Northern Local Supervoid
The Great Underdensity Beyond the Milky Way
Quick Reader
| Attribute | Details |
|---|---|
| Name | Northern Local Supervoid (also known as the Local Void) |
| Type | Cosmic Void / Large Underdense Region |
| Location | Northern Celestial Hemisphere — roughly behind constellations Hercules, Aquila, Ophiuchus, and Serpens |
| Distance from Earth | Near edge ~20–30 million light-years; extends to ~80–100 million light-years |
| Approx. Diameter | ~150–200 million light-years |
| Density Contrast (δρ/ρ) | −0.6 to −0.8 (significantly underdense) |
| Discovery | First identified in 1987 by Tully & Fisher through galaxy redshift mapping |
| Neighboring Structures | Virgo Supercluster, Hercules Supercluster, Southern Local Supervoid, Local Group |
| Composition | Sparse galaxies, isolated dwarfs, low gas density, dark matter deficit |
| Cosmic Flow Effect | Contributes to Local Group’s peculiar velocity and anisotropic expansion |
| Scientific Relevance | Key for studying local gravitational flows, dark matter distribution, and cosmic expansion asymmetries |
Introduction — The Empty Northern Horizon
Just beyond our own Local Group of galaxies, in the direction opposite to the Virgo Cluster, lies a vast region of space nearly devoid of galaxies — the Northern Local Supervoid, more commonly known as the Local Void.
This immense underdense zone begins just beyond the Milky Way’s neighborhood and stretches over 150–200 million light-years into the northern celestial hemisphere.
Despite its emptiness, the void plays a powerful gravitational role — shaping how nearby galaxies move, and even influencing our own Milky Way’s cosmic drift.
Together with its southern counterpart, the Southern Local Supervoid, this region forms part of the Laniakea Supercluster’s boundary architecture — the great underdense basins that frame our corner of the universe.
Discovery — From Galaxy Deficit to Cosmic Reality
Early Observations
In the mid-1980s, astronomers noticed a surprising scarcity of galaxies in redshift surveys aimed toward the constellation Hercules.
While the Virgo direction was crowded with galaxies, the opposite hemisphere appeared eerily empty.
The Work of Brent Tully and Colleagues
In 1987, Tully & Fisher formally identified this region as the Local Void, using velocity-distance data of nearby galaxies.
They found that galaxies near the void’s edge were moving outward faster than expected — evidence of gravitational evacuation caused by an underdense region.
Subsequent surveys, including Cosmicflows-3, 2MASS, and SDSS, confirmed that this is not a small cavity but a major void structure shaping local cosmic flows.
Size, Structure, and Boundaries
The Northern Local Supervoid is one of the closest major voids to Earth. It begins immediately beyond the Local Group and stretches roughly 80–100 million light-years into the northern celestial hemisphere.
| Boundary Region | Neighboring Structure | Nature |
|---|---|---|
| Southern Edge | Local Sheet (Milky Way + M31 region) | Dense interface |
| Eastern Boundary | Virgo Cluster | Gravitational attractor |
| Western Boundary | Hercules Supercluster | Dense filament wall |
| Northern Boundary | Coma–Berenices Ridge | Transition to higher-density zones |
The void’s shape is asymmetric and elongated, like a teardrop extending northward, partially enclosed by the Virgo–Hercules filamentary ridge.
It is not a perfect bubble — rather, a hierarchy of smaller sub-voids that merge into one large gravitational depression.
Matter Distribution — Almost Empty, but Not Quite
Inside the Northern Local Supervoid, galaxy density is only 20–30% of the cosmic mean.
Most galaxies here are small, irregular systems — faint, blue, and gas-rich.
Typical Examples:
ESO 461-36: A dwarf irregular galaxy drifting outward from the void’s center.
UGC 9128 and KK 246: Isolated dwarfs showing low metallicity and minimal interaction history.
Even dark matter halos are rare and diffuse. Gravitational lensing studies show extremely low mass density, confirming that the void is genuinely underdense — not merely hidden by dust or perspective.
