This is the loneliest galaxy in the known Universe

Throughout the cosmos, stars and galaxies appear everywhere.

new era astronomy

The principal galaxies of Stephan’s Quintet, as revealed by JWST on July 12, 2022. The galaxy on the left is only about 15% distant as the other galaxies, and the background galaxies are many times further away. Yet, they’re all equally sharp in JWST’s eyes, proving that the Universe is filled with stars and galaxies just about everywhere we look.

Credit: NASA, ESA, CSA and STScI

In our backyard we inhabit the Local Group of galaxies.

local group galaxies

This three-dimensional view of the Local Group shows the three largest galaxies and their relative positions in space: Andromeda (M31), the Milky Way and Triangulum (M33). Both Andromeda and Triangulum are visible to the naked eye, as are the Large and Small Magellanic Clouds. Over the next billion years, these galaxies will interact and merge, as our entire Local Group is gravitationally bound.

Credits: Antonio Ciccolella/Wikimedia Commons

We are one of many groups on the outskirts of a large cluster of galaxies.

Virgo supercluster

The various galaxies of our local supercluster, dominated by the dense Virgo Cluster of galaxies. Here, all the galaxies appear clustered and clustered together. On the largest scales, the Universe is uniform, but if you look at the scales of galaxies or clusters, overdense and underdense regions dominate. Each group and cluster of galaxies within this larger structure will remain gravitationally bound, individually, but the groups that make up the apparent larger structure are not bound together. As the Universe expands, they will disappear from each other’s reach.

Credit: Andrew Z. Colvin/Wikimedia Commons

On larger cosmic scales, our Universe clumps into a large filamentous web.

dark matter

This fragment of a medium-resolution structure formation simulation, with the expansion of the Universe scaled down, represents billions of years of gravitational growth in a dark matter-rich universe. Note that the filaments and rich clusters, which form at the intersection of the filaments, arise mainly due to dark matter; normal matter plays only a minor role. The bigger your simulation, however, the more that smaller-scale structure is inherently underrated and “smoothed out”.

Credit: Ralf Kaehler and Tom Abel (KIPAC)/Oliver Hahn

Galaxies inhabit these filaments, with clusters forming at their nexus.

coma clustered zwicky dark matter

The Coma cluster of galaxies, seen with a composite of modern space and ground-based telescopes. The Coma Cluster, the largest cluster of galaxies in our nearby Universe, is dominated by two giant elliptical galaxies, with over 1000 other spirals and ellipticals inside. The velocity of individual galaxies within the Coma Cluster is too great for the cluster to remain a bound entity based on its normal matter content alone. Only unless there is a substantial amount of additional matter, i.e. a source of dark matter, throughout this cluster can it remain a bound object according to Einstein’s laws of General Relativity. The total mass of the cluster comes to a few quadrillion solar masses.

Credit: NASA / JPL-Caltech / L. Jenkins (GSFC)

But the matter-poor space between these filaments creates great cosmic voids.

Herschel, Lockman hole cluster of galaxies

A matter-free region of space in our galaxy reveals the Universe beyond, where every point is a distant galaxy. The cluster/void structure can be seen very clearly, demonstrating that our Universe does not have exactly uniform density on all scales. While there are many regions rich in galaxies, regions poor in galaxies or even without galaxies are also abundant, like holes inside a cosmic swiss cheese.

Credit: ESA/Herschel/SPIRE/HerMES

These underdense regions lose their matter to the surrounding denser areas.

large-scale structure growth

Over time, gravitational interactions will transform a mostly uniform, equal-density Universe into one with large concentrations of matter and huge voids separating them. Because simulations are limited in the number of particles they can handle simultaneously, the largest-scale cosmic simulations are inherently limited in their ability to resolve individual primitive galaxies. However, the large subdense regions, the cosmic voids within our Universe, are well understood.

Credit: Volker Springel/MPE

They typically have fewer, smaller, and fainter galaxies than the richer cluster regions.

Subdense supervoid dipole repeller

The relative pull and pull effects of overdense and underdense regions on the Milky Way are mapped here at distance scales of hundreds of millions of light years. Overdense and underdense regions pull and push matter, giving it velocities hundreds or even thousands of kilometers faster than we would expect from redshift measurements and the Hubble flux alone. These gigantic collections of galaxies can be divided into superclusters, but their subdense counterparts, the great cosmic voids, play an equally important role on a cosmic scale.

Credit: Y. Hoffman et al., Nature Astronomy, 2017

However, a relatively deep void has the remarkable galaxy MCG+01-02-015.

Loneliest galaxy MCG+01–02–015 Hubble

The galaxy MCG+01–02–015, shown here, lies in the center of a void in the direction of the constellation Pisces. The galaxy, located about 293 million light-years away, is the only known galaxy within 100 million light-years of its location.

Credits: ESA/Hubble & NASA and N. Grogin (STScI); Thanks: Judy Schmidt

This impressive Milky Way-like spiral has many classic features.

