Webb finds surprising carbon-rich materials around young star

Using Webb’s Mid-Infrared Instrument (MIRI), the team investigated the contents of ISO-Chal 147’s disk by observing it in the mid-infrared and collecting spectral data. From this data, they constructed an emission spectrum of light that highlighted the elements and compounds present within the disk.

Webb found the disk to contain the richest hydrocarbon chemistry to date within a protoplanetary disk, as the spectrum revealed the disk to contain 13 carbon-bearing molecules up to benzene. These included:

  • Ethane (C2H6) – the first time this molecule has been detected outside of our solar system, and the largest fully-saturated hydrocarbon ever detected outside our solar system
  • Ethylene (C2H4)
  • Propyne (C3H4)
  • The methyl radical CH3

Detecting fully saturated hydrocarbons like ethane around ISO-Chal 147 gives scientists insight into the chemical environment surrounding low-mass stars, as these hydrocarbons are expected to form from more basic molecules.

The team explains that these results have large implications for the astrochemistry around young stars and in the inner 0.1 AU region around them, as well as for the planets forming there. “This is profoundly different from the composition we see in discs around solar-type stars, where oxygen-bearing molecules dominate (like carbon dioxide and water). This object establishes that these are a unique class of objects,” said co-author Inga Kamp of the University of Groningen.

The detection of ethane (C2H6) around ISO-Chal 147 is particularly significant as it marks the first time this molecule has been observed outside of our solar system. Ethane is a fully saturated hydrocarbon, meaning all of its carbon atoms are bonded to the maximum possible number of hydrogen atoms. This makes ethane the largest fully saturated hydrocarbon ever detected beyond our solar system.

The presence of ethane and other saturated hydrocarbons around the young star suggests a unique chemical environment compared to the protoplanetary disks around sun-like stars. In the latter, oxygen-bearing molecules such as carbon dioxide and water tend to dominate.

Co-author Agnés Perrin of Centre National de la Recherche Scientifique in France expressed amazement at the ability to detect and quantify familiar molecules like benzene in an object over 600 light-years away, highlighting the incredible sensitivity of Webb’s instruments.

In addition to ethane, Webb’s MIRI also detected the first instances of ethylene (C2H4), propyne (C3H4), and the methyl radical (CH3) in a protoplanetary disk. The discovery of these hydrocarbons provides valuable clues about the complex chemistry taking place in the planet-forming environment around the young, low-mass star.

The detection of fully saturated hydrocarbons like ethane is particularly noteworthy as they’re expected to form from more basic molecules through chemical processes occurring in the disk. Their presence suggests a unique astrochemical environment compared to disks around more massive stars, potentially influencing the composition of any planets that may form.