James Webb Telescope Uncovers Varied Chemistry in Planetary 'Nursery'

An international team from 11 countries has utilized data from the James Webb Telescope to examine the protoplanetary disks that form new rocky planets around two young stars. Detailed in two separate articles, the research sheds light on the initial conditions of these planetary "nurseries."

The Mid-Infrared Instrument (MIRI) spectrograph's data offers insights into the composition of gases and dust in these protoplanetary disks. Since the elements present in these environments can vary significantly, identifying those that may create habitable worlds is crucial.

The findings, set to be published in Nature Astronomy and The Astrophysical Journal Letters, reveal the presence of intricate and unusual organic molecules such as benzene, as well as a surprising scarcity of water.

Dry Disk and Carbon Richness

In one of the papers, Sierra Grant, a postdoctoral researcher at the Max Planck Institute for Extraterrestrial Physics (MPE), discusses a hot, dry disk surrounding a young, low-mass star named GW Lup. Grant notes that while carbon and oxygen molecules were detected, there is significantly less water than anticipated.

Several explanations exist for this water deficiency, including a gap in the disk near the star, possibly beyond the water snow line (the region where temperatures drop enough for certain molecules to freeze). Planets formed in this area could be extremely dry, with only comets and other frozen objects from the outermost part of the star system supplying water. Alternatively, a forming planet may have "stolen" water from the environment through interaction with the disk.

The team also discovered a rare carbon dioxide molecule containing a heavier carbon isotope than the standard version, which exists only on the disk's hottest surface, where temperatures reach 225 degrees Celsius. In areas with only the heavier molecule, the temperature is -75 degrees Celsius.

Diverse Organic Molecules

CNRS researcher Benoît Tabone, from the Institut d'Astrophysique Spatiale in France, studied the star J160532 and found its disk to be unusually rich in hydrocarbons such as acetylene, diacetylene, and benzene—the latter two identified for the first time in a protoplanetary disk.

These carbon-rich mixtures, in combination with low levels of oxygen and water, will undoubtedly influence the atmospheres of future planets orbiting this star. Most of the disk's water might be trapped on its outermost side, beyond the reach of current observations.

Sources: Max Planck Institute for Astronomy, The Astrophysical Journal Letters, arXiv.org