After three years of puzzling over a striking “ribbon” of energy and particles discovered by
NASA’s Interstellar Boundary Explorer (IBEX) at the edge of our solar system, researchers may be on the verge of
cracking the mystery.
In a paper published Feb. 4, 2013, in the Astrophysical Journal, researchers including Nathan Schwadron,
an associate professor at UNH's Institute for the Study of Earth, Oceans, and Space and department of
physics, of the University of New Hampshire, propose a “retention theory” that for the first time explains all the key
observations of this astrophysical enigma.
“If the theory is correct, the ribbon can be used to tell us how we’re moving through the magnetic
fields of the interstellar medium and how those magnetic fields then influence our space environment,” Schwadron
A three-dimensional diagram of the retention region shown as a "life preserver" around our heliosphere bubble
along with the original IBEX ribbon image. The interstellar magnetic field lines are shown running from upper left
to lower right around the heliosphere, and the area where the field lines "squeeze" the heliosphere corresponds to
the ribbon location. The red arrow at the front shows the direction of travel of our solar system. Image credit:
Adler Planetarium/IBEX Team.
In particular, these strong magnetic fields appear to play a critical role in shaping our heliosphere—the huge bubble
that surrounds our solar system and shields us from much of harmful galactic cosmic radiation that fills the galaxy.
This may have important ramifications for the history and future of radiation in space, and its impact here on Earth,
as the heliosphere changes in response to changing conditions in the interstellar medium or the “space between the stars.”
According to the retention theory, the ribbon exists in a special location where neutral hydrogen atoms from the solar
wind move across the local galactic magnetic field. Neutral atoms are not affected by magnetic fields, but when their
electrons get stripped away they become charged ions and begin to gyrate rapidly around magnetic field lines.
That rapid rotation creates waves or vibrations in the magnetic field, and the charged ions then become trapped by the
waves. This is the process that creates the ribbon.
“Think of the ribbon as a harbor and the solar wind particles it contains as boats. The boats can be trapped
in the harbor if the ocean waves outside it are powerful enough. This is the nature of the new ribbon model,"
The ribbon is a region where particles, originally from the solar wind, become trapped or ‘retained’ due to intense
waves and vibrations in the magnetic field.”
“This is a perfect example of the scientific process: we observe something completely new and unexpected
with IBEX, develop various hypotheses to explain the observations, and then develop mathematical models to try to
validate the hypotheses,” Dave McComas, principal investigator for the IBEX mission adds.
Click on image to enlarge
In 2009, NASA's Interstellar Boundary Explorer (IBEX) mission science team constructed the first-ever all-sky
map of the interactions occurring at the edge of the solar system, where the sun's influence diminishes and interacts
with the interstellar medium. A 2013 paper provides a new explanation for a giant ribbon of energetic neutral atoms –
shown here in light green and blue -- streaming in from that boundary. Credit: NASA/Goddard Space Flight Center
Scientific Visualization Studio
Indeed, since the discovery of the ribbon, more than a dozen competing theories seeking to explain the phenomenon have
been put forth. The retention theory “checks all the boxes, agrees with all the available observations, and the
mathematical modeling results look remarkably like what the ribbon actually looks like,” notes Schwadron.
“This substantially raises the bar for models that attempt to explain the ribbon.”
IBEX was launched in October 2008 and has provided images of the invisible interactions between the solar wind and
the local galactic medium. The ribbon was captured using ultra-high sensitive cameras—one of which has components
designed and built at the UNH Space Science Center—that image energetic neutral atoms (instead of photons of light)
to create maps of the boundary region between our solar system and the rest of our galaxy.