January 19, 2008 | David F. Coppedge

Million-Degree Plasma Found in Orion

The Orion nebula, an object of beauty to stargazers (picture, Hubble view) is pervaded by plasma heated to two million degrees Kelvin, reported astronomers in Science.1  Two funnel-shaped regions of x-ray emitting plasma in the extended nebula were observed by astronomers using the X-Ray Multi-Mirror (XMM)-Newton satellite.
    “The energy requirement to heat the large-scale x-ray emitting plasma is severe,” they said.  What could heat up gas to emit 55 billion trillion trillion ergs per second?  Not the molecular flows of gas in the nebula.  Not the microjets from numerous young stars.  Their suggestion: “The only efficient energy source is provided by the fast winds from the hot Trapezium stars” (picture).  The high-velocity wind, flowing tens of kilometers per second, is four orders of magnitude more energetic than the observed plasma, they said, and “can easily heat the observed plasma.”
    Those stars are short-lived, however.  The massive Trapezium stars in the brightest part of the nebula (picture) can only last a few millions of years or less – far less than the assumed age of the Milky Way.  The plasma bubble would disperse in hundreds of thousands of years without replenishment.  Do they see a pattern?

Our Galaxy (and other star-forming galaxies) could thus maintain a network of x-ray bubbles and plasma flows, cooling over a few million years but continuously being replenished by shocked winds from a multitude of modest Orion-like star-forming regions, gently leaking out from the parent molecular clouds, in addition to being fed by discrete, but rare, supernova explosions.

O’Dell and Townsley, commenting on this paper in the same issue of Science,2 said “Orion continues to surprise.”  Though they found the hot-wind mechanism plausible, “many questions remain in Orion,” they said.

Why is the x-ray emission confined to these two areas?  Is there a channeling effect of the stellar wind, a rapid cooling of any other shocked gas closer to the star, or does extinction in the veil simply preclude observation of hot gas in the optically brightest part of the nebula?

The last question suggests that the entire nebula may be glowing hot.  Further observations may help answer these questions.  “Once these observational questions have been resolved, the ball will be in the theoreticians’ court; it is they who must then confront the problems of why the Orion gas is at 2 million K and why it is located where it is.”

1.  Gudel, Briggs et al, “Million-Degree Plasma Pervading the Extended Orion Nebula,” Science, 18 January 2008: Vol. 319. no. 5861, pp. 309-312, DOI: 10.1126/science.1149926.
2.  O’Dell and Townsley, “Orion Continues to Surprise,” Science, 18 January 2008: Vol. 319. no. 5861, pp. 289-290, DOI: 10.1126/science.1153476.

This story is provided as an example of a “surprise discovery” in science, and how scientists typically deal with them.  It’s analogous to finding erupting volcanoes on Io or geysers on Enceladus when theories had predicted they would be cold and dead.  Scientists delight in puzzles but typically try to solve them in accordance with the presuppositions of the paradigm they learned and the beliefs of their peers.  It’s rare for a maverick scientist to think outside the box.
    It may be that the mechanism suggested can account for the phenomenon.  How they will deal with the age problem is left as an exercise.  New high-energy massive stars will be needed continually to account for the ongoing emissions and plasma flows.  The stars in the Trapezium are thought to be much more short-lived than most stars.  When they have burned out, like bright sparklers, new ones will be needed to take their place.  Otherwise, the hot plasma would long ago have cooled down.
    One subject these astronomers did not delve into was plasma physics.  Because plasma is electrically charged, it can move and form structures much more rapidly than material under gravitational forces alone.  One creationist who has given a good deal of thought to this is Barry Setterfield.  His explanations about how plasma might cause dramatic changes in galaxies and stars rapidly can be found at setterfield.org.  This link is provided without comment, not necessarily as an endorsement, for those interested in pursuing the pros or cons of his “maverick” model, which is controversial even among creationists.  It should be noted, however, that some secular astronomers have also argued that plasma physics is much more important (and neglected) in formulating cosmological models.

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Categories: Physics

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