Cosmos Reveals More Secrets

Published Online November 29, 2007
ScienceDOI: 10.1126/science.1149926
Million-Degree Plasma Pervading the Extended Orion Nebula 
                      * To whom correspondence should be addressed.
Manuel Güdel , E-mail: guedel@astro.phys.ethz.ch
Most stars form as members of large associations within dense, very cold (10–100 K) molecular clouds. The nearby giant molecular cloud in Orion hosts several thousand stars of ages less than a few million years, many of which are located in or around the famous Orion Nebula, a prominent gas structure illuminated and ionized by a small group of massive stars (the Trapezium). We present X-ray observations obtained with the X-ray Multi-Mirror satellite XMM-Newton revealing that a hot plasma with a temperature of 1.7-2.1 million K pervades the southwest extension of the nebula. The plasma flows into the adjacent interstellar medium. This X-ray outflow phenomenon must be widespread throughout our Galaxy. 
       see photos …right————->
ScienceDOI: 10.1126/science.1148666
Stellar Feedback in Dwarf Galaxy Formation 
    * To whom correspondence should be addressed.
Sergey Mashchenko , E-mail: syam@physics.mcmaster.ca
Dwarf galaxies pose significant challenges for cosmological models. In particular, current models predict a dark matter density that is divergent at the center, in sharp contrast with observations which indicate an approximately constant central density core. Energy feedback, from supernova explosions and stellar winds, has been proposed as a major factor shaping the evolution of dwarf galaxies. We present detailed cosmological simulations with sufficient resolution both to model the relevant physical processes and to directly assess the impact of stellar feedback on observable properties of dwarf galaxies. We show that feedback drives large-scale, bulk motion of the interstellar gas resulting in significant gravitational potential fluctuations and a consequent reduction in the central matter density, bringing the theoretical predictions in agreement with observations.
                                   Peace     Gandalf
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