There’s alcohol up in space. No, it’s not wine bottles thrown away by careless astronauts; rather, it is in microscopic molecular form. Now researchers believe they have discovered the largest alcohol molecule in space to date, propanol.
Propanol molecules exist in two forms, or isomers, both of which have now been identified through observation: normal propanol, detected for the first time in a star-forming region, and isopropanol (the main ingredient in hand sanitizer). ), which has never before been seen in interstellar form.
These discoveries should shed light on how celestial bodies such as comets and stars are formed.
“Detecting both isomers of propanol is uniquely powerful in determining the mechanism of formation of each,” says University of Virginia astrochemist Rob Garrod. “Because they are so similar, physically they behave very similarly, which means that the two molecules should be present in the same places at the same time.”
“The only open question is the exact amounts that are present — making their interstellar relationship much more accurate than would be the case with other pairs of molecules.” It also means that the chemical network can be tuned much more carefully to determine the mechanisms that make them up.”
These alcohol molecules were found in a so-called “delivery room” of stars, the gigantic star-forming region called Sagittarius B2 (Sgr B2). The region lies near the center of the Milky Way and near Sagittarius A* (Sgr A*), the supermassive black hole around which our galaxy is built.
While this type of molecular analysis of space has been going on for more than 15 years, the arrival of the Atacama Large Millimeter/submillimeter Array (ALMA) telescope in Chile 10 years ago increased the level of detail astronomers can access.
ALMA offers higher resolution and a higher level of sensitivity, allowing researchers to identify molecules that were previously invisible. Being able to tell apart the specific frequency of radiation emitted by each molecule in a busy part of space like Sgr B2 is crucial to calculating what’s out there.
“The larger the molecule, the more spectral lines it generates at different frequencies,” says physicist Holger Müller from the University of Cologne. “In a source like Sgr B2, so many molecules contribute to the observed radiation that their spectra overlap and it is difficult to unravel their fingerprints and identify them individually.”
The discovery was made thanks to the way ALMA can detect very narrow spectral lines, as well as laboratory work that extensively characterized the signatures that propanol isomers would emit in space.
Finding closely linked molecules — like regular propanol and isopropanol — and measuring how common they are relative to one another allows scientists to take a closer look at the chemical reactions that produced them.
Work continues to discover more interstellar molecules in Sgr B2 and to understand the nature of the chemical crucible that leads to star formation. ALMA also discovered the organic molecules isopropyl cyanide, N‑methylformamide and urea.
“There are still many unidentified spectral lines in the ALMA spectrum of Sgr B2, which means there is still a lot of work left to decipher its chemical composition,” says astronomer Karl Menten from the Max Planck Institute for Radio Astronomy in Germany.
“In the near future, extending the ALMA instrumentation to lower frequencies will likely help us reduce spectral confusion even further and potentially enable the identification of additional organic molecules in this spectacular source.”
The research was published in Astronomy & Astrophysics here and here.
