On the Nature of Organic Dust in Novae

Abstract

Recent astronomical observations and planetary missions have found that complex organics are prevalent throughout the universe, from the solar system to distant galaxies. However, the detailed chemical composition and the synthesis pathway of these organics are still unclear. Circumstellar envelopes represent excellent laboratories to study the abiological synthesis of extraterrestrial organics. Novae, having very short dynamical lifetimes, can put severe constraints on the chemical pathway of organic synthesis. Here, we report a laboratory simulation of carbonaceous dust with inclusion of Nitrogen in the form of Quenched Nitrogen-included Carbonaceous Composite (QNCC). QNCC is produced by the quenched condensation of plasma gas generated from the nitrogen gas, and aromatic and/or aliphatic hydrocarbon solids by applying microwave discharge (2.45 GHz, 300 W). We have shown that the spectra of QNCC have a close resemblance to the observed infrared spectra of novae. The results of the infrared and X-ray analyses suggest that the nitrogen inclusion in the form of amine plays an important role in the origin of the broad 8 μ m feature of dusty novae. We conclude that QNCC is at present the best laboratory analog of organic dust formed in the circumstellar medium of dusty classical novae, which carries the unidentified infrared bands in novae via thermal emission process.