illuminating science

I have to say, even though I’m not an astronomer by profession, I really love learning and reading about astronomy and astrophysics, and, on occasion, doing a little bit of observing myself. A few times, I’ve gone with the Brisbane Astronomical Society (BAS) on one of the “AstroCamps”, where they all take their telescopes and go out west away from the city. It’s absolutely amazing what they’re able to see - particularly when they use computerised systems to “dial up” a galaxy or cluster of their choice. (If you ever get a chance, get your binoculars out and check out the constellation Orion (also known as “the saucepan” - there’s three bright stars in a row, plus a “handel”) - there’s some great stuff there!)

The bigger the telescope, the more light it can collect, and hence the more distance object you can look at (the light from far away galaxies is so faint, you need to gather a lot of it and focus it to a point before your sensors or film can detect it). I have a small, 10 centimetre telescope which is fine for small clusters and the moon. The members of BAS have large scopes, up to about 40cm diameter, say, which is great for close galaxies. Hubble’s telescope is 2.4 metres in diameter - and best of all, because it’s in orbit, there’s no air and no (or very little)heat to distort the image (just think of mirage effects on a hot day!) But if you really want to do some observing, I think the new TMT has got to take the cake. TMT stands for Thirty Metre Telescope - it’s going to be built at the top of a mountain, probably in Chile or Hawaii, and unlike a normal telescope, it’s going to be made up of 800 smaller mirrors arranged in a parabolic shape. Each of these mirrors will be controlled by a high precision motor, and be adjusted 750 times a second to a precision of 1/40th of the width of a human hair! This means if heat, vibrations or other environmental factors affect the telescope, ever different part of the telescope can be adjusted precisley - essential when your telescope spreads over 700 square metres! Moreover, each mirror will be flexible so they can be adjusted to give the best quality image possible.

But probably the most amazing thing, at least for me, is the way that they’ll correct for atmospheric effects. I mentioned above that Hubble could make such good images because the space around it is so clear - there’s no air! On Earth, however, as the air moves or heats, its refractive index can change, which means that the telescopes image would become distorted. If you knew what the air was going to do, you might be able to correct for it - but how do you measure the entire atmosphere above your scope? The answer is you measure a brighter, closer star whose image you know well, and look at how it changes - analyse this data, and use your incredibly high precision mirrors to keep the focus updated (750 times a second!). Don’t have a good star? Then use a highly focused laser to excite sodium atoms in the upper atmosphere to create a super bright point source of light to use as a reference!

It’s still 10 years away, but it’s just the first of a new generation of “Giant Segmented Mirror Telescopes” that are going to open up a whole new era of observing, and with it, a deeper understanding of our universe. Truly incredible science.