One of the great scientific mysteries that have remained a mystery for over a hundred years despite dozens of attempts to solve it is the composition of interstellar gas and dust. This has weird spectral features in the infrared.
Searches have been made for other objects both artificially made and out is space with a distinct lack of success – the spectrum doesn’t match anything from the Moon, from planets, asteroids, comets, stars, nebulae etc. The closest match has been with an object known as the Red Rectangle but even there the spectrum match is not particularly good.
Attempted explanations of interstellar gas and dust in the past have ranged from metallic grains to nanoparticles to complicated gas molecules. None of these has been convincing, the latest before now, buckyballs, hasn’t matched the observations anywhere near closely enough to satisfy me.
Now there’s a new contender, C23H12++ http://arxiv.org/ftp/arxiv/papers/1412/1412.0009.pdf The spectrum match is superb, I just hope it isn’t an example of the “Texas Sharpshooter” problem – ie. correlation doesn’t necessarily apply causality.
The interstellar gas and dust show featured
mid-infrared emission from 3 to 20μm. Discrete
emission features at 3.3, 6.2, 7.6, 7.8, 8.6, 11.2, and
12.7μm are ubiquitous peaks observed at many
astronomical objects. Current common understanding is that these
astronomical spectra come from the vibrational modes
of polycyclic aromatic hydrocarbon (PAH) molecules.
“This study intentionally stepped into void created
molecules as like C23H12. Among several model
molecules, a single void induced cation C23H12++
brought successful spectrum. Calculated peaks were
3.2, 6.4, 7.6, 7.8, 8.6, 11.4, and 12.9μm, which were
amazing coincidence with the observation.”
In order to find out a selected number of molecules to reproduce the infrared spectrum of interstellar gas and
dust, model coronene molecules with void and charge have been computed using density functional theory. Among
them, a single void induced cation C23H12++ have successfully reproduced a wide range spectrum (3~20 μm) of
typical interstellar gas and dust. Well known astronomically observed emission peaks were 3.3, 6.2, 7.6, 7.8, 8.6,
11.2, 12.7, 13.5 and 14.3μm. Whereas, calculated peaks of C23H12++ were 3.2, 6.4, 7.6, 7.8, 8.6, 11.4, 12.9, 13.5, and
14.4μm. It should be noted that a single kind of molecule could reproduce very well not depending on the
decomposition method using many polycyclic aromatic hydrocarbon (PAH) data. Such coincidence suggested that
some astronomical chemical evolution may select a particular PAH. Molecular structure of C23H12++ was
dramatically deformed by the Jahn-Teller effect. There is a featured carbon skeleton having two pentagons
connected to highly symmetric five hexagons. Such unique structure brings above infrared mode.