據(jù)國外媒體報道,，多年前世界末日預言者曾預言，稱一顆未探測到的同伴恒星將周期性地向地球釋放彗星,，像宇宙時鐘一樣周期性地導致地球物種大滅絕,。目前，一位天文學家已掌握確鑿證據(jù),，并聲稱彗星或者小行星周期性變遷并不存在,。
在最新一項研究中，研究人員指出叫做“涅墨西斯”或者死亡之星的一顆黑暗同伴星體將于2012年碰撞地球,，帶來毀滅性災難,。像其它神秘的2012災難論，涅墨西斯假設論具有一定的科學研究支持：1984年,，古生物學家提議每間隔2700萬年天外星體將對地球構(gòu)成毀滅性災難,。最初認為一顆褐矮星或者紅矮星在太陽系邊境破壞彗星軌道，并將彗星噴射釋放至地球方向,。
“涅墨西斯”具有X行星假設——它有一顆未探測到的行星潛在碰撞地球,，同時，這種假設也與古代瑪雅日歷上的預言相符,。但顯然這種擔憂性完全是臆造的,，瑪雅人“長期計算”的預言僅是一個日歷而已，當時并沒有任何科學工具進行計算分析,。
2010年,，研究人員報道稱，如果鄰近太陽系不遠的“涅墨西斯”的確存在,，那么它并不一定環(huán)繞一個2700萬年的精密運行周期,。這項研究發(fā)表在《皇家天文學會快報》上，并對涅墨西斯假設論描述為“最后的棺材釘”,，但研究人員仍不能解釋為什么地球物種滅絕周期為2700萬年,。美國堪薩斯大學物理學家艾德里安-米勞特稱,，對我而言，”這是一個非常棘手的問題“,。
目前,，德國馬克思-普朗克天文學會研究員哥倫-巴勒-瓊斯稱，米勞特應當不必對此感到頭疼,。他發(fā)表在《皇家天文學會月刊》的分析文章指出,，所謂“涅墨西斯”星體周期性釋放彗星可能僅是一個模型，除非是經(jīng)過統(tǒng)計學人工計算得出該結(jié)論,。
瓊斯在馬克斯-普朗克學會的報道中指出,，人們傾向于發(fā)現(xiàn)并不存在的自然現(xiàn)象，但不幸的是,，一些確鑿的統(tǒng)計分析數(shù)據(jù)顯示出它的弱點,。他觀測了歷史時期地球成坑比率，使用一種替代性方法評估了貝葉斯統(tǒng)計分析法的可能性,。貝葉斯統(tǒng)計分析法提供了統(tǒng)計學的真實性檢測,，該分析排除了簡單的周期性變化。相反,，統(tǒng)計分析數(shù)據(jù)顯示在過去2.5億年以來地球隕坑成坑率逐漸增大,。（生物谷 Bioon.com）
doi:10.1111/j.1365-2966.2011.19112.x
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PMID:
Bayesian time series analysis of terrestrial impact cratering
Bailer‐Jones, C. A. L.
Keywords:methods: data analysis;methods: statistical;Earth;meteorites, meteors, meteoroids;planets and satellites: surfacesABSTRACTGiant impacts by comets and asteroids have probably had an important influence on terrestrial biological evolution. We know of around 180 high‐velocity impact craters on the Earth with ages up to 2400 Myr and diameters up to 300 km. Some studies have identified a periodicity in their age distribution, with periods ranging from 13 to 50 Myr. It has further been claimed that such periods may be causally linked to a periodic motion of the Solar system through the Galactic plane. However, many of these studies suffer from methodological problems, for example misinterpretation of p‐values, overestimation of significance in the periodogram or a failure to consider plausible alternative models. Here I develop a Bayesian method for this problem in which impacts are treated as a stochastic phenomenon. Models for the time variation of the impact probability are defined and the evidence for them in the geological record is compared using Bayes factors. This probabilistic approach obviates the need for ad hoc statistics, and also makes explicit use of the age uncertainties. I find strong evidence for a monotonic decrease in the recorded impact rate going back in time over the past 250 Myr for craters larger than 5 km. The same is found for the past 150 Myr when craters with upper age limits are included. This is consistent with a crater preservation/discovery bias modulating an otherwise constant impact rate. The set of craters larger than 35 km (so less affected by erosion and infilling) and younger than 400 Myr is best explained by a constant impact probability model. A periodic variation in the cratering rate is strongly disfavoured in all data sets. There is also no evidence for a periodicity superimposed on a constant rate or trend, although this more complex signal would be harder to distinguish.
