The chemistry of interstellar dust through the scattering halo of Cyg X-2

We propose to observe the bright Xray source Cyg X2 as an ideal candidate tostudy the chemistry of the diffuse Interstellar Medium (ISM). We will study thetwo phases of ISM (gas and dust) through spectroscopy of the absorbed spectrumand the spectral and spatial analysis of the Xray dust scattering halo. Thestudy of the scattering halo of Cyg X2 unveiled for the first time featuresfrom the ID constituents. To perform a quantitative measurement of the chemistryof the Interstellar Dust (ID) grains a large collective area, a large field ofview, and a broad band coverage, like the one provided by XMM, is needed. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]