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Voyager 2 Detects Odd Shape of Solar System's Edge

Friday, May 26, 2006

VoyagerVoyager 2 could pass beyond the outermost layer of our solar system, called the "termination shock," sometime within the next year. The milestone, which comes about a year after Voyager 1's crossing, comes earlier than expected and suggests to scientists that the edge of the shock is about one billion miles closer to the Sun in the southern region of the solar system than in the north.
This implies that the heliosphere, a spherical bubble of charged low-energy particles created by our Sun's solar wind, is irregularly shaped, bulging in the northern hemisphere and pressed inward in the south.
Scientists determined that Voyager 1 was approaching the termination shock when it began detecting charged particles that were being pushed back toward the Sun by charged particles coming from outside our solar system. This occurred when Voyager 1 was about 85 AU from the Sun.
One AU is the distance between the Earth and the Sun, or 93 million miles.
In contrast, Voyager 2 began detecting returning particles while only 76 AU from the Sun.
"This tells us that the shock down where Voyager 2 is must be closer the sun than where Voyager 1 is," said Ed Stone, Voyager project scientist at the California Institute of Technology in Pasadena.
The researchers think that the heliosphere's asymmetry might be due to a weak interstellar magnetic field pressing inward on the southern hemisphere.
"The [magnetic] field is only 1/100,000 of the field on the Earth's surface, but it's over such a large area and pushing on such a faint gas that it can actually push the shock about a billion miles in," Stone explained.

credit: Space.com, Ker Than

NASA to BLast the Moon in Search of Water

Tuesday, May 9, 2006

LCROSS

In this artist's rendering, the satellite and the launcher's second stage approach the moon. Meanwhile, the Lunar Reconnaissance Orbiter is orbiting the moon.
Credit: NASA/John Frassanito and Associates

NASA will send an impactor spacecraft to the moon with liftoff of the Lunar Reconnaissance Orbiter, scheduled for October 2008. The Lunar Crater Observation and Sensing Satellite (LCROSS) will travel independently of the orbiter and crash violently into the lunar surface, at a speed of 5,592 miles per hour (or about 2.5 kilometers per second) to search for water. It should blast out a crater about a hundred feet wide and 15 feet deep.

First, the craft will direct the upper stage used to leave Earth orbit to crash into a permanently-shadowed crater at the lunar south pole, creating a plume visible on Earth through a telescope. Next, the satellite will observe the plume and fly through it using several instruments to look for water. At the end of its mission, the satellite will itself become an impactor, creating a second plume visible to lunar-orbiting spacecraft and Earth-based observants.


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