How was the first black hole image captured?

The first image of a black hole — the shadow of M87* — was published in April 2019 by the Event Horizon Telescope (EHT) collaboration. The EHT linked eight radio observatories across four continents into a virtual Earth-sized telescope using very-long-baseline interferometry (VLBI). The result was a fuzzy orange ring: the bright accretion disk seen through the gravitational lensing effect of the 6.5 billion solar mass black hole 55 million light-years away.

Yes — Stephen Hawking predicted in 1974 that black holes slowly emit thermal radiation (Hawking radiation) due to quantum effects near the event horizon, causing them to lose mass and eventually evaporate. The timescale is enormous: a stellar-mass black hole would take roughly 10⁶⁷ years to evaporate — vastly longer than the current age of the universe (1.38 × 10¹⁰ years). Supermassive black holes would take even longer.

The Extremes — 01

Inside a Black Hole, the Rules You Know Stop Working

Q: What happens if you fall into a black hole?

For a supermassive black hole (like M87*, 6.5 billion solar masses), tidal forces at the event horizon are relatively gentle — a falling observer might not notice the moment of crossing. However, from an outside perspective, the infaller appears to slow down and redden, never quite reaching the horizon due to extreme time dilation. Inside the event horizon, all trajectories lead to the singularity; no information can escape to the outside universe.

Q: What is the difference between a stellar-mass and a supermassive black hole?

Stellar-mass black holes (3–100 solar masses) form from the collapse of massive stars at the end of their lives. Supermassive black holes (millions to billions of solar masses) reside at the centres of most large galaxies, including our own Milky Way (Sagittarius A*, 4 million solar masses). The formation mechanism for supermassive black holes is not fully understood; they may grow from stellar-mass seeds or form directly from the collapse of massive gas clouds in the early universe.

Every black hole began as something that could no longer hold itself together. What remained rewrote the laws of physics.

14 min read · Interactive article

01 — The Collapse

What Remains

There is something unsettling about a place the universe keeps secrets from itself.

A black hole is not a thing. It is an absence — a region where matter was once so dense it folded spacetime shut. No light escapes. No signal returns. Whatever crosses the boundary stays. Not destroyed, exactly. Just unreachable. Forever.

They are born from collapse. A star that has burned through its fuel, lost its outward pressure, and surrendered to gravity so completely that nothing — no force in the known universe — can stop the infall. The most powerful objects in existence begin with surrender.

“The black holes of nature are the most perfect macroscopic objects there are in the universe: the only elements in their construction are our concepts of space and time.”
— Subrahmanyan Chandrasekhar

They come in sizes. The universe builds them all.

Stellar

Stellar Mass

3–100 solar masses

≈ size of a city

Born from the death of massive stars. A few dozen kilometres across — a city-sized object with the mass of a sun.

Intermediate

100–100,000 solar masses

≈ the missing middle

Too large for a single star’s death, too small to anchor a galaxy. Only recently confirmed — their origin remains open.

Supermassive

Millions–Billions M⊙

≈ larger than our solar system

Anchoring nearly every galaxy. Sagittarius A* holds 4 million solar masses. M87* holds 6.5 billion. How they grew so massive remains unknown.

02 — The Boundary

The Event Horizon

There is a distance from the centre of a black hole at which escape becomes impossible. Not improbable. Not difficult. Impossible. This is the event horizon — where the escape velocity exceeds the speed of light itself.

The horizon is invisible. There’s no wall, no surface, no flash of warning. An astronaut crossing it would notice nothing in the moment. But to a distant observer watching them approach, something extraordinary happens: the astronaut slows. Their light redshifts. Time, as seen from outside, stretches toward infinity. They never quite arrive — they fade, frozen on the threshold.

Below, you’re looking straight at a black hole from a spacecraft. Drag the slider to approach it. Watch the sky warp around the shadow. Watch your clock and theirs diverge.

Gravitational Lensing — First Person You are looking at the black hole

∞ Safe distance

Your Clock

1.0

seconds elapsed

Distant Observer

1.0

seconds elapsed

Shadow Size

0.2°

Light Bending

0.0°

Escape Velocity

11 km/s

This first-person gravitational lensing simulation lets you approach a black hole and observe how gravity bends light. As you move closer, the starfield behind the black hole warps and distorts — light rays curve around the event horizon, creating an Einstein ring where background stars appear to stretch into arcs. The simulation tracks three measurements in real time: the apparent shadow size of the black hole grows from a dot to filling your view; light bending increases from 0 degrees to beyond 360 degrees at the photon sphere; and escape velocity rises from 11 km/s to nearly the speed of light. Twin clocks demonstrate relativistic time dilation — your clock slows relative to a distant observer as you approach the event horizon.

