Why Black Holes aren’t cosmic vacuum cleaners

Margarita is your Student Ambassador in Greece, leading a series of articles about Aerospace Engineering as part of her leadership project.

When people hear the words ‘Black Hole’, they often imagine a giant cosmic hole that sweeps everything in its path. Despite their terrifying reputation, black holes aren’t really holes. Instead, they are huge concentrations of matter packed into very tiny spaces. A black hole is so dense that its gravity is absolute. Beneath its surface, a boundary called the event horizon has a pull so strong that not even light can escape; this can make them seem like terrifying objects, with an insatiable diet for stars and planet. But this isn’t so.

Even if we replaced our Sun with a black hole of the same mass, most planets would continue their motion around the Sun as they are now, with only the closest planets noticing some tidal forces from the black hole. And even if the Earth were replaced with a black hole of the same mass, the moon’s orbit wouldn’t change much either. That is because the mass they are orbiting remains the same.

The real danger is when matter draws close to a black hole; objects like stars are literally stretched apart by gravitational tugging. This material collects in a ring, called an accretion disk, where the material spins around rapidly and is superheated to millions of degrees.

So black holes aren’t relentless cosmic vacuum cleaners with unnatural gravitational powers. They are better understood as extraordinary compact objects with immense gravity, though the common conception that they are deeply eerie is definitely real, as many aspects of black holes remain mysterious.