Will the Sun Enter a Million-Degree Cloud of Interstellar Gas?

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ScienceDaily (May 24, 2010) — Is the Sun going to enter a million-degree galactic cloud of interstellar gas soon?


Scientists from the Space Research Centre of the Polish Academy of Sciences, Los Alamos National Laboratory, Southwest Research Institute, and Boston University suggest that the ribbon of enhanced emissions of energetic neutral atoms, discovered last year by the NASA Small Explorer satellite IBEX, could be explained by a geometric effect coming up because of the approach of the Sun to the boundary between the Local Cloud of interstellar gas and another cloud of a very hot gas called the Local Bubble. If this hypothesis is correct, IBEX is catching matter from a hot neighboring interstellar cloud, which the Sun might enter in a hundred years.

First full-sky maps of the emissions of energetic neutral atoms (ENA), obtained last year by IBEX, showed a surprising arc-like feature called the Ribbon. This astonishing discovery was later announced by NASA as one of the most important findings in space exploration made in 2009. Shortly after the discovery six hypotheses were proposed to explain the Ribbon, all of them predicting its relation to processes going on within the heliosphere or in its neighborhood. In a paper recently published in the Astrophysical Journal Letters, a Polish-US team of scientists led by Prof. Stan Grzedzielski from the Space Research Centre of the Polish Academy of Sciences in Warsaw, Poland, offers a different explanation. "We observe the Ribbon," says Grzedzielski "because the Sun is approaching a boundary between our Local Cloud of interstellar gas and another cloud of a very hot and turbulent gas."

Energetic neutral atoms, registered by IBEX detectors, are born out of ions (protons) speeding from the very hot Local Bubble when they exchange charge with the relatively cool atoms "evaporating" from the Local Interstellar Cloud. The newly created ENA have no electrical charge and therefore can dash freely in straight lines from their birth site, oblivious of the impeding magnetic fields. Some of them may reach Earth orbit and be detected by IBEX. "Had the Ribbon ENA been created at the boundaries of the heliosphere, their birth site would be relatively nearby, within just a couple of hundreds of astronomical units," explains Dr Andrzej Czechowski from SRC PAS, one of the co-authors of the paper. "According to our hypothesis, they are born much, much farther away."

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http://www.sciencedaily.com/releases/2010/05/100521191114.htm

[Orsino]

1. A rather purple headline, calculated to frighten. n/t