15NH3 in the atmosphere of a cool brown dwarf.
15NH3 in the atmosphere of a cool brown dwarf.
复制标题
冷褐矮星大气中的 15NH3。
DOI：
10.1038/s41586-023-06813-y
复制
发表时间：
2023
期刊：
影响因子：
64.8
通讯作者：
Barrado D
中科院分区：
文献类型：
--
作者：
Barrado D
褐矮星是研究宽轨道上巨大系外行星大气的理想实验室，因为它们内部的主导物理和化学过程几乎相同。了解气态巨行星的形成是具有挑战性的，通常涉及到将大气丰度比（如碳氧比）与形成情景联系起来。然而，行星形成的复杂性需要进一步的示踪剂，因为对测量的碳氧比的明确解释充满了复杂性。同位素比率，如氘对氢和14n /15N，为进一步了解这一形成过程提供了一个有希望的途径，反映了它们在太阳系中的使用。对于系外行星来说，只有少数限制12c /13C的条件存在，这表明富含13C的冰从圆盘的CO线之外吸积。本文报道了JWST中红外仪器（MIRI）在有效温度为380 K的冷褐矮星大气中对14nh3和15nh3同位素的中红外探测。正如预期的那样，我们的结果揭示了14n /15N值与引力坍缩形成的类星一致，表明该比率可以精确地约束。因为年轻的恒星和它们的行星应该更富含15n同位素，我们预计15nh3将在几个寒冷的、宽距离的系外行星上被探测到。
Brown dwarfs serve as ideal laboratories for studying the atmospheres of giant exoplanets on wide orbits, as the governing physical and chemical processes within them are nearly identical,. Understanding the formation of gas-giant planets is challenging, often involving the endeavour to link atmospheric abundance ratios, such as the carbon-to-oxygen (C/O) ratio, to formation scenarios. However, the complexity of planet formation requires further tracers, as the unambiguous interpretation of the measured C/O ratio is fraught with complexity. Isotope ratios, such as deuterium to hydrogen and14N/15N, offer a promising avenue to gain further insight into this formation process, mirroring their use within the Solar System, –. For exoplanets, only a handful of constraints on12C/13C exist, pointing to the accretion of13C-rich ice from beyond the CO iceline of the disks,. Here we report on the mid-infrared detection of the14NH3and15NH3isotopologues in the atmosphere of a cool brown dwarf with an effective temperature of 380 K in a spectrum taken with the Mid-Infrared Instrument (MIRI) of JWST. As expected, our results reveal a14N/15N value consistent with star-like formation by gravitational collapse, demonstrating that this ratio can be accurately constrained. Because young stars and their planets should be more strongly enriched in the15N isotope, we expect that15NH3will be detectable in several cold, wide-separation exoplanets.