planet goth... haunted house
the astronomy room
Of all the negativity that lurks in the Universe, black holes are the most terrifying. They are indiscriminate about what they destroy, dooming anything that comes their way, from brilliant new born stars to dark, cloudy planets. Even light can’t escape. So how much do we know about these dark evil Universe suckers?
• Black holes come in many different sizes from small primordial ones one billion billionth the mass of our Sun, to supermassive black holes occupying the centre of galaxies that can be a billion times more massive than the Sun.
• Some black holes are blacker than others. As material falls inwards it heats up (the temperature can be higher than the surface of the Sun) and starts to glow. If a black hole has little or no material falling in then it will be very dim, while black holes with lots of material to consume will glow brightly and be very visible.
• Black holes are not like the holes we know on Earth. They are spherical which means you can fly all around them and fall in from any position. The ‘surface’ of a black hole is an imaginary sphere called the event horizon. Once something falls inside the event horizon it will never come out again….
• Black holes distort spacetime. If an astronaut was foolish enough to get close to one, time would slow down for them. While the astronaut might think that only one hour had passed, their family back on Earth would think a year had gone by. The astronaut could eventually come back to Earth to find their grandchildren as old as them…
• Surprisingly, for such big suckers, black holes can lose mass. Pairs of particles are produced in the distorted spacetime outside the event horizon. One of the pair carries negative energy into the black hole while the other fires off into space with extra energy. The end result is that the black hole loses energy and mass, and will slowly evaporate. The smaller the black hole the faster the evaporation – it would take a black hole the mass of the Sun a billion, billion, billion, billion, billion, billion, billion years to disappear.
• If the Sun suddenly turned into a black hole the Earth would continue to orbit it as though nothing had happened… This is because black holes only consume material that falls into them; something in orbit will stay that way as long as its mass doesn’t change. The one thing we would notice is that it would become very dark.
• Although black holes exist throughout our galaxy and in many others, we are lucky that there do not appear to be any close enough to the solar system to be a danger to us in the near future. A wandering black hole could disrupt the delicate balance of our planets’ orbits sending them plummeting into the Sun or spiralling out into space. Others may suffer an even worse fate, being ripped apart as they fall into the all-consuming black hole.
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