First Detection of Methyl Alcohol in a Planet-forming Disc
The organic molecule methyl alcohol (methanol) has been found by the Atacama Large Millimeter/Submillimeter Array (ALMA) in the TW Hydrae protoplanetary disc. This is the first such detection of the compound in a young planet-forming disc. Methanol is the only complex organic molecule as yet detected in discs that unambiguously derives from an icy form. Its detection helps astronomers understand the chemical processes that occur during the formation of planetary systems and that ultimately lead to the creation of the ingredients for life.
The protoplanetary disc around the young star TW Hydrae is the closest known example to Earth, at a distance of only about 170 light-years. As such it is an ideal target for astronomers to study discs. This system closely resembles what astronomers think the Solar System looked like during its formation more than four billion years ago.
The Atacama Large Millimeter/Submillimeter Array (ALMA) is the most powerful observatory in existence for mapping the chemical composition and the distribution of cold gas in nearby discs. These unique capabilities have now been exploited by a group of astronomers led by Catherine Walsh (Leiden Observatory, the Netherlands) to investigate the chemistry of the TW Hydrae protoplanetary disc.
The ALMA observations have revealed the fingerprint of gaseous methyl alcohol, or methanol (CH3OH), in a protoplanetary disc for the first time. Methanol, a derivative of methane, is one of the largest complex organic molecules detected in discs to date. Identifying its presence in pre-planetary objects represents a milestone for understanding how organic molecules are incorporated into nascent planets.
Furthermore, methanol is itself a building block for more complex species of fundamental prebiotic importance, like amino acid compounds. As a result, methanol plays a vital role in the creation of the rich organic chemistry needed for life.
Catherine Walsh, lead author of the study, explains: “Finding methanol in a protoplanetary disc shows the unique capability of ALMA to probe the complex organic ice reservoir in discs and so, for the first time, allows us to look back in time to the origin of chemical complexity in a planet nursery around a young Sun-like star.”