IBEX illuminates a dark corner of our neighborhood

Posted by David Eicher
on Wednesday, February 01, 2012

Yesterday, scientists at a NASA press conference described the first findings from IBEX, the Interstellar Boundary Explorer satellite, which was launched in 2008 and is the first craft to study the region between our solar system and interstellar space. Astronomers don’t know much about the edge of our solar system and how it interacts with our neighborhood in the galaxy beyond. By contrast, we know a great deal about various objects far away in the Milky Way (and in other galaxies), but the ghostly region that defines our neighborhood is a different matter. Studying this boundary requires analyzing neutral atoms floating in a soup beyond the heliosphere, the bubble of particles blown out by the Sun.

The neon-to-oxygen ratio in the neutral gas of the local cloud, as obtained with IBEX, in comparison with that ratio for the Sun and the Milky Way Galaxy. There appears to be much less oxygen in the gas of the local cloud, meaning either a substantial portion of the essential ingredient for life (oxygen) locks up in interstellar dust, or there were different conditions at the birthplace of the Sun compared to our immediate neighborhood. Photo credit: NASA/GSFC
The results announced January 31 give us our first glimpse into this netherworld. The measurements by IBEX will give astronomers data about how our solar system’s formation and forces that shape it, as well as information about other stars in the Milky Way. These first glimpses of the interstellar wind beyond our solar system are surprising, even stunning, in some ways. Perhaps foremost is the observed oxygen-neon ratio. In the solar system, we have 111 oxygen atoms for every 20 neon atoms. The interstellar wind shows only 74 oxygen atoms for every 20 neon atoms — a much lower level of oxygen.

“Our solar system is different than the space right outside it, suggesting two possibilities ,”said David McComas, the mission‘s project scientist. “Either the solar system evolved in a separate, more oxygen-rich part of the galaxy than where we currently reside, or a great deal of critical, life-giving oxygen lies trapped in interstellar dust grains or ices, unable to move freely throughout space.”

The results also provide more clues about the origin of the universe. The Big Bang created hydrogen and helium, but later supernova explosions created heavier elements like neon and oxygen. Mapping the amounts of these elements will ultimately reveal how the galaxy has evolved over its lifetime.

IBEX is also providing the first good look at the structure of the heliosphere, which protects the solar system from radiation on our journey around the center of the galaxy. The spacecraft found the speed of the interstellar wind was 20 percent slower than that measured previously by the Ulysses spacecraft. Astronomers are just getting their basic understanding of how the solar system interacts with the surrounding space. Stay tuned for much more to come on this issue as more IBEX results are announced.

For more on the results, see “NASA spacecraft reveals new observations of interstellar matter.”

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