Tuesday, 13 January 2009

The Red Rectangle


The Red Rectangle, courtesy of NASA/JPL-Caltech and ESA.

It was great to spend a little time at the summit last week on my own science project. Actually, it's not my own, it's a collaboration with researchers at The University of Nottingham in the UK where I spent a couple of years as a post-doc., but still, it felt as though I had a little bit of telescope time for myself.

We observed an object called the Red Rectangle, one of the most unusual objects in our Galaxy. We've been observing it for a number of years now and it's certainly become a bit of a pet project, but it's such a fascinating thing.

It's called the Red Rectangle because that's what it looked like on photographic film when it was first discovered decades ago. Technology improves all the time and the above image is one of the latest images of this protoplanetary nebula - this one is from the Hubble Space Telescope.

Planetary nebulae are quite common. The name is a little bit misleading as these nebulae have little to do with planets, the name is a historical accident. They're formed by stars similar to our own sun reaching the end of their lives, and due to complicated processes which I won't go into here, blow off their outer layers to form nebulae - some of them are particularly beautiful. The Red Rectangle, however, is a protoplanetary nebula, that is its central star (actually, there are two of them orbiting each other) has just entered old age and is blasting off its outer atmospheric layers in an old age-induced grumpy temper fit. That's one of the theories behind the ladder effect in the image above, each step resulted from nuclear fusion driven eruptive episodes deep within the star over the last few hundred thousand years.

Why is it such a unique object? Well, although its current protoplanetary phase has being going on for so long, you need to relate that to the total lifetime of the star which is billions of years, therefore the protoplanetary stage is a tiny fraction of the star's total lifetime. Even though we can see millions of stars, it's statistically unlikely we'll be able to observe a star in this stage of its life, especially one as easy to see as the Red Rectangle. We know of a few, but there aren't that many we can easily observe or as beautiful as the Red Rectangle.

It's also unique because of the geometry. The old age pensioner central star has a thick dust disk surrounding it that is edge-on to us and constrains the outflow into an X-shape. There's some pretty complicated physics occurring there as well as chemistry, and it's the latter that interests our small group (actually, I like the physics stuff even more but my research has taken me into the dark and scary world of chemistry in recent years).

The Red Rectangle produces some large molecules and is in effect a chemistry laboratory in space. It creates polycyclic aromatic hydrocarbons (PAHs) which are essentially large molecules made of hydrogen and carbon, as you might guess from the name. You and I create them all the time when we drive our cars or burn a sausage on the grill. They're also important molecules in the formation of life, so are quite important to understand!

So now I'm boring myself. I could probably write a book about the Red Rectangle and don't want to do that here. Suffice to say, we've published a few papers on it over the last decade or so and hopefully there are a few more to come. We've been using an "integral field unit" (IFU) to take spectra of the object at several wavelengths over quite a large part of the nebula looking for molecules and how they're distributed throughout the region. We've already published some nice results and I hope we have more to come. The analysis is difficult though, the picture below shows some raw IFU data from the run last week:

14 spectra and and we have seven different positions where we took data. If the data are treated correctly we'll have hundreds of individual spectra, lots of spectral images and a good idea of the distribution of certain molecules throughout the nebula. Enough for someone's PhD I hope.

You see, I actually do a little astronomical work from time to time and don't just go to the summit to take pictures of the snow and sunsets!

6 comments:

Protege said...

Tom, this was your most interesting and exciting post ever, at least to me!
I would love to talk to you about the universe. Although I am not an astronomer, being a biochemist I know a bit about atoms and molecules.;)So, how do you actually know that the rectangle produces hydrogen and carbon? How can you actually detect those?
To the "artist" in me, the IFU data looks a lot like window blinds, very cool.;))

invaderxan said...

Hope you're all having fun... :)

Diane said...

I think it looks very UFO-y. Cool.

Beep said...

I find the Red Rectangle photo to be interesting but also somehow inspiring. It's beautiful in its own right, at least in this photo, but also there is so much yet to discover and to learn that it makes me hope human beings will get to be around and will be able to allocate the resources to keep discovering all of the fascinating and incredible things that await in the new frontier...

And I have to agree with Protege about the second photo looking like window blinds. I am sure it was the first thing I thought of because my exciting life has had me experiencing so many peak experiences such as cleaning window blinds...and then sometimes going on to the thrill of dusting or perhaps even vacuuming...I know the entire world wants to read my blog now...I hope so because I really need help deciding whether to stick with OxyClean pre-wash stain remover or whether something like Spray and Wash is really better...

Tom said...

Protege - very good questions and my answers would be too long for a simple comment here, in fact invaderxan might be in a better position to answer them! Very briefly though, carbon molecules have been detected directly, hydrogen is everywhere and the spectroscopic features in the thermal infrared (i.e., 3 to 15 microns in this case) are consistent with PAHs, which of course contain hydrogen and carbon. In fact we've published a few papers in the last few years about the thermal infrared spectroscopic features and although a 100% identification of the exact molecules is beyond us right now, the case that they're caused by large hydrocarbons is easily strong enough to convict.

invaderxan - I think Keith and Amit had a good time and they're off exploring the island right now! Amit gave a very interesting seminar here by the way.

Diane - no UFOs involved, I promise you! We shoot them down and then are not allowed to say another word about them. It's all terribly secret work...

Beep - just avoid any cleaning products with PAHs in them - not sure if any do, but worth checking! Despite the fist-clenching nature of the OxyClean adverts, I actually think that product works quite well, especially on cat vomit as I discovered tonight...

John Powell said...

This is very cool - it's hard for me to get beyond the fact that it looks like a photographic anomaly, and accept that this amazing shape has physical reality. Thanks for sharing this!