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arXiv 1801.02744astro-ph.EP
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UV能力对于使用下一代Space Telescopes识别有人居住的系外行星的重要性

The Importance of UV Capabilities for Identifying Inhabited Exoplanets with Next Generation Space Telescopes

Edward Schwieterman, Christopher Reinhard, Stephanie Olson, Timothy Lyons

摘要:

当今地球上最强的可远程探测的生命特征是大气中光合作用产生的氧气(O2)。然而,最近对地球地球化学代用记录的研究表明,除了过去的5亿年外,大气中的O2对远程观测者来说是无法检测到的,因此可能是生命的假阴性。在地球历史中期(20 - 7亿年前,Ga)的很长一段时间内,O2可能存在,但浓度较低,pO 2估计为现今水平的0.1 - 1%。虽然O2在这些低丰度下具有微弱的光谱影响,但与O2处于光化学平衡的O3将在UV Hartley-Huggins波段(~0.25 um)中产生显著的光谱特征,在9.7 um附近的中红外波段中具有较弱的影响。因此,以地球历史为例,很可能存在一类系外行星,其常规生物特征只能在紫外线中识别。在本文中,我们强调了紫外能力的重要性,在未来的空间直接成像望远镜,如HabEx或LUVOIR检测O3的行星上的中间氧化状态的设计。我们还讨论了缓解“假阳性”的策略-即非生物过程产生的O3。更一般地说,这个具体的例子突出了研究地球历史作为了解潜在系外行星生物特征的窗口的广泛意义。

英文摘要:

The strongest remotely detectable signature of life on our planet today is the photosynthetically produced oxygen (O2) in our atmosphere. However, recent studies of Earth's geochemical proxy record suggest that for all but the last ~500 million years, atmospheric O2 would have been undetectable to a remote observer--and thus a potential false negative for life. During an extended period in Earth's middle history (2.0 - 0.7 billion years ago, Ga), O2 was likely present but in low concentrations, with pO2 estimates of ~0.1 - 1% of present day levels. Although O2 has a weak spectral impact at these low abundances, O3 in photochemical equilibrium with that O2 would produce notable spectral features in the UV Hartley-Huggins band (~0.25 um), with a weaker impact in the mid-IR band near 9.7 um. Thus, taking Earth history as an informative example, there likely exists a category of exoplanets for which conventional biosignatures can only be identified in the UV. In this paper, we emphasize the importance of UV capabilities in the design of future space-based direct imaging telescopes such as HabEx or LUVOIR to detect O3 on planets with intermediate oxygenation states. We also discuss strategies for mitigating against 'false positives'--that is, O3 produced by abiotic processes. More generally, this specific example highlights the broad implications of studying Earth history as a window into understanding potential exoplanet biosignatures.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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