Cosmic Flow — The Void Push Effect
Voids do not simply sit still; they expand faster than the rest of the universe, creating outward “flows” of galaxies from their interiors toward denser regions.
This phenomenon gives rise to the void push — the gravitational repulsion caused by the lack of mass inside.
In the Northern Local Supervoid:
Galaxies at its boundary exhibit outflow velocities up to 260 km/s.
The Milky Way, positioned on its edge, is being subtly pushed away from the void while simultaneously pulled toward Virgo.
This dual influence explains part of the Local Group’s peculiar velocity (roughly 630 km/s relative to the cosmic microwave background).
Thus, the void indirectly affects our galaxy’s cosmic motion — a striking reminder that even emptiness has gravitational consequences.
Relationship with the Local Sheet and Virgo Cluster
The Local Sheet, which includes the Milky Way, Andromeda, and nearby galaxies, forms a dense membrane separating the Local Void from the Virgo attractor.
Matter from the sheet is gradually draining toward Virgo, while the void on the opposite side expands freely.
This creates a dipolar flow pattern:
Outflow from the void (pushing)
Infall toward Virgo (pulling)
Together, they shape the Laniakea Supercluster’s inner velocity field, where the balance between emptiness and clustering defines our cosmic neighborhood.
Observational Evidence — Mapping the Invisible
1. Galaxy Redshift Surveys
The underdensity first appeared in 2MASS and SDSS data as a conspicuous gap in galaxy counts behind the Local Group.
2. Peculiar Velocity Analysis
The Cosmicflows-3 database maps galaxy velocities showing outward flow from the void’s interior.
3. HI (Radio) Surveys
Sensitive HI observations detect isolated gas-rich dwarfs inside the void — evidence of galaxies evolving in isolation.
4. CMB Correlations
Subtle cold regions in the Planck and WMAP maps correlate with the void’s direction, consistent with an Integrated Sachs–Wolfe (ISW) imprint due to the low gravitational potential.
These independent methods together confirm that the Northern Local Supervoid is a real physical structure — not an observational artifact.
Scientific Relevance
Cosmic Expansion Laboratory
Its proximity allows precise study of how voids evolve and expand under dark energy.Environmental Galaxy Evolution
Void galaxies provide insight into how isolation affects star formation, metallicity, and gas retention.Local Flow Calibration
By analyzing the void’s push against the Virgo pull, cosmologists refine models of our Local Group’s motion.Testing ΛCDM Predictions
Comparing observed void sizes and shapes with simulations validates standard cosmological models — and challenges them where discrepancies arise.
Visualizing the Northern Local Supervoid
Imagine the universe as a vast cosmic foam.
In this foam, the Northern Local Supervoid is a bubble attached to our own Local Sheet, surrounded by glowing filaments — Virgo, Hercules, and Coma.
Inside lies a faint mist of galaxies, glowing weakly amid darkness.
Though visually empty, its presence defines the geometry of our cosmic home.
Internal Structure and Sub-Void Complexity
The Northern Local Supervoid is not a simple hollow space; it is composed of multiple nested sub-voids separated by faint filaments of galaxies and dark matter. These internal “cells” form a network of smaller cavities that together create one of the most complex near-field underdense systems ever mapped.
Major Sub-Voids and Features
| Subregion | Approx. Distance (Mly) | Notes |
|---|---|---|
| Inner Local Void | 20–60 | Nearest underdense zone bordering the Local Sheet |
| Aquila–Hercules Void | 70–100 | Largest sub-void; extends behind Hercules and Serpens |
| Ophiuchus Extension | 100–130 | Links to the Hercules Supercluster boundary |
| Coma Ridge Transition | 140–180 | Gradual gradient into the Coma–Berenices filament |
Each layer shows decreasing galaxy density toward the center, with sparse islands of dwarf systems and HI gas filaments marking residual structure.
Flow Field — A Push from the Void
Outward Expansion
Galaxies inside the Northern Local Supervoid are not stationary.
