|
+ Play
Audio
|
+ Download Audio | +
Email to a friend | +
Join mailing list
October
15, 2009: For years, researchers have known that
the solar system is surrounded by a vast bubble of magnetism.
Called the "heliosphere," it springs from the sun
and extends far beyond the orbit of Pluto, providing a first
line of defense against cosmic rays and interstellar clouds
that try to enter our local space. Although the heliosphere
is huge and literally fills the sky, it emits no light and
no one has actually seen it.
Until
now.
NASA's
IBEX (Interstellar Boundary Explorer) spacecraft has made
the first all-sky maps of the heliosphere and the results
have taken researchers by surprise. The maps are bisected
by a bright, winding ribbon of unknown origin:
Above:
IBEX's all-sky map of energetic neutral atom emission reveals
a bright filament of unknown origin. V1 and V2 indicate the
positions of the Voyager spacecraft. [more]
"This
is a shocking new result," says IBEX principal investigator
Dave McComas of the Southwest Research Institute. "We
had no idea this ribbon existed--or what has created it. Our
previous ideas about the outer heliosphere are going to have
to be revised."
Although
the ribbon looks bright in the IBEX map, it does not glow in
any conventional sense. The ribbon is not a source of light,
but rather a source of particles--energetic neutral atoms or
ENAs. IBEX's sensors can detect these particles, which are produced
in the outer heliosphere where the solar wind begins to slow
down and mix with interstellar matter from outside the solar
system.
"This
ribbon winds between the two Voyager spacecraft and was not
observed by either of them," notes Eric Christian, IBEX
deputy mission scientist at NASA's Goddard Space Flight Center.
"It's like having two weather stations, but missing the
big storm that runs between them."
Unlike
the Voyager spacecraft, which have spent decades traveling
to the edge of the solar system for in situ sampling,
IBEX stayed closer to home. It is in Earth orbit, spinning
around and collecting ENAs from all directions. This gives
IBEX the unique "big picture" view necessary to
discover something as vast as the ribbon.
The
ribbon also has fine structure--small filaments of ENA emission
no more than a few degrees wide: image.
The fine structure is as much of a mystery as the ribbon itself,
researchers say.
 One
important clue: The ribbon runs perpendicular to the direction
of the galactic magnetic field just outside the heliosphere,
as shown in the illustration at right.
"That
cannot be a coincidence," says McComas. But what does
it mean? No one knows. "We're missing some fundamental
aspect of the interaction between the heliosphere and the
rest of the galaxy. Theorists are working like crazy to figure
this out."
Understanding
the physics of the outer heliosphere is important because
of the role it plays in shielding the solar system against
cosmic rays. The heliosphere's size and shape are key factors
in determining its shielding power and, thus, how many cosmic
rays reach Earth. For the first time, IBEX is revealing how
the heliosphere might respond when it bumps into interstellar
clouds and galactic magnetic fields.
"IBEX
is now making a second all-sky map, and we're eager to see
if the ribbon is changing," says McComas. "Watching
the ribbon evolve--if it is evolving--could yield more clues."
Stay
tuned for updates.
Author: Dr.
Tony Phillips | Credit: Science@NASA
| more
information |
|
IBEX
Home Page
(NASA)
IBEX
Mission Page (SWRI)
IBEX
is the latest in NASA's series of low-cost, rapidly
developed Small Explorers space missions. Southwest
Research Institute in San Antonio, Tx., leads and developed
the mission with a team of national and international
partners. NASA's Goddard Space Flight Center in Greenbelt,
Md., manages the Explorers Program for NASA's Science
Mission Directorate in Washington.
|
|
