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Astrophysics Colloquium
Why Interstellar Grains Align and Why You Should Care
Presented by B-G Andersson
Associate Director for Science Operations, Stratospheric Observatory for Infrared Astronomy, NASA Ames Research Center
Tuesday, June 21, 2016
12:00 noon in 169-336
Abstract
Interstellar polarization is known to trace the magnetic field, but the physical causes of the implied grain alignment has remained unclear. More than 60 years after the discovery of interstellar polarization we finally have a quantitative, empirically tested, theory of grain alignment. This Radiative Alignment Torque (RAT) theory, predicts that dust grain are spun up by an anisotropic radiation field, if the wavelength of the light is less than the grain diameter. If the grain is made of a paramagnetic material, it will then align with the magnetic field. A number of specific, observationally testable, predictions follow from the theory, many of which have already been addressed.
With a full testing of the theory and quantification of its parameters, polarimetry has the promise to not only allow efficient and reliable tracing of interstellar and interplanetary magnetic fields, but also to provide new and unique probes of the dust and the interstellar environment.
I will review the the basics of the theory, its empirical testing, and some of the possible tools we will acquire from it.
JPL Contact: Jorge Pineda (4-3347)
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