UV-driven chemistry as a signpost of late-stage planet formation
UV-driven chemistry as a signpost of late-stage planet formation
复制标题
紫外线驱动的化学作为晚期行星形成的路标
DOI：
10.1038/s41550-022-01831-8
复制
发表时间：
2023
期刊：
影响因子：
14.1
通讯作者：
Ilee, John D.
中科院分区：
文献类型：
--
作者：
Calahan, Jenny K.;Bergin, Edwin A.;Bosman, Arthur D.;Rich, Evan A.;Andrews, Sean M.;Bergner, Jennifer B.;Cleeves, L. Ilsedore;Guzmán, Viviana V.;Huang, Jane;Ilee, John D.
原行星盘中的化学储存对行星的组成和生命的潜力有直接的影响。在低温（≤ 50 K）下，在寒冷和演化的行星形成盘中观察到长寿命的富碳和富氮化学。这一点可以从1- 1000万年老化系统中的小有机自由基的明亮发射中得到证明，否则这些自由基将在100万年内冻结在晶粒上。我们解释了行星形成盘的化学是如何从宇宙射线/X射线主导的制度演变为紫外线主导的化学平衡的。反过来，这将导致化学储存库的暂时过渡，行星将从中吸积。这种以光化学为主的气相化学随着尘埃的生长、沉降和漂移而发展，小颗粒的数量从盘状大气中耗尽。更高的气体与尘埃质量比允许紫外光子更深地穿透，与富碳气体（C/O > 1）耦合以形成含碳自由基和离子。这进一步导致有机分子的气相形成，然后被演化盘中存在的任何活跃形成的行星吸积。
The chemical reservoir within protoplanetary disks has a direct impact on planetary compositions and the potential for life. A long-lived carbon- and nitrogen-rich chemistry at cold temperatures (≤ 50 K) is observed within cold and evolved planet-forming disks. This is evidenced by bright emission from small organic radicals in 1–10 Myr aged systems that would otherwise have frozen out onto grains within 1 Myr. We explain how the chemistry of a planet-forming disk evolves from a cosmic-ray/X-ray-dominated regime to a ultraviolet-dominated chemical equilibrium. This, in turn, will bring about a temporal transition in the chemical reservoir from which planets will accrete. This photochemical dominated gas phase chemistry develops as dust evolves via growth, settling and drift, and the small grain population is depleted from the disk atmosphere. A higher gas-to-dust mass ratio allows for deeper penetration of ultraviolet photons is coupled with a carbon-rich gas (C/O > 1) to form carbon-bearing radicals and ions. This further results in gas phase formation of organic molecules, which then would be accreted by any actively forming planets present in the evolved disk.