Brown Dwarfs in the Galactic Halo

X CANARY ISLANDS WINTER SCHOOL OF ASTROPHYSICS "Globular Clusters"

Course: OBSERVATIONAL APPROACH TO POPULATIONS IN GLOBULAR CLUSTERS

Prof. Ivan R. King
University of California U.S.A.

BROWN DWARFS IN THE HALO OF THE GALAXY

The brightest stars in present-day globular clusters, thousands of millions of years after their formation, have a mass less than 80 per cent of that of our Sun and still retain a portion of the elements of the cloud from which they were formed. The higher-mass stars leave fossil remnants, such as neutron stars and brown dwarfs, whereas lower-mass objects, like the substellar brown dwarfs, have yet to be detected in globular clusters. Professor Ivan R. King gives an overview of these stellar and substellar objects for the student of stellar evolution.

Do you think that it will be possible in the near future to discover brown dwarfs in globular clusters? How could they be imaged, by using microlensing effects?

"They will probably be discovered, won’t be imaged, but probably detected by microlensing."

Wha fraction of the matter in the globular clusters could be in brown dwarfs if we extrapolate your results to low-mass stellar population?

"10 to 50% by number, but a much smaller fraction by mass."

What is the most interesting problem in your current investigation in relation to globular clusters?

"Pushing toward the hydrogen-burning limit."

Which discovery has had the greatest impact on your career in astrophysics?

"The whole development of the field of stellar populations."

PROFILE

IVAN R. KING was born in New York in 1927.
He studied at Harvard University, where he obtained his doctorate in 1952.
He then worked as a mathematician for a private firm, as an instructor for Harvard University (1951-52) and, during the following four years was attached on Active Duty to the US Naval Reserve and the Department of Defense (1954-56) as a methods analyst.
From then onwards, his career followed a more academic line: professor of the University of Illinois from 1956 to 1964, and Professor of the University of California Berkeley, where he occupied a chair from 1966 to 1992 and where his is a present Emeritus Professor.
King has served as President of the Dynamical Astronomy Division of American Astronomical Society and of the Astronomy Section of the American Association for the Advancement of Science (1973-1974). He was elected member of the American Academy of Arts and Sciences in 1980 and of the National Academy of Science in 1982.