CfA Colloquium Schedule Spring 2006
 23 February 2006

23 February 2006

Speaker: Bruce Draine (Princeton)

Title:New Views of Interstellar Dust: From Infrared to X-Rays

Abstract:Most of the atoms of elements like Si and Fe in the interstellar medium are incorporated into dust grains that absorb and scatter light, much to the annoyance of astronomers interested only in stars. This dust plays an important role in interstellar gas dynamics, heating and cooling of the gas, chemistry, and even ionization balance in predominantly neutral regions. It is therefore very important to try to figure out what it is! Observations with Spitzer Space Telescope are allowing us to test our models for interstellar dust. In particular, we can now ask whether our models of interstellar dust, heated by starlight, produce infrared emission with the spectral energy distribution measured by Spitzer. The emission features attributed to polycyclic aromatic hydrocarbons are present in the emission from other galaxies; we can now estimate the PAH abundances in other galaxies, and compare with what we estimate for the Milky Way. Interstellar dust grains in the Milky Way produce polarization of starlight, which implies that at least some of the dust grains must be both nonspherical and aligned. X-ray scattering from aligned grains will produce angular structure in X-ray scattering halos. This structure should be observable with Chandra or XMM-Newton, allowing a new test of interstellar dust models.

Video of the Presentation (Talks can be viewed with RealPlayer. Free download is available from )


Section Photo