论文标题
天体生物学哥白尼弱和强大的限制外星智能生活
The Astrobiological Copernican Weak and Strong Limits for Extraterrestrial Intelligent Life
论文作者
论文摘要
我们通过利用最新的天体物理学信息来介绍寻找生活的宇宙观点，并研究我们银河系中可能的交流外智能文明（CETI）的数量。我们的计算涉及银河恒星形成历史，金属性分布以及恒星在宜居区中托管类似地球行星的可能性，在我们描述为天文生物学哥白尼薄弱和较强条件下的特定假设下。这些假设是基于一种情况，即在我们自己的星球上已知存在智能，交流生活。这种类型的生活已经在金属丰富的环境中发展起来，大约需要5 Gyr来做到这一点。我们根据不同情况研究了可能的CETI数量。在一个极端是天体生物学的哥白尼原理 - 使得行星在5 GYR之后的某个时候形成聪明的生活，但并非更早。另一种是强烈的状况，在地球上，生命必须在4.5至5.5 Gyr之间形成。在强烈的状态（严格的假设）中，我们的银河系中应至少有36美元{ - 32}^{+175} $文明：这是一个下限，基于以下假设：一个通信文明的平均寿命为L，是100年（目前是我们本身）。如果在整个银河系中均匀扩散，这意味着最近的CETI最多是17000 $ _ { - 10000}^{+33600} $ LIGHT年，并且很可能由低质量的M-Warf Star托管，远远超过了我们在可预见的未来中检测到它的能力。此外，这一生的主人是太阳能型明星的可能性非常小，大多数人必须是M-warfs，这可能不够稳定，无法在长时间的时间内托管生活。我们还探索了其他场景，并根据我们的假设的变化来解释我们银河系中的CETI数量。
We present a cosmic perspective on the search for life and examine the likely number of Communicating Extra-Terrestrial Intelligent civilizations (CETI) in our Galaxy by utilizing the latest astrophysical information. Our calculation involves Galactic star-formation histories, metallicity distributions, and the likelihood of stars hosting Earth-like planets in Habitable Zones, under specific assumptions which we describe as the Astrobiological Copernican Weak and Strong conditions. These assumptions are based on the one situation in which intelligent, communicative life is known to exist - on our own planet. This type of life has developed in a metal-rich environment and has taken roughly 5 Gyr to do so. We investigate the possible number of CETI based on different scenarios. At one extreme is the Weak Astrobiological Copernican principle - such that a planet forms intelligent life sometime after 5 Gyr, but not earlier. The other is the Strong Condition in which life must form between 4.5 to 5.5 Gyr, as on Earth. In the Strong Condition (a strict set of assumptions), there should be at least 36$_{-32}^{+175}$ civilizations within our Galaxy: this is a lower limit, based on the assumption that the average life-time, L, of a communicating civilization is 100 years (based on our own at present). If spread uniformly throughout the Galaxy this would imply that the nearest CETI is at most 17000$_{-10000}^{+33600}$ light-years away, and most likely hosted by a low-mass M-dwarf star, far surpassing our ability to detect it for the foreseeable future. Furthermore, the likelihood that the host stars for this life are solar-type stars is extremely small and most would have to be M-dwarfs, which may not be stable enough to host life over long timescales. We furthermore explore other scenarios and explain the likely number of CETI there are within our Galaxy based on variations of our assumptions.
