HPM@SU-AI@sri-unix.UUCP (08/18/83)
From: Hans Moravec <HPM@SU-AI>
n085 1721 09 Aug 83
AM-PLANET
Evidence of Infant Planetary System Circling Nearby Star
By WALTER SULLIVAN
c. 1983 N.Y. Times News Service
NEW YORK - The possibility that an infant planetary system is
circling a nearby star has been raised by new evidence from an
orbiting observatory.
The Infra Red Astronomy Satellite launched last January has
discovered that the star Vega is surrounded by a giant disk or shell
of material.
The Jet Propulsion Laboratory of the California Institute of
Technology described the discovery Tuesday as the first direct
evidence of solid objects orbiting a star other than the sun.
The sizes of objects within the cloud could be anywhere from those
of buckshot to full-fledged planets. According to the jet propulsion
laboratory the objects must be larger than dust grains, which long
since would have been removed from orbit.
The discovery provides, the laboratory said, ''the first scientific
opportunity to study what may be an early solar system accreting from
stellar debris'' in the same manner as the sun and planets of this
system.
Vega is relatively near and is the third brightest star in the sky.
It is currently prominent in the ''summer triangle'' of Vega, Deneb
and Altair and in the northeast can be seen almost directly overhead
at this season.
Vega is thought to be less than a billion years old - less than a
quarter the age of the sun and its family of planets. It is believed
that the solar system, in its infancy, was also a cloud of dust, gas
and meteoritic fragments that formed into a disc and then into
objects as large as moons and, finally, planets.
Vega is twice the size of the sun and 60 times as luminous. It is 26
light years away - the distance traveled by light in that length of
time. The nearest star is 4.3 light years distant.
The cloud of matter around Vega extends 80 astronomical units from
the star. One astronomical unit is the distance of the earth from the
sun. Pluto, the outermost planet, is almost 40 astronomical units
from the sun, so the cloud (or disk) is somewhat larger than the
region inhabited by the planets of the solar system.
The discovery was serendipitous. Operators of the satellite, which
is controlled from the Appleton-Rutherford Laboratory in Chilton,
England, aimed IRAS at Vega to test the sensitivity of its detectors,
since that star is often used for such calibration. It was found that
the star was enveloped in an enormous cloud, ring or shell of
material.
The discovery was made by Dr. H.H. Aumann of the Jet Propulsion
Laboratory and Fred Gillett of the Kitt Peak National Observatory
near Tucson, Arizona. The satellite, a joint venture of Britain, the
Netherlands and the United States, has already discovered a number of
comets and other phenomena most readily detected at the infrared
wavelengths emitted by relatively cool objects.
The cloud around Vega is estimated to be at about minus 300 degrees
Fahrenheit, which is similar to the temperature of Saturn's rings.
It is not possible to determine the composition of the material in
the cloud nor how much of it there is, the statement added.
While this is the first direct evidence suggesting another planetary
system, there has been speculation in the past about the possibility
that such systems exist.
It has been hypothesized, for instance, that some stars appeared to
fly a winding path through space because of the gravitational
influence of unseen planets. Most often discussed among these stars
is the small, faint red star discovered in 19l6 by Edward E. Barnard
and known as Barnard's star. It is only six light years away.
Evidence for such perturbations has never been strong enough to
convince the astronomical community that planets were the cause.
Clouds of dust and gas are also observed in various parts of the sky
and are thought to mark where new stars and possibly planets are
forming. But the evidence was indirect. Radio emissions from such
clouds indicate they are rich in molecules that could provide
starting materials for the evolution of living organisms.
But this evidence suggests matter much less substantial than that
reported Tuesday.
nyt-08-09-83 2013edt
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