北京时间 2017 年 5 月 31 日深夜 , LIGO 和 Virgo 科学合作组织举行了一次内部媒体发布会 , 确认了第三次引力波事件。 LIGO 发言人麻省理工学院教授大卫 • 舒梅克首先宣布 aLIGO 发现了来自两个黑洞并合的新引力波事件 GW170104 , 以及本次新发现引力波事件的基本特征。为此 , 我们特邀 LIGO 科学合作组清华团队成员李瑾副教授和范锡龙副教授进行了点评 , 李瑾副教授还对 LIGO 的新闻发布原稿进行了翻译。关于 GW170104, 请见官方主页: http://www.ligo.org/detections/GW170104.php . 自 aLIGO (advanced LIGO) 于 2015 年首次直接探测到双黑洞并合的引力波事件 GW150914 之后 , 紧接着于同年的 12 月又一次探测到新的双黑洞引力波事件 GW151226 。这两次探测共同验证了广义相对论预言引力波存在的正确性 , 并证实了宇宙中的确存在能在宇宙学年龄内并合的双黑洞系统。此次探测到的引力波事件 GW170104 是继前两次探测之后 , aLIGO 又经过改进后探测到的不同质量的双黑洞并合事件 , 相关的结果发表在近期的 Physical Review Letter 期刊上 。此次探测不仅为已观测到的双黑洞 “ 家族 “ 增添了新的成员 , 还拓展了人类观测宇宙的范围 ( 此次引力波源相距地球 30 亿光年 ) 。 与前两次探测相比 , 本次探测具有更深远的物理意义。主要表现在以下几方面 : 本次观测是从 aLIGO 经新一轮性能提升后采集的数据 ( 官方称为 O2 轮数据 ) 中发现了该引力波信号。位于华盛顿州 Hanford 和路易斯安娜州 Livingston 的两台探测器在 2017 年 1 月 4 日同时记录到了这一信号。由于此次的数据质量较好 , 系统灵敏度更高 , 因此在 O2 轮数据开始运行不久就捕获到了来自如此遥远距离的引力波信号。 图 1 aLIGO 第二轮数据采集时间表。图片版权 : LIGO 科学合作团队 第一次观测到双黑洞自旋正方向可以与相互旋转轨道的角动量方向不一致。这一结果可以用来区分双黑洞的起源模型。从此次观测结果来看 , 双黑洞很可能形成于致密的恒星簇中。另外 , 广义相对论预言黑洞自旋会对波形演化产生至关重要的影响。因此 , 通过观测引力波波形进一步对黑洞自旋进行限制将有助于我们理解和检验广义相对论的动力学预言。 图 2 黑洞自旋与双黑洞轨道角动量示意图。图片版权 : LIGO 科学合作团队 图 3 双黑洞环绕、自旋、轨道进动与引力波辐射。图片版权 : LIGO 科学合作团队 根据广义相对论预言 , 引力波不存在色散现象。由于 GW170104 从较远的双黑洞系统传播到地球 , 这将更利于我们测试引力波是否存在色散。结合前两次探测到的引力波 , 这次对色散因子的上限给出了更严格的限制。目前的结果与广义相对论预言的零色散非常吻合。 引力波科学合作组织 仍在不断拓展其探测网络 , 同时继续进行着系统升级 。 相信在不久的将来人类能探测到更多的引力波信号。这不仅为验证广义相对论提供更多的实例 , 还将大大提高人类对宇宙的复合观测能力。 我们期待在 aLIGO 公布的 6 个触发信号中发现更多有趣的问题。 参考文献 B. Abbott, et al. (LIGOScientific Collaboration and Virgo Collaboration), GW170104: Observation of a50-Solar-Mass Binary Black Hole Coalescence at Redshift 0.2, Phys. Rev. Lett. 118,221101 (2017) https://doi.org/10.1103/PhysRevLett.118.221101 http://www.ligo.org 李瑾 , 重庆大学物理学院副教授 ( 硕士生导师 ), 中国引力与相对论天体物理学会会员、 LIGO 科学合作组清华团队成员。 2008 年- 2010 年期间在 LIGO 科学团队 Ringdown 小组中从事数据分析工作 , 2010 年获得博士学位。曾获得中国国家自然科学基金资助。目前的主要研究领域有 : 引力波探测的数据处理、黑洞引力扰动下的引力似正规模辐射。 范锡龙 , 物理学博士。湖北第二师范学院副教授 , LIGO 科学合作组清华团队成员。曾获得中国国家自然科学基金资助。主要研究领域 : 引力波天文学 , 引力波数据处理。 新闻发布会文字版 ( 中英对照 ): LIGO Detects Gravitational Waves for Third Time Results confirm new population of black holes LIGO 第三次直接探测到引力波 这一结果为新的恒星级黑洞的存在提供有力的证据 https://www.ligo.caltech.edu/page/press-release-gw170104 The Laser Interferometer Gravitational-wave Observatory (LIGO) has made a third detection of gravitational waves, ripples in space and time, demonstrating that a new window in astronomy has been firmly opened. As was the case with the first two detections, the waves were generated when two black holes collided to form a larger black hole. 激光干涉引力波天文台第三次成功捕捉到宇宙时空的涟漪-引力波。这项成果将全面开启人类认识宇宙的新窗口。与前两次探测到的引力波信号 (GW150914、GW151226) 类似 , 本次信号来自于双黑洞系统融合为更大质量黑洞过程中释放的引力波。 The newfound black hole, formed by the merger, has a mass about 49 times that of our sun. This fills in a gap between the masses of the two merged black holes detected previously by LIGO, with solar masses of 62 (first detection) and 21 (second detection). 本次观测对应的双黑洞并合组成的新型黑洞质量约为太阳的 49 倍。这刚好介于 LIGO 前两次观测到的双黑洞系统的质量 , 其中第一次观测对应的双黑洞系统质量为太阳质量为 62 倍 , 第二次为太阳质量的 21 倍。 We have further confirmation of the existence of stellar-mass black holes that are larger than 20 solar masses—these are objects we didn't know existed before LIGO detected them, says MIT's David Shoemaker, the newly elected spokesperson for the LIGO Scientific Collaboration (LSC), a body of more than 1,000 international scientists who perform LIGO research together with the European-based Virgo Collaboration. It is remarkable that humans can put together a story, and test it, for such strange and extreme events that took place billions of years ago and billions of light-years distant from us. The entire LIGO and Virgo scientific collaborations worked to put all these pieces together. 作为 LIGO 科学合作组新当选的发言人 , 麻省理工学院的 David Shoemaker 教授谈到 : “ 我们已经进一步证实了质量大于 20 个太阳质量的黑洞的存在 , 这是在 LIGO 观测到相应引力波信号之前我们所不能确定的事情。 ”LIGO 科学合作组是一个拥有一千多名来自世界各国科学家组成的科学合作研究机构 , 他们与欧洲的 Virgo 科学合作组一起进行引力波的联合探测。 The new detection occurred during LIGO's current observing run, which began November 30, 2016, and will continue through the summer. LIGO is an international collaboration with members around the globe. Its observations are carried out by twin detectors—one in Hanford, Washington, and the other in Livingston, Louisiana—operated by Caltech and MIT with funding from the National Science Foundation (NSF). 本次观测到的引力波发生在 LIGO 现阶段观测运行期间 , 该运行从 2016 年 11 月 30 日开始一直采集数据到 2017 年夏季结束。涉及到的两架结构完全相同的探测器位于华盛顿州的 Hanford 和路易斯安娜州的 Livingston, 这两架探测器都由美国自然科学基金 (NSF) 资助。 LIGO made the first-ever direct observation of gravitational waves in September 2015 during its first observing run since undergoing major upgrades in a program called Advanced LIGO. The second detection was made in December 2015. The third detection, called GW170104 and made on January 4, 2017, is described in a new paper accepted for publication in the journal Physical Review Letters. 经过主体升级后的 LIGO 称为高新 LIGO, 即第二代激光干涉引力波天文台。在 Advanced LIGO 在开始第一轮数据观测期间 , 就第一次成功捕捉到了来自于双黑洞系统融合过程释放的引力波信号 , 该信号被观测到的时间为 2015 年 9 月。紧接着在同年 12 月 , 它第二次检测到了另一双黑洞源释放的引力波信号。第三次于今年 1 月 4 日观测到 , 命名为 GW170104 。针对这一结果 , LIGO 科学合作小组 (LSC) 共同撰写了一篇论文 , 在 Physical Review Letters 期刊上发表。 In all three cases, each of the twin detectors of LIGO detected gravitational waves from the tremendously energetic mergers of black hole pairs. These are collisions that produce more power than is radiated as light by all the stars and galaxies in the universe at any given time. The recent detection appears to be the farthest yet, with the black holes located about 3 billion light-years away. (The black holes in the first and second detections are located 1.3 and 1.4 billion light-years away, respectively.) 在这三次探测中 , LIGO 的每一个探测器都能直接观测从双黑洞融合瞬间释放的引力波。这种引力辐射比宇宙中所有发光星体以及星系在相同时间内的光辐射还要强。最近这次观测到的双黑洞系统所处的位置最远 , 它距离地球约 30 亿光年 ( 第一次和第二次观测到的黑洞距离地球分别为 13 和 14 亿光年 ) 。 The newest observation also provides clues about the directions in which the black holes are spinning. As pairs of black holes spiral around each other, they also spin on their own axes—like a pair of ice skaters spinning individually while also circling around each other. Sometimes black holes spin in the same overall orbital direction as the pair is moving—what astronomers refer to as aligned spins—and sometimes they spin in the opposite direction of the orbital motion. What's more, black holes can also be tilted away from the orbital plane. Essentially, black holes can spin in any direction. 最新的观测结果进一步给出了与双黑洞相互旋转以及自旋方向有关的参数。