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巨大的太阳系外行星大气的稳定性极限
Tommi T Koskinen1, Alan D Aylward, Steve Miller
1Atmospheric Physics Laboratory, Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK. tommi@apl.ucl.ac.uk
Nature
|December 8, 2007
概括
行星大气层变得不稳定,并在木星类系外行星的0.16au内从水力动力学上逃脱. 这种大气逃逸是由分子的热解离驱动的,关闭了冷却机制.
科学领域:
- 外系行星科学 外系行星科学
- 行星大气层的行星大气层
- 天体物理学 天体物理学
背景情况:
- 观测表明HD209458b有一个逃逸的气氛.
- 理论模型表明,水力动力学逃逸在0.1 AU内是可能的.
- H3+离子对于冷却系外行星上层大气至关重要.
研究的目的:
- 为了确定木星类系外行星大气稳定的交叉点.
- 为了研究H3+冷却在大气逃逸中的作用.
- 改进系外行星大气动力学的模型.
主要方法:
- 使用了一个3D,时间依赖的热层-离子层合模型.
- 集成的H3+离子冷却用于准确的大气模型.
- 模拟热量再分配和组成变化.
主要成果:
- 发现大气稳定性在0.14至0.16 AU之间出现了急剧的崩.
- 发现H3+冷却平衡恒星加热在0.2至0.16 AU之间.
- 在0.16au内观察到分子的热解离,抑制H3+的形成和冷却.
结论:
- 外行星大气层表现出不稳定性和水力动力逃逸,距离太阳型恒星0.16 AU以内.
- 分子的热解离是大气损失的一个关键因素.
- 结果与先前的模型相反,这些模型预测较远距离的不稳定性.
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