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Showing posts from February, 2013

The Three-Dimensional Structure of the M31 Satellite System; Strong Evidence for an Inhomogeneous Distribution of Satellites

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Back in Sydney after a busy couple of days in Brisbane at the Seventh ANITA (Australian National Institute for Theoretical Astrophysics) Workshop. It was a good two days listening to talks on the cutting edge theory (a lot by very smart PhD students and postdocs). A quick look at the program shows the incredibly diverse range of cool science being done in Australia.

But a quick post (as I am still playing astro-ph catch-up), but it's time to post an excellent paper from proto-doctor Anthony Conn (proto- as his PhD has been submitted and is being examined). But the paper provides a key input to our recent Nature paper, namely nailing the distance to the dwarf galaxies orbiting Andromeda.

I've written before about Anthony's sterling work using Bayesian techniques to provide the most accurate and robust distances, using the tip of the Red Giant Branch. It's not easy work and has consumed more than three years of work. But results, as you know, have been excellent.

What is…

Pale Blue Dot....

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... but how blue?

I'm a fan of learning things through problems. Specifically, in this example, I wanted to shuffle off my dinosaur image with regards to programming, and learn more python, which is the language of choice of the younger generation (although why people think that an interpretative language is better than a "deeper" programming language, I don't know - grumble, grumble, grumble....).

Right, to the problem in hand. The Pale Blue Dot is our planet Earth, our home. We know that it is a Water-World, but luckily not the Waterworld, but a planet whose surface area is 70% water. We're plodding along on a minority of the planet.

So, I woke up on Sunday and thought - "What is the view of the Earth that shows the maximum amount of ocean?" and conversely "What is the view of the Earth that shows the most land?". Yeah, I know, but my head chugs through things like this on a Sunday morning.

So, the question I have, to be answered with python…

The Milky Way is on a diet

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Watching the Russian meteor explosion sent a shiver down my spine. When I was young, I avidly devoured a magazine called The Unexplained, about the paranormal and mysterious events (although, as a good friend of mine said, the only unexplained thing is why I paid for the rag) and so was familiar with the Tunguska Event in 1908. The rock that exploded in 1908 was roughly 10x larger than yesterday's explosion, but seeing the effect of the shock-wave gives us a feeling of what Tunguska must have been like!

I wrote a little about a result by my student, Prajwal, on measuring the mass of the Milky Way, but we just wrote up a short media story on it. I've popped the entire story below. We're not expecting the story to be travel to far and wide, but it has appeared on the roof of the world, at Nepal News.

The Milky Way is on a diet

A team of University of Sydney astronomers, led by international PhD student, Prajwal Kafle, and his collaborators, Joss Bland-Hawthorn, Geraint Lewis a…

The only thing that isn't moving at the speed of light is light itself!

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Time to give you some brain food. The title of this post is correct, and I will go further.
"and the speed that light travels is not the speed of light, it is zero" I hope that this has opened your eyes and got the cog-wheels turning. You might be even thinking that I have gone slightly mad. But stick with me, and you'll see that this is true, and you can use these facts to wow your mates down the pub.

The key issue is the difference of traveling through space, and traveling through space-time. I think the latter is more fundamental, and so my statement is more truerer than the usual comments you hear. But to understand this, we need to remember what speed actually is!

Remember from school that speed is simply the distance travelled divided by the time that it took to travel the distance. If we moving at uniform speed, then our speed at all points in the journey would be the distance covered divided by the time.

Maths time!
Where the triangle (the greek letter delta) mea…