Joanie October 19th, 2008
SUN’S PROTECTIVE ‘BUBBLE’ IS SHRINKING
By Richard Gray
October 19, 2008
The protective bubble around the sun that helps to shield the Earth from
harmful interstellar radiation is shrinking and getting weaker, Nasa
scientists have warned.
New data has revealed that the heliosphere, the protective shield of energy
that surrounds our solar system, has weakened by 25 per cent over the past
decade and is now at it lowest level since the space race began 50 years
Scientists are baffled at what could be causing the barrier to shrink in
this way and are to launch mission to study the heliosphere.
The Interstellar Boundary Explorer, or IBEX, will be launched from an
aircraft on Sunday on a Pegasus rocket into an orbit 150,000 miles above the
Earth where it will “listen” for the shock wave that forms as our solar
system meets the interstellar radiation.
Dr Nathan Schwadron, co-investigator on the IBEX mission at Boston
University, said: “The interstellar medium, which is part of the galaxy as a
whole, is actually quite a harsh environment. There is a very high energy
galactic radiation that is dangerous to living things.
“Around 90 per cent of the galactic cosmic radiation is deflected by our
heliosphere, so the boundary protects us from this harsh galactic
The heliosphere is created by the solar wind, a combination of electrically
charged particles and magnetic fields that emanate a more than a million
miles an hour from the sun, meet the intergalactic gas that fills the gaps
in space between solar systems.
At the boundary where they meet a shock wave is formed that deflects
interstellar radiation around the solar system as it travels through the
The scientists hope the IBEX mission will allow them to gain a better
understanding of what happens at this boundary and help them predict what
protection it will offer in the future.
Without the heliosphere the harmful intergalactic cosmic radiation would
make life on Earth almost impossible by destroying DNA and making the
Measurements made by the Ulysses deep space probe, which was launched in
1990 to orbit the sun, have shown that the pressure created inside the
heliosphere by the solar wind has been decreasing.
Dr David McComas, principal investigator on the IBEX mission, said: “It is a
fascinating interaction that our sun has with the galaxy surrounding us.
This million mile an hour wind inflates this protective bubble that keeps us
safe from intergalactic cosmic rays.
“With less pressure on the inside, the interaction at the boundaries becomes
weaker and the heliosphere as a whole gets smaller.”
If the heliosphere continues to weaken, scientists fear that the amount of
cosmic radiation reaching the inner parts of our solar system, including
Earth, will increase.
This could result in growing levels of disruption to electrical equipment,
damage satellites and potentially even harm life on Earth.
But Dr McComas added that it was still unclear exactly what would happen if
the heliosphere continued to weaken or what even what the timescale for
changes in the heliosphere are.
He said: ³There is no imminent danger, but it is hard to know what the
future holds. Certainly if the solar wind pressure was to continue to go
down and the heliosphere were to almost evaporate then we would be in this
sea of galactic cosmic rays. That could have some large effects.
³It is likely that there are natural variations in solar wind pressure and
over time it will either stabilise or start going back up.²
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Published by David Sunfellow
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