The NRAO Special Colloquium will feature guest speaker Karl Gordon of Space Telescope Science Institute this week. Gordon will speak on "Extragalactic Dust Mass Determinations in the Optical and Infrared: Evidence for Dust Emissivity Variations” at 2 p.m. Friday, December 7, at the NRAO Auditorium in Socorro. Gordon will discuss an investigation using the HERITAGE Herschel Key Project far-IR/submillimeter observations of the Magellanic Clouds that indicate there are wavelength dependent variations in the dust emissivity law with environment. All NRAO employees are invited to attend via video.