NGC 6384 Milky Way-like galaxy

The spiral arms of the galaxy NGC 6384 are where new stars mainly form in this galaxy. Under normal circumstances, the spiral arms in the disk of a spiral galaxy are where most new stars form. With many features in common with our own Milky Way, NGC 6384 is one of the best candidates for a near-twin of the Milky Way. Its similarities to MCG_01-02-015 are also striking.

Credit: ESA/Hubble and NASA

It has a gas-rich disk, dusty arms, center bar and bulge, and abundant heavy elements.

empty cluster structure universe

Between the great clusters and filaments of the Universe are great cosmic voids, some of which can extend hundreds of millions of light-years in diameter. While some voids are larger than others, spanning a billion light-years or more, they all contain matter to some degree. Even the void hosting MCG+01–02–015, the loneliest galaxy in the Universe, likely contains small, low-surface-luminosity galaxies that are below the current detection limit of telescopes like Hubble.

Credits: Andrew Z. Colvin and Zeryphex/Astronom5109; Wikimedia Commons

But it is centrally located within a particularly sparse and low-density “empty” region.

Loneliest galaxy MCG+01–02–015 Hubble

Despite the visual appearance of other galaxies near MCG+01-02-015, none of these galaxies are actually in the same region of space. With only one or two notable exceptions of small, faint nearby galaxies, nearly all of the galaxies shown in this image lie behind MCG+01-02-015; they are background galaxies that are simply along the same line of sight.

Credits: ESA/Hubble & NASA and N. Grogin (STScI); Thanks: Judy Schmidt

Our best telescopes do not identify any other substantial galaxies within ~100 million light years.

large and small magellanic cloud

The Large (top right) and Small (bottom left) Magellanic Clouds are visible in the southern skies and helped guide Magellan on his famous journey some 500 years ago. In reality, the LMC is about 160-165,000 light-years away, with the SMC slightly further away at 198,000 light-years. Both galaxies, along with Triangulum and Andromeda, are visible to the naked eye.

Credit: ESO/S. brunier

In contrast, four galaxies beyond the Milky Way are visible to naked human eyes.

Hubble discovers andromeda cepheid

Hubble’s discovery of a Cepheid variable in the Andromeda galaxy, M31, opened up the Universe for us, gave us the observational evidence we needed for galaxies beyond the Milky Way and led us, in a short time, to the discovery of the Universe in expansion.

Credits: NASA, ESA and Hubble Heritage Team (STScI/AURA); Illustration via NASA, ESA and Z. Levay (STScI)

Their extragalactic nature has been confirmed by 1920s technology.

hubble storyline expanding universe

Edwin Hubble’s original plot of galaxy distances to redshift (left), establishing the expanding Universe, compared to a more modern counterpart some 70 years later (right). According to both observation and theory, the Universe is expanding, and the slope of the line relating distance to the recession rate is a constant.

Credit: E. Hubble; R. Kirshner, PNAS, 2004

This cosmic company revealed the expanding Universe for the first time.

maffei 1 2 infrared galaxies

Italian astronomer Paolo Maffei’s promising work on infrared astronomy culminated in the discovery of galaxies — such as Maffei 1 and 2, shown here — in the plane of the Milky Way itself. Maffei 1, the giant elliptical galaxy at lower left, is the closest giant elliptical to the Milky Way, but it wasn’t discovered until 1967. For more than 40 years after the Great Debate, no spirals were known in the plane of the Milky Way , thanks to the light blocking powder that is very effective at visible wavelengths.

Credit: NASA/JPL-Caltech/UCLA

But discovering another galaxy, from within MCG+01-02-015, requires 60s-level telescopes.

x-ray emission 3c 295 clusters

Galaxy 3C 295, at the center of galaxy cluster ClG J1411+5211, is shown in a composite X-ray/optical view in violet, with X-rays exploded to reveal the central radio and X-ray noisy nucleus. A 5 6 billion light-years away, this was the most distant known object in the Universe from 1960 to 1964. Only with X-ray or radio telescopes, or with a huge optical telescope, would the first extragalactic objects be detectable from the perspective of the MCG +01-02-015.

Credit: X-ray: NASA/CXC/Cambridge/S.Allen et al; Optician: NASA/STScI

From this isolated perspective, discovering our cosmic origins would have been much more challenging.

penzias wilson cmb holmdel horn antenna

According to the original observations by Penzias and Wilson, the galactic plane was emitting some astrophysical sources of radiation (center), but above and below all that was left was a nearly perfect and uniform radiation background. The temperature and spectrum of this radiation have now been measured, and the agreement with Big Bang predictions is remarkable. If we could see microwave light with our eyes, the entire night sky would look like the green oval shown.

Credit: NASA/WMAP Science Team

Mostly Mute Monday tells an astronomical story with pictures, images and no more than 200 words.

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