Archive for April, 2008

Herstmonceux Astronomy Festival 2008 lecture

I’m very pleased to announce that I will be giving a talk at this year’s Herstmonceux Astronomy Festival, held at the famous Herstmonceux observatory in Sussex. The subject of my talk will be the science behind the Hubble Space Telescope’s greatest images. To find out more about the festival, which will be held on the 5th, 6th and 7th of September, visit the Observatory Science Centre’s website here.

Hubble’s magnificent mergers


OK I admit it. Galaxies are my favourite objects that the Hubble Space Telescope studies and images. But it’s true; there’s something so awesome about the HST images that ooze detail in a way that captures the vast and magnificent nature of these ‘stellar cities’. But it’s not all about the pictures. Hubble has allowed scientists to see the farthest galaxies in the Universe, that also happen to be some of the earliest too. Those observations have given us a real insight into how the galaxies we see today form. Hubble has studied Cepheid variables in distant galaxies too, allowing us to make accurate distance measurements of far off galaxies.

Today the Hubble team have released the most stunning collection of galaxy images I have ever seen. Fifty nine images in total showing many galaxies merging. What’s fascinating is that you can piece together a rough idea of how a merger takes place, out of several images of different ‘collisions’. This isn’t unusual. Astronomers do it all the time. If you wanted to see the lifetime of a Sun-like star you obviously wouldn’t hang around for 10 billion years to watch it from start to finish. What you do is look around the Universe for different Sun-like stars at different points in their life. We can do this now to get at a very basic overview of how a galaxy merger unfolds.


The above image is made from six separate images of differing collisions. Yet put together they show the progression of a galaxy merger. In reality a galaxy collision is a slow and stately affair. In fact during galaxy mergers the stars within the galaxy generally don’t smash together. That’s because of the vast distances between stars; however some stars will ultimately be thrown from the galaxies out into the depths of space.


Over millions of years the gravity of the galaxies begins to twist and shape streams of stars. In the first panel you can see the left hand galaxy is slowly starting to deform as the two galaxies begin to interact. Emerging from the lower left of the left galaxy is a noticeable stream of stars – the first sign that a merger is underway. In the second panel the merger is further along. Here much bigger streams, called ‘tidal tails’, extend out from the galaxies as the two get ever closer. In the third panel the merger is advanced even more with a massive bridge of millions of stars stretching between the two galaxies’ cores. In the last three images the mergers show dramatic twisting and swirling shapes. As the collisions of clouds of dust and gas take place, shockwaves travel through the galaxies. This results in a staggering burst of star formation (note the young blueish stars in the fourth image). Eventually the two galaxies will become one – usually a enormous dusty elliptical galaxy.

To see the full catalogue of the Hubble merger images view the press release here and of course you can watch the latest episode of the Hubblecast about the images here.

First image credit: NASA, ESA, the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration and K. Noll (STScI). Second image credit: NASA, ESA, the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University), K. Noll (STScI), and J. Westphal (Caltech). Third image credit: NASA, ESA, the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University)

BBC Sky At Night magazine podcast now on iTunes

What the title says really. For those of you that want to subscribe it’s on iTunes here.

BBC Sky At Night magazine podcast released

Our new podcast is now out on its very own webpage here. In the first episode Sky At Night magazine’s editor Graham Southorn and I chat about the Royal Astronomical Society’s National Astronomy Meeting that I visited a few weeks ago.

If you listen to the podcast you can also find out what James Bond has been doing at one of the world’s largest observatories (the VLT in Chile), hear about the latest on the plans to upgrade Hubble this summer and the discovery of the youngest extrasolar planet ever found.

Where do comets really come from?

I have a new feature in May’s BBC Sky At Night magazine (out in the shops early next week) entitled “Where do comets really come from?”. It’s about how new results from the NASA Stardust mission are unveiling new insights into the origin of cometary material.

Left: Comet Wild 2. Credit: Stardust/JPL/NASA

International Year of Astronomy 2009 trailer

Turn up the sound on your computer, get ready and watch this! It’s a new trailer for the International Year of Astronomy 2009. Very cool indeed. The Year is fast approaching and there will be lots happening around the globe. If you haven’t got any ideas on what to do (but want to get involved) contact your national node, get some ideas from here and get involved!

Credit: International Year of Astronomy 2009, IAU and UNESCO

P.S. another new site definitely worth a look is the new International Astronomical Union website. There’s a wealth of information on there. Especially make sure to check out the ‘themes’ section – it’s the definitive IAU reference for lots of subjects like naming stars, classifying planets and much more. Oh and if you want the HD version of the above trailer be sure to get it here.

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