Their velocities relative to the cosmic background reveal a steady outward motion — sometimes called the Local Void expansion.
Typical peculiar velocity: 250–300 km/s outward
Expansion rate: Slightly higher than the average cosmic Hubble flow
Direction: Away from the void center, toward Virgo and Hercules
This outflow reflects the fact that underdense regions expand faster than the universe as a whole, while dense regions (like Virgo) lag behind, forming the opposite gravitational poles of the local flow field.
The Local Sheet as a “Cosmic Membrane”
Our Milky Way and the Andromeda Galaxy (M31) lie within a thin region called the Local Sheet, which acts as a dense boundary between the Local Void (north) and the Virgo Cluster (south).
It functions as a gravitational membrane — galaxies on one side are pushed outward by the void’s expansion and pulled inward by Virgo’s mass.
This geometry helps explain:
The 630 km/s peculiar velocity of the Local Group (CMB dipole)
The asymmetric galaxy distribution in the nearby universe
The large-scale balance of the Laniakea Supercluster’s inner flows
Galaxy Evolution Inside the Void
Galaxies within the Northern Local Supervoid live in near-total isolation. With few neighbors and weak tidal interactions, they evolve slowly and often remain primitive — preserving characteristics of early galaxies.
| Environment | Typical Galaxy Type | Properties | Example |
|---|---|---|---|
| Void Core | Dwarf irregular | Low metallicity, extended HI disks | KK 246, ESO 461-36 |
| Inner Filament | Spiral | Mild star formation, small bulges | UGC 9128 |
| Outer Boundary | Lenticular, spiral mix | Transitional; denser gas, tidal hints | NGC 6503, NGC 6946 |
Distinct Traits:
- High Gas Content: Many contain vast HI reservoirs despite small stellar mass.
- Blue Colors: Indicate continuous, low-level star formation over billions of years.
- Low Metallicity: Evidence of limited recycling of stellar material.
- Minimal Mergers: Weak gravitational field prevents major collisions.
These galaxies provide a window into primordial galaxy evolution, effectively serving as time capsules of the early universe’s isolated environments.
Gravitational Effects and Cosmic Flows
The Local Void’s influence extends beyond its immediate boundary, contributing to the peculiar velocities of nearby galaxy groups.
Key Flow Interactions:
| Flow Region | Effect | Direction |
|---|---|---|
| Milky Way / Local Group | Outward push + Virgo pull | Toward Virgo Cluster |
| Leo Spur (south) | Moving toward the Local Sheet | Counteracting void expansion |
| Hercules Boundary | Compression zone | Merging into Hercules Supercluster |
| Coma Filament | Mild infall | Joining northern cosmic ridge |
This interplay creates anisotropy in local expansion — an uneven rate of motion depending on direction. While the Hubble flow is uniform on large scales, the Local Void introduces local directional gradients in velocity, a phenomenon confirmed through Cosmicflows-3 and 6dFGS datasets.
Interaction with the Southern Local Supervoid
The Northern and Southern Local Supervoids together form a dual-void system enclosing the Laniakea Supercluster’s equatorial plane.
Shared Characteristics:
- Connected through a corridor behind the Milky Way’s plane
- Combined span exceeds 1 billion light-years end-to-end
- Together balance gravitational flows feeding into Virgo, Fornax, and Hydra–Centaurus
| Feature | Northern Void | Southern Void |
|---|---|---|
| Mean Density Contrast | −0.7 | −0.8 |
| Size | ~150–200 Mly | ~600 Mly |
| Nearest Wall | Virgo Cluster | Sculptor–Fornax Wall |
| Dominant Flow | Outward from Local Sheet | Outward from Sculptor core |
| Role | Northern expansion counterweight | Southern gravitational release |
This hemispheric symmetry demonstrates how the Local Universe maintains equilibrium — dense superclusters are surrounded by vast voids that expand in opposite directions, distributing gravitational tension evenly across the Laniakea domain.
CMB and the Local Cold Spot Correlation
While the Local Void itself does not fully account for the famous “CMB Cold Spot” in the constellation Eridanus, it contributes to nearby temperature asymmetries in the northern sky.