由于双黑洞系统中的两成员彼此旋转 , 同时它们具有自旋 , 这如同一对在冰上各自旋转又绕着彼此旋转的滑冰运动员。双黑洞系统中单个黑洞的自旋方向有时与两者相互旋转轨道的旋转方向一致 —— 天文学家称之为平行自旋 , 有时它们的自旋与轨道旋转方向相反 —— 这被称为反平行自旋。此外 , 黑洞自旋平面也可以与轨道平面倾斜。一般而言 , 黑洞可以在任何方向上自旋。 The new LIGO data cannot determine if the recently observed black holes were tilted but they imply that at least one of the black holes may have been non-aligned compared to the overall orbital motion. More observations with LIGO are needed to say anything definitive about the spins of binary black holes, but these early data offer clues about how these pairs may form. 新的 LIGO 数据无法确定最近观测到的双黑洞的自旋正方向是否倾斜 , 但是它们可以显示出与相互旋转轨道运动方向是否一致或相反 , 并且能提供如何形成这一现象的依据。要想更加明确地给出双黑洞自旋的任何信息需要更多的被 LIGO 观测到的双黑洞引力波事件 , 但这些早期的数据可以为寻求双黑洞形成机制提供线索。 This is the first time that we have evidence that the black holes may not be aligned, giving us just a tiny hint that binary black holes may form in dense stellar clusters, says Bangalore Sathyaprakash of Penn State and Cardiff University, one of the editors of the new paper, which is authored by the entire LSC and Virgo Collaborations. 作为该论文的主要作者之一的宾夕法尼亚州立大学和加迪夫大学的教授 Bangalore Sathyaprakash 说 : “ 这是我们第一次有证据表明黑洞可能为反向旋转型 , 这给我们一个暗示 , 双黑洞系统可能在密集的恒星簇中形成。 ” There are two primary models to explain how binary pairs of black holes can be formed. The first model proposes that the black holes are born together: they form when each star in a pair of stars explodes, and then, because the original stars were spinning in alignment, the black holes likely remain aligned. 目前 , 对于双黑洞的形成有两个主流的模型来解释。在第一个模型中 , 处于稠密恒星簇中的黑洞在其生命后期会逐渐聚集到一起。当它们陷入星簇中心后就形成了双黑洞系统。在这种情况下 , 黑洞的自旋可以在任何方向。 In the other model, the black holes come together later in life within crowded stellar clusters. The black holes pair up after they sink to the center of a star cluster. In this scenario, the black holes can spin in any direction relative to their orbital motion. Because LIGO sees some evidence that the GW170104 blackholes are non-aligned, the data slightly favor this dense stellar cluster theory. 另一种模型预言双黑洞是同时诞生的 : 它们形成于双星系统塌缩 , 由于最初的双星具有同向自旋 , 因此产生的双黑洞系统应该也具有同向自旋特征。从 LIGO 最新一次的探测结果来看 , GW170104 引力波信号反映出相应的双黑洞系统具有反向自旋。这样 , 貌似前一种模型 ( 致密恒星簇模型 ) 与实验更相符。 We're starting to gather real statistics on binary black hole systems, says Keita Kawabe of Caltech, also an editor of the paper, who is based at the LIGO Hanford Observatory. That's interesting because some models of black hole binary formation are somewhat favored over the others even now and, in the future, we can further narrow this down. 该论文的另一位作者 , 加州理工学院的资深科学家 Keita Kawabe 谈到 “ 最近我们开始收集关于双黑洞系统的真实统计数据。这很有趣 , 因为目前有一些双黑洞系统的形成过程更倾向于另一些理论模型。通过类似的引力波观测 , 将来我们可以进一步筛选出合理的理论模型。 The study also once again puts Albert Einstein's theories to the test. For example, the researchers looked for an effect called dispersion, which occurs when light waves in a physical medium such as glass travel at different speeds depending on their wavelength; this is how a prism creates a rainbow. Einstein's general theory of relativity forbids dispersion from happening in gravitational waves as they propagate from their source to Earth. LIGO did not find evidence for this effect. 这项研究能再次通过实验来验证爱因斯坦的一些理论。 例如 , 研究人员企图寻找一种称为色散的物理效应 , 当自然光进入某种物理介质如玻璃后 , 不同波长的光波以不同的速度在介质中传播就会产生色散效应。这就是棱镜将白光分成彩虹色的过程。 爱因斯坦在广义相对论中预言 , 当引力波从波源传播到地球时不会产生类似的色散现象。目前 , LIGO 的确没有发现引力波有色散效应的证据。 It looks like Einstein was right—even for this new event, which is about two times farther away than our first detection, says Laura Cadonati of Georgia Tech and the Deputy Spokesperson of the LSC. We can see no deviation from the predictions of general relativity, and this greater distance helps us to make that statement with more confidence. Shoemaker 说 : “ 对于这个新的黑洞事件 , 它的发生地点比我们第一次探测到的波源要远两倍。我们仍然没有找到偏离广义相对论的结果 , 更大的距离使我们能够更有信心地认为爱因斯坦的理论看来是正确的。 ” “The LIGO instruments have reached impressive sensitivities,” notes Jo van den Brand, the Virgo Collaboration spokesperson, a physicist at the Dutch National Institute for Subatomic Physics (Nikhef) and professor at VU University in Amsterdam. We expect that by this summer Virgo, the European interferometer, will expand the network of detectors, helping us to better localize the signals.” 荷兰国家亚原子物理研究所 (Nikhef) 的物理学家 , 阿姆斯特丹 VU 大学的教授 , Virgo 团队发言人 Jo van den Brand 表示 : “LIGO 探测器的灵敏度已经达到惊人的程度。我们预计到今年夏天 , Virgo, 欧洲激光干涉仪 , 将扩大联合探测网络 , 帮助我们更好地对信号进行定位。 The LIGO-Virgo team is continuing to search the latest LIGO data for signs of space-time ripples from the far reaches of the cosmos. They are also working on technical upgrades for LIGO's next run, scheduled to begin in late 2018, during which the detectors' sensitivity will be improved. LIGO-Virgo 科学家们将继续从最新的 LIGO 数据中搜索宇宙中更遥远地方传来的引力波信号。 同时 , 他们将于 2018 年年底开始为 LIGO 的下一次运行进行技术升级 , 届时探测器的灵敏度将得到进一步提高。 With the third confirmed detection of gravitational waves from the collision of two black holes, LIGO is establishing itself as a powerful observatory for revealing the dark side of the universe, says David Reitze of Caltech, executive director of the LIGO Laboratory. While LIGO is uniquely suited to observing these types of events, we hope to see other types of astrophysical events soon, such as the violent collision of two neutron stars. LIGO 天文台负责人 David Reitze 说 : “ 通过第三次明确探测到由两个黑洞碰撞产生的引力波 , LIGO 逐步建立起探索宇宙黑暗区域的强大观测能力。虽然 LIGO 对观测双黑洞碰撞产生引力波这类事件比较敏感 , 但我们仍希望将来它能观测到其他类型的天体物理事件 , 例如两个中子星的碰撞。 ” LIGO is funded by the National Science Foundation (NSF), and operated by MIT and Caltech, which conceived and built the project. Financial support for the Advanced LIGO project was led by NSF with Germany (Max Planck Society), the U.K. (Science and Technology Facilities Council) and Australia (Australian Research Council) making significant commitments and contributions to the project. Morethan 1,000 scientists from around the world participate in the effort through the LIGO Scientific Collaboration, which includes the GEO Collaboration. LIGO partners with the Virgo Collaboration, a consortium including 280 additional scientists throughout Europe supported by the Centre National de la Recherche Scientifique (CNRS), the Istituto Nazionale di Fisica Nucleare (INFN), and Nikhef, as wellas Virgo’s host institution, the European Gravitational Observatory. Additional partners are listed at: http://ligo.org/partners.php . LIGO 由 NSF 资助 , 由加州理工学院和麻省理工学院经营、负责构建和建造该项目。来自世界各地的 1000 多名科学家通过 LIGO 科学合作组参与该项目具体工作 , 包括 GEO 。 LIGO 与 Virgo 合作 , 将另外的 280 位欧洲科学家联合起来 , 得到了包括欧洲国家科学中心 (CNRS), 国际自然科学基金委员会 (INFN) 和 Virgo 主体机构及欧洲重力观测站的资助。其他合作伙伴参见 : http://ligo.org/partners.php 。 相关阅读: 《中国科学》出版引力波天文学英文学术专题 最新学术类解读引力波直接探测事件的论文 LIGO负责人David Reitze教授在SCPMA发表引力波综述文章 订阅《中国科学: 物理学 力学 天文学》微信公众号 , 手机同步关注最新热点文章、新闻、科技资讯 , 请添加微信号 SCPMA2014 或扫描下方图片关注.
