Defective Carbon Onions in Interstellar Space as the Origin of the Optical Extinction Bump at 217.5 Nanometers

Abstract

It is known that carbonaceous dust in interstellar space shows a strong extinction bump at 217.5 nm (4.6 μm-1, 5.7 eV). One of the possible candidates for such carbonaceous interstellar dusts is a new member of the fullerene family called the carbon onion. Recently, we conducted a laboratory experiment to study the optical extinction properties of carbon onions. In order to explain the experimental results, a new dielectric model of the onions, the spherical onion model, was proposed. Here we show that the defective carbon onions are likely to be one of the origins of the interstellar extinction bump. This report also suggests that carbonaceous interstellar dust particles may be replicated by onions produced in the laboratory.