Arcetri Astrophysical Observatory

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ALMA finds an ingredient of Life around infant Sun-like stars

ALMA has observed the early stages of stars like the Sun and detected the presence of methyl isocyanate, a chemical building block of life. This is the first ever detection of this prebiotic molecule in solar-type protostars, the sort from which our Solar System evolved. The discovery could help astronomers understand how life arose on Earth.

 

Fig.1

The discovery was made by two teams of astronomers: one led by Rafael Martín-Doménech at the Centro de Astrobiología in Madrid (Spain) and Víctor M. Rivilla at the Arcetri Observatory in Florence (Italy), and the other by Niels Ligterink at the Leiden Observatory in the Netherlands. They both harnessed the power of the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile to detect the prebiotic complex organic molecule known as methyl isocyanate (CH3NCO) (see Fig. 2) in the multiple star system IRAS 16293-2422.

Dr. Víctor M. Rivilla comments: "We are particularly excited about the result because methyl isocyanate belong to a family of molecules that is key for the synthesis of peptides and amino acids, which, in the form of proteins, are the biological basis for life as we know it.

IRAS 16293-2422 is a triple system of very young stars, around 400 light-years away in a large star-forming region called Rho Ophiuchi in the constellation of Ophiuchus. The combined results show that all components of the system contain methyl isocyanate.

“These protostars are very similar to the Sun at the beginning of its lifetime, with the sort of conditions that are well suited for Earth-sized planets to form. By finding prebiotic molecules in this study, we may now have another piece of the puzzle in understanding how life came about on our planet, explains Dr. Rivilla.

ALMA's capabilities allowed both teams to observe the molecule at several different wavelengths across the radio spectrum. They found the unique chemical fingerprints located in the warm, dense inner regions of the dusty envelope of the protostars. Each team identified and isolated the signatures of the complex organic molecule methyl isocyanate. They then followed this up by computer chemical modelling analysis and laboratory experiments to improve upon our understanding of the molecule's origin.

Earth and the other planets in our Solar System formed from the material left over after the formation of the Sun. Studying solar-type protostars can therefore open a window to the past for astronomers and allow them to observe similar conditions that led to the formation of our Solar System over 4.5 billion years ago.

 Fig.2

Fig. 1: Integrated intensity maps of two representative CH3NCO unblended lines observed toward IRAS16293 B protostar . Black contours indicate 50% and 90% of the peak line emission, while white contours indicate 20%, and 80% of the continuum peak emission at 232 GHz. The rest frequency and Eup of the transitions are shown. Beam sizes are shown in the bottom right corner.

Fig.3

Fig. 2: CH3NCO unblended lines measured toward IRAS16293 B with ALMA (solid black). The synthetic LTE spectrum generated by the software MADCUBA is overplotted in red.

 

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References:

- R. Martín-Doménech, V. M. Rivilla, I. Jiménez-Serra, D. Quénard, L. Testi, and J. Martín-Pintado, “Detection of methyl isocyanate (CH3NCO) in a solar-type protostar”, accepted for publication in “Astronomy & Astrophysics”. The article is available online at https://arxiv.org/abs/1701.04376

- N. F. W. Ligterink, A. Coutens, V. Kofman, H. S. P. Müller, R. T. Garrod, H. Calcutt, S. F. Wampfler, J. K. Jørgensen, H. Linnartz and E. F. van Dishoeck. accepted for publication in “Astronomy & Astrophysics”. The article is available online at https://arxiv.org/abs/1703.03252

Contact:

Víctor M. Rivilla

Osservatorio Astrofisico di Arcetri (OAA-INAF), Florence, Italy

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