How Many Galaxies Are in the Universe? Names, Distances, and the Latest Science

Two trillion. That is the number of galaxies astronomers now believe populate the observable universe — a figure so staggering that even the scientists who calculated it struggled to contextualise it when their paper landed in The Astrophysical Journal in 2016. The estimate, produced by a team led by Professor Christopher Conselice at the University of Nottingham, was not a guess or a simulation artefact. It was the result of painstakingly converting three-dimensional deep-field images from the Hubble Space Telescope into galaxy number counts across cosmic time — and then correcting for the vast population of galaxies too faint, too distant, or too obscured for even Hubble to detect. The previous consensus figure of 200 billion was wrong by a factor of ten. The universe, it turned out, was dramatically more crowded than anyone had imagined.

Each of those two trillion galaxies is itself a gravitationally bound system containing anywhere from a few hundred million to several trillion individual stars, along with vast reservoirs of gas, dust, dark matter, and in almost every case examined so far, at least one supermassive black hole at its centre. The Milky Way — the barred spiral galaxy that contains our solar system — is a mid-sized example, home to an estimated 100 to 400 billion stars and spanning roughly 100,000 light-years from edge to edge. Its own central black hole, Sagittarius A*, masses approximately four million times the mass of the Sun and was directly imaged for the first time in May 2022 by the Event Horizon Telescope collaboration.

The study of galaxies — their formation, structure, evolution, and eventual fate — has been transformed in the past three years by the operational deployment of the James Webb Space Telescope, which has pushed the observable frontier back to within 300 million years of the Big Bang and produced images of galaxies whose light has been travelling toward Earth for more than 13 billion years. What Webb has found at those extreme distances has repeatedly surprised cosmologists, revealing galaxies far more massive and structurally mature than the standard model of cosmic evolution predicted should exist so early in the universe's history. The catalogue of what humanity knows about galaxies is being rewritten in real time.

The Local Group: Our Cosmic Neighbourhood

The Milky Way does not exist in isolation. It belongs to a gravitationally bound collection of approximately 80 galaxies known as the Local Group, which spans roughly 10 million light-years and is anchored by two large spiral galaxies — the Milky Way itself and the Andromeda Galaxy, designated M31. Andromeda, located 2.537 million light-years from Earth, is the most distant object visible to the unaided human eye under dark skies, appearing as a faint smudge of light in the constellation of the same name. It contains approximately one trillion stars — roughly twice the stellar population of the Milky Way — and is currently approaching at approximately 110 kilometres per second. In roughly 4.5 billion years, the two galaxies will merge into a single elliptical system that astronomers have already named Milkomeda.

The Local Group's smaller members include two irregular dwarf galaxies orbiting the Milky Way as gravitational satellites: the Large Magellanic Cloud, located 160,000 light-years away and visible as a bright smear from the southern hemisphere, and the Small Magellanic Cloud at 200,000 light-years. Closer still — and only discovered in 2003 — is the Canis Major Dwarf Galaxy, a disrupted satellite being actively shredded by the Milky Way's tidal forces at a distance of just 25,000 light-years from Earth, making it technically the nearest external galaxy currently known. The Sagittarius Dwarf Spheroidal Galaxy, at 70,000 light-years, is undergoing a similar tidal disruption, its stars now forming a visible stream that wraps around the Milky Way's halo. The third-largest member of the Local Group is the Triangulum Galaxy, designated M33, a spiral approximately 2.73 million light-years distant and just barely detectable without optical aid under exceptional conditions.

Beyond the Local Group: Notable Galaxies Across the Cosmos

Beyond the Local Group, the universe's galaxy population organises itself into clusters, superclusters, and the vast cosmic web of filaments and voids that constitutes large-scale structure. The nearest significant galaxy cluster is the Virgo Cluster, centred approximately 53.5 million light-years from Earth and containing over 1,300 confirmed member galaxies. Its most massive resident is Messier 87 — M87 — a giant elliptical galaxy that achieved worldwide recognition in April 2019 when the Event Horizon Telescope collaboration released the first direct image of its central black hole, a structure of 6.5 billion solar masses whose shadow was resolved against the glowing accretion disk surrounding it. M87's central black hole is roughly 1,600 times more massive than Sagittarius A* and ejects a relativistic jet of plasma extending 5,000 light-years into intergalactic space.

