Probably one of the coolest missions designed to study the termination shock (the region of space where the solar wind and interstellar medium interact) located a little under 100 AU from the Sun, will be launched today (Sunday). The Interstellar Boundary Explorer (IBEX) will be carried into space on board a Pegasus rocket installed under a L-1011 carrier aircraft from the Reagan Test Site at Kwajalein Atoll in the South Pacific (about 2500 miles from Hawaii in the direction of Australia). Out of interest, the aircraft will take off from the same region that SpaceX use to send their Falcon 1 rocket (and first ever commercial orbital vehicle) into space…
The termination shock is a mysterious region of space as yet to be explored. Although Voyager 1 and 2 passed through this point, it is of critical importance to astrophysicists to measure the temporal and spatial changes at the boundary between the Solar System and the rest of interstellar space, as my previous Universe Today article explains:
In 2004, Voyager 1 hit it and in 2006, Voyager 2 hit it. The first probe flew through the termination shock at around 94 AU (8 billion miles away); the second measured it at only 76 AU (7 billion miles). This result alone suggests that the termination shock may be irregularly shaped and/or variable depending on solar activity. Before the Voyager missions, the termination shock was theorized, but there was little observational evidence until the two veteran probes traversed the region. The termination shock is of paramount importance to understanding the nature of the outer reaches of the solar system as, counter-intuitively, the Sun’s activity increases, the region beyond the termination shock (the heliosheath) becomes more efficient at blocking deadly cosmic rays. During solar minimum, it becomes less efficient at blocking cosmic rays. – Excerpt from IBEX Mission Will View the Final Frontier of the Solar System
So how will IBEX aid astrophysicists? It will count energetic neutral atoms (or ENAs for short) originating from the turbulent interaction region of the termination shock and build up a distribution of where the ENAs come from.
Scientists have known for a long time that neutral atoms appear to be generated at the termination shock. The solar wind carries energetic charged particles (or ions, mainly protons) into the far reaches of the heliosphere which eventually encounter interstellar neutral atoms. It is important to keep in mind at this point that any interstellar ions trying to get into the heliosphere are swept aside as the Solar System carries on its merry way through the galaxy; the heliospheric magnetic field deflects them. Therefore, only neutral interstellar particles are allowed in.
As the solar wind protons interact with the interstellar medium at the termination shock, they collide with the interstellar neutral atoms. When this happens, a mechanism known as charge exchange occurs. Electrons are ripped from these neutral interstellar atoms, creating very energetic neutral hydrogen atoms (i.e. 1× solar wind proton + 1× interstellar neutral atom electron). These ENAs are then blasted away from the point of charge exchange in a straight line (as energetic neutral atoms are not deflected by magnetic fields).
IBEX will be ideally placed to detect these ENAs whilst it orbits Earth so a better idea about termination shock dynamics can be gained. So, IBEX is set for launch on Sunday at 1:48 pm EDT during an eight minute launch window on board an aircraft-launched Pegasus rocket. I can’t wait for the results it will return, IBEX will, quite literally, paint a picture of how our Solar System interacts with the interstellar medium…
For more information on IBEX:
- IBEX, The Energetic Neutral Atom Hunter – Astroengine (the physics behind ENAs)
- IBEX Mission Will View the Final Frontier of the Solar System – Universe Today (information and news)
Original source: NASA