Unambiguous identification of diffuse interstellar band carriers

Determine the molecular carriers responsible for the Diffuse Interstellar Bands and establish their unambiguous identification in interstellar space.

Background

Diffuse Interstellar Bands (DIBs) are commonly associated with near-ultraviolet to near-infrared absorption signals from complex molecular species, including polycyclic aromatic hydrocarbons and related large cyclic molecules. Although such species are important candidates for explaining the observed interstellar absorption features, the specific carriers have not been conclusively identified.

The paper highlights this unresolved identification problem while motivating further study of complex cyclic and aromatic molecules in interstellar environments. Resolving the carriers would improve understanding of the composition and chemistry of interstellar matter.

References

Some of the most pressing open questions are: Carbon and the composition of dust. What is the composition of dust? What is the overall amount of C, Si, O, and other elements in dust? Chemically-enhanced 3D/4D dust maps. Can dust depletion enhance 3D/4D maps of dust extinction with the information of the chemical properties in individual clouds? Diffuse Interstellar Bands and C-rich grains molecules. What are the sources of Diffuse Interstellar Bands? What are the carriers of C-rich dust grains?

— The future of high-resolution UV spectroscopy: Science with a UV Échelle spectrograph on the Habitable Worlds Observatory, or a dedicated mission  (2609.09329 - Cia et al., 8 Sep 2026) in Section 5, subsection “Cosmic dust”

However, their unambiguous identification remains an open question .

— Collisional excitation of cyclopentadiene by helium. A complete set of rate coefficients and astrophysical applications  (2609.01314 - Demes et al., 1 Sep 2026) in Section 1, Introduction