国际性合作的结晶: LIGO 第三次观测到引力波 诸平 据麻省理工学院( Massachusetts Institute of Technology ) 2017 年 6 月 1 日提供的消息, 激光干涉引力波天文台( LIGO ) 国际性 科学家 研究 团队 , 2017 年 6 月 2 日在《 物理评论快报 》 ( Physical Review Letters ) 网站 发 表 文章 , 声称 他们第三次探测到了引力波。此次探测结果不仅再次验证了广义相对论,也为了解双黑洞系统的成因提供了线索。 参与此项研究的是多国科学家合作的结晶,其中包括中国清华大学的科学家,既有北京清华大学的研究者,也有台湾新竹清华大学的研究者。仅合作单位就要 170 余家,合作科学家人数众多,非常罕见。但是,对于如此庞大的国际性合作研究团队的研究成果,也有不同的看法,详见 “吴中祥老师的博文: LIGO 3 次探测的两个黑洞合并产生的都只能是光波 ”。将 《 物理评论快报 》发表论文的 部分合作单位翻译如下 ,仅供参考,更多信息请注意浏览原文( 点击论文标题可以免费下载原文 ): B. P. Abbott, R. Abbott, T. D. Abbott, F. Acernese, K. Ackley, C. Adams, T. Adams, P. Addesso, R. X. Adhikari, et al . GW170104: Observation of a 50-Solar-Mass Binary Black Hole Coalescence at Redshift 0.2 ( 点击论文标题可以免费下载原文 ) . Phys. Rev. Lett. 118, 221101 – Published 1 June 2017 . DOI: https://doi.org/10.1103/PhysRevLett.118.221101 ABSTRACT We describe the observation of GW170104, a gravitational-wave signal produced by the coalescence of a pair of stellar-mass black holes. The signal was measured on January 4, 2017 at 10∶11:58.6 UTC by the twin advanced detectors of the Laser Interferometer Gravitational-Wave Observatory during their second observing run, with a network signal-to-noise ratio of 13 and a false alarm rate less than 1 in 70 000 years. The inferred component black hole masses are 31. 2 + 8.4 − 6.0 M ⊙ and 19. 4 + 5.3 − 5.9 M ⊙ (at the 90% credible level). The black hole spins are best constrained through measurement of the effective inspiral spin parameter, a mass-weighted combination of the spin components perpendicular to the orbital plane, χ eff = − 0.1 2 + 0.21 − 0.30 . This result implies that spin configurations with both component spins positively aligned with the orbital angular momentum are disfavored. The source luminosity distance is 88 0 + 450 − 390 Mpc corresponding to a redshift of z = 0.1 8 + 0.08 − 0.07 . We constrain the magnitude of modifications to the gravitational-wave dispersion relation and perform null tests of general relativity. Assuming that gravitons are dispersed in vacuum like massive particles, we bound the graviton mass to m g ≤ 7.7 × 10 − 23 eV / c 2 . In all cases, we find that GW170104 is consistent with general relativity. Received 9 May 2017 DOI: https://doi.org/10.1103/PhysRevLett.118.221101 庞大的科研团队: B. P. Abbott 1 , R. Abbott 1 , T. D. Abbott 2 , F. Acernese 3,4 , K. Ackley 5 , C. Adams 6 , T. Adams 7 , P. Addesso 8 , R. X. Adhikari 1 , V. B. Adya 9 , C. Affeldt 9 , M. Afrough 10 , B. Agarwal 11 , M. Agathos 12 , K. Agatsuma 13 , N. Aggarwal 14 , O. D. Aguiar 15 , L. Aiello 16,17 , A. Ain 18 , P. Ajith 19 , B. Allen 9,20,21 , G. Allen 11 , A. Allocca 22,23 , P. A. Altin 24 , A. Amato 25 , A. Ananyeva 1 , S. B. Anderson 1 , W. G. Anderson 20 , S. Antier 26 , S. Appert 1 , K. Arai 1 , M. C. Araya 1 , J. S. Areeda 27 , N. Arnaud 26,28 , K. G. Arun 29 , S. Ascenzi 30,17 , G. Ashton 9 , M. Ast 31 , S. M. Aston 6 , P. Astone 32 , P. Aufmuth 21 , C. Aulbert 9 , K. AultONeal 33 , A. Avila-Alvarez 27 , S. Babak 34 , P. Bacon 35 , M. K. M. Bader 13 , S. Bae 36 , P. T. Baker 37,38 , F. Baldaccini 39,40 , G. Ballardin 28 , S. W. Ballmer 41 , S. Banagiri 42 , J. C. Barayoga 1 , S. E. Barclay 43 , B. C. Barish 1 , D. Barker 44 , F. Barone 3,4 , B. Barr 43 , L. Barsotti 14 , M. Barsuglia 35 , D. Barta 45 , J. Bartlett 44 , I. Bartos 46 , R. Bassiri 47 , A. Basti 22,23 , J. C. Batch 44 , C. Baune 9 , M. Bawaj 48,40 , M. Bazzan 49,50 , B. Bécsy 51 , C. Beer 9 , M. Bejger 52 , I. Belahcene 26 , A. S. Bell 43 , B. K. Berger 1 , G. Bergmann 9 , C. P. L. Berry 53 , D. Bersanetti 54,55 , A. Bertolini 13 , J. Betzwieser 6 , S. Bhagwat 41 , R. Bhandare 56 , I. A. Bilenko 57 , G. Billingsley 1 , C. R. Billman 5 , J. Birch 6 , R. Birney 58 , O. Birnholtz 9 , S. Biscans 14 , A. Bisht 21 , M. Bitossi 28,23 , C. Biwer 41 , M. A. Bizouard 26 , J. K. Blackburn 1 , J. Blackman 59 , C. D. Blair 60 , D. G. Blair 60 , R. M. Blair 44 , S. Bloemen 61 , O. Bock 9 , N. Bode 9 , M. Boer 62 , G. Bogaert 62 , A. Bohe 34 , F. Bondu 63 , R. Bonnand 7 , B. A. Boom 13 , R. Bork 1 , V. Boschi 22,23 , S. Bose 64,18 , Y. Bouffanais 35 , A. Bozzi 28 , C. Bradaschia 23 , P. R. Brady 20 , V. B. Braginsky 57,* , M. Branchesi 65,66 , J. E. Brau 67 , T. Briant 68 , A. Brillet 62 , M. Brinkmann 9 , V. Brisson 26 , P. Brockill 20 , J. E. Broida 69 , A. F. Brooks 1 , D. A. Brown 41 , D. D. Brown 53 , N. M. Brown 14 , S. Brunett 1 , C. C. Buchanan 2 , A. Buikema 14 , T. Bulik 70 , H. J. Bulten 71,13 , A. Buonanno 34,72 , D. Buskulic 7 , C. Buy 35 , R. L. Byer 47 , M. Cabero 9 , L. Cadonati 73 , G. Cagnoli 25,74 , C. Cahillane 1 , J. Calderón Bustillo 73 , T. A. Callister 1 , E. Calloni 75,4 , J. B. Camp 76 , M. Canepa 54,55 , P. Canizares 61 , K. C. Cannon 77 , H. Cao 78 , J. Cao 79 , C. D. Capano 9 , E. Capocasa 35 , F. Carbognani 28 , S. Caride 80 , M. F. Carney 81 , J. Casanueva Diaz 26 , C. Casentini 30,17 , S. Caudill 20 , M. Cavaglià 10 , F. Cavalier 26 , R. Cavalieri 28 , G. Cella 23 , C. B. Cepeda 1 , L. Cerboni Baiardi 65,66 , G. Cerretani 22,23 , E. Cesarini 30,17 , S. J. Chamberlin 82 , M. Chan 43 , S. Chao 83 , P. Charlton 84 , E. Chassande-Mottin 35 , D. Chatterjee 20 , K. Chatziioannou 85 , B. D. Cheeseboro 37,38 , H. Y. Chen 86 , Y. Chen 59 , H.-P. Cheng 5 , A. Chincarini 55 , A. Chiummo 28 , T. Chmiel 81 , H. S. Cho 87 , M. Cho 72 , J. H. Chow 24 , N. Christensen 69,62 , Q. Chu 60 , A. J. K. Chua 12 , S. Chua 68 , A. K. W. Chung 88 , S. Chung 60 , G. Ciani 5 , R. Ciolfi 89,90 , C. E. Cirelli 47 , A. Cirone 54,55 , F. Clara 44 , J. A. Clark 73 , F. Cleva 62 , C. Cocchieri 10 , E. Coccia 16,17 , P.-F. Cohadon 68 , A. Colla 91,32 , C. G. Collette 92 , L. R. Cominsky 93 , M. Constancio, Jr. 15 , L. Conti 50 , S. J. Cooper 53 , P. Corban 6 , T. R. Corbitt 2 , K. R. Corley 46 , N. Cornish 94 , A. Corsi 80 , S. Cortese 28 , C. A. Costa 15 , M. W. Coughlin 69 , S. B. Coughlin 95,96 , J.