sponsored by the National Science Foundation (NSF)
continued to contribute new knowledge about the origins,
composition, and dynamics of the universe and Earth's
near-space environment. NSF-sponsored scientists have
discovered many new outer solar system objects as
a result of ongoing optical surveys. For example,
scientists now believe that the region beyond the
orbit of Neptune is home to hundreds of thousands
of minor planets and perhaps billions of comet-like
objects. Astronomers have begun to develop a picture
of the relationship between these objects and the
formation of planets, the origin of comets, and the
existence of dust disks around stars.
addition, NSF-sponsored scientists began monitoring a previously
unremarkable binary star that suddenly began emitting x-rays
and radio waves. Scientists believe that one of the pair
is either a black hole or a neutron starboth very
compact objects. Astronomers theorize that, in such systems,
the neutron star or black hole is drawing material away
from its companion star and that the material is formed
into a rotating disk around the compact companion. The x-rays,
they believe, come from superheated material in this "accretion
disk" and are ejected at right angles to the plane of the
disk. Because scientists do not fully understand the relevant
physical processes, astronomers are eager to gain as much
new information as possible whenever one of these systems
have discovered a way to study so-called "dark matter"matter
we cannot see because it does not give off any radiation.
Astronomers have known for several years that a small galaxy
is orbiting our home galaxy, the Milky Way. New calculations
indicate that the small galaxy orbits the Milky Way in less
than 1 billion years and that it has completed 10 orbits.
Amazingly, the strong gravitational forces of the Milky
Way have not destroyed the small galaxy as would have been
expected. This indicates that the small galaxy contains
far more mass than indicated by its number of stars, thus
signaling the presence of a significant amount of dark matter.
Astronomers think that at least 90 percent of the matter
in the universe is dark and hope to clarify the nature of
this dark matter.
telescope studies of the fiery afterglow of a gamma ray
burst have provided astronomers with the best clues yet
about the origins of these tremendous cosmic cataclysms
since their discovery more than 30 years ago. Observations
with NSF's Very Large Array radio telescope confirm that
a blast seen to occur on March 29, 1998, had its origin
in a star-forming region of a distant galaxy. There are
two leading theories for the causes of gamma ray bursts.
According to one theory, the blasts occur when a pair of
superdense neutron stars collide. The second is that a single,
very massive star explodes in a "hypernova," more powerful
than a supernova, at the end of its normal life. Observations
favor this second hypothesis.
have found evidence for the most powerful magnetic field
ever seen in the universe. They have observed a long-sought,
short-lived "afterglow" of subatomic particles ejected from
a magnetara neutron star with a magnetic field billions
of times stronger than any on Earth and 100 times stronger
than any previously known in the universe. The afterglow
is believed to be the aftermath of a massive starquake on
the neutron star's surface.
researchers at Hughes STX Company developed a method for
the early warning of solar events using interplanetary radio
bursts observed remotely by both the Ulysses and Wind spacecraft.
These emissions are generated when coronal mass ejections
create shocks in the interplanetary medium. The investigators
have been successful in using the timing of these radio
emissions to estimate the arrival time of the shocks on
at Science Applications International Corporation in San
Diego developed a comprehensive, three-dimensional, magnetohydrodynamic
model to use remote observations of the Sun to predict the
state of the solar wind at Earth's orbit. Researchers have
already used the model to determine the coronal magnetic
field and heliospheric current sheet structure during the
period from February 1997 to March 1998. Scientists also
have used the model to simulate the triggering of a coronal
mass ejection, including its appearance as seen by a space-based
from Cornell University used a sensitive all-sky imaging
camera to study the behavior of structured airglow layers
in the thermosphere over Puerto Rico. These elongated structures
are believed to be a result of enhanced geomagnetic activity.
Their behavior is consistent with plasma irregularities
commonly seen near the magnetic equator, but scientists
do not yet completely understand the connection between
the two phenomena.
at SRI International and the University of Alaska's Geophysical
Institute in Fairbanks discovered new evidence for a theory
explaining the presence of thin sporadic layers of sodium
in Earth's upper atmosphere. Scientists believe that these
sporadic layers, distinct from the better understood layer
of neutral sodium atoms found between 80 and 100 kilometers
altitude, are a byproduct of meteors vaporizing when entering
the atmosphere. Using data from the NSF-supported incoherent
scatter radar and sodium LIDAR, the investigators demonstrated
that thin ion layers are pushed downward to a region in
which chemical catalysts recombine the ionized sodium, leaving
behind a thin layer of neutral sodium.
scientists at the High Altitude Observatory of the National
Center for Atmospheric Research continued to develop instruments
to assist in studying solar irradianceenergy flux
in the plane of Earth's orbit. Solar irradiance and total
solar luminosity vary over time scales from days to years.
Not only do astronomers not know the physical mechanisms
that cause these changes in the Sun's brightness, but astronomers
cannot even identify which of the components of the Sun's
visible outer photosphere are responsible for the solar
energy flux variations that have been detected by satellite
experiments. In response to mounting documentation that
terrestrial climate is correlated with such changes in the
Sun, NSF researchers have developed a long-range plan and
experiment to address how and why the Sun's irradiance changes.