Wild Chemical Environment Detected Inside A Newly Forming Star

Astronomers have discovered a previously unknown chemical processing factory inside the workings of a newly forming star—a discovery that may change fundamental models of how stars and planetary systems are born (Nature 2014, DOI: 10.1038/nature13000). A team led by Nami Sakai of the University of Tokyo used the Atacama Large Millimeter/submillimeter Array radio telescopes in Chile to study a nearby star-forming region. The system consists of a flat rotating envelope of gas that is being fed by a stream of gas from interstellar clouds, with a more concentrated rotating disk at the center. The scientists say they discovered a drastic chemical change at the boundary between the envelope and disk. In the larger envelope, they predominantly detected cyclic C₃H₂, but this compound abruptly diminishes and is suddenly replaced by SO in the disk. The researchers conclude that this transition results from the sudden change in environment as the gas hits the rapidly swirling disk: The kinetic energy of the gas is converted to rotational energy and, as a result, a lot of heat. They suggest that two unrelated processes may be occurring: The C₃H₂ is destroyed by reaction with O, while SO is ripped off dust grains and liberated as gas. In solar evolutionary models, astronomers had been presuming that an unchanging chemical composition of interstellar clouds served as the starting conditions for forming stars.