Photons traveling through the void lose slight energy due to the Integrated Sachs–Wolfe (ISW) effect, producing faint temperature dips (~20 µK) detectable by WMAP and Planck missions.
This confirms that even nearby voids imprint the cosmic microwave background, linking local large-scale structure to the geometry of the observable universe.
Observational Techniques
Mapping such a close yet diffuse region requires combining multiple methods:
Redshift Surveys (2MASS, SDSS, Cosmicflows): Identify the three-dimensional deficit in galaxy density.
Velocity Field Mapping: Derive peculiar velocities to infer gravitational potential gradients.
HI Radio Observations (ALFALFA, ASKAP): Detect faint, gas-rich dwarf galaxies.
Weak Gravitational Lensing: Quantify the void’s low dark matter content.
Numerical Simulations: Compare observed flows with ΛCDM predictions for local structure growth.
Together, these tools provide a comprehensive 3D map of the Local Void’s shape, mass deficit, and gravitational influence.
Environmental Gradient — From Emptiness to Density
Across the Local Sheet and beyond Virgo, the cosmic environment changes dramatically.
| Region | Density | Morphology | Behavior |
|---|---|---|---|
| Void Core | Very low | Dwarfs, irregulars | Expanding outward |
| Transition Zone | Moderate | Spirals | Mild infall |
| Boundary Wall | High | Ellipticals, clusters | Gravitationally bound |
| Virgo Supercluster | Extreme | Clustered galaxies | Strong infall |
This progression illustrates the morphology–density relation across a void-to-cluster continuum, showing how gravity and isolation shape galaxies differently along the same cosmic structure.
Importance in Cosmology
The Northern Local Supervoid remains one of the most accessible cosmic voids for studying near-field cosmology, because of its proximity and direct dynamical connection to our Local Group.
It is used to:
Calibrate cosmic flow models
Measure Hubble constant variations locally
Analyze void expansion and dark energy effects
Test anisotropic cosmological parameters
Thus, this “empty” region provides the empirical foundation for understanding how space expands and how gravity sculpts the local cosmic web.
Evolution and Future of the Northern Local Supervoid
The Northern Local Supervoid, though vast and nearly empty, is far from static. Like all cosmic voids, it evolves with time — expanding, reshaping, and subtly influencing the flow of galaxies around it.
Formation and Early Growth
Shortly after the Big Bang, tiny quantum fluctuations in matter density began to grow under gravity.
Regions slightly less dense than average expanded faster, gradually evacuating matter and leaving behind underdense zones.
Over billions of years, these regions merged into larger voids.
The Northern Local Supervoid likely formed when neighboring dense areas — such as the Virgo and Hercules Superclusters — pulled mass away, deepening the local underdensity.
By around 6–8 billion years ago, the void had reached most of its current size (~150 million light-years), and has continued to expand slowly since then.
Present-Day State
Today, the Northern Local Supervoid is in a mature expansion phase, characterized by:
Density contrast: δρ/ρ ≈ −0.7 (about 30% of the mean cosmic density)
Core expansion velocity: ~300 km/s relative to the cosmic average
Dominant mass components: Dark matter (~80%), baryons (~20%)
Shape: Irregular ellipsoid connected to multiple minor sub-voids
It continues to expand faster than its surroundings, gently pushing galaxies along its edges and sustaining an outward flow into the Virgo and Hercules basins.
The Far Future — A Void-Dominated Era
In the distant future, the Northern Local Supervoid will expand further under the influence of dark energy, gradually detaching from neighboring walls and clusters.
| Timeframe | Predicted Evolution | Description |
|---|---|---|
| +10 billion years | Boundary thinning | Sparse filaments and dwarfs drift farther apart |
| +50 billion years | Isolation phase | The void expands beyond gravitational connection with Virgo |
| +100 billion years | Dark energy domination | The Local Group and Virgo remain bound; the void becomes effectively infinite |
| +1 trillion years | “Island Universe” epoch | All surrounding structures recede beyond visibility; the void defines our entire observable region |
Thus, the Northern Local Supervoid’s destiny reflects the cosmic fate of all structure — gradual isolation and expansion until only local groups remain gravitationally intact.
