Space search for ‘brown dwarfs’

Press, 7 February 1985, Page 17

Space search for ‘brown dwarfs’

By

WALTER SULLIVAN

of NYT news service (through NZPA)

Tucson, Arizona

The reported discovery of an object too big to be a planet and too small to be a true star has touched off an intensive search to determine whether such “brown dwarfs” may have formed by themselves and might account for the “missing mass” in nearby space.

Astronomers on Kitt Peak, Arizona, are searching for more “brown dwarfs” by observing about 30 stars whose irregular motion hints that each may be under the gravitational influence of a smaller companion. It was the observation of such an orbital companion that led to the discovery of the “brown dwarf” orbiting the small, dim star, van

Biesbroeck 8. Now at least two more candidates are under special scrutiny.

Scientists theorise that there is “missing mass” in space because the rotation of stars in the Milky Way galaxy, to which Earth and Sun belong, indicates that they are under the gravitational influence of a great deal of material that cannot be observed. Dr Frank Low of the University of Arizona’s Steward Observatory, said that the Milky Way appeared to contain as much invisible material as observable material in the form of stars, planets, and other objects.

“Brown dwarfs,” said Dr Low, “are one of the better hypotheses” to account for at least some of the missing mass in the Milky Way. If such dwarfs were discovered, it would mean that they could form independ-

ently, rather than as part of a system such as the one to which Earth belonged. It is widely believed that such planetary systems form from the contraction of a swirling nebula of dust and gas, most of which condenses to form one or more stars, with what is left over becoming planets and moons.

Recordings from the extensive sky surveys performed in 1983 by the InfraRed Astronomy Satellite had now been made public, Dr Low said. Astronomers could now search them for the faint infrared glow of brown dwarfs, which are too small to ignite the nuclear fusion reactions that make stars shine brightly.

The searches for brown dwarfs are part of a longstanding effort to learn how common planets may be elsewere in the galaxy and universe.