When a massive star dies, it's believed something truly terrifying is born.
A black hole.
When a star burns, nuclear reactions are taking place inside its core, creating an outward force able to balance the inward force of gravity.
When it runs out of fuel, this outward force disappears and the core of the star collapses in on itself.
When the core has a mass greater than about four times that of our Sun.
At least 4 times as heavy as the Sun
It's condensed into a single point, smaller than the size of a pea.
This is called the singularity.
As this happens, the surface layers of the star blast outwards, in a supernova explosion.
What's left behind is the black hole.
A star collapsing in on itself
The gravitational pull around the singularity is enormous.
The force close to it is so strong, that not even light can escape.
This region is called the event horizon.
Anything inside this area will be pulled towards the singularity and lost forever.
The event horizons of many black holes are surrounded by an area of hot, in-falling gas, called an accretion disc.
Event Horizon. The Singularity. The Accretion Disc
If the disc is spinning rapidly some of its matter can be shot out into space at incredible speeds.
Jets of material are fired outwards
It's propelled along the powerful magnetic field, which the disc generates, creating colossal jets of radiation.
Propelled by the magnetic field
Black holes are among the most violent and fascinating phenomena in the Universe, but their destructive reputation is greatly exaggerated.
They don't devour everything around them.
If the Sun was replaced by a black hole with the same mass, the Earth and other planets wouldn't suddenly be pulled into it.
They would continue to orbit around it in the same way that they orbit around the Sun.
It's thought that there is a supermassive black hole at the centre of the Milky Way, with perhaps hundreds more lower-mass black holes lurking throughout our galaxy, but these will only be a threat to us if our paths happen to cross.
Supermassive black hole. Billions of solar masses
This is unlikely to happen any time soon, as the nearest black hole to be detected so far is 1600 light years from Earth.
1600 light years from Earth
More than 3 million times further from us than Neptune.