ALMA observations detect complex carbon-chain molecule HC5N in the TW Hya protoplanetary disk

Star system: TW Hydrae | Distance from the Sun: 196 light years

Protoplanetary disks, the rotating disks of gas and dust that surround young stars, are the environments where planets are born. Scientists study these disks to understand the chemical ingredients available during planet formation, which can provide clues about the potential for life. A recent investigation has identified a new, complex molecule within the disk surrounding the star TW Hya, known as a Class II disk, which is in a mature phase of development where planet building is well underway.

The research team utilized the Atacama Large Millimeter/submillimeter Array, or ALMA, to survey the molecular content of the TW Hya disk. Their work led to the first detection of HC5N, a molecule belonging to a group called cyanopolyynes, within a Class II disk. This is the largest molecule of its kind ever identified in this type of system, representing a significant addition to our knowledge of carbon-chain chemistry in environments where planets form.

By measuring specific rotational signals of the molecule, researchers calculated a column density of approximately 10 to the power of 12 molecules per square centimeter. Chemical modeling suggests that this molecule originates in the warm molecular layer of the disk, a region where specific chemical pathways involving cyanide are highly active. These findings demonstrate that long carbon-chain molecules can successfully form and persist in the complex, dynamic environments of planet-forming disks.

Key findings
- First detection of the complex molecule HC5N in a Class II protoplanetary disk.
- The observation was made in the disk surrounding the star TW Hya using ALMA.
- HC5N is the largest cyanopolyyne identified to date in such a system.
- The molecule likely originates in the warm molecular layer of the disk where active chemistry occurs.

Scientific study

First Detection of HC5N in a Class II Disk around TW Hya (external link)