• Black holes are the densest objects in the universe, which gives them a powerful gravitational pull on the space around them.
  • They can be millions of times larger than suns and planets, or as small as a city.
  • Using just gravity, black holes can rip entire planets and stars apart - but how powerful they are depends on how much mass is inside.
  • For more stories, go to Business Insider SA.

The cosmos can be a dangerous place. Take black holes for example, some of the most violent objects in our universe and powerful enough to rip entire stars to pieces.

They’re really, really big. To make Earth into a black hole, for instance, you'd have to shrink it to less than 2.5cm across.

Their secret weapon is gravity. The more mass you can shrink into a small space, the stronger your gravitational force will become.

There are three common types of black holes.

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The smallest are stellar black holes, which form after a giant star explodes and collapses in on itself, which measure about 64 km across. But in that small space is enough mass to equal 11 of our suns.

In another galaxy called M33, there's a black hole that is almost 100km across and packs as much mass as 15.7 suns inside.

Up next are the intermediate-mass black holes. At 2,350km across, they can reach almost the same distance as it is from Cape Town to Bulawayo.  and according to some calculations, contains the mass of 400 suns.

But these black holes are nothing compared to supermassive black holes, like Sagittarius A*, which lives at the centre of our Milky Way galaxy.

It covers a region about 24.4 million kilometres in diameter. That's roughly 168 Jupiters across, and inside is the same amount of mass as 4 million suns combined – still its small.

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We're finally getting to some of the largest black holes in the universe, and yet, we haven't reached one that surpasses the size of our solar system.

Another supermassive black hole at the centre of Messier 87. It is so huge that astronomers could see it from 55 million light-years away. It's 38.6 billion kilometres across and contains the same mass as 6. 5 billion suns.

This supermassive black hole, as large as it is, could still fit within our solar system with plenty of room to spare.

For the biggest we must look at one that has a diameter of about 125.5 billion miles. For perspective, that's about 40% the size of our solar system, according to some estimates. And it's estimated to be about 21 billion times the mass of our sun.

So there you have it, black holes can be millions of times larger than suns and planets or as small as a city. It all depends on how much mass is inside. Turns out, when it comes to the cosmos, size isn't the only thing that matters. 

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