3 November 2011

US astronomers give nod to complex organics in space

by Kate Melville

The controversial notion that complex organic molecules could be relatively common in interstellar space has garnered support from US and European astronomers' new observations of a series of diffuse interstellar bands that were first recorded 90 years ago. The new findings, published in Nature, are the work of Donald Figer, of the Rochester Institute of Technology, Paco Najarro, from the Center of Astrobiology in Madrid and Thomas Geballe, from the Gemini Observatory in Hawaii.

The spectral signatures in question are called diffuse interstellar bands (DIBS) and have the longest wavelengths recorded to date. "These diffuse interstellar bands - or DIBs - have never been seen before," says Figer. "The most recent ideas are that diffuse interstellar bands are relatively simple carbon bearing molecules, similar to amino acids. Maybe these are amino acid chains in space, which supports the theory that the seeds of life originated in space and rained down on planets."

DIBS have remained something of a puzzle since their initial discovery 90 years ago. The 500 bands identified back then mostly occur at visible and near-infrared wavelengths.

Importantly, the 13 newly identified lines do not match predicted lines of simple molecules and cannot be pinned to a single carbon-based organic molecule. And it seems that these mysterious molecules may be relatively common. "We saw the same absorption lines in the spectra of every star," Figer says. This means that the material responsible for these DIBs "survives" under different physical conditions of temperature and density.

Further study of the stronger emissions may lead to an understanding of their molecular structure and origin. But to date, no one has been successful at reproducing the spectral bands in the laboratory due to the multitude of possibilities and the difficulty of reproducing the temperatures and pressures experienced in space.

"None of the diffuse interstellar bands has been convincingly identified with a specific element or molecule, and indeed their identification, individually and collectively, is one of the greatest challenges in astronomical spectroscopy," concluded Geballe.

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Source: Rochester Institute of Technology