Comparison with Other Major Voids
| Property | Northern Local Supervoid | Southern Local Supervoid | Boötes Void | Eridanus Void |
|---|---|---|---|---|
| Mean Distance (Mly) | 20–100 | 100–300 | 700 | 500 |
| Diameter (Mly) | 150–200 | 600 | 1,100 | 800 |
| Density Contrast | −0.6 to −0.8 | −0.8 to −0.9 | −0.9 | −0.7 |
| Nearby Clusters | Virgo, Hercules | Fornax, Pavo–Indus | Boötes Wall | Eridanus–Pavo |
| Relation to Milky Way | Adjacent (north) | Opposite (south) | Distant (north galactic cap) | Mid-southern hemisphere |
| Role | Drives local outflow | Balances southern gravitational field | Prototype deep void | Links southern large-scale flows |
The Northern Local Supervoid is smaller but dynamically more significant due to its proximity to the Milky Way. Its “push” helps explain the Local Group’s peculiar velocity and contributes to the Laniakea Supercluster’s equilibrium between attraction and repulsion.
Cosmological Significance — What the Void Reveals
A Laboratory for Cosmic Expansion
Because it is nearby, the Local Void allows astronomers to measure how dark energy accelerates expansion in low-density environments.Clues to Galaxy Formation
Void galaxies evolve slowly, preserving early-universe properties — vital for understanding primordial star formation and chemical enrichment.Defining the Laniakea Flow Field
The Local Void’s outward expansion balances the Virgo Cluster’s inward pull, helping maintain the overall velocity coherence of our local cosmic basin.Testing Cosmological Uniformity
Observing anisotropic flows caused by voids helps test whether Hubble expansion is truly isotropic or subtly influenced by nearby underdensities.
Frequently Asked Questions (FAQ)
Q1. Is the Northern Local Supervoid the same as the Local Void?
Yes. The Northern Local Supervoid is often called the “Local Void.” It lies adjacent to the Local Group, primarily extending northward from our galactic plane.
Q2. How large is it compared to other voids?
It’s relatively small (~150–200 million light-years) but very influential because it’s so close to us. Many large-scale voids, like Boötes, are 5–10 times larger but much farther away.
Q3. How does the void affect our galaxy’s motion?
The Milky Way sits on the void’s southern edge. The void’s expansion pushes us outward, while the Virgo Cluster pulls us inward. This combination helps explain our Local Group’s velocity relative to the cosmic background.
Q4. Are there galaxies inside the void?
Yes, but very few — mostly isolated dwarf irregulars and small spirals that evolve slowly and retain lots of gas.
Q5. Can the void be observed directly?
Not visually. It’s mapped through galaxy redshift surveys and velocity field data, which show where galaxies aren’t.
Q6. What is its role in the larger universe?
It defines one of the gravitational “basins” around the Laniakea Supercluster, balancing cosmic flows and demonstrating how underdensities structure space on the largest scales.
Related Pages:
Southern Local Supervoid – The Great Cosmic Hollow of the Southern Sky
Virgo Supercluster – The Core of Laniakea
Laniakea Supercluster – Mapping Our Cosmic Home
Cosmic Voids – Where the Universe Breathes
Boötes Void – The Deepest Known Abyss
Final Thoughts
The Northern Local Supervoid is a silent architect of our cosmic motion — an invisible engine behind the Milky Way’s drift through space.
Though defined by absence, it exerts real influence, proving that even emptiness has gravitational form.
Its counterpart in the south completes the balance of the local universe: together, they carve the great hollow corridors through which galaxies flow, shaping the cosmic architecture we inhabit.
In studying this nearby void, we glimpse not only how the universe expands but also how it breathes — through alternating patterns of density and silence, creation and emptiness, matter and space itself.
