The influence of shape on the temperature of small graphite grains
Abstract
The anisotropic optical properties of graphite result in a strong dependence of the temperatures of small graphitic grains (a ≈ 0.02 μm) on their shape. The temperature attained in the diffuse interstellar medium increases from 20.4K for spheres to 27K for oblate spheroids with axial ratios close to 5. A population of graphite discs is therefore proposed as an explanation for the unexpectedly high temperatures (≡25K) derived from IRAS observations of diffuse medium dust. The semi-metallic character of graphite is analyzed and it is shown that bulk infrared properties, modified only to account for surface scattering of charge carriers, cannot be applied to particles smaller than 0.01 μm.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- July 1987
- Bibcode:
- 1987A&A...181..127C
- Keywords:
-
- Graphite;
- Infrared Astronomy;
- Interstellar Matter;
- Infrared Astronomy Satellite;
- Optical Properties;
- Particle Size Distribution;
- Shapes;
- Temperature Distribution;
- Astrophysics