GOOSE DOWN SOX 
Great travel, bed or sleeping-bag sox. 
Ultra-warm Bauer Goose Down is 
quilted in tough nylon taffeta. A pair 
weighs mere ounces and takes little 
space in luggage. Machine washable. 
Colors, Men's: Taupe, Red, Winter Blue. 
Women's: Winter Blue, Red, Powder 
Blue. Sizes: Men's S(6’/z-8), M(8’/2-10), 
L(10’/2-1 1 Vz), XL(1 2-1 3). Women's 
S(5-6'/ 2 ), M(7-8’/2), L(9- 1 0 V 2 ). $17.95 ppd. 
Order Today! Money Back Guarantee! 
Here is my check or money order for $ 
(Add sales tax where applicable.) 
□ #0347 Men’s Goose Down Sox 
Size Color 
□ #0348 Women’s Goose Down Sox 
Size. Color 
Name 
Address 
City 
State Zip 
□ Send me your FREE outdoor catalog. 
Dept NNH. Fifth & Union. Seattle. WA 98124 
The true story 
of the gorilla 
who can chat, 
tease, argue, 
joke, question, 
insult — 
and even lie. 
“ The Education ofKoko is more 
than a charming story about 
animals; it is a valuable tool in 
our exploration of how we 
learn to communicate, how we, 
as well as apes, learn language.” 
— Publishers Weekly 
THE “EDUCATION OF 
by Francine Patterson and 
Eugene Linden 
Main Selection of Book-of-the-Month Club/ Science 
Alternate Selection of Book-of-the-Month and Natural t T 
Science Book Clubs \i 
$15.95 Holt. Rinehart &Winston*^y 
only occurs when an additional force 
(other than the gravity of the two stars) 
helps to slow the pair down. One sug- 
gested additional force is the gravity of a 
third star that may be nearby. But close 
approaches of one star to another are 
very rare and a three-way close ap- 
proach would be extremely unlikely 
among unrelated stars. Two stars that 
already compose a binary system might 
be able to capture a third star and form 
a triple system, but at first glance, cap- 
ture is an improbable way to form a 
binary to begin with. 
In the fragmentation theory, a proto- 
star does not condense toward the cen- 
ter, as is assumed in the fission theory. 
Instead, the protostar is supposedly 
shaped like a huge torus, or doughnut, 
and eventually breaks up into several 
fragments. Two of the fragments con- 
dense and form a binary star. Computer 
calculations by Lucy, which start out 
with the hypothesized torus, show that 
the protostar fragments can form a 
short-period binary. Further, in contra- 
distinction to the fission theory, frag- 
mentation does seem capable of making 
binaries with nearly equal masses. We 
are not certain, however, that protostars 
will form toruses rather than condensing 
toward their centers. 
The theory that binary stars form by 
cluster disruption assumes that the 
members of a small star cluster escape, 
leaving just two stars, which then consti- 
tute a binary. There is more to it, but 
that is the general idea. This theory begs 
the question of how the cluster itself 
formed. Further, if virtually all stars are 
at least binary, as determined by Abt 
and Levy, then how do the escaped stars 
get their companions? 
Finally, the theory that binary sys- 
tems are created by the condensation of 
adjacent protostars is the least profound 
of all. It postulates that from a single 
nebula two protostars condense close 
enough to each other to enable gravity 
to make them a binary star. This theory 
is applicable to widely separated, long- 
period binary stars: protostars are so 
much larger than the stars they eventu- 
ally become that if two protostars were 
close enough to form a close binary, they 
might merge into a single protostar or 
tidally disrupt each other. 
What if two protostars formed at dis- 
tant locations within a large nebula and 
then happened to pass each other? One 
star might capture the other since the 
nebula would be a retarding medium, 
and the retardation could constititute 
the additional force that (as explained 
above) is necessary for the capture proc- 
ess. This variant of the capture theory 
could account for the formation of long- 
period binaries with their unrelated sec- 
ondary and primary star masses. 
The work of Trimble, Abt, and Levy 
tells us that two processes are at work, 
forming two different kinds of binary 
stars. We are not sure how that happens, 
but another process — the process of 
elimination — suggests that, among cur- 
rent theories, fragmentation can best 
account for the short-period, close bina- 
ries with their members’ comparable 
masses. Either capture in a nebular envi- 
ronment or condensation of adjacent 
protostars may explain the long-period 
binaries with their unrelated masses. 
In some binary systems, mass flows 
from one star to its partner in the form 
of a gas stream or of a stellar wind. This 
further complicates astronomers’ efforts 
to interpret the mass ratios. Explaining 
exactly how a single star is bom is hard 
enough, but binary stars are clearly dou- 
ble trouble. 
Stephen P. Maran is a senior staff sci- 
entist in the Laboratory for Astronomy 
and Solar Physics at NASA ’s Goddard 
Space Flight Center in Greenbelt, 
Maryland. 
WHEN YOU WRITE TO 
NATURAL HISTORY 
about a change of address, renewal of sub- 
scription, billing, or any kind of adiustment. 
send the present address label from the mag- 
azine wrapper 
Moving? Please notify 6 weeks in ad- 
vance. You can use this form to tell us about 
a move or order a subscription 
Change of address — Attach your address 
label in the dotted area and fill in your new 
address below, clip and mail to Natural History 
Membership Services. P 0 Box 4300, Ber- 
genfield. N J 07621 
28 
