo of the much larger forest of dark matter filaments that forms the scaffold of galaxies and galaxy clusters outside the void.
#Sutter, Paul M. (2025): “Vast cosmic voids are far from empty — they're hiding something dark”, Space
Quote: “computer simulations show that there are filaments and tendrils of dark matter crisscrossing the voids like a faint echo of the grand cosmic web, repeating itself in miniature.”
#Sutter, Paul M. (2025): "Are the Cosmic Voids Really Empty?”, Ask a Spaceman!
Quote: “We know that there is this substructure inside of voids where if you look at a giant void in the universe, if you look carefully, especially in computer simulations, you can see these threads of material, these dwarf galaxies inside of the void like a faint echo of the cosmic web.”
—Before we could look deep into space, astronomers thought we lived in a uniform cosmos with galaxies spread out evenly. But instead, we found that galaxies, cosmic gas and dark matter were arranged into a vast cosmic web. A recurring pattern of sheets and filaments, organized around enormous empty gaps, meeting at dense knots with galaxy clusters and super clusters.
#Thompson, Laird A.; Gregory, Stephen A. (2011): “An Historical View: The Discovery of Voids in the Galaxy Distribution”
https://arxiv.org/abs/1109.1268
Quote: “Voids in the large scale distribution of galaxies were first recognized and discussed as an astrophysical phenomenon in two papers published in 1978. We published the first (Gregory and Thompson 1978) and Joeveer, Einasto and Tago (1978) published the second. The discovery of voids altered the accepted view of the large scale structure of the universe. In the old picture, the universe was filled with field galaxies, and occasional density enhancements could be found at the locations of rich galaxy clusters or superclusters. In the new picture, voids are interspersed between complex filamentary supercluster structure that forms the so-called cosmic web.”
#Scientific American (2024): “How Analyzing Cosmic Nothing Might Explain Everything”
https://www.scientificamerican.com/article/how-analyzing-cosmic-nothing-might-explain-everything/
Quote: “The discovery of cosmic voids in the late 1970s to mid-1980s came as something of a shock to astronomers, who were startled to learn that the universe didn’t look the way they’d always thought. They knew that stars were gathered into galaxies and that galaxies often clumped together into clusters of dozens or even hundreds. But if you zoomed out far enough, they figured, this clumpiness would even out: at the largest scales the cosmos would look homogeneous.”
#Hamaus, Nico et al. (2016): “Constraints on Cosmology and Gravity from the Dynamics of Voids”, Physical Review Letters, vol. 117, 9, 091302
https://link.aps.org/accepted/10.1103/PhysRevLett.117.091302
Quote: “The universe is mostly composed of large and relatively empty domains known as cosmic voids, whereas its matter content is predominantly distributed along their boundaries. The remaining material inside them, either dark or luminous matter, is attracted to these boundaries and causes voids to expand faster and to grow emptier over time.”
#Stapelberg, Sebastian (2022): “The Cosmic Web of Galaxies, Dark Matter and How It Emerged”, STRUCTURES Blog
https://structures.uni-heidelberg.de/blog/posts/2022_12_cw/
Quote: “Instead of being randomly, uniformly scattered in space, galaxies are distributed along geometric patterns outlined by huge, tenuous filaments and planar features known as sheets [...]. These filaments and sheets are separated by cosmic voids – vast regions nearly empty of galaxies. While prominent filaments can reach lengths of several 100 million light-years, voids have typical diameters between 30 and 300 million light-years.”
#Sutter, Paul M. (2021): “Is the Universe a Fractal?”, Ask a Spaceman!
https://www.pmsutter.com/shows/askaspaceman-archive/2021/04/06/aas149-is-the-universe-a-fractal
Quote: “With computer work, you can explore the dark matter structure of a void of what's happening to the dark matter, and you'll see voids and there are sub voids in it, and then you zoom into those sub voids and you'll get tinier voids, sub sub voids and then sub sub sub voids sub sub sub sub sub sub voids. And just like with the Halos, there's a self similar structure. This is actually something I worked on myself. Well, not myself myself, but there was. I was part of a team we were all working on together, but we discovered a self similar universal structure to voices, so they're not just nested. They're also self similar. A tiny void, a sub sub sub void just looks like a scaled down version of a big void, and vice versa. If you take a big void and squeeze it down, you get a good description of a smaller void of one of its sub voids. It's It's a fractal like structure. Obviously, these fractals don't exist at all scales because eventually, if you get too small, you get down to like, absolutely nothing inside of a void, or you get inside of a galaxy inside of a cluster and bigger at the homogeneity scale.”
