10 Facts About The Universe That Make Your Brain Hurt

7. Black Holes Are Often The Brightest Objects In The Universe

OK, so now I've lost it and you reckon I'm just making up stories in the hope you'll carry on reading. The clue is in the name, isn't it? Black hole! Well yes, I have been careful to use the word 'often' for this fact. Black holes are indeed super-compact concentrations of stellar material of such enormous mass that they tend to deform space-time. And yes, they are so dense that they even eat up passing light so that all you can see of them is an empty space. Were you able to carry a black hole to Earth on a teaspoon it would probably weigh in excess of 100,000 tonnes, (100,000,000 kg). But there is one variety of black hole known as a quasar, (quasi-stellar radio source). Around many black holes is an accretion disk of material emitting energy as it falls into the black hole. A quasar is a compact region in the centre of a massive galaxy that surrounds its central super massive black hole. Around quasars, if you can imagine it, you get radiation acting outwardly and a huge gravitational force acting inwardly upon it. That's where the light begins to get emitted due to something called the Eddington limit, or Eddington luminosity. When there is an imbalance between those two forces, gravity and radiation, the Eddington limit is exceeded and the quasar starts pumping out an intense solar wind resulting in highly luminous light. Quasars are the extraordinarily bright nuclei of galaxies and the brightest quasars have a luminosity of L = 100,000 LMW = 1042 watts, which is something like a trillion times brighter than our sun. This is not too surprising when you get their size into perspective. Often as large as 1 kiloparsec across that puts them on average bigger than our entire solar system.