Interstellar Cloud And Disk Make Up Are Not Identical

Lee Rannals for redOrbit.com – Your Universe Online

A team of scientists led by the University of Tokyo say that the chemical compositions of an interstellar cloud and the disk are not identical.

Stars are formed by the contraction of interstellar gas and dust, and this mix ends up helping to eventually form planets. However, scientists have wondered whether the chemical compositions of the interstellar cloud and the disk that creates the planets are identical. The latest findings, published in the journal Nature, have an impact on understanding the formation process of planets and protoplanetary disks.

The scientists observed a baby star known as L1527 in the constellation Taurus. They looked at radio emission coming from cyclic-C3H2 and sulfur monoxide (SO) molecules to help analyze the motion and temperature of the gas around the star.

The protostar in the study has been used by many astronomers for observations. Even NASA’s Spitzer Space Telescope has taken infrared images of the star. L1526 gives off stellar light that escapes through a cavity excavated by a powerful bipolar gas flow from the star and illuminates the surrounding gas. Previous studies found that gas is circling around the star to form a disk.

Dr. Nami Sakai of the University of Tokyo, and colleagues conducted high-sensitivity, high-spatial-resolution observations with the Atacama Large Millimeter/submillimeter Array (ALMA). The team found that carbon chain molecules and their related species, such as cyclic-C3H2, almost completely disappear from the gas phase inside a radius of 100 astronomical units around the protostar.

“It is not at all anticipated that such a drastic chemical change occurs in the transition zone between the infalling envelope and the inner disk,” officials from the National Astronomical Observatory of Japan (NAOJ) wrote in a statement. “The disk formation and the associated chemical change have successfully been detected by observations of the two chemical species, cyclic-C5H2 and SO.”

The astronomers said it is interesting to examine how widely applicable the picture seen in L1527 is to other star-forming regions. Although many observational efforts have been made into studying planetary system formation, this is a unique study that focused on the chemical change.

“By extending this new method to various solar-type protostars using ALMA, the diversity and generality of the chemical evolution from interstellar matter to planetary matter will be unveiled within the next few years,” the NAOJ said. “Then, we can critically examine whether the Solar System experienced this drastic chemical change.”