Showing posts from March, 2013

Fun with Planck

Easter is here, and so a little weekend's diversion. I thought I would have a little fun with Planck maps of the CMB sky we looked at previously. As a reminder, here's what Planck saw
and what the blue and red spots indicate are structures in the Universe when it was only 400,000 years old.

Also remember that we describe these bumps and wiggles by the power spectrum which tells us how many blobs of particular sizes we should see in the image. Our theories tell us the power spectrum, but not the location of each individual blob in the image.

As I mentioned last time, we describe the structure we see in terms of spherical harmonics, which are particularly useful functions to use on a sphere, and the power spectrum basically tells us how much of a particular function we need to add in to get the map above.

But we have a freedom, called the "phase" of the spherical harmonics. Basically, while the power spectrum tells you much of a function you need to add, it doesn't…

Inflation deflation.... The Universe from Planck

I've been away for a few days at the Synthetic Universes for Future Survey at the University of Western Australia (phew - Perth is a long way away!). It was an excellent meeting, presenting just what we need to do with regards to making synthetic universes so we can understand what is going on in our own.

As well as coinciding with the equinox, we also watched the press conference covering the latest results  from the Planck Satellite. While this was a spectacular success, it also was a bit of a disappointment. You might wonder how this can be. Let me explain.

The Cosmic Microwave Background (CMB) was discovered in 1964, and it was realised that this was the ever-cooling radiation left over from the Big Bang. I have to show ab obligatory history of the universe to explain how it has trundled through the universe.
You can think that the CMB was born at the end of inflation, and for a few hundreds of thousands of years the universe was a plasma soup, with protons, electrons and radi…

A kinematic study of the Andromeda dwarf spheroidal system

Argh!! Another couple of weeks have flown by like a huge fast flying thing! So fast, I almost missed my birthday (which I share with another random person). And the pressure ain't off, so a quick post.

This time, a great paper by Michelle Collins.

As you will have guessed by now, we've been doing a lot of work on the dwarf galaxy population that orbits around our nearest large cosmological neighbour, namely the Andromeda Galaxy. We, and other groups, have been measuring lots of properties of these dwarfs, including their positions and distances. Over the last few years, we've also managed to get the spectra of many stars in the dwarfs which, for one thing, allows us to measure the velocities of stars (via the famous Doppler effect).

Michelle's paper focuses upon the velocities found in 18 of the 28 dwarfs we know live near Andromeda, and basically tries to find out lots of the nature of the dwarf population - such as are they all the same, or different, and how?

The pa…

Cutting through the spin on supermassive black holes

It's the week for submission of Discovery Projects, our main funding route through the Australian Research Council. Our current proposal is almost 150 pages long, and I feel like we've been working on it since the Cosmological Dark Ages. It will be good to submit it, but don't think that means I get a break. No, it's time to catch up on all the stuff that has been on the back-burner when grant writing :)

So, a quick post today on an article I wrote for The Conversation called "Cutting through the spin on supermassive black holes". As the name suggests, I describe how astronomers can not only measure the mass of black holes, but can also calculate their spin.

I must admit that the article is a little long compared to others I've written for The Conversation, and what is published is the shortened version. It's a topic that I think is pretty cool and I put in too much detail.

I'll let you read the article, and will happily answer any questions below…