the whole cosmos as its agenda, the meeting of the American Astronomical
Society last week in Washington was a sounding board for scientists
with new findings and ideas about nearly everything from mysterious
gamma ray bursts in deep space to revealing images penetrating the
turbulent heart of the Milky Way, Earth's home galaxy.
Two new discoveries described at the meeting underscored the
growing and bewildering realization that planetary systems abound in
the nearby universe and that they come in all shapes and sizes,
bearing little apparent resemblance to the Sun's family of
Both discoveries revealed unexpected configurations of stars and
In observations by telescopes in Hawaii, astronomers were
surprised to detect an object that is no ordinary planet orbiting a
sunlike star 58 light- years from Earth. The object is a brown
dwarf, the name given to what are thought to be failed stars that
lacked the mass to ignite their nuclear furnaces.
Dr. Michael Liu, an astronomer at the University of Hawaii,
reported that the brown dwarf was estimated to have a mass about 65
times as great as that of Jupiter, the solar system's largest
planet. The brown dwarf is orbiting the star called 15 Sge at a
distance of 1.3 billion miles — 14 times the distance between Earth
and the Sun.
Of the more than 80 giant objects that have recently been found
orbiting nearby stars, most have been estimated to be Jupiter-size
But several are so massive that they are suspected of having
starlike origins and thus of being brown dwarfs.
"This companion is probably too massive to have formed the way we
believe that planets do, namely from a circumstellar disk of gas and
dust when the star was young," Dr. Liu said. "This finding suggests
that a diversity of processes act to populate the outer regions of
other solar systems."
Other astronomers said the brown- dwarf discovery was important
because it was the first of these extrasolar companion objects to be
detected by direct observations, not indirectly by measuring the
effects of their gravity on the motions of the host stars.
A new technology called adaptive optics, a spinoff of military
research, uses computers to compensate for atmospheric distortions
and produce sharper images of faint cosmic objects.
Dr. Alan Boss, an astrophysicist at the Carnegie Institution of
Washington and a theorist who specializes in the new planetary
systems, said such discoveries were "really just tantalizing
appetizers for things to come."
In a report of a related discovery, astronomers said they had
made the first detection of a planet orbiting an extremely large
star — one that had already burned its hydrogen fuel and was
The star, iota Draconis, has expanded to a radius that is 13
times as great as that of the Sun, which is an average-size
"Until now, it was not known if planets existed around such giant
stars," said Dr. Sabine Frink of the University of California at San
Diego, a member of the discovery team. "This provides the first
evidence that planets at Earth-like distances can survive the
evolution of their host star into a giant."
Sometimes, coming down to Earth, astronomers speak an almost
ordinary language, as when they talked at the meeting about cosmic
bubbles, fountains and halos.
The bubbles are in this case ghostly cavities in huge galactic
clusters. The clusters of 100 or more galaxies stretch millions of
light-years across and are considered the largest stable objects in
From the centers of the clusters, cavities virtually devoid of
X-ray and radio emissions rise like bubbles in a glass of soda pop.
Some bubbles are as large as 60,000 light-years wide, almost as big
as the Milky Way.
Dr. Brian McNamara, an astronomer at Ohio University in Athens,
described the discovery and analysis of the bubbles with data from
the Chandra X-ray Observatory in Earth orbit.
The bubbles, Dr. McNamara said, were most likely created by
extremely powerful explosions, probably involving material plunging
toward grasping black holes.
Observations show that the bubbles are not completely empty, but
contain some hot gas, high-energy particles and magnetic fields. The
bubbles may play a major role in transporting magnetic fields
through the clusters.
"We think magnetism in some locations of the universe could have
been as important as gravity in shaping" the galaxies and even
larger- scale cosmic structures, Dr. McNamara said.
Dr. Edward M. Murphy, an astronomer at the University of
Virginia, reported on other spacecraft observations that have
yielded evidence for a towering fountain of gas in a nearby galaxy,
NGC 4631, which in telescopes bears a resemblance to a whale.
The spacecraft is the Far Ultraviolet Spectroscopic Explorer, or
FUSE, operated for NASA by Johns Hopkins University.
In describing the phenomenon at a news conference, Dr. Murphy
managed to use all three evocative terms — bubbles and halos, as
well as fountains. He did that in proposing a possible solution to
the longstanding mystery of the ultimate fate of energy from
exploding stars, or supernovas.
A profusion of stellar explosions, Dr. Murphy suggested, would
probably start the circulation of hot gas, rising in a fountain of
bubbles out of the galaxy and into the halo of diffuse gas that
surrounds the galaxy. Gas remaining in the halo for perhaps a
million years would presumably cool and fall back into the galaxy,
bringing with it material for the next generation of new stars.
Dr. Murphy said the FUSE data provided the "first good evidence"
for the long-theorized "galactic fountain" cycle of circulating
Some of the same ultraviolet observations have enabled
astronomers to detect clouds of hydrogen gas raining onto the Milky
Way galaxy and glowing on contact with the intergalactic medium,
like showers of meteors that streak through Earth's upper
From the FUSE data, the astronomers found that beyond the
previously known and denser halo around the Milky Way there was
another one — less dense and hot, possibly one million degrees
Fahrenheit. That outer halo, invisible in ordinary light, can be
seen in ultraviolet light as a blue, football-shape envelope around
the entire galaxy.
Astronomers said the outer halo could be left over from the
formation of the Milky Way or it may have been created by early
episodes of star formation in which the hot gas was heaved by
supernovas and expelled from the galactic disk — perhaps in some
kind of fountain of bubbles. In any event, because astronomers are
still detecting the hydrogen clouds that are falling into the
galaxy, they think the Milky Way is still pulling in new
The new findings, said Dr. Kenneth Sembach of the Space Telescope
Science Institute in Baltimore, are "going to help astronomers
understand better how galaxies are assembled and hopefully how they
evolved over time."