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Unveiling the ice and gas nature of active centaur (2060) Chiron using the James Webb Space Telescope
Astronomy & Astrophysics ( IF 5.4 ) Pub Date : 2024-12-18 , DOI: 10.1051/0004-6361/202450124 N. Pinilla-Alonso, J. Licandro, R. Brunetto, E. Henault, C. Schambeau, A. Guilbert-Lepoutre, J. Stansberry, I. Wong, J. I. Lunine, B. J. Holler, J. Emery, S. Protopapa, J. Cook, H. B. Hammel, G. L. Villanueva, S. N. Milam, D. Cruikshank, A. C. de Souza-Feliciano
Astronomy & Astrophysics ( IF 5.4 ) Pub Date : 2024-12-18 , DOI: 10.1051/0004-6361/202450124 N. Pinilla-Alonso, J. Licandro, R. Brunetto, E. Henault, C. Schambeau, A. Guilbert-Lepoutre, J. Stansberry, I. Wong, J. I. Lunine, B. J. Holler, J. Emery, S. Protopapa, J. Cook, H. B. Hammel, G. L. Villanueva, S. N. Milam, D. Cruikshank, A. C. de Souza-Feliciano
Context. (2060) Chiron is a large centaur that has been reported active on multiple occasions at relatively large heliocentric distances, including during aphelion passage. Studies of Chiron’s coma during active periods have resulted in the detection of C≡N and CO outgassing. Additionally, Chiron is surrounded by a disk of debris that varies with time. Significant work remains to be undertaken to comprehend the activation mechanisms on Chiron and the parent molecules of the gas phases detected.Aims. This work reports the study of the ices on Chiron’s surface and coma and seeks spectral indicators of volatiles associated with the activity. Additionally, we discuss how these detections could be related to the activation mechanism for Chiron and, potentially, other centaurs.Methods. In July 2023, the James Webb Space Telescope (JWST) observed Chiron when it was active near its aphelion. We present JWST/NIRSpec spectra from 0.97 to 5.27 μm with a resolving power of ∼1000, and compare them with laboratory data for identification of the spectral bands.Results We report the first detections on Chiron of absorption bands of several volatile ices, including CO2, CO, C2H6, C3H8, and C2H2. We also confirm the presence of water ice in its amorphous state. A key discovery arising from these data is the detection of fluorescence emissions of CH4, revealing the presence of a gas coma rich in this hyper-volatile molecule, which we also identify to be in non-local thermal equilibrium (non-LTE). CO2 gas emission is also detected in the fundamental stretching band at 4.27 μm. We argue that the presence of CH4 emission is the first proof of the desorption of CH4 due to a density phase transition of amorphous water ice at low temperature in agreement with the estimated temperature of Chiron during the JWST observations (61 K). Detection of photolytic and proton irradiation products of CH4 and CO2 on the surface, in the coma ice grains, or in the ring material is also detected via a forest of absorption features from 3.5 to 5.3 μm.
中文翻译：
使用詹姆斯韦伯太空望远镜揭开活跃的半人马 （2060） 凯龙星的冰和气体性质
上下文。（2060） 凯龙星是一个大型半人马，据报道在相对较大的日心距离上多次活跃，包括在远日点通过期间。对活动期 Chiron 昏迷的研究导致检测到 C≡N 和 CO 脱气。此外，凯龙星被一个随时间变化的碎片盘所包围。要理解 Chiron 上的激活机制和检测到的气相的母体分子，仍有大量工作要做。目标。这项工作报告了对凯龙星表面和彗发中的冰的研究，并寻找与该活动相关的挥发物的光谱指标。此外，我们还讨论了这些检测如何与 Chiron 和其他半人马的激活机制相关联。方法。2023 年 7 月，詹姆斯韦伯太空望远镜 （JWST） 在凯龙在其远日点附近活跃时观测了它。我们提供了 0.97 至 5.27 μm 的 JWST/NIRSpec 光谱，分辨率为 ∼1000，并将它们与实验室数据进行比较以识别光谱带。结果我们报告了在 Chiron 上首次检测到几种挥发性冰的吸收带，包括 CO 2, CO, C2H6, C3H8, and C2H2. We also confirm the presence of water ice in its amorphous state. A key discovery arising from these data is the detection of fluorescence emissions of CH4, revealing the presence of a gas coma rich in this hyper-volatile molecule, which we also identify to be in non-local thermal equilibrium (non-LTE). CO2 gas emission is also detected in the fundamental stretching band at 4.27 μm. We argue that the presence of CH4 emission is the first proof of the desorption of CH4 due to a density phase transition of amorphous water ice at low temperature in agreement with the estimated temperature of Chiron during the JWST observations (61 K). Detection of photolytic and proton irradiation products of CH4 and CO2 on the surface, in the coma ice grains, or in the ring material is also detected via a forest of absorption features from 3.5 to 5.3 μm.
更新日期：2024-12-19
中文翻译：
使用詹姆斯韦伯太空望远镜揭开活跃的半人马 （2060） 凯龙星的冰和气体性质
上下文。（2060） 凯龙星是一个大型半人马，据报道在相对较大的日心距离上多次活跃，包括在远日点通过期间。对活动期 Chiron 昏迷的研究导致检测到 C≡N 和 CO 脱气。此外，凯龙星被一个随时间变化的碎片盘所包围。要理解 Chiron 上的激活机制和检测到的气相的母体分子，仍有大量工作要做。目标。这项工作报告了对凯龙星表面和彗发中的冰的研究，并寻找与该活动相关的挥发物的光谱指标。此外，我们还讨论了这些检测如何与 Chiron 和其他半人马的激活机制相关联。方法。2023 年 7 月，詹姆斯韦伯太空望远镜 （JWST） 在凯龙在其远日点附近活跃时观测了它。我们提供了 0.97 至 5.27 μm 的 JWST/NIRSpec 光谱，分辨率为 ∼1000，并将它们与实验室数据进行比较以识别光谱带。结果我们报告了在 Chiron 上首次检测到几种挥发性冰的吸收带，包括 CO 2, CO, C2H6, C3H8, and C2H2. We also confirm the presence of water ice in its amorphous state. A key discovery arising from these data is the detection of fluorescence emissions of CH4, revealing the presence of a gas coma rich in this hyper-volatile molecule, which we also identify to be in non-local thermal equilibrium (non-LTE). CO2 gas emission is also detected in the fundamental stretching band at 4.27 μm. We argue that the presence of CH4 emission is the first proof of the desorption of CH4 due to a density phase transition of amorphous water ice at low temperature in agreement with the estimated temperature of Chiron during the JWST observations (61 K). Detection of photolytic and proton irradiation products of CH4 and CO2 on the surface, in the coma ice grains, or in the ring material is also detected via a forest of absorption features from 3.5 to 5.3 μm.
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