[FPSPACE] Message from a craft at the solar system's final frontier holds surprises
ljk4 at msn.com
Wed Jul 2 16:14:25 EDT 2008
Postcards from the edge
Message from a craft at the solar system's final frontier holds surprises.
By Ron Cowen
July 2, 2008
There are no signs to announce the edge of the solar system, but when the
venerable Voyager 2 spacecraft approached this final frontier last Aug. 31
was in for quite a shock. So were the scientists who analyzed the data that
craft radioed back to Earth, along with related observations by NASAs twin
Earth-orbiting STEREO spacecraft.
The signals reveal that at a distance of 83.7 astronomical units (1 AU is
average Earth-sun separation), Voyager 2 had at least five encounters with a
turbulent region known as the termination shock, the researchers report in
July 3 Nature. Thats the place where the solar wind the suns hot
wind of protons and other charged particles, which carves the heliosphere, a
bubble in space extending well beyond the orbit of Pluto slams into cold
interstellar space and abruptly slows....
Researchers studying the flow of energy at the solar systems edge found
surprise. At the termination shock, the solar wind slows and dumps a large
amount of energy into space. This energy must then exist in some form, such
heat. But John Richardson of the Massachusetts Institute of Technology and
colleagues found that the temperature of protons a main constituent of the
solar wind in the slowed-down region is five to 10 times cooler than
Using the STEREO spacecraft, ROBERT LIN and LINGHUA WANG OF THE UNIVERSITY
CALIFORNIA, BERKELEY, and their colleagues trace the missing energy to a
group of pickup protonsparticles that started out as neutral hydrogen
from interstellar space and then infiltrated the solar system. The solar
ionized these atoms, turning them into protons that were then carried back
again by the wind, to the termination shock. About 80 percent of the energy
released when the solar wind slows goes into accelerating the pickup
the researchers report....
The Berkeley-led team concluded that these particles came from the
medium, providing the first map of particles from just beyond the solar
This new map is especially important because material at the solar systems
is too tenuous and faint to be imaged by a visible-light telescope....
More information about the FPSPACE