Large Amount of Spinning-top-like Organic Molecules Found in Sagittarius
Abstract In addition to molecules of hydrogen, water, carbon monoxide, and ammonia, the Universe is replete with organic molecules like methanol. Molecules floating in space are known as interstellar molecules and they are found in molecular clouds, accumulations of gas from which stars form. So far, over 200 interstellar molecules have been found and most them were identified by radio telescopes. These molecules rotate in space as a result of collisions with each other, and when their rotation states change, the molecules emit radio waves. Observing these radio waves can tell us where such molecules exist. A joint research team led by Dr. Mitsunori Araki from Tokyo University of Science focused on acetonitrile (CH3CN), one of the major organic molecules present in molecular clouds, and studied how this molecule rotates in molecular clouds. Acetonitrile has an elongate, symmetrical shape, which makes this molecule prone to rotate around its long axis. In high-density regions of typical molecular clouds, collisions between molecules occur relatively frequently, causing acetonitrile to rotate in various directions. In low-density regions, on the other hand, it has been thought that acetonitrile is more likely to rotate like a “spinning top.” However, low-density regions are difficult to observe and until now only interstellar clouds that show faint signs of such molecular spinning tops have been found. This time, the research team developed a method that can resolve even low-density regions, and used the Nobeyama 45-m Radio Telescope to observe several molecular clouds suited for observations by that telescope. As a result, they found a region where spinning-top-like acetonitrile molecules are particularly abundant in the molecular cloud Sgr B2(M) located in the constellation Sagittarius, close to the Galactic Center. This discovery enables us to estimate the amounts of acetonitrile more precisely. Since acetonitrile is one of the major interstellar organic molecules, these results have very important implications for understanding the amounts of organic molecules in molecular clouds.
Related Links Tokyo University of Science Nobeyama 45-m Radio Telescope