Real Observation — M87*

First image of a black hole — M87* captured by the Event Horizon Telescope

In April 2019, the Event Horizon Telescope — a network of radio dishes spanning the globe, acting as a single Earth-sized instrument — captured the first direct image of a black hole’s shadow.

M87*. Fifty-five million light-years away. Six and a half billion times the mass of our Sun. The bright ring is superheated plasma bent around the photon sphere. The dark centre is the shadow of the event horizon.

The image took two years to process. When it arrived, it looked exactly like the math predicted.

Image: EHT Collaboration / ESO

03 — The Glow

The Accretion Disk

Here is the paradox: the darkest object in the universe creates the brightest light.

Matter falling toward a black hole doesn’t plunge straight in. It spirals. Friction heats the infalling gas to millions of degrees — first infrared, then visible light, then X-rays. The innermost ring, just outside the event horizon, reaches temperatures that make the surface of a star look cold.

The disk itself is warped by gravity. From certain angles, the far side appears to bend over the top and under the bottom — light following curved spacetime along impossible paths.

Rotate the view below. Watch the disk reshape as your perspective shifts.

Accretion Disk Viewer Click + drag to orbit

Oblique 27°

Inner Temperature

10⁷ K

Orbital Velocity

0.5c

ISCO

3 rₛ

This 3D accretion disk viewer renders the superheated plasma spiraling into a black hole. Matter falling inward forms a flattened disk that reaches temperatures exceeding ten million kelvin, radiating across the electromagnetic spectrum from infrared to X-rays. The visualization demonstrates how spacetime curvature warps the disk's appearance: from an oblique angle, the far side of the disk bends over the top and under the bottom of the black hole as photons follow curved geodesics. Orbit the black hole by dragging to see the disk reshape. Key metrics include inner disk temperature, orbital velocity approaching half the speed of light, and the innermost stable circular orbit (ISCO) at 3 Schwarzschild radii.

Real Observation — Cygnus X-1

Chandra X-ray image of Cygnus X-1 — X-ray glow from matter spiraling into a stellar-mass black hole

Cygnus X-1 — one of the first confirmed stellar-mass black holes — was discovered not by sight, but by the X-ray glow of matter spiraling around an invisible point. We couldn’t see the black hole. We saw what it was doing to everything around it.

The physics you just rotated — we’ve been watching it for decades.

Image: NASA/CXC/SAO

04 — The Edge

Drawn to the Boundary

We will never visit a black hole. The nearest known stellar-mass black hole is roughly 1,500 light-years away — close by cosmic standards, impossibly far by ours. And even if we could make the journey, tidal forces would dismember any spacecraft long before the horizon.

And yet.

We built a telescope the size of a planet to photograph one. We wrote equations to describe the inside of a place no equation can reach. We simulate the approach because we cannot make the journey. We point our most sensitive instruments at the most lightless places in the universe and wait for a signal that, by definition, will never come.

“Wonder has its own gravitational pull. The most extreme object in the universe is also the most studied, most modelled, most obsessed-over. We can’t look away.”

A black hole is spacetime pushed past the breaking point. But it is also a mirror — held up to the species that insists on looking, on building instruments, on approaching the boundary, even knowing it can never cross and return.

That impulse — to go to the edge, to look into the dark, to see what the rules become when everything we know stops applying — might be the most human thing in the universe.

Frequently Asked Questions

What happens if you fall into a black hole?

It depends on the size. For a stellar-mass black hole (a few times the mass of our Sun), tidal forces would “spaghettify” you before you crossed the event horizon: the gravitational difference between your head and feet would stretch you into a strand of matter. For a supermassive black hole like M87* (6.5 billion solar masses), tidal forces at the event horizon are gentle enough that you might cross without noticing. From an outside observer’s perspective, you would appear to slow down and freeze at the horizon, redshifted into invisibility. From your own perspective, you would cross in finite time and fall toward the singularity.

How were black holes first discovered?

The concept emerged from general relativity: Einstein’s 1915 field equations allowed solutions describing regions of extreme density, though Einstein himself doubted they existed in nature. Cygnus X-1, identified in 1964 as a powerful X-ray source, became the first strong black hole candidate. By the 1990s, observations of stars orbiting our galaxy’s centre confirmed the existence of Sagittarius A*, a supermassive black hole at the Milky Way’s core. The first direct image arrived in April 2019, when the Event Horizon Telescope captured M87* at a distance of 55 million light-years.

What is the difference between a stellar-mass and a supermassive black hole?

Stellar-mass black holes form when a massive star (generally above 20 solar masses) collapses at the end of its life. They range from a few to roughly 100 solar masses. Supermassive black holes, found at the centres of most large galaxies, contain millions to billions of solar masses. How they formed remains an open question: they may have grown from smaller black holes merging and accreting matter over billions of years, or from the direct collapse of enormous gas clouds in the early universe. A third class, intermediate-mass black holes, is the subject of active research.