HPM%SU-AI@sri-unix.UUCP (01/09/84)
From: Hans Moravec <HPM@SU-AI>
n044 1217 08 Jan 84
(The Week in Review)
c.1984 N.Y. Times News Service
ASTRONOMICAL HIGHLIGHTS OF 1983 - A STELLAR YEAR
Old Data Yielded New Insights, New Instruments Unveiled Ancient
Phenomena and
Earth Waved A Very Long Goodbye to the Satellite Pioneer 10.
Earth's rotation is erratic, usually slowing, rarely speeding up. As
a result, scientists must insert ''leap seconds'' every few years to
keep world clocks in step. An extra second was added last year on
June 30. The minute beginning at 7:59 EDT that evening was 61 seconds
long. It was the 12th such second to be added since these kinds of
adjustments began in 1972, when two leap seconds were added to the
year. The variability in the rate of Earth's rotation is believed to
be caused by a number of factors, including friction in the planet's
atmosphere, in the oceans and in the core.
Without much hoopla, the standard for defining all units of length
in the world was changed by the General Conference on Weights and
Measures in Paris. What has this to do with astronomy? For one, the
definition affects the units of force, wavelength and radio
frequency. For another, the new standard is based on the speed of
light, in part because time-measuring methods are far more precise
than those applied to distances.
For many decades, all length measurements were based on the meter as
defined by the distance between two scratches on a platinum-iridium
bar stored in a vault at the International Bureau of Weights and
Measures at Sevres, near Paris. Since 1960, length measurements have
been based on a more accurate and more readily available standard -
the wavelength of orange light emitted by the gas krypton 86. Under
the new system, one meter is defined as the distance traveled by
light through a vacuum in one-299,792,458th of a second.
SOME STORM
-A reanalysis of data from the two Voyager spacecraft that passed
Saturn revealed recordings of a peculiar static. Astronomers said it
was the mark of a gargantuan atmospheric lightning storm 40,000 miles
long, wrapping a sixth of the way around the planet (almost twice
around Earth) and lasting at least 10 months.
-Information collected by Soviet Venera 13 and 14 landing craft,
together with data from orbiting Pioneer Venus spacecraft, indicated
that Venus should join the list of volcanically active objects in the
solar system. The list includes Earth and Jupiter's moon Io.
-Triton, a satellite of the planet Neptune, may have a near-global
ocean - not of water but of liquid nitrogen. Scientists at the
University of Hawaii in Honolulu announced that spectral data had
provided ''the first direct evidence for an ocean on an
extraterrestrial body'' - that body being Triton. The other leading
candidate for an ocean is the Saturnian moon Titan, whose seas are
thought to be 70 percent ethane, 25 percent methane and 5 percent
nitrogen.
SOLAR SIGNS
The appearance of twin dust rings around the Sun, hypothesized as
early as 1927, was recorded by Japanese astronomers over Indonesia
during a solar eclipse. Scientists had theorized that cosmic dust
spiraling in toward the Sun would begin to glow as it grew nearer and
would continue to do so until close enough to evaporate. Given the
geometry of the dust spiral, the glow seems brightest at the outer
and inner edges of the zone.
The picture was obtained with a video system suspended from a
balloon and a computer-based enhancement process. The glowing region
lies 900,000 to 1,500,000 miles above the solar surface. Scientists
calculated the distance from the Sun at which the inner dust
disappeared and used it as an indication of the ring's vaporization
temperature. From this, they guessed that the dust is a silicate
comparable in composition to quartz.
ASTEROID ALERT
Asteroids have struck Earth in the past, hurtling from space with
such speed that they vaporized on collision. Astronomical and
geological observations showed last year that large asteroid
collisions can still occur. More than 50 asteroids are known to be in
orbits that might send them charging into Earth, and recent samplings
of the asteroid population signal that the total number of
Earth-threatening asteroids may approach 100,000. Asteroid fragments
weighing about 500 tons plunge into the atmosphere, on average once a
year, but usually break up before hitting the surface.
