The NASA spacecraft IBEX is making a comprehensive map of the heliosphere, the magnetic boundary formed by the solar wind at the edge of the solar system--around 75 to 90 astronomical units (AU) from the Sun (where one AU is the mean distance between the Sun and Earth).

Unexpectedly, the IBEX spacecraft imaged a "bright, winding ribbon of unknown origin" that goes about 80% around the solar system.

At the termination shock, where the solar wind begins to slow down (from supersonic to subsonic speeds, or from above the speed of sound to below the speed of sound) from its journey from the Sun, this strange-looking ribbon appeared to the IBEX spacecraft.

Astronomers wonder: What is it?

The NASA Interstellar Boundary Explorer (IBEX) discovered this ribbon while making the first ever map of the heliosphere. Learn more about the Sun's magnetic bubble at the NASA website "The Heliosphere."

IBEX was launched on October 19, 2008, at 17:47:23 GMT, from Kwajalein Atoll in the South Pacific. It is in a highly eccentric, elliptical orbit about Earth.

Its orbital perigee (closest point to Earth) is about 5,000 kilometers (3,100 miles) from Earth, while its orbital apogee (furthest point from Earth) is approximately 250,000 to 300,000 kilometers (160,000 to 190,000 miles) from Earth.

Its apogee takes it about three-fourth the way to the Moon.

The NASA Interstellar Boundary Explorer (IBEX) discovered this ribbon while making the first ever map of the heliosphere. Learn more about the Sun's magnetic bubble at the NASA website "The Heliosphere."

IBEX was launched on October 19, 2008, at 17:47:23 GMT, from Kwajalein Atoll in the South Pacific. It is in a highly eccentric, elliptical orbit about Earth.

Its orbital perigee (closest point to Earth) is about 5,000 kilometers (3,100 miles) from Earth, while its orbital apogee (furthest point from Earth) is approximately 250,000 to 300,000 kilometers (160,000 to 190,000 miles) from Earth.

Its apogee takes it about three-fourth the way to the Moon.

The IBEX mission is to image the boundary between the solar system and interstellar space: that is, the edge of the heliosphere. And, while on this mission to map energetic neutral atom emissions, the spacecraft imaged a bright filament.

In the October 15, 2009 NASA media release "Giant Ribbon Discovered at the Edge of the Solar System," it is stated, "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."

Learn more about ENAs at the Southwest Research Institute's website "What are energetic neutral atoms?".

These ENAs are created when the solar wind begins to hit particles in interstellar space, that is the space outside of our solar system.

Go to the NASA website "IBEX NASA Science Update Visuals" to see numerous images and animations produced by the U.S. space agency.

Eric Christian, the IBEX deputy mission scientist, talks about the positioning of the ribbon with respect to two veterans of space travel.

Dr. Christian states, "This ribbon winds between the two Voyager spacecraft and was not observed by either of them. It's like having two weather stations, but missing the big storm that runs between them." [NASA]

Christian is referring to Voyager 1 and 2. Check out the NASA/Jet Propulsion Laboratory article "Voyager: The Interstellar Mission" for more information.

Right now NASA scientists are perplexed as to the ribbon.

Why it is here? Where did it come from?

The images from the IBEX spacecraft have produced far more questions than answers - so far, that is.

Astronomers are working on this 'mysterious ribbon at the edge of the solar system' to solve the questions that it is posing to the scientific world.

Read more about this exciting discovery in five articles published in Science Magazine under the title "Tying Up the Solar System With a Ribbon of Charged Particles."

In one article "Width and Variation of the ENA Flux Ribbon Observed by the Interstellar Boundary Explorer," the authors state, "The dominant feature in IBEX sky maps of heliospheric energetic neutral atom (ENA) flux is a ribbon of enhanced flux that extends over a broad range of ecliptic latitudes and longitudes."

"It is narrow (~20° average width), but long (extending over 300° in the sky) [360 degrees completes one circle] and is observed at energies from 0.2 keV to 6 keV [kiloelectron volt]."

For additional information on the ribbon structure at the edge of the solar system, read the U.S. News and World Report article "Galaxy Edge Surprises Astronomers: New Observations reveal a dense ribbon structure that current models don't explain."