-P. Coulon 62 , S. T. Countryman 46 , P. Couvares 1 , P. B. Covas 97 , E. E. Cowan 73 , D. M. Coward 60 , M. J. Cowart 6 , D. C. Coyne 1 , R. Coyne 80 , J. D. E. Creighton 20 , T. D. Creighton 98 , J. Cripe 2 , S. G. Crowder 99 , T. J. Cullen 27 , A. Cumming 43 , L. Cunningham 43 , E. Cuoco 28 , T. Dal Canton 76 , S. L. Danilishin 21,9 , S. D’Antonio 17 , K. Danzmann 21,9 , A. Dasgupta 100 , C. F. Da Silva Costa 5 , V. Dattilo 28 , I. Dave 56 , M. Davier 26 , D. Davis 41 , E. J. Daw 101 , B. Day 73 , S. De 41 , D. DeBra 47 , E. Deelman 102 , J. Degallaix 25 , M. De Laurentis 75,4 , S. Deléglise 68 , W. Del Pozzo 53,22,23 , T. Denker 9 , T. Dent 9 , V. Dergachev 34 , R. De Rosa 75,4 , R. T. DeRosa 6 , R. DeSalvo 103 , J. Devenson 58 , R. C. Devine 37,38 , S. Dhurandhar 18 , M. C. Díaz 98 , L. Di Fiore 4 , M. Di Giovanni 104,90 , T. Di Girolamo 75,4,46 , A. Di Lieto 22,23 , S. Di Pace 91,32 , I. Di Palma 91,32 , F. Di Renzo 22,23 , Z. Doctor 86 , V. Dolique 25 , F. Donovan 14 , K. L. Dooley 10 , S. Doravari 9 , I. Dorrington 96 , R. Douglas 43 , M. Dovale álvarez 53 , T. P. Downes 20 , M. Drago 9 , R. W. P. Drever 1,† , J. C. Driggers 44 , Z. Du 79 , M. Ducrot 7 , J. Duncan 95 , S. E. Dwyer 44 , T. B. Edo 101 , M. C. Edwards 69 , A. Effler 6 , H.-B. Eggenstein 9 , P. Ehrens 1 , J. Eichholz 1 , S. S. Eikenberry 5 , R. A. Eisenstein 14 , R. C. Essick 14 , Z. B. Etienne 37,38 , T. Etzel 1 , M. Evans 14 , T. M. Evans 6 , M. Factourovich 46 , V. Fafone 30,17,16 , H. Fair 41 , S. Fairhurst 96 , X. Fan 79 , S. Farinon 55 , B. Farr 86 , W. M. Farr 53 , E. J. Fauchon-Jones 96 , M. Favata 105 , M. Fays 96 , H. Fehrmann 9 , J. Feicht 1 , M. M. Fejer 47 , A. Fernandez-Galiana 14 , I. Ferrante 22,23 , E. C. Ferreira 15 , F. Ferrini 28 , F. Fidecaro 22,23 , I. Fiori 28 , D. Fiorucci 35 , R. P. Fisher 41 , R. Flaminio 25,106 , M. Fletcher 43 , H. Fong 85 , P. W. F. Forsyth 24 , S. S. Forsyth 73 , J.-D. Fournier 62 , S. Frasca 91,32 , F. Frasconi 23 , Z. Frei 51 , A. Freise 53 , R. Frey 67 , V. Frey 26 , E. M. Fries 1 , P. Fritschel 14 , V. V. Frolov 6 , P. Fulda 5,76 , M. Fyffe 6 , H. Gabbard 9 , M. Gabel 107 , B. U. Gadre 18 , S. M. Gaebel 53 , J. R. Gair 108 , L. Gammaitoni 39 , M. R. Ganija 78 , S. G. Gaonkar 18 , F. Garufi 75,4 , S. Gaudio 33 , G. Gaur 109 , V. Gayathri 110 , N. Gehrels 76,‡ , G. Gemme 55 , E. Genin 28 , A. Gennai 23 , D. George 11 , J. George 56 , L. Gergely 111 , V. Germain 7 , S. Ghonge 73 , Abhirup Ghosh 19 , Archisman Ghosh 19,13 , S. Ghosh 61,13 , J. A. Giaime 2,6 , K. D. Giardina 6 , A. Giazotto 23 , K. Gill 33 , L. Glover 103 , E. Goetz 9 , R. Goetz 5 , S. Gomes 96 , G. González 2 , J. M. Gonzalez Castro 22,23 , A. Gopakumar 112 , M. L. Gorodetsky 57 , S. E. Gossan 1 , M. Gosselin 28 , R. Gouaty 7 , A. Grado 113,4 , C. Graef 43 , M. Granata 25 , A. Grant 43 , S. Gras 14 , C. Gray 44 , G. Greco 65,66 , A. C. Green 53 , P. Groot 61 , H. Grote 9 , S. Grunewald 34 , P. Gruning 26 , G. M. Guidi 65,66 , X. Guo 79 , A. Gupta 82 , M. K. Gupta 100 , K. E. Gushwa 1 , E. K. Gustafson 1 , R. Gustafson 114 , B. R. Hall 64 , E. D. Hall 1 , G. Hammond 43 , M. Haney 112 , M. M. Hanke 9 , J. Hanks 44 , C. Hanna 82 , M. D. Hannam 96 , O. A. Hannuksela 88 , J. Hanson 6 , T. Hardwick 2 , J. Harms 65,66 , G. M. Harry 115 , I. W. Harry 34 , M. J. Hart 43 , C.-J. Haster 85 , K. Haughian 43 , J. Healy 116 , A. Heidmann 68 , M. C. Heintze 6 , H. Heitmann 62 , P. Hello 26 , G. Hemming 28 , M. Hendry 43 , I. S. Heng 43 , J. Hennig 43 , J. Henry 116 , A. W. Heptonstall 1 , M. Heurs 9,21 , S. Hild 43 , D. Hoak 28 , D. Hofman 25 , K. Holt 6 , D. E. Holz 86 , P. Hopkins 96 , C. Horst 20 , J. Hough 43 , E. A. Houston 43 , E. J. Howell 60 , Y. M. Hu 9 , E. A. Huerta 11 , D. Huet 26 , B. Hughey 33 , S. Husa 97 , S. H. Huttner 43 , T. Huynh-Dinh 6 , N. Indik 9 , D. R. Ingram 44 , R. Inta 80 , G. Intini 91,32 , H. N. Isa 43 , J.-M. Isac 68 , M. Isi 1 , B. R. Iyer 19 , K. Izumi 44 , T. Jacqmin 68 , K. Jani 73 , P. Jaranowski 117 , S. Jawahar 118 , F. Jiménez-Forteza 97 , W. W. Johnson 2 , N. K. Johnson-McDaniel 19 , D. I. Jones 119 , R. Jones 43 , R. J. G. Jonker 13 , L. Ju 60 , J. Junker 9 , C. V. Kalaghatgi 96 , V. Kalogera 95 , S. Kandhasamy 6 , G. Kang 36 , J. B. Kanner 1 , S. Karki 67 , K. S. Karvinen 9 , M. Kasprzack 2 , M. Katolik 11 , E. Katsavounidis 14 , W. Katzman 6 , S. Kaufer 21 , K. Kawabe 44 , F. Kéfélian 62 , D. Keitel 43 , A. J. Kemball 11 , R. Kennedy 101 , C. Kent 96 , J. S. Key 120 , F. Y. Khalili 57 , I. Khan 16,17 , S. Khan 9 , Z. Khan 100 , E. A. Khazanov 121 , N. Kijbunchoo 44 , Chunglee Kim 122 , J. C. Kim 123 , W. Kim 78 , W. S. Kim 124 , Y.-M. Kim 87,122 , S. J. Kimbrell 73 , E. J. King 78 , P. J. King 44 , R. Kirchhoff 9 , J. S. Kissel 44 , L. Kleybolte 31 , S. Klimenko 5 , P. Koch 9 , S. M. Koehlenbeck 9 , S. Koley 13 , V. Kondrashov 1 , A. Kontos 14 , M. Korobko 31 , W. Z. Korth 1 , I. Kowalska 70 , D. B. Kozak 1 , C. Krämer 9 , V. Kringel 9 , B. Krishnan 9 , A. Królak 125,126 , G. Kuehn 9 , P. Kumar 85 , R. Kumar 100 , S. Kumar 19 , L. Kuo 83 , A. Kutynia 125 , S. Kwang 20 , B. D. Lackey 34 , K. H. Lai 88 , M. Landry 44 , R. N. Lang 20 , J. Lange 116 , B. Lantz 47 , R. K. Lanza 14 , A. Lartaux-Vollard 26 , P. D. Lasky 127 , M. Laxen 6 , A. Lazzarini 1 , C. Lazzaro 50 , P. Leaci 91,32 , S. Leavey 43 , C. H. Lee 87 , H. K. Lee 128 , H. M. Lee 122 , H. W. Lee 123 , K. Lee 43 , J. Lehmann 9 , A. Lenon 37,38 , M. Leonardi 104,90 , N. Leroy 26 , N. Letendre 7 , Y. Levin 127 , T. G. F. Li 88 , A. Libson 14 , T. B. Littenberg 129 , J. Liu 60 , R. K. L. Lo 88 , N. A. Lockerbie 118 , L. T. London 96 , J. E. Lord 41 , M. Lorenzini 16,17 , V. Loriette 130 , M. Lormand 6 , G. Losurdo 23 , J. D. Lough 9,21 , G. Lovelace 27 , H. Lück 21,9 , D. Lumaca 30,17 , A. P. Lundgren 9 , R. Lynch 14 , Y. Ma 59 , S. Macfoy 58 , B. Machenschalk 9 , M. MacInnis 14 , D. M. Macleod 2 , I. Magaña Hernandez 88 , F. Magaña-Sandoval 41 , L. Magaña Zertuche 41 , R. M. Magee 82 , E. Majorana 32 , I. Maksimovic 130 , N. Man 62 , V. Mandic 42 , V. Mangano 43 , G. L. Mansell 24 , M. Manske 20 , M. Mantovani 28 , F. Marchesoni 48,40 , F. Marion 7 , S. Márka 46 , Z. Márka 46 , C. Markakis 11 , A. S. Markosyan 47 , E. Maros 1 , F. Martelli 65,66 , L. Martellini 62 , I. W. Martin 43 , D. V. Martynov 14 , J. N. Marx 1 , K. Mason 14 , A. Masserot 7 , T. J. Massinger 1 , M. Masso-Reid 43 , S. Mastrogiovanni 91,32 , A. Matas 42 , F. Matichard 14 , L. Matone 46 , N. Mavalvala 14 , R. Mayani 102 , N. Mazumder 64 , R. McCarthy 44 , D. E. McClelland 24 , S. McCormick 6 , L. McCuller 14 , S. C. McGuire 131 , G. McIntyre 1 , J. McIver 