Black Hole Coloring Page: Free Printable PDF Sheet

Black Holes and the Pull of Gravity

A Star That Collapsed Inward

A black hole forms when a massive star runs out of fuel and collapses in on itself, packing an enormous amount of matter into a space far smaller than the star used to fill. The result is a region of gravity so strong that nothing that crosses its boundary, called the event horizon, can escape, not even light, which is exactly why the middle of a black hole always looks completely black in real telescope images.

Only stars far bigger than the sun end this way. A star needs roughly 20 times the sun's mass or more before its core can crush down into a black hole once the star dies; smaller stars like the sun shrink into a much calmer leftover called a white dwarf instead.

The Swirling Disk Around the Center

Gas and dust pulled toward a black hole do not fall straight in. They spiral around it first, forming a flattened, fast-spinning ring called an accretion disk, similar to water circling a drain before disappearing. Friction inside that spinning disk heats the gas until it glows brightly, which is how astronomers spot black holes even though the black hole itself gives off no light of its own.

The swirl in this scene mirrors that real spinning disk shape, with each curving line standing in for a layer of gas circling faster the closer it gets to the center.

How Astronomers Finally Saw One

For decades, black holes were only known through their effect on nearby stars and gas, since a black hole cannot be photographed directly. That changed in 2019, when the Event Horizon Telescope project released the first-ever image of a black hole's silhouette, a supermassive black hole at the center of a galaxy called M87, showing a glowing ring of gas surrounding a dark circular shadow.

In 2022, the same global telescope network captured the black hole at the center of our own Milky Way galaxy, named Sagittarius A*, confirming that a supermassive black hole sits roughly 26,000 light-years from Earth at the galaxy's core.

Sizes From Tiny to Supermassive

Not all black holes are giants. Stellar black holes, formed from a single collapsed star, typically weigh somewhere between about 5 and 20 times the mass of the sun. Supermassive black holes, by contrast, sit at the centers of most large galaxies and can weigh millions or even billions of times the sun's mass, having grown over billions of years by pulling in gas, dust, and merging with other black holes.

Despite the intense gravity, a black hole is not a cosmic vacuum cleaner reaching out to grab everything nearby. Objects have to pass quite close to the event horizon before gravity overwhelms them, so planets and stars can safely orbit a black hole from a distance the same way Earth orbits the sun.

Time itself behaves strangely near a black hole's edge, a real effect predicted by Albert Einstein's theory of general relativity. A clock placed close to the event horizon would tick more slowly than a clock far away, an effect scientists call gravitational time dilation, and it grows more extreme the nearer an object gets to that dark boundary.