STAR LIGHTS
Infrared Astronomy Satellite, an orbiting observatory launched last
January and now out of service, discovered that the star Vega is
surrounded by a giant disk or shell of material. Scientists at the
Jet Propulsion Laboratory of the California Institute of Technology
hailed the discovery as the first direct evidence of solid objects
orbiting a star other than the Sun. Some astronomers suggested that
the shell may be an early planetary system in formation.
Vega is near our solar system, only 26 light years - or about 156
trillion miles - away. It is the brightest star in the constellation
Lyra (the Harp) and the third brightest star in the night sky. It is
thought to be less than a billion years old, less than one-fourth the
age of the Sun and its family of planets. Vega's properties have
turned it into an astronomical measuring piece on which scientists
train instruments to test equipment sensitivity. That's what
astronomers were doing with IRAS when they found the Vegan shell.
Data from the infrared satellite also indicate that cool, solid
material may be orbiting the star called Fomalhaut, the brightest
star in the constellation Piscis Austrinus and one of the 20
brightest in the heavens. It can be seen in the winter sky with the
unaided eye.
THE UNIVERSE...
A new variation on a recent theme of the cosmos' formation, the
''inflationary universe,'' was unveiled. The revised inflationary
model postulates, in part, that the universe did not start with a big
bang, but bubbled up out of virtually nothing and then suddenly
inflated to astronomical proportions. Dr.Alan H. Guth of the
Massachusetts Institute of Technology proposed the first inflationary
model several years ago.
Meanwhile, cosmic surveys by the Harvard-Smithsonian Center for
Astrophysics, along with some fancy computer modeling, led
cosmologists to picture the current universe as a piece of Swiss
cheese, with the force of gravity making particles of matter clump
together into long filaments and flat, pancake-like structures.
Between these areas of dense matter are bubbles of largely empty
space. The model assumes that neutrinos, atomic particles thought to
constitute about 90 percent of all matter in the universe, have some
mass and therefore clump together.
...AND BEYOND
Pioneer 10, the satellite launched March 3, 1972 from Cape
Canaveral, Fla., left the outer limits of the planetary system. No
human artifact had ever traveled so far. Its next stop - no one
knows. According to the National Aeronautics and Space
Administration, ground-based antennas should maintain communications
for eight years more, to a distance of five billion miles. Scientists
hope that in the time remaining the satellite will detect gravity
waves, the gravitational radiation that in theory emanates from
cataclysmic events, such as exploding stars, but in practice has not
been found. When it does turn a blind eye toward Earth, the craft
will carry on with a message for passersby - a plaque engraved with
images of a man, a woman, Earth's location and some terrestrial
scientific ABC's.
In November 1988, the satellite Voyager 1, which was launched five
and a half years ago, will become the first spacecraft to cross the
orbits of all nine planets in the solar system. (Pioneer's path took
it outside Pluto's orbit.) Voyager 2 and Pioneer 11 are also swinging
out beyond the outer planets.
METEORIC RISE
The Murchison meteorite, which fell on Australia in 1969, gave up
one of its greatest secrets - that it contains the five chemical
bases of human genes. Scientists at the University of Maryland's
Laboratory of Chemical Evolution said their detection of the bases -
precursors of life - and their ability to synthesize all five in a
single experiment simulating primordial conditions on Earth, boosted
the theory that terrestrial life arose by comparatively simple,
natural chemical processes.
Their success further suggested that life may have arisen by the
same processes elsewhere in the universe, wherever the appropriate
conditions existed.
COMET TRIALS
A new comet, named for its discoverers Sugano-Saigusa-Fujikawa, and
passing unusually close to Earth, was discovered as another comet,
IRAS-Araki-Alcock, receded from Earth. IRAS-Araki-Alcock passed
within 2.9 million miles of the planet - closer than any other comet
since 1770. Sugano-Saigusa-Fugikawa came within about 6 million miles.
Astronomers also estimated that the total number of comets roaming
the outer reaches of the solar system, beyond the outer planets, may
be at least 2 trillion - far more than the 100 billion previously
imagined. The recalculation resulted in part from the discovery of
several comets traversing the inner solar system. Most comets were
thought to be slowly circling the Sun far beyond the outer planets.
Finding these inner system trespassers hinted that other comets are
nearby successfully escaping detection from Earth.
nyt-01-08-84 1521est
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