A NEW WORLD IN SIGHT?

Press, 28 June 1989, Page 17

A NEW WORLD IN SIGHT?

Astronomers may have found another world outside our solar system. They have discovered that a sun-like star, known as HD 114762, has a small, unseen companion. The new body is either a planet, they say, or it falls into a category of astronomical object called a “brown dwarf” — strange star-like bodies with a range of masses between those of planets and stars.

ROBIN McKIE

While brown dwarfs may be enormous by planetary standards, they are not big enough for the gravitational collapse necessary to spark the nuclear fusion reactions that make stars shine. The feeble radiation they emit makes them particularly difficult to detect, and only a few possible candidates have yet been uncovered by astronomers.

Now David Latham, of the Harvard-Smithsonian

Centre for Astrophysics in Cambridge, Massachusetts, and his colleagues think they have uncovered a far more promising one.

While engaged in a routine survey of stars, they discovered, periodic changes in the behaviour of light received from HD 114762. On analysing these changes, it was revealed they were due to the effects of an unseen companion rotating round the star.

The star HD 114762, in the constellation of Coma Berenices, is about 90 light years from the Sun. (A light year is a measure of the distance

reports on the possible existence of a hitherto

unknown world outside our solar system, 10 times bigger than the planet Jupiter.

travelled by light in one year. The velocity of light is 186,000 miles per second.) The star’s companion orbits HD 114762 every 84 days. It has a mass that is about one tenthousandth of that of our sun, Latham calculates. That implies it is about 10 times bigger than Jupiter, the largest planet in our solar system, which in turn is more than 300 times more massive than Earth.

If HD 114762’s companion proves to a planet, it is likely that it will become a focus for research by those seeking to find signs of extra-terrestrial

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life in the universe. The presence of any planet at least encourages those seeking life “out there.” On the other hand, if the object proves to be a brown dwarf, then there are important implications for astronomy as well. Recently, scientists have found tantalising signs that the universe is much heavier than was previously thought. But the exact location of this missing mass, known as dark matter, is unknown. According to Ron Probst, of Kitt Peak National Observatory in Arizona, it is possible that brown dwarfs could make up that dark matter. The discovery by Latham and his team of such a promising brown dwarf candidate raises hopes of getting a more accurate assessment of their numbers — and therefore of the mass of the universe.