—In reality galaxies shoot through space at speeds of millions of kilometers per hour. They are on collision courses, orbiting each other, moving towards the center of larger galaxy clusters millions of light years away.
#Libeskind, Noam I.; Tully, R. Brent (2016): “How Astronomers Found Our Cosmic Address”
https://www.scientificamerican.com/article/how-astronomers-found-our-cosmic-address1/
—But they always seem to stick to the rims of voids like reflections of light on soap bubbles – which is kind of weird. If they are this fast and dynamic, shouldn’t a galaxy shoot into a void occasionally?
#Van de Weygaert, Rien (2002): “Froth across the Universe Dynamics and Stochastic Geometry of the Cosmic Foam”, Modern Theoretical and Observational Cosmology. Astrophysics and Space Science Library, vol. 276, edited by Plionis, M., Cotsakis, S. Springer, Dordrecht.
https://arxiv.org/abs/astro-ph/0206427
Quote:“The interior of the Universe is permeated by a tenuous space-filling frothy network. Welded into a distinctive foamy pattern, galaxies accumulate in walls, filaments and dense compact clusters surrounding large near-empty void regions. ”
—The way gravity works is that everything with mass in the universe attracts every other thing with mass. And since there is almost no mass inside, the cosmic web of galaxy super clusters on their edges are pulling things out of voids. The emptier a void is, the harder gravity is pulling on what remains. It's really like a tug of war where one side isn’t even trying. Over time voids are really only getting even emptier and the walls and knots around them denser and brighter.
#Chiou, Lyndie (2023): “How (Nearly) Nothing Might Solve Cosmology’s Biggest Questions”, Qanta Magazine
https://www.quantamagazine.org/how-nearly-nothing-might-solve-cosmologys-biggest-questions-20230725/
Quote: “The [voids] have a tendency to expand because inside them, there isn’t much matter to exert an inward gravitational pull. The stuff outside them tends to stay away. And any galaxies that start inside a void get tugged outward by the gravitational pull of the structures defining a void’s edge.”
#Hamaus, Nico et al. (2016): “Constraints on Cosmology and Gravity from the Dynamics of Voids”, Physical Review Letters, vol. 117, 9, 091302
https://link.aps.org/accepted/10.1103/PhysRevLett.117.091302
Quote: “The universe is mostly composed of large and relatively empty domains known as cosmic voids, whereas its matter content is predominantly distributed along their boundaries. The remaining material inside them, either dark or luminous matter, is attracted to these boundaries and causes voids to expand faster and to grow emptier over time.”
—Well not technically, the hardest part is escaping the gravity of your home galaxy.
Even though present technology is not able to reach the escape velocity to get away from our galaxy,
#New Scientist (2013): “Stars' escape velocity shows how to exit the Milky Way”
https://www.newscientist.com/article/dn24249-stars-escape-velocity-shows-how-to-exit-the-milky-way/
Quote: “To escape the gravitational clutches of our galaxy, a spaceship would need to zoom out of our solar system and hit 537 kilometres per second. For context, a rocket needs to roar off at just 11.2 kilometres per second to escape Earth’s gravity.”
a future civilization with spacecraft capable of the right velocities could. The hardest part to enter, for example, the Local Void, is still to leave the Milky Way, because the vast majority of the gravitational potential you have to climb to reach the void is inside your galaxy.
—Galaxies in the crowded cluster regions like our Milky Way are very active, since its neighbours gravity tugs and pulls at it, galaxies collide and merge. Void galaxies are so isolated that they are aging in slow motion.They tend to be smaller bluer and full of gas, birthing new stars slower and calmer.
