Black holes, Doughnuts and Galaxies with Indigestion.

In this blog post I decided to focus on one of my favourites

Quasars (which is the short name for Quasi-Stellar Objects) are highly luminous terrors that I have been fond of ever since I learnt of their existence at Galaxy Zoo. These galaxies are amazingly bright and can be seen blazing billions of light years away. So what are they?

Most galaxies have a super massive black hole lurking at their nucleus. They can be quiet things, only grabbing the odd unlucky wisp of matter and not causing too much trouble, these are the non-active ones. In a galaxy hosting a Quasar its super massive black hole is active (also known as an AGN; an Active Galactic Nucleus) and pulling dust, gas and whatever other objects it can grab along the way into a hot doughnut shaped disk – an accretion disk. As this disk swirls around the black hole awaiting its fate, the matter that it consists of causes friction and creates huge amounts of energy, causing the centre of the galaxy to get so bright that it outshines the galaxy itself many times over.

For an example of a quasar here is 3C 273:

This monster lurks in the constellation Virgo, at around 2 billion light years away it isn’t the farthest quasar known, in fact it is actually one of the nearest. To give you an idea of just how bright it is, it outshines our galaxy over a hundred times. You may have wondered what the fuzzy line poking out of 3C 273 is, I first thought it was a distant galaxy but it is actually the quasars jet. The energy created in the accretion disk also gets concentrated into jets of plasma at the poles of the black hole by the magnetic fields; these jets can beam out for thousands of light years and travel at near to the speed of light. And to think all of that is caused by something only the size of a solar system. 3C 273’s jet stretches through space for over 200,000 light years, that’s twice the size of our galaxy!