NASA satellite tastes atoms away from the solar system

NASA's Interstellar Boundary Explorer, the centerpiece of a $169 million mission map the boundary of the sun's influence, has detected atoms from interstellar space streaming by Earth, finding the material is dissimilar from the chemical make-up of the solar system, scientists announced Tuesday.

The data recommend the area of interstellar space just outside the solar system may be deficient in oxygen compared to its abundance inside the heliosphere, a teardrop-shaped bubble blown out by the energy from the solar wind. The heliosphere's bubble is compressed ahead of the sun's motion like a bow shock in front of a ship, while it stretches behind the solar system similar to a boat's wake.

The heliosphere blocks most hazardous cosmic radiation from reaching Earth.

Researchers published their results in the Astrophysics Journal on Jan. 31. IBEX found 74 oxygen atoms for every 20 neon atoms in the interstellar material, compared with 111 oxygen atoms for every 20 neon atoms within the solar system.

IBEX, launched in October 2008, uses two instruments to identify energetic neutral atoms as they strike the spacecraft. If the imagers are facing the right direction when the particle meets the satellite, the atom registers and the instrument can distinguish its elemental composition.

IBEX is in an orbit stretching 200,000 miles from Earth, placing the craft outside of the planet's magnetic field, a constraint to detect energetic particles streaming in from the outer heliosphere and interstellar space.