Imaging the Universe – 27th January 2005

Robert Massey from the Royal Observatory , Greenwich, gave a talk called Imaging the Universe. Since telescopes were first turned to the heavens they’ve been used to make discoveries. As larger and better telescopes were made, so the nature of the discoveries changed, but eventually limits were reached. For 40 years the 200-inch at Palomar was the best instrument available. Then, in 1990, the Hubble Space Telescope changed everything. The idea of putting a telescope in space, above all the degradation and distortion caused by the Earth’s atmosphere, had been proposed by Lyman Spitzer nearly 40 years earlier. The HST’s 2.4 metre mirror, while much smaller than Palomar’s, was also more precisely made (even the spherical aberation was precise), and it has therefore been able to look much deeper into the Universe’s past than any previous optical telescope. The HST has helped to determine the age of the Universe, and has also provided excellent images of objects nearer Earth, including the outer planets. It is the only instrument that has so far been able to reveal any detail at all on Pluto, and its ability to monitor the planets when there are no space probes visiting them has led to discoveries about Uranus’s seasons and Neptune’s weather. It has shown us images of events within (and near) our own galaxy that have helped confirm theories on planetary system formation. Other images have led to greater understanding of pulsars, supernovae, gamma-ray bursts, super-giant stars, and very strange old galaxies. Sadly, it seems that the HST will not last much longer, but there have also been developments in ground-based telescope design that mean some of the work the HST has done can be continued using telescopes on Earth. The significant developments have been in making larger mirrors and in adaptive optics which can compensate for the distortion caused by the Earth’s atmosphere. Work is also being done on optical interferometry, which holds the promise of resolution sufficient to resolve planets circling nearby stars. We can expect many more exciting discoveries to be made using images from these new telescopes in the years to come.

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