Recent X-ray observations by the space mission Chandra confirmed the astonishing evidence of a diffuse, hot, thermal plasma at a temperature of ∼9 × 107 K (∼8 keV) that was found by previous surveys to extend over a few hundred parsecs in the Galactic center region. This plasma coexists with the usual components of the interstellar medium, such as cold molecular clouds and a soft (0.8 keV) component produced by supernova remnants, and its origin remains uncertain. First, simple calculations using a mean sound speed for a hydrogen-dominated plasma have suggested that it should not be gravitationally bound, and thus it requires a huge energy source to heat it in less than the escape time. Second, an astrophysical mechanism must be found to generate such a high temperature. No known source has been identified to fulfill both requirements. Here we address the energetics problem and show that the hot component could actually be a gravitationally confined helium plasma. We illustrate the new prospects that this opens up by discussing the origin of this gas and by suggesting possible heating mechanisms.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science