IBEX (Interstellar Boundary Explorer) satellite (Courtesy of NASA)
IBEX is a NASA-funded Small Explorer satellite mission that orbits Earth and maps the boundary of the Solar System. The acronym IBEX stands for Interstellar Boundary Explorer.
The boundary of our Solar System is created by the interaction between particles from the Sun that are streaming outward, called the "solar wind," and material between the stars, called the "interstellar medium" (ISM). The solar wind streams out into space and carves out a protective bubble, called the "heliosphere," in the ISM around our Solar System. The interactions between the solar wind particles and the ISM particles create "energetic neutral atoms" (ENAs), which are particles with no charge that move very fast and unaffected by magnetic fields. As it orbits Earth, IBEX collects some of the ENAs which stream inward toward our location in the interior of the heliosphere. The mass, location, direction of origin, and energy of these particles provide information about the Solar System's boundary. Without IBEX, mapping this region would not be possible as the boundary gives off no light of its own and can only be studied because of the detection of ENA particles.
MISSION UPDATE
Since its launch in October 2008, IBEX, a spacecraft about the size of a bus tire, has used two specially designed ENA detectors to map the entire heliosphere boundary over the course of six months. These maps provide detailed information - for the first time - about the interactions occurring there.
IBEX Explores Galactic Frontier, Releases First-Ever All-Sky Map (Courtesy of NASA)WHAT THEY FOUND
The first results are summarized in five papers published online (linked to the IBEX website) in October 2009 by Science magazine. Along with the expected detections of ENAs in varying amounts across the sky, they chronicle the remarkable discovery of many ENAs coming from a narrow band in the sky. The IBEX team is calling this an ENA "ribbon." This ribbon was totally unpredicted by any previous scientific theories or models about the Solar System boundary. The ribbon may be shaped by external magnetic fields in the interstellar medium, which seem to imprint our heliosphere in a very strong, but not yet understood, way. Amazingly, an even closer look at segments of the ribbon shows fine details, which suggests that the numbers of ENAs may be significantly enhanced in highly localized regions at the interstellar boundary. The IBEX Science Team is working hard to try to understand what is happening at the boundary to create this ribbon and its features.
In addition to the ENA detections and the "ribbon", the team also announced the first detections of atoms of hydrogen and oxygen drifting inward from the interstellar medium, outside the heliosphere.
"Together, these remarkable observations show just how little we currently understand about the outer reaches of our heliosphere and our place in the Galaxy," said Paul H. Knappenberger Jr., Ph.D., president of the Adler Planetarium. "This discovery is an exciting one for the Adler, the IBEX mission's lead Education and Public Outreach partner. In this role, the Adler is interpreting the mission's findings and results to the general public, helping people understand the process of research - and the surprising results that can occur as a result of science in action."
WHAT DOES THIS DATA MEAN AND WHY IS IT IMPORTANT?
The heliosphere, our home in the Galaxy, is like a protective cocoon being inflated in the interstellar medium by the Sun's million miles per hour solar wind. As our Sun orbits the center of the Galaxy every 225 million years, it bobs in and out of the disk of the Galaxy like a horse on a merry-go-round. As it does this, it passes through areas of the interstellar medium that are more and less dense, causing the heliosphere to change in shape and size. Denser areas can compress the heliosphere, while less dense regions allow the bubble to expand. In addition, the strength of the solar wind varies over the Sun's cycle, "breathing" periodically.
The heliosphere is a crucial layer of protection against dangerous cosmic rays that are harmful to living things. As cosmic rays approach the heliosphere, they are deflected, and the majority of them are not able to pass into the inner Solar System. Fortunately, our Earth's magnetic field is usually able to shield life on Earth from the remaining cosmic rays. However, astronauts on deep space missions cannot bring the Earth's protection with them. Other NASA missions have observed a recent surge in cosmic ray intensities, making it even more important to better understand the heliosphere's ability to shield us from cosmic rays. We must also consider how the heliosphere will protect us in the distant future or how it did protect us in the past. Understanding the heliosphere and how it protects us is part of understanding our home in the Galaxy.
WHAT COMES NEXT?
IBEX continues to gather data. The team plans to release the next set of maps around Spring 2010.
