Centaurs are transitional objects between primitive trans-Neptunian objects and Jupiter-family comets. Their compositions and activities provide fundamental clues regarding the processes affecting the evolution of and interplay between these small bodies. Here we report observations of centaur 29P/Schwassmann–Wachmann 1 (29P) with the James Webb Space Telescope (JWST). We identified localized jets with heterogeneous compositions driving the outgassing activity. We employed the NIRSpec mapping spectrometer to study the fluorescence emissions of CO and obtain a definitive detection of CO₂ for this target. The exquisite sensitivity of the instrument also enabled carbon and oxygen isotopic signatures to be probed. Molecular maps reveal complex outgassing distributions, such as jets and anisotropic morphology, which indicate that 29P’s nucleus is dominated by active regions with heterogeneous compositions. These distributions could reflect that it has a bilobate structure with compositionally distinct components or that strong differential erosion takes place on the nucleus. As there are no missions currently planning to visit a centaur, these observations demonstrate JWST’s unique capabilities in characterizing these objects.

半人马座是原始的海王星外天体和木星族彗星之间的过渡天体。它们的组成和活动为影响这些小天体的进化和相互作用的过程提供了基本线索。在此，我们报告了使用詹姆斯·韦伯太空望远镜 (JWST) 对半人马座 29P/Schwassmann-Wachmann 1 (29P) 的观测结果。我们发现具有异质成分的局部射流驱动了除气活动。我们使用 NIRSpec 映射光谱仪来研究 CO 的荧光发射，并获得该目标的 CO ₂ 的明确检测结果。该仪器的精湛灵敏度还可以探测碳和氧同位素特征。分子图揭示了复杂的放气分布，例如喷流和各向异性形态，这表明 29P 的核主要由具有异质成分的活性区域主导。这些分布可能反映出它具有成分不同的双叶结构或核上发生了强烈的差异侵蚀。由于目前没有计划访问半人马星的任务，这些观测结果证明了 JWST 在描述这些物体特征方面的独特能力。