Sunday, February 28, 1999 Published at 09:52 GMT
Far-sighted telescope opens eyes
By BBC News Online Science Editor Dr David Whitehouse
One of the most powerful arrays of telescopes on the planet is about to
open to astronomers.
Its telescopes will peer further into space and see objects in finer detail
than any other telescope, including the Hubble Space Telescope.
The European Southern Observatories Paranal Observatory will be officially
opened for use by astronomers from Monday. It is due to be completed in
The finished observatory will consist of four reflecting telescopes, each
with light-collecting mirrors that are 8m across. Only one of the
telescopes has been completed but during its performance tests it has
produced some stunning images of the sky.
The second of the four telescopes will come online within weeks, followed
by the remaining two in 2000.
Each of the four telescopes at Paranal is world-class but it is when they
work together that the great leap forward is made.
By combining the light from more than one telescope astronomers can
simulate the performance of a much larger telescope.
This technique, called interferometry, has been successfully carried out
with radio telescopes for decades but is only a recent development for
This is because combining the light beams from more than one telescope
involves some very fine measurements. Radio waves have much longer
wavelengths than optical light waves, so less accuracy is required to
combine the radio beams.
Astronomers could mimic the performance of a telescope whose mirror was 16
metres across, by far the largest in the world. They would do this by
combining the light from two or more of the Paranal telescopes and
augmenting them with three smaller telescopes in the vicinity.
In interferometric mode the observatory will be able to peer deep into the
cosmos. It will be able to search for planets circling nearby stars.
Many Jupiter-sized planets have been found circling nearby stars in recent
years. The Paranal observatory will be able to detect much smaller planets,
possibly as small as 10 Earth masses around thousands of Sun-like stars.
It will also get a detailed view of the mysterious centre of our own
galaxy, which is difficult to observe. But by measuring the velocities of
objects in the central core, it is hoped to learn more about the
super-massive black hole that many astronomers believe resides there.
The telescopes could even make detailed studies of the surfaces of nearby
stars. They may also compile sharp maps of the central regions of quasars,
exploding galaxies at the edge of the observable universe.