Brown dwarfs and red stars in focus

New frontiers: Conference hears how scientists are closer than ever to unlocking some of the Universe's most elusive secrets

TOM WILKIE

Science Editor

Astronomers will today hear about the discovery of steam in the emptiness of interstellar space, near a cool red giant star, and new research that suggests so-called "brown dwarfs" - solid matter that exists in a state between planet and star - may be plentiful throughout the Universe.

The European Space Agency's Infrared Space Observatory (ISO) has detected the distinctive "heat" from water vapour around the pulsating variable star W Hydrae, 300 light years away from the Earth, the UK National Astronomy Meeting in Liverpool will be told.

The vapour is also known to condense small, solid silicate particles. The chemical identification of these particles will help shed further light on the origins of the solid material out of which the Earth is made.

The instrument which has detected the water vapour was built by an international consortium led by Professor Peter Clegg of Queen Mary and Westfield College, London, and including scientists from France and Italy.

Water vapour had been predicted to be an important constituent of the gas flowing from red giant stars such as W Hydrae. Its surface temperature is about 3,000C, although the water vapour is much cooler.

Previous searches from high-flying aircraft and balloons for the tell- tale far-infrared signatures of water in stars and nebulae had all failed because water vapour in the Earth's atmosphere absorbs radiation emitted by water vapour in space. The ISO, launched last year from Kourou in French Guiana, orbits far above the Earth's obscuring water vapour and so can search unhindered.

However, according to Professor Mike Barlow of University College London, leading the analysis of data: "The detection of water in the spectrum of W Hydrae will provide vastly more information about how water molecules are formed and excited in the gas which flows out from these stars into interstellar space."

Meanwhile, new research on brown dwarfs, strange objects which are a in a sort of half-way state between a planet and a star, indicates they could be scattered throughout space.

The finding may help explain one of the big mysteries of the universe, the nature of the unseen "dark matter" which, in theory, must fill the cosmos.

Several brown dwarfs have been found within 150 light years of the Sun. Unlike dwarfs spotted orbiting in other solar systems in clusters, these are alone in space.

Brown dwarfs are thought to fill the gap between the largest planets and the smallest stars. They are too cool to set off the nuclear reactions that cause normal stars to shine and are therefore very faint and hard to find.

Scientists think they could account for at least some of the unexplained "dark matter", known from measurements of gravitational influences to make up much of the universe.

Dr Hugh Jones of Liverpool John Moores University and Dr Mike Hawkins from the Royal Observatory, Edinburgh, found four cool and faint brown dwarfs during an investigation with astronomers in France.

Using special equipment at Edinburgh, they examined photographs taken with a telescope in Australia to search for the objects. It was only when more than 100 photographic images were added together by computer that the faint objects were noticed.

In another search the same technique was used to find a fifth brown dwarf, 296A, which appears to be 60 times more massive than the planet Jupiter.

The object is about 100 light years away from Earth.