#Domínguez-Gómez, Jesús et al. (2023): “Galaxies in voids assemble their stars slowly”, Nature, vol. 619, 269–271
https://www.nature.com/articles/s41586-023-06109-1
Quote: “Indeed, previous studies have shown that galaxies in voids are, on average, bluer and less massive, and have later morphologies and higher current star formation rates than galaxies in denser large-scale environments. However, it has never been observationally proved that the star formation histories (SFHs) in voids are substantially different from those in filaments, walls and clusters. Here we show that void galaxies have had, on average, slower SFHs than galaxies in denser large-scale environments. We also find two main SFH types present in all the environments: ‘short-timescale’ galaxies are not affected by their large-scale environment at early times but only later in their lives; ‘long-timescale’ galaxies have been continuously affected by their environment and stellar mass. Both types have evolved more slowly in voids than in filaments, walls and clusters.”
#Kreckel, Kathryn Joyce (2011): “Gas in Void Galaxies”, Doctoral Thesis.
https://academiccommons.columbia.edu/doi/10.7916/D8BV7PMR
Quote: “We find that the void galaxies are generally gas rich, low luminosity, blue disk galaxies, but identify three as early type galaxies.”
—There is one more thing that makes voids unique places: Dark Energy. The mysterious force that most scientists think is accelerating the expansion of the universe and will ultimately cause its demise.
Check these links for an introduction on Dark Energy and its impact on the fact of the Universe:
#NASA (2025): “Dark Energy”
https://science.nasa.gov/dark-energy/
#Rubin Observatory: “Dark Energy and the Fate of the Universe” (consulted 2025)
https://www.lsst.org/science/dark-energy/universe
—We can’t see dark energy do anything inside our galaxy or inside clusters because there is too much stuff pulling things together via gravity – but we can see its effects inside voids. Here dark energy blows up the bubbles of nothing. This is where the acceleration of cosmic expansion becomes visible.
#Sutter, Paul M. (2025): "Are the Cosmic Voids Really Empty?”, Ask a Spaceman!
Quote: “Dark energy is always present even in empty spaces. In fact, the voids are where dark energy calls its home. Here in a high density environment like the galaxy, dark energy is in the background. The amount of matter, the amount of radiation, the amount of energies here in a galaxy completely swamp anything that dark energy is capable of.
Go out in the void to get rid of all the stuff. All that's left is dark energy. The accelerated expansion of the universe is happening in the voids. That's where that work is taking place to accelerate the expansion of the universe. And that's always present.”
We thank expert Alice Pisani for the following comment:
Quote: “Since dark energy rules in cosmic voids, scientists know now that voids are our best bet to understand this mysterious component. Using voids to understand dark energy is one of the main reasons (if not the main one) voids are becoming so popular.”
— As the emptiness encroaches walls of thousands of galaxies, are thinned out and pulled towards the edges – attracted by much denser regions at the margins, giving space to the emptiness of two void bubbles becoming one.
#Sutter, Paul M. (2014): “The life and death of cosmic voids”, Monthly Notices of the Royal Astronomical Society, vol. 445, 2, 1235–1244.
https://academic.oup.com/mnras/article/445/2/1235/1408011
“[P]ure merging, occurs when high-density barriers between two voids completely dissolve due to outflows. When the barrier becomes too low, the separate voids become indistinguishable from each other, forming a single larger void. However, as we will discuss below, this is a very rare process. Instead, what more frequently occurs is annexation of subvoids as a larger parent void assembles, generating a hierarchy”
We thank expert Sofia Contarini for the following comment:
Quote: “The filaments around voids will become thinner and thinner over time, pushing matter toward the knots (galaxy clusters). ”
—In the far, far future supervoids will take over the observable universe. Crushing clusters, and expanding further and further, until the entire observable universe is nothing more than a gigantic void of nothingness.
We thank expert Sofia Contarini for the following comment:
Quote: “Voids will ultimately take over the cosmic volume, but the dominant force remains the gravity generated by filaments and knots.[...]Clusters will actually become denser in the future, and their central black holes may eventually accrete most of the surrounding matter.”
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