Open your eyes, SOFIA

Today, I was very lucky to meet Bob Gehrz, Professor of Physics and Astronomy at the University of Minnesota and principal investigator for a rather exciting telescope project. SOFIA (short for Stratospheric Observatory for Infrared Astronomy) is a project being run as a collaboration between NASA and the German Aerospace Centre, DLR. Its aim is to carry a 2.5 metre telescope to altitudes of around 12 – 14 km aboard a specially modified Boeing 747. While the idea of airborne telescopes dates back to 1967, it’s still an ambitious project. All the same, they’re making rather good progress.

While it’s generally rather convenient for us to have a nice thick atmosphere to keep our planet nice and habitable, it can be a bit troublesome for astronomers. The atmosphere absorbs a lot of the light which we need to make observations. In the range of visible light (roughly 400 – 700 nm), the atmosphere is fairly transparent, but in the ultraviolet and the infrared, most of not all light is absorbed. While this prevents the Sun’s UV from frying us and stops Earth’s warmth escaping into space, it also means that you don’t always get a very good view from down here. That’s where facilities like SOFIA fit in. Easier to maintain and upgrade than a space telescope, but able to fly above 99.8% of the Earth’s atmosphere, SOFIA can make observations which would be impossible from the ground.

One of the things SOFIA is aiming to look at in detail is the mid to far infrared (30 – 300 microns). Earth’s atmosphere normally blocks this out completely. Take a look at the images to the left, here. The top one shows how how much light the atmosphere absorbs (in blue) from the top of Mauna Kea, where the highest ground-based telescopes are. As you can see, it’s mostly blue. Between 30 and 300 microns, nothing reaches the surface. The lower one shows what SOFIA sees from high altitude. The difference is pretty impressive. There’s still some atmospheric absorption, but there’s more than enough to work with!

One thing which struck me is that while SOFIA was constructed primarily for infrared astronomy, it also covers the entire optical wavelength range up to the near ultraviolet! In fact, it has one of the largest wavelength ranges of any telescope I know of, stretching from 300 nm down to 1.6 mm! That’s near UV right the way down to far infrared. SOFIA’s going to be capable of some very interesting science, and chemical types like me are bound to get a lot of good use out of it, especially given that it’s estimated to operate for far longer than most space-based telescopes. Astrochemistry, PAHs, exoplanet atmospheres and star formation are just some of the things that SOFIA’s going to be ideal to observe. Actually, it covers essentially all of the wavelengths us astrochemists find interesting (the ones I’ve recently been grumbling about being unable to observe).

Just a few months ago, in December SOFIA successfully flew for the first time with its door open. Rather a feat, given the engineering required to actually do that. Since that was a success, they’re currently preparing for the telescope to see first light sometime next month, and I’m pretty sure it should go rather well. Hopefully I might even submit a proposal to get some observing time on it. I’m certainly going to be keeping track of how things progress!

Incidentally, the talk given by Bob Gehrz is giving while he’s here in the UK is available to download here (52MB .ppt file). Conveniently, all SOFIA related talks are available from this web page.

About Invader Xan

Molecular astrophysicist, usually found writing frenziedly, staring at the sky, or drinking mojitos.
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