From: Reuters
Published December 10, 2007 07:56 PM

Voyager 2 finds solar system's shape is 'dented'

By Mark Lawin

SAN FRANCISCO (Reuters) - NASA's Voyager 2 spacecraft has found that our solar system is not round but is "dented" by the local interstellar magnetic field of deep space, space experts said on Monday.

The data was gathered by the craft on its 30-year journey into the edge of the solar system when it crossed into a sweeping region called the termination shock, they said.

It showed that the southern hemisphere of the solar system's heliosphere is being pushed in or "dented."

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Voyager 2 is the second spacecraft to enter this region of the solar system behind Voyager 1, which entered the northern region of the heliosheath in December 2004.

The termination shock is a turbulent area far beyond Pluto's orbit where the solar winds emanating from the sun are significantly slowed as they run up against the thin gas of interstellar space. Solar winds blow in all directions from our sun, and shape what was once thought to be a bubble around the solar system called the heliosphere.

"Voyager 2 entered the termination shock almost 1 billion miles closer within the southern hemisphere of the heliosphere of the solar system than Voyager 1 previously had," said Voyager Project scientist Edward Stone of the California Institute of Technology.

Voyager 2's data is scientifically exciting for a number of reasons, NASA said. The spacecraft has a working plasma instrument that can directly measure the velocity, density and temperature of the solar wind. A similar instrument on Voyager 1 stopped functioning long ago.

Voyager scientists had expected the temperatures within the termination shock to be about 1,000,000 degrees Fahrenheit (555,500 C) as material normally slows down and is heated up when it encounters an obstacle in a normal shock wave.

But according to Edward Stone of California Institute of technology, the temperatures registered were much lower, at around 200,000 degrees F (111,100 C). Also, Voyager 1 made only one crossing into the termination shock while Voyager 2 has made at least five shock crossings over several days which allowed them to collect more data.

Scientists believe Voyager 2 will reach interstellar space within seven to 10 years and estimate that the spacecraft has enough power to last until 2020.

(Editing by Eric Walsh)

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