Cosmic Horizons

The end of the year is rapidly approaching (just where did 2013 go). I've just spend the week in Canberra at a very interesting meeting, but on the way down I actually thought I was off in to space. Why? Because the new Qantas uniform looks like something from  Star Trek . Doesn't Qantas know what happens to  red shirts? Anyway - why was I in Canberra? I was attending  MaxEnt 2013 , which, to give it its full name, was the  33rd International Workshop on Bayesian Inference and Maximum Entropy Methods in Science and Engineering.  It was a very eclectic meeting, with astronomers, economists, quantum physicists, even people who work on optimizing train networks.  So, what was it that brought this range of people together? It was the most important equation in science. Which equation is that, you may ask? It's this one. Huh, you may say. I've spoken about this equation multiple times in the past, and what it is, of course, is  Bayes Rule . Why is it so importan

And now for a major paper from the  Pan-Andromeda Archaeological Survey (PAndAS) , led by astronomer-extraordinare  Rodrigo Ibata . I've written a lot about PAndAS over the years (or maybe a year and a bit I've been blogging here) and we've discovered an awful lot, but one of the key things we wanted to do is measure the size and shape of the  stellar halo  of the Andromeda Galaxy. The stellar halo is an interesting place. It's basically made up of the first generation of stars that formed in the dark matter halo in which the spiral galaxy of Andromeda was born, and the properties of the halo are a measure of the  formation history of the galaxy, something we can directly compare to our theoretical models. But there is always a spanner in the works, and in this case it is the fact that Andromeda, like the Milky Way, is a cannibal and has been eating smaller galaxies. These little galaxies get ripped apart by the gravitational pull of Andromeda, and their stars litt