Click on NASA image to enlarge
Space is actually not a vacuum contrary to what many
believe. In fact the solar system medium is largely made of ionized gas
from the sun. This medium of ionized gas is extremely low density from
a human perspective; however, the interaction with the expanding ionized
gas with interstellar space could have enormous implications for life
on earth. There comes a point at which this expansion of the Sun's energy
comes to a halt as the result of the implosion of interstellar wind. This
is a point where many of the low energy cosmic rays from interstellar
space are prevented from entering the solar system. Many scientists currently
believe that the solar system is traveling through a "vacuum bubble"
in which there is a reduced density of cosmic rays and interstellar wind
and dust affecting our solar system, but this field of astrophysics is
one of the least understood
An Interview
With a NASA Scientist On the Planned Interstellar Probe to Study the Heliosphere
BY Eric Storm
(4/4/01)
To understand more accurately how the Sun interacts in it's interstellar
environment and to come to know what makes up the surrounding interstellar
environment NASA plans on setting sail into the unknown, driven by photons
of light.
Dr. Paulett Liewer at the Jet Propulsion Laboratory in Pasadena, Ca.
is intrigued by what laws are governing our solar system as a result of
the Sun's interaction with the vast interstellar medium surrounding it.
Dr. Liewer states that our present knowledge of the heliosphere "comes
mostly from astronomical observations" These observations are measurements
of sunlight resonantly scattered back towards us by interstellar Hydrogen
and Helium, and measurements of the dust and neutral gas that penetrates
the heliosphere.* "I view it as pure science" says Dr. Liewer
and her ever growing curiosity of the heliosphere, along with the curiosity
of many other scientists at NASA, is the driving force behind a new project
which promises to be a first of its kind and will carry humans farther
from their cosmic shore.
Dr. Liewer explains that Scientists believe the solar system's location
is near the edge of a local interstellar cloud of low density material
blowing from the direction of stellar nurseries in the constellations
Scorpius and Centaurus. The solar wind, a low density plasma or flux of
charged particles, blows outward from the corona and expands faster than
the speed of sound, passing the outer planets. The solar wind pushes the
interstellar medium away from the sun until a balance is created between
the pressure of solar wind and interstellar wind and this creates what
scientists call the heliosphere. The balance of this pressure determines
the size of the heliosphere. When the solar wind is overcome by the interstellar
wind pressure the solar wind goes through a transition from supersonic
to subsonic. This is called the termination shock.
"The Voyager 1 spacecraft has almost reached the termination shock
at about 80 A.U", says Dr. Liewer.
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