At the center of nearly every major galaxy lurks one of the most massive and enigmatic objects in the cosmos: a supermassive black hole (SMBH). These cosmic titans have masses ranging from millions to billions of times that of the Sun, compressed into a space no larger than a solar system. Some galaxies appear quiet — like our own Milky Way — while others "ignite": the black hole actively devours surrounding gas, shining as a quasar that outshines hundreds of billions of stars combined. How did they form? Why do they always sit at the center? And what is the James Webb Space Telescope uncovering about them?
🌌 Does Every Galaxy Have Its Own Black Hole?
According to NASA, most galaxies of comparable size to ours or larger appear to harbor a supermassive black hole (SMBH) at their core. This is now considered a near-universal rule, not the exception. Even some dwarf galaxies appear to have disproportionately massive central black holes — like the Leo I dwarf galaxy, whose center hosts a ~3 million solar mass black hole, despite the galaxy itself being only ~20 million solar masses total.
In most cases, the black hole lies dormant, revealing its presence only through the unusually fast orbital motions of nearby stars. In galaxies with an active nucleus, however, the black hole is continuously fed by a swirling disk of gas and releases enormous amounts of energy. A recent NASA/Chandra study found that some small galaxies may “break the rule” and lack supermassive black holes — challenging existing models of galaxy formation.
⭐ Sagittarius A*: The Monster at the Heart of Our Galaxy
The core of our own Milky Way hosts Sagittarius A* (Sgr A*, pronounced “A-star”). With a mass 4 million times that of the Sun and located ~26,000 light-years from Earth, Sgr A* is currently in a relatively quiet state — producing only occasional small flares.
Its existence was confirmed by tracking the orbits of stars near the galactic center over decades. This discovery earned Andrea Ghez (UCLA) and Reinhard Genzel (Max Planck) the Nobel Prize in Physics 2020. In 2022, the Event Horizon Telescope released the first real photograph of Sgr A* — a glowing ring of photons around an absolutely dark center.
The James Webb Space Telescope has detected both bright flares and rapid flickers from Sgr A*, suggesting activity very close to the black hole itself, according to NASA.
📏 How “Large” Is Sagittarius A*?
Despite its mass of 4 million solar masses, Sagittarius A* has a diameter of only ~23.6 million kilometers — roughly the distance from Earth to the Sun. By comparison, the galaxy surrounding it spans 100,000 light-years. The supermassive black hole weighs an enormous amount but occupies a cosmically insignificant point in space.
🔭 M87 and the Historic 2019 Photograph
Galaxy Messier 87 (M87), located ~53 million light-years away, harbors a 6.5 billion solar mass black hole at its center — far larger than Sgr A*. M87 is an “active” galaxy: its black hole is continuously fed by gas, producing a spectacular jet of radiation extending 3,000 light-years into space.
In 2019, the Event Horizon Telescope (EHT) — a network of 8 radio telescopes spanning the entire Earth — succeeded in imaging the shadow of M87's black hole: a glowing orange ring of heated gas around an absolutely dark center. Astronomers observed in 2025 that this same jet continues to launch from the black hole's shadow in real time, according to Space.com.
"The accretion disk surrounding M87's black hole emits radiation — the photon ring structure confirms the predictions of general relativity with remarkable precision."
— Event Horizon Telescope (EHT) Collaboration, Space.com💫 Quasars: When a Black Hole Is “On”
When a supermassive black hole is actively feeding, its accretion disk releases tremendous amounts of energy — powering a quasar or active galactic nucleus (AGN). A quasar can shine 1,000 times brighter than all the stars in its host galaxy combined. Quasars were among the first supermassive objects detected — and remained mysterious for decades, until identified as black holes in feeding mode.
Modern observations show that particles accelerated near supermassive black holes reach nearly the speed of light — these black holes literally function as “particle accelerators” at cosmic scale, according to NASA.
🚀 JWST Is Changing What We Know About Their Formation
One of the biggest cosmological puzzles was: how could gigantic supermassive black holes exist only 700 million years after the Big Bang — not enough time to grow through conventional stellar evolution and mergers?
JWST discovered mysterious “Little Red Dots” in the early universe, likely representing supermassive black holes formed through direct gas collapse — bypassing stellar evolution entirely. This discovery could resolve one of the greatest puzzles in cosmology, according to Space.com.