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BACKGROUND
Dr. Shiv S. Kumar (born 1939) earned his PhD. degree in Astronomy from the University of Michigan (USA) on February 3, 1962. Dr. Kumar has
been working on the problems of the origin and evolution of very low-mass
stars, the origin of the Solar System, the theory of stellar atmospheres,
the existence and characteristics of planets beyond the Solar System,
the origin and evolution of life in the universe, and other problems
since 1957.
During the
period 1958-1962, he developed the theory of the very-low-mass gaseous
objects that are unable to sustain hydrogen-burning thermonuclear
reactions. This theory led to the prediction (in 1962) of the possible
existence in the universe of the astronomical objects currently
called brown dwarfs. The main results of the then-new theory were
presented by Dr. Kumar at a meeting of the American Astronomical
Society held at Yale University in August 1962. The abstract of
this paper was published in the Astronomical Journal in November
1962 and it can be accessed online:
STUDY
OF DEGENERACY IN VERY LIGHT STARS
http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1962AJ.....67S.579K
Details of
his theory were submitted to the Astrophysical Journal in October
1962 in the form of two papers. These papers were accepted for publication
in November 1962 by the Astrophysical Journal. You may access the
papers online:
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THE STRUCTURE OF STARS OF VERY LOW MASS
Shiv S. Kumar
NASA Goddard Space Flight Center
Institute for Space Studies
New York 27, N.Y.
Received October 20, 1962; revised November 27, 1962
ABSTRACT
Completely convective models have been constructed for stars of masses 0.09, 0.08, 0.07, 0.06, 0.05, and 0.04 (solar units),
taking into account the non-relativistic degeneracy of the stellar material. It is
shown that there is a lower limit to the mass of a main-sequence star. The stars with mass less than this
limit become completely degenerate stars or "black" dwarfs as a consequence of gravitational contraction, and, therefore, they
never go through the normal stellar evolution.
(click here for full article)
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THE HELMHOLTZ-KELVIN TIME SCALE FOR STARS OF VERY LOW MASS
Shiv S. Kumar
NASA Goddard Space Flight Center
Institute for Space Studies
New York 27, N.Y.
Received October 20, 1962; revised November 21, 1962
ABSTRACT
Assuming that the contracting stars in convective equilibrium evolve vertically downward in the H-R
diagram, a simple expression for the Helmholtz-Kelvin time scale tHK is derived. Application of this
expression to stars of mass M < 0.1M shows that these stars contract to a radius of about 0.1R in a
time scale of approximately 1 billion years, while the earlier estimates, based on horizontal evolution,
gave a time scale tHK greater than a hundred billion years.
(click here for full article)
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After a very
long search lasting over a period of 32 years, the existence of
brown dwarfs (also known as Kumar objects/black dwarfs) was observationally
confirmed in 1994. Recent observational work clearly demonstrates
that the Milky Way Galaxy contains a very large population (billions
and billions!) of the luminous and dark very-low-mass objects as
predicted back in 1962. The story behind the theoretical discovery
of brown dwarfs (Kumar objects) during the period 1958-1962 may
be found by clicking here. This paper
was published in June 2003 in the Proceedings of the International
Astronomical Union Symposium #211 held at Waikoloa, Hawaii (May
2002).
A short biography of Dr. Kumar is available here.
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