Tracing Our Place In Outer Space

A spacecraft, for the first time, has detected neutral hydrogen, oxygen, and neon atoms streaming into our solar system from clouds of interstellar matter. The discoveries by the National Aeronautics & Space Administration’s IBEX (Interstellar Boundary Explorer) craft pinpoint our solar system’s location at the edge of a large interstellar cloud in the Milky Way galaxy. The findings may also trace the solar system’s movement through matter that lies outside the solar system and makes up the interstellar medium.

Scientists announced the results on Jan. 31 at a press conference at NASA headquarters in Washington, D.C. The event coincided with publication of the research in Astrophysical Journal Supplements.

The incoming atoms are “the stuff that stars and planets are made of,” David McComas, IBEX mission principal investigator said at the conference. “It’s very important to measure these species directly.”

NASA launched IBEX in 2008 on a mission to study the boundaries of the solar system. The magnetic solar wind produced by our sun forms a protective heliosphere around the solar system, preventing high-energy, charged particles from the interstellar medium from entering the neighborhood. But neutral atoms can sail through the heliosphere, unimpeded by magnetic fields.

IBEX has detected dozens of these neutral atoms: hydrogen, oxygen, neon, and helium (helium was first detected by the Ulysses spacecraft 10 years ago).

The direction and speed of the atoms suggests that the solar system might—within a thousand years—move out of the interstellar cloud where it now sits into a very different space environment.

IBEX also detected less oxygen than expected streaming into our solar system in comparison with neon. The ratio of oxygen to neon in the interstellar cloud is less than the ratio in the sun. This implies that the interstellar environment in which the sun formed five billion years ago is different from the current environment of our solar system. The IBEX team hypothesizes that the missing oxygen could be tied up in dust or ice grains.