The largest alcohol molecule found in space

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Researchers at the Max Planck Institute for Forest Radio Astronomy have for the first time detected an isopropanal molecule in interstellar space. It is the largest alcohol molecule ever discovered in space. This was observed in the molecular cloud Sagittarius B2, located far from the center of our galaxy. This discovery could shed light on the process of star formation.

Astronomers have been searching for space for molecules for decades. To date, more than 270 molecules have already been detected in interstellar media. The purpose is to understand how organic molecules are formed in space, especially where stars are born, and to connect them to the chemical structure of the bodies of the solar system, such as comets. The Sagittarius B2 (Sgr B2) cloud, located near the Sgr A * black hole in our galaxy, quickly became of interest for this study; Many organic molecules have been identified there.

Our group began studying the chemical structure of Sgr B2 more than 15 years ago, with a 30-meter telescope at IRAM “, Explained Arnaud Beloch from the Max Planck Institute for Radio Astronomy in the Forest, who took part in the discovery. Thanks to the Atacama Large Millimeter / Submillimeter Array (ALMA), located in northern Chile and launched in 2011, astronomers have been able to deepen their research. The high angular resolution and sensitivity of ALMA allow the detection of new molecules (such as isopropyl cyanide, N-methylformide and urea). A new molecule has now been added to the list.

An invention that would not have been possible without Alma

Propanol (c3H.7OH) is an alcohol that exists in the form of two isomers: propan-1-ol and propan-2-ol (also called isopropanol) – the latter being used mainly in combination with hydroalcoholic solutions and other disinfectants. Beloche and his colleagues recently reported the detection of these two molecular forms in space. This is the first time isopropanal has been detected by interstellar, and the first time normal propanol has been detected in a star formation region.

However, it is not easy to identify organic molecules in the spectrum associated with star-forming regions. In fact, each molecule emits radiation at a specific frequency; The larger it is, the more lines it creates at different frequencies. However, the scattering of molecules in Sgr B2 is such that the spectrum overlaps and interconnects – which makes the identification of molecules more difficult.

But thanks to ALMA’s high angular resolution, it was possible to isolate parts of the Sgr B2 that emit very narrow spectral lines – five times narrower than those detected on a larger scale by a 30-meter radio telescope from IRAM. The narrowness of the lines made it possible to distinguish different radiation frequencies – thus limiting spectral confusion – and to detect two isomers of propanol in Sgr B2.

The identification of these two very similar molecules, which differ somewhat in their structure (the -OH functional group is not located in the same place), and in particular their abundance ratio, provides insights into the chemical reaction networks that lead to their production. Via interstellar ” Since they look very similar, they behave very similarly physically, which means that both molecules should be present in the same place and at the same time. “, Explained Rob Gard of the University of Virginia, co-author of the study.

The two families of molecules have similarities

The team reports Astronomy and astrophysics That isopropanals are almost as abundant as normal propanals, with an abundance ratio of 0.6 – a value similar to the 0.4 ratio they previously obtained for isopropyl cyanide (H3VS)2CHCN) and its linear isomer, Sgr B2. The researchers noted that these results are consistent with those obtained through astronomical chemical models and suggest similarities between the chemical processes that make up the family of these two molecules.

Since the discovery of isopropyl cyanide in 2014, no other branched molecule has been identified. ” Normal propanal and isopropanal detection and ratios indicate that modest choice for the normal form of pre-determined isopropyl cyanide may be a more common feature among interstellar molecules of the same size. 6, the team ends. In other words, branched carbon chained molecules can usually be abundant through interstellar means (as abundant as their linear equivalents).

However, more research is needed to confirm this hypothesis. To do this, astronomers hope to find other pairs of organic molecules, the functional group of which is linked to the primary or secondary carbon of the carbon skeleton. Butanol (which has four carbon atoms) and its three isomers may be the next candidates in the alcohol family. Identifying them, though, can be more difficult than propanol, the team underlines.

The researchers further noted that many spectral lines in the ALMA spectrum of Sgr B2 are still unknown. It is hoped that radio telescopes will soon benefit from an extension at lower frequencies, which will further reduce spectral confusion. Thus, in the near future, other organic molecules could be detected in this huge cloud of gas and dust, revealing the chemical processes that lead to star formation.

Sources: A. Belloche et al., Astronomy & Astrophysics

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