1 , D. J. McManus 24 , T. McRae 24 , S. T. McWilliams 37,38 , D. Meacher 82 , G. D. Meadors 34,9 , J. Meidam 13 , E. Mejuto-Villa 8 , A. Melatos 132 , G. Mendell 44 , R. A. Mercer 20 , E. L. Merilh 44 , M. Merzougui 62 , S. Meshkov 1 , C. Messenger 43 , C. Messick 82 , R. Metzdorff 68 , P. M. Meyers 42 , F. Mezzani 32,91 , H. Miao 53 , C. Michel 25 , H. Middleton 53 , E. E. Mikhailov 133 , L. Milano 75,4 , A. L. Miller 5 , A. Miller 91,32 , B. B. Miller 95 , J. Miller 14 , M. Millhouse 94 , O. Minazzoli 62 , Y. Minenkov 17 , J. Ming 34 , C. Mishra 134 , S. Mitra 18 , V. P. Mitrofanov 57 , G. Mitselmakher 5 , R. Mittleman 14 , A. Moggi 23 , M. Mohan 28 , S. R. P. Mohapatra 14 , M. Montani 65,66 , B. C. Moore 105 , C. J. Moore 12 , D. Moraru 44 , G. Moreno 44 , S. R. Morriss 98 , B. Mours 7 , C. M. Mow-Lowry 53 , G. Mueller 5 , A. W. Muir 96 , Arunava Mukherjee 9 , D. Mukherjee 20 , S. Mukherjee 98 , N. Mukund 18 , A. Mullavey 6 , J. Munch 78 , E. A. M. Muniz 41 , P. G. Murray 43 , K. Napier 73 , I. Nardecchia 30,17 , L. Naticchioni 91,32 , R. K. Nayak 135 , G. Nelemans 61,13 , T. J. N. Nelson 6 , M. Neri 54,55 , M. Nery 9 , A. Neunzert 114 , J. M. Newport 115 , G. Newton 43,§ , K. K. Y. Ng 88 , T. T. Nguyen 24 , D. Nichols 61 , A. B. Nielsen 9 , S. Nissanke 61,13 , A. Nitz 9 , A. Noack 9 , F. Nocera 28 , D. Nolting 6 , M. E. N. Normandin 98 , L. K. Nuttall 41 , J. Oberling 44 , E. Ochsner 20 , E. Oelker 14 , G. H. Ogin 107 , J. J. Oh 124 , S. H. Oh 124 , F. Ohme 9 , M. Oliver 97 , P. Oppermann 9 , Richard J. Oram 6 , B. O’Reilly 6 , R. Ormiston 42 , L. F. Ortega 5 , R. O’Shaughnessy 116 , D. J. Ottaway 78 , H. Overmier 6 , B. J. Owen 80 , A. E. Pace 82 , J. Page 129 , M. A. Page 60 , A. Pai 110 , S. A. Pai 56 , J. R. Palamos 67 , O. Palashov 121 , C. Palomba 32 , A. Pal-Singh 31 , H. Pan 83 , B. Pang 59 , P. T. H. Pang 88 , C. Pankow 95 , F. Pannarale 96 , B. C. Pant 56 , F. Paoletti 23 , A. Paoli 28 , M. A. Papa 34,20,9 , H. R. Paris 47 , W. Parker 6 , D. Pascucci 43 , A. Pasqualetti 28 , R. Passaquieti 22,23 , D. Passuello 23 , B. Patricelli 136,23 , B. L. Pearlstone 43 , M. Pedraza 1 , R. Pedurand 25,137 , L. Pekowsky 41 , A. Pele 6 , S. Penn 138 , C. J. Perez 44 , A. Perreca 1,104,90 , L. M. Perri 95 , H. P. Pfeiffer 85 , M. Phelps 43 , O. J. Piccinni 91,32 , M. Pichot 62 , F. Piergiovanni 65,66 , V. Pierro 8 , G. Pillant 28 , L. Pinard 25 , I. M. Pinto 8 , M. Pitkin 43 , R. Poggiani 22,23 , P. Popolizio 28 , E. K. Porter 35 , A. Post 9 , J. Powell 43 , J. Prasad 18 , J. W. W. Pratt 33 , V. Predoi 96 , T. Prestegard 20 , M. Prijatelj 9 , M. Principe 8 , S. Privitera 34 , G. A. Prodi 104,90 , L. G. Prokhorov 57 , O. Puncken 9 , M. Punturo 40 , P. Puppo 32 , M. Pürrer 34 , H. Qi 20 , J. Qin 60 , S. Qiu 127 , V. Quetschke 98 , E. A. Quintero 1 , R. Quitzow-James 67 , F. J. Raab 44 , D. S. Rabeling 24 , H. Radkins 44 , P. Raffai 51 , S. Raja 56 , C. Rajan 56 , M. Rakhmanov 98 , K. E. Ramirez 98 , P. Rapagnani 91,32 , V. Raymond 34 , M. Razzano 22,23 , J. Read 27 , T. Regimbau 62 , L. Rei 55 , S. Reid 58 , D. H. Reitze 1,5 , H. Rew 133 , S. D. Reyes 41 , F. Ricci 91,32 , P. M. Ricker 11 , S. Rieger 9 , K. Riles 114 , M. Rizzo 116 , N. A. Robertson 1,43 , R. Robie 43 , F. Robinet 26 , A. Rocchi 17 , L. Rolland 7 , J. G. Rollins 1 , V. J. Roma 67 , J. D. Romano 98 , R. Romano 3,4 , C. L. Romel 44 , J. H. Romie 6 , D. Rosińska 139,52 , M. P. Ross 140 , S. Rowan 43 , A. Rüdiger 9 , P. Ruggi 28 , K. Ryan 44 , M. Rynge 102 , S. Sachdev 1 , T. Sadecki 44 , L. Sadeghian 20 , M. Sakellariadou 141 , L. Salconi 28 , M. Saleem 110 , F. Salemi 9 , A. Samajdar 135 , L. Sammut 127 , L. M. Sampson 95 , E. J. Sanchez 1 , V. Sandberg 44 , B. Sandeen 95 , J. R. Sanders 41 , B. Sassolas 25 , B. S. Sathyaprakash 82,96 , P. R. Saulson 41 , O. Sauter 114 , R. L. Savage 44 , A. Sawadsky 21 , P. Schale 67 , J. Scheuer 95 , E. Schmidt 33 , J. Schmidt 9 , P. Schmidt 1,61 , R. Schnabel 31 , R. M. S. Schofield 67 , A. Schönbeck 31 , E. Schreiber 9 , D. Schuette 9,21 , B. W. Schulte 9 , B. F. Schutz 96,9 , S. G. Schwalbe 33 , J. Scott 43 , S. M. Scott 24 , E. Seidel 11 , D. Sellers 6 , A. S. Sengupta 142 , D. Sentenac 28 , V. Sequino 30,17 , A. Sergeev 121 , D. A. Shaddock 24 , T. J. Shaffer 44 , A. A. Shah 129 , M. S. Shahriar 95 , L. Shao 34 , B. Shapiro 47 , P. Shawhan 72 , A. Sheperd 20 , D. H. Shoemaker 14 , D. M. Shoemaker 73 , K. Siellez 73 , X. Siemens 20 , M. Sieniawska 52 , D. Sigg 44 , A. D. Silva 15 , A. Singer 1 , L. P. Singer 76 , A. Singh 34,9,21 , R. Singh 2 , A. Singhal 16,32 , A. M. Sintes 97 , B. J. J. Slagmolen 24 , B. Smith 6 , J. R. Smith 27 , R. J. E. Smith 1 , E. J. Son 124 , J. A. Sonnenberg 20 , B. Sorazu 43 , F. Sorrentino 55 , T. Souradeep 18 , A. P. Spencer 43 , A. K. Srivastava 100 , A. Staley 46 , M. Steinke 9 , J. Steinlechner 43,31 , S. Steinlechner 31 , D. Steinmeyer 9,21 , B. C. Stephens 20 , S. P. Stevenson 53 , R. Stone 98 , K. A. Strain 43 , G. Stratta 65,66 , S. E. Strigin 57 , R. Sturani 143 , A. L. Stuver 6 , T. Z. Summerscales 144 , L. Sun 132 , S. Sunil 100 , P. J. Sutton 96 , B. L. Swinkels 28 , M. J. Szczepańczyk 33 , M. Tacca 35 , D. Talukder 67 , D. B. Tanner 5 , M. Tápai 111 , A. Taracchini 34 , J. A. Taylor 129 , R. Taylor 1 , T. Theeg 9 , E. G. Thomas 53 , M. Thomas 6 , P. Thomas 44 , K. A. Thorne 6 , K. S. Thorne 59 , E. Thrane 127 , S. Tiwari 16,90 , V. Tiwari 96 , K. V. Tokmakov 118 , K. Toland 43 , M. Tonelli 22,23 , Z. Tornasi 43 , C. I. Torrie 1 , D. Töyrä 53 , F. Travasso 28,40 , G. Traylor 6 , D. Trifirò 10 , J. Trinastic 5 , M. C. Tringali 104,90 , L. Trozzo 145,23 , K. W. Tsang 13 , M. Tse 14 , R. Tso 1 , D. Tuyenbayev 98 , K. Ueno 20 , D. Ugolini 146 , C. S. Unnikrishnan 112 , A. L. Urban 1 , S. A. Usman 96 , K. Vahi 102 , H. Vahlbruch 21 , G. Vajente 1 , G. Valdes 98 , M. Vallisneri 59 , N. van Bakel 13 , M. van Beuzekom 13 , J. F. J. van den Brand 71,13 , C. Van Den Broeck 13 , D. C. Vander-Hyde 41 , L. van der Schaaf 13 , J. V. van Heijningen 13 , A. A. van Veggel 43 , M. Vardaro 49,50 , V. Varma 59 , S. Vass 1 , M. Vasúth 45 , A. Vecchio 53 , G. Vedovato 50 , J. Veitch 53 , P. J. Veitch 78 , K. Venkateswara 140 , G. Venugopalan 1 , D. Verkindt 7 , F. Vetrano 65,66 , A. Viceré 65,66 , A. D. Viets 20 , S. Vinciguerra 53 , D. J. Vine 58 , J.