Effect of Shape on the Temperature of a Blackbody: Implications for Remote Sensing of Interplanetary Dust Particles

Infrared spectroscopy is based on the emission from a heated body, oftentimes dust particles. This body is generally assumed to have a spherical shape. We explore the temperature of blackbodies with non-spherical shapes. Five non-spherical shapes are considered: (1) a prolate cylinder and (2) a prolate spheroid, both with aspect ratio 2:1, (3) agglomerated debris particles, equidimensional in size, (4) ballistic particle–cluster aggregates (BPCAs), and (5) ballistic cluster–cluster aggregates (BCCAs). Such particles have been used to model the light-scattering response of particles in cometary comae and debris disks. The first three types of particles yield remarkably similar blackbody temperatures that are only ~9 K lower than a spherical blackbody. Blackbodies with BPCA and BCCA morphologies are much colder than the spherical blackbody due to the large surface area of the fractal aggregates.