Star Wars science brings space into close-up
The first pictures produced by a giant telescope have stunned astronomers, writes Charles Arthur
Thursday 28 May 1998
The European Southern Observatory (ESO) yesterday released the first images from its pounds 374m Very Large Telescope (VLT) project, which will use an array of four telescopes each 8.2m (27ft) across to produce images of distant stars and perhaps their planets.
Among the first images is a stunning picture of the Butterfly Nebula, the remnants of a huge star that has blown off much of its hydrogen "fuel" in glowing gas clouds, while the original star has shrunk to a "white dwarf" in the centre of the picture. The details available, from three exposures each lasting 10 minutes, is as good as any from previous telescopes.
But this is only the beginning. When completed in around 2001, the VLT will consist of four identical telescopes, and be capable of resolving objects so tiny that it is like picking out an astronaut on the surface of the Moon, 400,000km (250,000 miles) away.
The key to its powers of resolution will be that the optical signals from the mirrors of the four telescopes will be combined, so that they function like a single mirror 16m across. That is bigger than any built on Earth and much larger than that on the orbiting Hubble Space Telescope - and thus gives rise to its extraordinary resolution.
The ESO team have farsighted goals for it. One possibility is to capture images of giant planets that, scientists are increasingly sure, orbit distant stars in our galaxy.
Riccardo Giacconi, director-general of the ESO, said before the first results appeared that "the VLT's investigations will shed light on how likely it is that conditions for the emergence of life exists in the universe". Another aim is to look at light from stars formed when the universe was very young - perhaps just 5 per cent of its present age.
The Star Wars technology was originally developed by American military engineers to allow laser weapons to keep their beam steady on a missile "target". Now its use in the mirrors of the telescopes means that they can be based on the ground rather than having to go to the expense of putting them into orbit, as with Nasa's Hubble telescope.
Normally, ground-based telescopes have problems because gravity makes their mirrors sag, and they also have to compensate for the effects of the atmosphere, where air layers make images tremble (making the stars appear to twinkle). The VLT overcomes this by using tiny motors which can individually move elements of the mirror. A computer monitors the reflection of a reference star in some part of the scene in different parts of the main mirror: if that seems to shift, the motor moves a part of the mirror so that the image remains stable. The same system is also used to compensate for the sagging of the mirror under its own weight.
The ESO has also minimised atmospheric problems by building the VLT on the summit of the Cerro Paranal mountain in the Atacama desert, Chile, one of the driest places on Earth.
The UK does not belong to ESO, and has not been involved in the VLT's construction over the past 10 years. But non-member countries can participate, and individual astronomers can submit requests for telescope time. The Astronomer Royal, Sir Martyn Rees, of Cambridge University, thinks UK involvement in Gemini - a twin-telescope project, with 8m telescopes in Chile and Hawaii - makes up for it. "It is a pity the UK does not have a larger stake in next-generation telescopes. But I am not sure whether the British community would wish to be involved in the VLT rather than in an other large-telescope project."
r A "sunquake" 40,000 times more powerful than the earthquake which devastated San Francisco in 1906 has been observed, it was disclosed yesterday. It was first proof that solar flares produce seismic waves in the Sun's interior similar to terrestrial earthquakes.
However, a quake on the Sun is on a different scale from any on Earth. The one spotted by the Solar and Heliospheric Observatory spacecraft produced waves nearly two miles high, travelling at 250,000mph over the Sun's surface. The quake, following a moderate-sized solar flare on in July 1996, appeared like ripples spreading from a rock dropped into a pool of water.
The findings were reported in the Nature science journal by researchers from Glasgow University and Stanford University, California, and presented at a news conference at the spring meeting of the American Geophysical Union in Boston.
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