-Y. Vinet 62 , S. Vitale 14 , T. Vo 41 , H. Vocca 39,40 , C. Vorvick 44 , D. V. Voss 5 , W. D. Vousden 53 , S. P. Vyatchanin 57 , A. R. Wade 1 , L. E. Wade 81 , M. Wade 81 , R. M. Wald 86 , R. Walet 13 , M. Walker 2 , L. Wallace 1 , S. Walsh 20 , G. Wang 16,66 , H. Wang 53 , J. Z. Wang 82 , M. Wang 53 , Y.-F. Wang 88 , Y. Wang 60 , R. L. Ward 24 , J. Warner 44 , M. Was 7 , J. Watchi 92 , B. Weaver 44 , L.-W. Wei 9,21 , M. Weinert 9 , A. J. Weinstein 1 , R. Weiss 14 , L. Wen 60 , E. K. Wessel 11 , P. Weßels 9 , T. Westphal 9 , K. Wette 9 , J. T. Whelan 116 , B. F. Whiting 5 , C. Whittle 127 , D. Williams 43 , R. D. Williams 1 , A. R. Williamson 116 , J. L. Willis 147 , B. Willke 21,9 , M. H. Wimmer 9,21 , W. Winkler 9 , C. C. Wipf 1 , H. Wittel 9,21 , G. Woan 43 , J. Woehler 9 , J. Wofford 116 , K. W. K. Wong 88 , J. Worden 44 , J. L. Wright 43 , D. S. Wu 9 , G. Wu 6 , W. Yam 14 , H. Yamamoto 1 , C. C. Yancey 72 , M. J. Yap 24 , Hang Yu 14 , Haocun Yu 14 , M. Yvert 7 , A. Zadrożny 125 , M. Zanolin 33 , T. Zelenova 28 , J.-P. Zendri 50 , M. Zevin 95 , L. Zhang 1 , M. Zhang 133 , T. Zhang 43 , Y.-H. Zhang 116 , C. Zhao 60 , M. Zhou 95 , Z. Zhou 95 , X. J. Zhu 60 , A. Zimmerman 85 , M. E. Zucker 1,14 , and J. Zweizig 1 (LIGO Scientific and Virgo Collaboration) 作者单位近150家: 1 LIGO, California Institute of Technology, Pasadena, California 91125, USA 2 Louisiana State University, Baton Rouge, Louisiana 70803, USA 3 Università di Salerno, Fisciano, I-84084 Salerno, Italy 4 INFN, Sezione di Napoli, Complesso Universitario di Monte S. Angelo, I-80126 Napoli, Italy 5 University of Florida, Gainesville, Florida 32611, USA 6 LIGO Livingston Observatory, Livingston, Louisiana 70754, USA 7 Laboratoire d’Annecy-le-Vieux de Physique des Particules (LAPP), Université Savoie Mont Blanc, CNRS/IN2P3, F-74941 Annecy, France 8 University of Sannio at Benevento, I-82100 Benevento, Italy and INFN, Sezione di Napoli, I-80100 Napoli, Italy 9 Albert-Einstein-Institut, Max-Planck-Institut für Gravitationsphysik, D-30167 Hannover, Germany 10 The University of Mississippi, University, Mississippi 38677, USA 11 NCSA, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA 12 University of Cambridge, Cambridge CB2 1TN, United Kingdom 13 Nikhef, Science Park, 1098 XG Amsterdam, Netherlands 14 LIGO, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA 15 Instituto Nacional de Pesquisas Espaciais, 12227-010 São José dos Campos, São Paulo, Brazil 16 Gran Sasso Science Institute (GSSI), I-67100 L’Aquila, Italy 17 INFN, Sezione di Roma Tor Vergata, I-00133 Roma, Italy 18 Inter-University Centre for Astronomy and Astrophysics, Pune 411007, India 19 International Centre for Theoretical Sciences, Tata Institute of Fundamental Research, Bengaluru 560089, India 20 University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201, USA 21 Leibniz Universität Hannover, D-30167 Hannover, Germany 22 Università di Pisa, I-56127 Pisa, Italy 23 INFN, Sezione di Pisa, I-56127 Pisa, Italy 24 OzGrav, Australian National University, Canberra, Australian Capital Territory 0200, Australia 25 Laboratoire des Matériaux Avancés (LMA), CNRS/IN2P3, F-69622 Villeurbanne, France 26 LAL, Univ. Paris-Sud, CNRS/IN2P3, Université Paris-Saclay, F-91898 Orsay, France 27 California State University Fullerton, Fullerton, California 92831, USA 28 European Gravitational Observatory (EGO), I-56021 Cascina, Pisa, Italy 29 Chennai Mathematical Institute, Chennai 603103, India 30 Università di Roma Tor Vergata, I-00133 Roma, Italy 31 Universität Hamburg, D-22761 Hamburg, Germany 32 INFN, Sezione di Roma, I-00185 Roma, Italy 33 Embry-Riddle Aeronautical University, Prescott, Arizona 86301, USA 34 Albert-Einstein-Institut, Max-Planck-Institut für Gravitationsphysik, D-14476 Potsdam-Golm, Germany 35 APC, AstroParticule et Cosmologie, Université Paris Diderot, CNRS/IN2P3, CEA/Irfu, Observatoire de Paris, Sorbonne Paris Cité, F-75205 Paris Cedex 13, France 36 Korea Institute of Science and Technology Information, Daejeon 34141, Korea 37 West Virginia University, Morgantown, West Virginia 26506, USA 38 Center for Gravitational Waves and Cosmology, West Virginia University, Morgantown, West Virginia 26505, USA 39 Università di Perugia, I-06123 Perugia, Italy 40 INFN, Sezione di Perugia, I-06123 Perugia, Italy 41 Syracuse University, Syracuse, New York 13244, USA 42 University of Minnesota, Minneapolis, Minnesota 55455, USA 43 SUPA, University of Glasgow, Glasgow G12 8QQ, United Kingdom 44 LIGO Hanford Observatory, Richland, Washington 99352, USA 45 Wigner RCP, RMKI, H-1121 Budapest, Konkoly Thege Miklós út 29-33, Hungary 46 Columbia University, New York, New York 10027, USA 47 Stanford University, Stanford, California 94305, USA 48 Università di Camerino, Dipartimento di Fisica, I-62032 Camerino, Italy 49 Università di Padova, Dipartimento di Fisica e Astronomia, I-35131 Padova, Italy 50 INFN, Sezione di Padova, I-35131 Padova, Italy 51 MTA Eötvös University, “Lendulet” Astrophysics Research Group, Budapest 1117, Hungary 52 Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, 00-716, Warsaw, Poland 53 University of Birmingham, Birmingham B15 2TT, United Kingdom 54 Università degli Studi di Genova, I-16146 Genova, Italy 55 INFN, Sezione di Genova, I-16146 Genova, Italy 56 RRCAT, Indore MP 452013, India 57 Faculty of Physics, Lomonosov Moscow State University, Moscow 119991, Russia 58 SUPA, University of the West of Scotland, Paisley PA1 2BE, United Kingdom 59 Caltech CaRT, Pasadena, California 91125, USA 60 OzGrav, University of Western Australia, Crawley, Western Australia 6009, Australia 61 Department of Astrophysics/IMAPP, Radboud University Nijmegen, P.O. Box 9010, 6500 GL Nijmegen, Netherlands 62 Artemis, Université Côte d’Azur, Observatoire Côte d’Azur, CNRS, CS 34229, F-06304 Nice Cedex 4, France 63 Institut de Physique de Rennes, CNRS, Université de Rennes 1, F-35042 Rennes, France 64 Washington State University, Pullman, Washington 99164, USA 65 Università degli Studi di Urbino “Carlo Bo,” I-61029 Urbino, Italy 66 INFN, Sezione di Firenze, I-50019 Sesto Fiorentino, Firenze, Italy 67 University of Oregon, Eugene, Oregon 97403, USA 68 Laboratoire Kastler Brossel, UPMC-Sorbonne Universités, CNRS, ENS-PSL Research University, Collège de France, F-75005 Paris, France 69 Carleton College, Northfield, Minnesota 55057, USA 70 Astronomical Observatory Warsaw University, 00-478 Warsaw, Poland 71 VU University Amsterdam, 1081 HV