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.
Data has shown that the sun's heliosphere is shrinking
Photo: AP
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 ago.
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 environment."
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 galaxy.
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 climate uninhabitable.
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: “There 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.
“It is likely that there are natural variations
in solar wind pressure and over time it will either
stabilise or start going back up.”
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