Diffuse interstellar bands

Diffuse interstellar bands (DIBs) are absorption features seen in the spectra of astronomical objects in the Milky Way and other galaxies.

[1] The origin of most DIBs remains unknown, with common suggestions being polycyclic aromatic hydrocarbons and other large carbon-bearing molecules.

A typical stellar spectrum will consist of a continuum, containing absorption lines, each of which is attributed to a particular atomic energy level transition in the atmosphere of the star.

In 1922, though, astronomer Mary Lea Heger[5] first observed a number of line-like absorption features which seemed to be interstellar in origin.

The first detection-limited survey was published by Peter Jenniskens and Xavier Desert in 1994 (see Figure above),[9] which led to the first conference on The Diffuse Interstellar Bands at the University of Colorado in Boulder on May 16–19, 1994.

[11][12] The great problem with DIBs, apparent from the earliest observations, was that their central wavelengths did not correspond with any known spectral lines of any ion or molecule, and so the material which was responsible for the absorption could not be identified.

[6][13] These types of molecule experience rapid and efficient deactivation when excited by a photon, which both broadens the spectral lines and makes them stable enough to exist in the interstellar medium.

[18] In the early 1990s, laboratory spectra of C60+ were obtained by embedding the molecule in solid ices, which showed strong bands in the near-infrared.

[22] New objections were raised by other researchers,[23] but by 2019 the C60+ bands and their assignment had been confirmed by multiple groups of astronomers[24][25] and laboratory chemists.