At intermediate distances, several galaxies have become reference objects for specific branches of astrophysics. The Sombrero Galaxy, designated M104, lies 31.1 million light-years away in the constellation Virgo and is distinguished by an unusually large central bulge and a prominent dust lane that gives it its distinctive hat-like profile in optical imaging. The Whirlpool Galaxy, M51, at 23 million light-years, is one of the most studied examples of galaxy interaction, its spiral arms visibly distorted by a gravitational encounter with its smaller companion NGC 5195. The Antennae Galaxies, NGC 4038 and NGC 4039, located 45 million light-years away, represent a more advanced merger in progress — two spiral galaxies whose collision has triggered one of the most intense bursts of star formation observed in the nearby universe, producing thousands of massive star clusters in a region where interstellar gas clouds have been violently compressed by the collision.

The Farthest Shores: Galaxies at the Edge of Time

The most distant galaxies are not merely far away in space — they are far away in time. Because light travels at a finite speed, observing a galaxy 13 billion light-years distant means observing it as it existed 13 billion years ago, when the universe was less than a billion years old. For decades, the practical limit of that temporal reach was set by the Hubble Space Telescope, whose deepest images — the Hubble Ultra Deep Field and its successors — captured galaxies at redshifts up to approximately z = 8, corresponding to a lookback time of about 13 billion years. The record holder in the Hubble era was GN-z11, a compact, intensely star-forming galaxy at a distance of 13.4 billion light-years, confirmed spectroscopically in 2016.

The James Webb Space Telescope, with its infrared-optimised mirror array spanning 6.5 metres, has shattered that frontier repeatedly since its first science observations in 2022. In 2024, the JADES survey — the JWST Advanced Deep Extragalactic Survey — confirmed the spectroscopic redshift of JADES-GS-z14-0, a galaxy observed at z = 14.32, placing it at a distance of approximately 13.5 billion light-years and situating its existence just 290 million years after the Big Bang. What makes JADES-GS-z14-0 scientifically remarkable is not merely its distance but its properties: it is luminous, extended, and already contains a substantial stellar population, implying that galaxy formation began earlier and proceeded faster than cosmological models built on pre-Webb data had predicted.

The Unexpected Maturity Problem

Webb's early-universe discoveries have exposed a tension at the heart of the standard cosmological model, known as Lambda-CDM. That model predicts that galaxies in the first few hundred million years after the Big Bang should be small, irregular, and relatively low in stellar mass — because there simply has not been enough time for gravity to assemble large amounts of matter into coherent structures. What Webb has observed instead is a population of galaxies at z > 10 that are larger, more massive, and more structurally organised than the model permits. Dr. Ivo Labbé of Swinburne University of Technology, whose team identified several of these anomalously massive early galaxies in 2023, described them informally as "universe breakers" — a phrase that captured the scientific community's collective surprise more accurately than any formal terminology.

The resolution to this tension is not yet clear. Proposed explanations include revised assumptions about the efficiency of star formation in the early universe, the possibility that early black hole growth contributed significantly to galaxy luminosity and was being misinterpreted as stellar mass, and more radical suggestions involving modifications to the underlying cosmological model itself. None of these explanations has yet achieved consensus, and the JADES survey continues to accumulate spectroscopic confirmations that will constrain the competing theories over the next several years.

"We have found galaxies that should not exist according to our models — and that is exactly the kind of discovery that moves science forward."

What This Means for Our Understanding of the Cosmos

The inventory of galaxies humanity has assembled — from the Canis Major Dwarf at 25,000 light-years to JADES-GS-z14-0 at 13.5 billion — represents not just a catalogue of objects but a temporal map of cosmic evolution spanning nearly the entire history of the universe. Every galaxy in that map is a data point in the story of how gravity, gas physics, dark matter, and black hole feedback combined over 13.8 billion years to produce the structured cosmos that exists today. The two trillion galaxies that Conselice's team counted are not merely a large number — they are the accumulated output of a universe that has been building complexity, at every scale, since the first moments after the Big Bang.

For observers on Earth, the practical ceiling of that map is set not by the size of telescopes but by the expansion of the universe itself. Galaxies beyond a certain distance are receding faster than light can cross the growing space between us and them — meaning their light will never reach Earth regardless of how powerful future observatories become. The observable universe has a hard edge, a cosmic horizon roughly 46 billion light-years in radius, beyond which humanity is permanently blind. Within that horizon sit two trillion galaxies. Outside it, an unknown number more — perhaps infinite — exist in a darkness that no instrument will ever penetrate, each one a complete universe of stars, gas, and time, unreachable and unknowable from this particular point in space.