From missiles to galaxies

Many years ago the radio dish, shown in the picture below, was used to track missiles at the Woomera Missile Range in Australia. The missile range was set up in 1947 (around the time that Jodrell Bank was set up) as a place to try out Britain and Australia's weapons systems. The first Skylark rocket was launched there in 1957, a few months before the USSR launched Sputnik. Of course the site had all the things you would associate with a space programme such as launchpads and tracking dishes but it also had its own theatre and even a song.

7m telescope
The 7-m telescope at Jodrell Bank Observatory with the 42-ft and Lovell telescopes in the background. CREDIT: Stuart
Around twenty years ago - in the mid 1980s - some of the tracking dishes were going to be scrapped. Through some international links, astronomers at Jodrell Bank were able to get two of these dishes delivered to the UK to be used for astronomy. One was named the 42-ft telescope and the other the 7-m. Actually, the 7-m telescope is not 7 metres but 6.4 metres in diameter. It got the name because of a rather poor conversion from feet to metres, although as this didn't result in the loss of a spacecraft it doesn't matter too much.

These days, the 7-m telescope is used by both undergraduate students at the University of Manchester and students undertaking Jodrell Bank's distance learning course in radio astronomy. It is a nice little dish that gets used to look at the Sun, map the spiral arms of the Milky Way and measure the mass of galaxies like M31 and M33. I think it is amazing to be able to measure how much hydrogen there is in an entire galaxy from the middle of Cheshire.

The 42-ft telescope, sitting next to the entrance of the main observatory building (you can just see it peeking out from behind the 7-m in the picture), now spends almost all its time monitoring pulsars. If the Crab Nebula is above the horizon, chances are that the 42-ft will be observing it as a pulsar lies at the centre. Pulsars usually emit two beams of radio waves and as they spin, these beams can sweep past us giving a 'tick' at the radio telescope. The ticks from the Crab pulsar have been recorded for many years, so an extremely precise value for the rotation rate is now known - it is currently 29.7808515419 +/- 0.0000000001 Hertz in case you were wondering. Even the slow down of the rotation has been carefully measured and occasional glitches - thought to be due to re-arrangements in the pulsar surface - are sometimes seen.

The two dishes have travelled a long way (quite literally) and are still doing lots of useful scientific research.

Posted in astro blog by Stuart on Friday 19th Aug 2005 (19:50 UTC) | Permalink
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