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Tuesday, September 22, 1998 Published at 13:57 GMT 14:57 UK


Sci/Tech

The search for New Worlds

Scientists at the University of Arizona pioneer new techniques to secure images of planets

Scientists at the University of Arizona have demonstrated a technique that could provide the first images of planets circling other stars. Our science editor Dr David Whitehouse explains.

In recent years the discovery of many planets circling other stars has been a true revolution in astronomy. For the first time in history we know of more planets around other stars than orbit our own sun.

They were detected using their gravitational influence on their parent star. No pictures of them have been possible, but that may change in the future.

The problem with getting an image of a planet in orbit around another star is that the main star is millions of time brighter than the planet. The planet gets drowned-out. What is needed is a way to blot-out the stars light.

That is just what the team of astronomers at the University of Arizona have done using a technique called 'interferometric nulling.'

Using two telescopes looking at the same star they have been able to combine the starlight in such a way that it cancels itself out or 'interferes' with itself.

With the main stars light blotted out this way astronomers can look for the faint light of any planets that remain.

It is a promising technique that still has a long way to go but could form the basis for future space mission to capture images of so-called extra-solar planets or exoplanets.

Such as the Darwin mission currently being studied by the European Space Agency. It will consist of six satellite telescopes flying in formation in space so that the light from the stars it observes will be cancelled out. It could be launched in 2009.

Or the Nasa Space Interferometry Mission (Sim) that the space agency is studying under its 'Origins' initiative.

The Sim will not be a series of satellite-telescopes but two large telescopes placed at either end of a large cylindrical spacecraft.

It could be launched at about the same time as Darwin (experts say that only one of them will be chosen) but first a much smaller proof-of-concept mission called Deep Space 3 may be launched in 2002.

Another space mission to search for planets around other stars was proposed to Nasa earlier this summer. Called Kepler it will look for the minute dimming effect that occurs when a planet passes in front of a star.





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