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Wednesday, June 24, 1998 Published at 15:13 GMT 16:13 UK


Star flare causes stir

The tiny star is in there somewhere

The faint star at the centre of the image may seem an insignificant member of the cosmos but it is causing big excitement among astronomers. Our science correspondent David Whitehouse reports:

Last week a network of telescopes spread across the southern hemisphere noticed that the tiny star had increased in brightness. Astronomers issued an international alert to monitor the star.

Usually an increase in brightness of such an insignificant star would arouse little scientific interest. This time astronomers believe that it became brighter because of a so-called 'microlensing' event.

It happens when an unseen body passes in front of the star. Then the gravity of this object acts like a lens distorting and magnifying the light from the distant star.

[ image: A network of monitoring telescopes]
A network of monitoring telescopes
It is important that scientists see such events because such events may be caused by so-called 'dark matter.'

It is know that 90% of the universe is unseen. It is out there but is not in the form of stars, gas or galaxies.

It could be in the form of large, dark planets that circle galaxies in vast numbers.

About the only way to detect such objects, called Massive Compact Halo Astrophysical Objects or Machos, is to look for the microlensing effect.

Over the next week or so numerous telescope will be turned towards the star to detect any more changes in brightness as the unseen object completes its passage.

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