A "Forest” Of Organic Molecules Has Been Observed In Another Galaxy For The First Time

A breathtaking view of the Sculptor Galaxy. ESO/J. Emerson/VISTA/Cambridge Astronomical Survey Unit

Astronomers have discovered a treasure trove of organic molecules in the heart of the Sculptor Galaxy, which is located 11 million light-years from us. The team discovered eight massive dust clouds in the galaxy and were able to take incredibly detailed observations of these objects.

As reported in the Astrophysical Journal, the team used the Atacama Large Millimeter/submillimeter Array (ALMA) to zoom in on molecular clouds about 30 light-years across. In one particular cloud, they detected 19 different organic molecules, an incredible richness not seen before outside the Milky Way.

“The data are filled with the signals of various molecules,” lead author Ryo Ando, from the University of Tokyo, said in a statement. “It is like a forest of molecules.”

This is the first time “molecular forests” have been detected in another galaxy. The term "forest" comes from the appearance that the light spectrum has when lots of different chemicals are seen next to each other. These forests are formed in the large reservoirs of gas and dust surrounding newly born stars. This environment appears to be particularly suitable for chemical reactions that allow for the formation of many molecular species.

ALMA detected radio signals from 19 different molecules at the center of this galaxy. ESO/J. Emerson/VISTA, ALMA (ESO/NAOJ/NRAO), Ando et al. Cambridge Astronomical Survey Unit

The team observed formaldehyde, hydrogen cyanide, methanol, acetic acid, and many other organic molecules in the eight clouds. The number of chemical signals observed varied between clouds suggesting that although located near each other, they might have evolved in different ways.

“With its unprecedented resolution and sensitivity, ALMA showed us the detailed structure of the clouds,” added Ando. “To my surprise, the gas clouds have a strong chemical individuality despite their similarity in size and mass.”

One particularly striking difference is between the cloud with the 19 species and another one only a dozen or so light years away. The latter cloud has a very sparse chemical composition. The assembly and evolution of these clouds could be very important in understanding the evolution of galaxies as a whole.

The Sculptor Galaxy, also known as NGC 253, is an extremely active spiral galaxy. It is a starburst galaxy as it is undergoing an intense period of star formation. Researchers hope that by studying Sculptor, which is relatively close-by, they will be able to work out what goes on in the many starburst galaxies that we have observed around the universe.

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