Amsterdam, Netherlands 72 University of Maryland, College Park, Maryland 20742, USA 73 Center for Relativistic Astrophysics and School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332, USA 74 Université Claude Bernard Lyon 1, F-69622 Villeurbanne, France 75 Università di Napoli “Federico II,” Complesso Universitario di Monte S. Angelo, I-80126 Napoli, Italy 76 NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA 77 RESCEU, University of Tokyo, Tokyo, 113-0033, Japan 78 OzGrav, University of Adelaide, Adelaide, South Australia 5005, Australia 79 Tsinghua University, Beijing 100084, China 80 Texas Tech University, Lubbock, Texas 79409, USA 81 Kenyon College, Gambier, Ohio 43022, USA 82 The Pennsylvania State University, University Park, Pennsylvania 16802, USA 83 National Tsing Hua University, Hsinchu City, 30013 Taiwan, Republic of China 84 Charles Sturt University, Wagga Wagga, New South Wales 2678, Australia 85 Canadian Institute for Theoretical Astrophysics, University of Toronto, Toronto, Ontario M5S 3H8, Canada 86 University of Chicago, Chicago, Illinois 60637, USA 87 Pusan National University, Busan 46241, Korea 88 The Chinese University of Hong Kong, Shatin, NT, Hong Kong 89 INAF, Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, I-35122 Padova, Italy 90 INFN, Trento Institute for Fundamental Physics and Applications, I-38123 Povo, Trento, Italy 91 Università di Roma “La Sapienza,” I-00185 Roma, Italy 92 Université Libre de Bruxelles, Brussels 1050, Belgium 93 Sonoma State University, Rohnert Park, California 94928, USA 94 Montana State University, Bozeman, Montana 59717, USA 95 Center for Interdisciplinary Exploration Research in Astrophysics (CIERA), Northwestern University, Evanston, Illinois 60208, USA 96 Cardiff University, Cardiff CF24 3AA, United Kingdom 97 Universitat de les Illes Balears, IAC3–IEEC, E-07122 Palma de Mallorca, Spain 98 The University of Texas Rio Grande Valley, Brownsville, Texas 78520, USA 99 Bellevue College, Bellevue, Washington 98007, USA 100 Institute for Plasma Research, Bhat, Gandhinagar 382428, India 101 The University of Sheffield, Sheffield S10 2TN, United Kingdom 102 University of Southern California Information Sciences Institute, Marina Del Rey, California 90292, USA 103 California State University, Los Angeles, 5151 State University Drive, Los Angeles, California 90032, USA 104 Università di Trento, Dipartimento di Fisica, I-38123 Povo, Trento, Italy 105 Montclair State University, Montclair, New Jersey 07043, USA 106 National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan 107 Whitman College, 345 Boyer Avenue, Walla Walla, Washington 99362 USA 108 School of Mathematics, University of Edinburgh, Edinburgh EH9 3FD, United Kingdom 109 University and Institute of Advanced Research, Gandhinagar Gujarat 382007, India 110 IISER-TVM, CET Campus, Trivandrum Kerala 695016, India 111 University of Szeged, Dóm tér 9, Szeged 6720, Hungary 112 Tata Institute of Fundamental Research, Mumbai 400005, India 113 INAF, Osservatorio Astronomico di Capodimonte, I-80131, Napoli, Italy 114 University of Michigan, Ann Arbor, Michigan 48109, USA 115 American University, Washington, D.C. 20016, USA 116 Rochester Institute of Technology, Rochester, New York 14623, USA 117 University of Białystok, 15-424 Białystok, Poland 118 SUPA, University of Strathclyde, Glasgow G1 1XQ, United Kingdom 119 University of Southampton, Southampton SO17 1BJ, United Kingdom 120 University of Washington Bothell, 18115 Campus Way NE, Bothell, Washington 98011, USA 121 Institute of Applied Physics, Nizhny Novgorod, 603950, Russia 122 Seoul National University, Seoul 08826, Korea 123 Inje University Gimhae, South Gyeongsang 50834, Korea 124 National Institute for Mathematical Sciences, Daejeon 34047, Korea 125 NCBJ, 05-400 Świerk-Otwock, Poland 126 Institute of Mathematics, Polish Academy of Sciences, 00656 Warsaw, Poland 127 OzGrav, School of Physics Astronomy, Monash University, Clayton 3800, Victoria, Australia 128 Hanyang University, Seoul 04763, Korea 129 NASA Marshall Space Flight Center, Huntsville, Alabama 35811, USA 130 ESPCI, CNRS, F-75005 Paris, France 131 Southern University and AM College, Baton Rouge, Louisiana 70813, USA 132 OzGrav, University of Melbourne, Parkville, Victoria 3010, Australia 133 College of William and Mary, Williamsburg, Virginia 23187, USA 134 Indian Institute of Technology Madras, Chennai 600036, India 135 IISER-Kolkata, Mohanpur, West Bengal 741252, India 136 Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126 Pisa, Italy 137 Université de Lyon, F-69361 Lyon, France 138 Hobart and William Smith Colleges, Geneva, New York 14456, USA 139 Janusz Gil Institute of Astronomy, University of Zielona Góra, 65-265 Zielona Góra, Poland 140 University of Washington, Seattle, Washington 98195, USA 141 King’s College London, University of London, London WC2R 2LS, United Kingdom 142 Indian Institute of Technology, Gandhinagar Ahmedabad Gujarat 382424, India 143 International Institute of Physics, Universidade Federal do Rio Grande do Norte, Natal RN 59078-970, Brazil 144 Andrews University, Berrien Springs, Michigan 49104, USA 145 Università di Siena, I-53100 Siena, Italy 146 Trinity University, San Antonio, Texas 78212, USA 147 Abilene Christian University, Abilene, Texas 79699, USA * Full author list given at the end of the Letter. * Deceased, March 2016. † Deceased, March 2017. ‡ Deceased, February 2017. § Deceased, December 2016. 参加此项研究的单位除了美国加州理工大学激光干涉引力波天文台( LIGO , California Institute of Technology ) 的研究人员,还有美国路易安娜州立大学( Louisiana State University )、佛罗里达大学( University of Florida ) 、 LIGO 利文斯顿天文台( LIGO Livingston Observatory )、密西西比大学( University of Mississippi )、伊利诺伊大学香槟分校( University of Illinois at Urbana-Champaign )、麻省理工学院( LIGO, Massachusetts Institute of Technology )、美国威斯康星 - 密尔沃基大学( University of Wisconsin-Milwaukee )、加利福尼亚州立大学富勒顿 分校( California State University Fullerton )、 美国雪城大学( Syracuse University )、明尼苏达大学( University of Minnesota )、 LIGO 汉福德观测站( LIGO Hanford Observatory )、 哥伦比亚大学( Columbia University )、斯坦福大学( Stanford University )、美国安柏 - 瑞德航空大学 ( Embry-Riddle Aeronautical University )、 美国西弗吉尼亚大学( West Virginia University )、 意大利萨勒诺大学( Università di Salerno )、蒙特 S. 