Alien Star System Mirrors Earth’s 4 Billion Years Ago –“A Milestone Revealing Rich Organics Needed for Life”

 

 

117511_web

 

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, closely resembling what astronomers think the Solar System looked like during its formation more than four billion years ago, representing a milestone for understanding how organic molecules are incorporated into nascent planets.


The Atacama Large Millimeter/Submillimeter Array (ALMA – http://www.eso.org/public/teles-instr/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. 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.”

 

Img

 

Gaseous methanol in a protoplanetary disc has a unique importance in astrochemistry. While other species detected in space are formed by gas-phase chemistry alone, or by a combination of both gas and solid-phase generation, methanol is a complex organic compound which is formed solely in the ice phase via surface reactions on dust grains.

The sharp vision of ALMA has also allowed astronomers to map the gaseous methanol across the TW Hydrae disc. They discovered a ring-like pattern in addition to significant emission from close to the central star.

The observation of methanol in the gas phase, combined with information about its distribution, implies that methanol formed on the disc’s icy grains, and was subsequently released in gaseous form. This first observation helps to clarify the puzzle of the methanol ice-gas transition, and more generally the chemical processes in astrophysical environments.

“Methanol in gaseous form in the disc is an unambiguous indicator of rich organic chemical processes at an early stage of star and planet formation,” says Ryan Loomis, a co-author of the study.”This result has an impact on our understanding of how organic matter accumulates in very young planetary systems.”

This successful first detection of cold gas-phase methanol in a protoplanetary disc means that the production of ice chemistry can now be explored in discs, paving the way to future studies of complex organic chemistry in planetary birthplaces. In the hunt for life-sustaining exoplanets, astronomers now have access to a powerful new tool.

The Daily Galaxy via ESO

 

"The Galaxy" in Your Inbox, Free, Daily