Free Astronomy Magazine January-February 2024

43 JANUARY-FEBRUARY 2024 ASTRO PUBLISHING forming regions of disks in the Lob- ster Nebula using the Medium Res- olution Spectrometer on Webb’s Mid-Infrared Instrument (MIRI). This first result focuses on the protoplan- etary disk termed XUE 1, which is lo- cated in the star cluster Pismis 24. “Only the MIRI wavelength range and spectral resolution allow us to probe the molecular inventory and physical conditions of the warm gas and dust where rocky planets form,” added team member Arjan Bik of Stockholm University in Sweden. Due to its location near several mas- sive stars in NGC 6357, scientists ex- pect XUE 1 to have been constantly exposed to high amounts of ultravi- olet radiation throughout its life. However, in this extreme environ- ment the team still detected a range of molecules that are the building blocks for terrestrial planets. “We find that the inner disk around XUE 1 is remarkably similar to those in nearby star-forming regions,” said team member Rens Waters of Rad- boud University in the Netherlands. “We’ve detected water and other molecules like carbon monoxide, carbon dioxide, hydrogen cyanide and acetylene. However, the emis- sion found was weaker than some models predicted. This might imply a small outer disk radius.” “We were surprised and excited because this is the first time that these molecules have been detected under these extreme conditions,” added Lars Cuijpers of Radboud Uni- versity. The team also found small, partially crystalline silicate dust at the disk’s surface. This is considered to be the building blocks of rocky planets. These results are good news for rocky planet formation, as the sci- ence team finds that the conditions in the inner disk resemble those found in the well-studied disks lo- cated in nearby star-forming re- gions, where only low-mass stars form. This suggests that rocky plan- ets can form in a much broader range of environments than previ- ously believed. The team notes that the remaining observations from the XUE program are crucial to establish the common- ality of these conditions. “XUE 1 shows us that the conditions to form rocky planets are there, so the next step is to check how com- mon that is,” says Ramírez-Tannus. “We will observe other disks in the same region to determine the fre- quency with which these conditions can be observed.” ! T his is an artist’s impression of a young star surrounded by a pro- toplanetary disk in which planets are forming. [ESO]