The Largest Alcohol Molecule Found in Space Yet May Be The Key to Star Formation

There is booze in space. No, it's not bottles of wine dumped by reckless astronauts; rather, it's in minuscule molecule form. Now, researchers believe they have identified the biggest alcohol molecule in space, propanol.

Propanol molecules exist in two forms, or isomers, which have now been found in observations: normal-propanol, which has been detected in a star-forming area for the first time, and iso-propanol (the primary element in hand sanitizer), which has never been observed in interstellar form previously.

These results should give insight on how celestial things like comets and stars arise.

"The detection of both isomers of propanol is uniquely powerful in determining the formation mechanism of each," says University of Virginia astrochemist Rob Garrod. "Because they resemble each other so much, they behave physically in very similar ways, meaning that the two molecules should be present in the same places at the same times."

"The only open question is the exact amounts that are present – this makes their interstellar ratio far more precise than would be the case for other pairs of molecules. It also means that the chemical network can be tuned much more carefully to determine the mechanisms by which they form."

These alcohol molecules were discovered in what is known as a 'delivery chamber' of stars, the massive star-forming area known as Sagittarius B2 (Sgr B2). The area lies at the Milky Way's core and close to Sagittarius A* (Sgr A*), the supermassive black hole that our galaxy revolves around.

While this type of deep space molecular study has been going on for more than 15 years, the introduction of the Atacama Large Millimeter/submillimeter Array (ALMA) telescope in Chile ten years ago has increased the amount of information that astronomers can access.

ALMA has a superior resolution and sensitivity, allowing researchers to discover compounds that were previously invisible. The ability to separate the exact radiation frequency emitted by each molecule in a crowded region of space like Sgr B2 is critical in determining what's out there.

"The bigger the molecule, the more spectral lines at different frequencies it produces," explains physicist Holger Müller of the University of Cologne in Germany. "In a source like Sgr B2, there are so many molecules contributing to the observed radiation that their spectra overlap and it is difficult to disentangle their fingerprints and identify them individually."

The finding was made possible by ALMA's ability to identify very fine spectral lines, as well as lab studies that completely analyzed the signs that propanol isomers would emit in space.

Finding molecules that are closely related - such as normal-propanol and iso-propanol - and evaluating how prevalent they are compared to one other allows scientists to investigate the chemical interactions that formed them in more depth.

More interstellar molecules are being discovered in Sgr B2, and the chemical melting pot that leads to star creation is being studied. ALMA has also detected the chemical compounds isopropyl cyanide, N-methylformamide, and urea.

"There are still many unidentified spectral lines in the ALMA spectrum of Sgr B2 which means that still a lot of work is left to decipher its chemical composition," says astronomer Karl Menten of Germany's Max Planck Institute for Radio Astronomy.

"In the near future, the expansion of the ALMA instrumentation down to lower frequencies will likely help us to reduce the spectral confusion even further and possibly allow the identification of additional organic molecules in this spectacular source." 
The research has been published in Astronomy & Astrophysics here and here.