Number 246, October 25, 1995 by Phillip F. Schewe and Ben Stein
A PLANET ORBITING A NEARBY STAR has been discovered. Astronomers with
the Geneva Observatory in Switzerland reported the finding at a recent
meeting in Florence, Italy. Planets around pulsars have been detected before,
but in the present case the star (51 Pegasus, 40 light years away) is similar
to our own sun. The planet is estimated to have a mass at least half that
of Jupiter. Its orbit, only about 5% of the earth-sun distance, places
it uncomfortably within the star's corona. Following up the announcement
in Florence, astronomers at the Lick Observatory in California have confirmed
the presence of the planet. At the Florence meeting the possible sighting
of another planet was also announced. The star is GL229 (about 30 light
years from Earth) while the orbiting object has a mass about 20 times that
of Jupiter. An alternative interpretation is that the object is a brown
dwarf. (Science News, 21 October 1995.)
IN INERTIAL CONFINEMENT FUSION (ICF) a "driver" consisting
of multiple laser or particle beams converge on a target. The resulting
compression heats up a deuterium-tritium mixture until fusion reactions
begin. Scientists studying this fusion fireball have both practical applications
in mind---they aim to convert fusion energy into commercial electrical
energy---and military applications---since fusion reactions are at the
heart of modern nuclear weapons. In what is likely to become the ICF bible
for years to come, Livermore physicist John Lindl (510- 422-5430) lays
out the nuts and bolts of ICF research in the November issue of the journal
Physics of Plasmas. Lindl's 90-page report includes extensive discussion
of research that until the past year or so was classified as secret information.
Much of the declassified material has to do with target design. In the
indirect-drive approach to ICF, the driver beams do not strike the fuel
capsule but rather an outer casing consisting of high-atomic-weight material,
which heats up and emits x rays. It is the x rays which cause the implosion
of the fuel capsule. At the proposed National Ignition Facility (which,
if approved, would be constructed by about 2002) scientists hope to extract
10 times as much energy from the fuel as goes in. (Journalists can obtain
copies of the article from AIP Public Information at physnews@aip.org)
ISOTOPE EFFECTS IN SONOLUMINESCENCE have been observed by Seth Putterman
and Robert Hiller at UCLA. Sonoluminescence (SL) is a mysterious phenomenon
in which acoustic energy is transduced into light energy; high frequency
sound waves are absorbed by tiny bubbles in water. The bubbles, oscillating
wildly, re-emit the energy in the form of tiny, focused light bursts. Many
things about SL are still unknown, such as the nature of the light-emitting
process or why the light pulses are so short. The UCLA work has established
one new fact: substituting heavy water (D2O) for ordinary water (H2O) as
the liquid medium causes the center of the SL spectrum to dramatically
shift from ultraviolet toward red wavelengths. This result seems to represent
yet a new mystery. According to the researchers, "The shift is remarkably
large, especially in view of the small difference in chemical and elastic
properties between light and heavy water." (Robert A. Hiller and Seth
Putterman, upcoming article in Physical Review Letters; journalists can
obtain copies from AIP Public Information, physnews@aip.org)
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