安吉洛综合大学( Complesso Universitario di Monte S. Angelo )、意大利桑尼奥大学贝内文托分校( University of Sannio at Benevento, ) ; 意大利格兰 ·萨索科学研究所( Gran Sasso Science Institute , GSSI )、意大利国际核物理研究院罗马第二大学分院( INFN, Sezione di Roma Tor Vergata )、意大利比萨大学( Università di Pisa )、意大利国际核物理研究院比萨分院( INFN, Sezione di Pisa )、意大利国际核物理研究院罗马分院( INFN, Sezione di Roma ) 、 Università di Roma Tor Vergata 、意大利比萨欧洲引力波观测站( European Gravitational Observatory , EGO) 、 意大利佩鲁贾大学( Università di Perugia ) 、 意大利国际核物理研究院佩鲁贾分院( INFN, Sezione di Perugia )、 意大利国际核物理研究院帕多瓦分院( INFN, Sezione di Padova )、 意大利国际核物理研究院热那亚分院( INFN, Sezione di Genova )、 意大利卡梅里诺大学( Università di Camerino )、帕多瓦大学( Università di Padova )、热那亚工业大学( Università degli Studi di Genova )、意大利乌比诺工业大学( Università degli Studi di Urbino )、 意大利国际核物理研究院佛罗伦萨分院( INFN, Sezione di Firenze ); 法国白萨瓦山大学( Université Savoie Mont Blanc )、法国先进材料实验室( Laboratoire des Matériaux Avancés , LMA) 、 法国巴黎南部大学( Univ. Paris-Sud )、巴黎 - 萨克雷大学( Université Paris-Saclay ); 德国马克斯 - 普朗引力物理研究所( Max-Planck-Institut für Gravitationsphysik )、莱布尼兹汉诺威大学( Leibniz Universität Hannover )、 英国剑桥大学( University of Cambridge )、 荷兰国家亚原子物理研究所( Nikhef )、 巴西 Instituto Nacional de Pesquisas Espaciais 、 印度校际天文与天体物理中心( Inter-University Centre for Astronomy and Astrophysics )、 印度塔塔基础研究所 ( Tata Institute of Fundamental Research )、 印度金奈数学研究所( Chennai Mathematical Institute )、印度 RRCAT; 澳大利亚国立大学 ( Australian National University )、 德国汉堡大学( Universität Hamburg )、 法国巴黎狄德罗大学 ( Université Paris Diderot )、 韩国科技信息研究所( Korea Institute of Science and Technology Information ) 英国格拉斯哥大学 ( University of Glasgow )、 匈牙利 MTA Eötvös 大学( MTA Eötvös University )、 Wigner RCP, RMKI; 波兰科学院( Polish Academy of Sciences )、 英国伯明翰大学 ( University of Birmingham )、 西苏格兰大学( University of the West of Scotland )、 俄罗斯罗蒙诺索夫莫斯科国立大学 ( Lomonosov Moscow State University )、 美国加州理工学院( Caltech CaRT )、 华盛顿州立大学( Washington State University )、 西澳大学( University of Western Australia )、 荷兰内梅亨大学 ( Radboud University Nijmegen )、 法国蔚蓝海岸大学( Université Côte d ’ Azur )、 雷恩大学( Université de Rennes )、法国居里夫妇大学 - 索邦大学( UPMC-Sorbonne Universités )、法国 ENS-PSL 研究大学( ENS-PSL Research University )、 美国俄勒冈大学( University of Oregon )、 美国诺斯菲尔德的卡尔顿学院( Carleton College, Northfield )、 波兰华沙大学 ( Warsaw University ) 、 荷兰 阿姆斯特丹大学 ( VU University Amsterdam )、 美国马里兰大学( University of Maryland )、乔治亚理工学院( Georgia Institute of Technology )、 美国宇航局哥达德航天中心( NASA Goddard Space Flight Center )、 法国伯尔纳里昂大学( Université Claude Bernard Lyon )、 日本东京大学( University of Tokyo ) 澳大利亚阿德莱德大学 ( University of Adelaide )、查尔斯特大学( Charles Sturt University )、 中国清华大学 、 包括北京清华大学( Tsinghua University ) 和台湾新竹清华大学( National Tsing Hua University ); 美国德克萨斯理工大学( Texas Tech University )、 凯尼恩学院( Kenyon College )、 宾夕法尼亚州立大学( Pennsylvania State University )、 加拿大多伦多大学 ( University of Toronto )、....... LIGO detects gravitational waves for third time June 1, 2017 An international team of researchers has made a third detection of gravitational waves, ripples in space and time, in a discovery that provides new insights into the mysterious nature of black holes and, potentially, dark matter. Credit: LSC/OzGrav The Laser Interferometer Gravitational-wave Observatory (LIGO) has made a third detection of gravitational waves, ripples in space and time, demonstrating that a new window in astronomy has been firmly opened. As was the case with the first two detections, the waves were generated when two black holes collided to form a larger black hole. The newfound black hole, formed by the merger, has a mass about 49 times that of our sun. This fills in a gap between the masses of the two merged black holes detected previously by LIGO, with solar masses of 62 (first detection) and 21 (second detection). We have further confirmation of the existence of stellar-mass black holes that are larger than 20 solar masses—these are objects we didn't know existed before LIGO detected them, says MIT's David Shoemaker, the newly elected spokesperson for the LIGO Scientific Collaboration (LSC), a body of more than 1,000 international scientists who perform LIGO research together with the European-based Virgo Collaboration. It is remarkable that humans can put together a story, and test it, for such strange and extreme events that took place billions of years ago and billions of light-years distant from us. The entire LIGO and Virgo scientific collaborations worked to put all these pieces together. The new detection occurred during LIGO's current observing run, which began November 30, 2016, and will continue through the summer. LIGO is an international collaboration with members around the globe. Its observations are carried out by twin detectors—one in Hanford, Washington, and the other in Livingston, Louisiana—operated by Caltech and MIT with funding from the National Science Foundation (NSF). LIGO made the first-ever direct observation of gravitational waves in September 2015 during its first observing run since undergoing major upgrades in a program called Advanced LIGO. The second detection was made in December 2015. The third detection, called GW170104 and made on January 4, 2017, is described in a new paper accepted for publication in the journal Physical Review Letters . In all three cases, each of the twin detectors of LIGO detected gravitational waves from the tremendously energetic mergers of black hole pairs. These are collisions that produce more power than is radiated as light by all the stars and galaxies in the universe at any given time. The recent detection appears to be the farthest yet, with the black holes located about 3 billion light-years away. (The black holes in the first and second detections are located 1.3 and 1.4 billion light-years away, respectively.) The newest observation also provides clues about the directions in which the black holes are spinning. As pairs of black holes spiral around each other, they also spin on their own axes—like a pair of ice skaters spinning individually while also circling around each other. Sometimes black holes spin in the same overall orbital direction as the pair is moving—what astronomers refer to as aligned spins—and sometimes they spin in the opposite direction of the orbital motion. What's more, black holes can also be tilted away from the orbital plane. Essentially, black holes can spin in any direction. The new LIGO data cannot determine if the recently observed black holes were tilted but they imply that at least one of the black holes may have been non-aligned compared to the overall orbital motion. More observations with LIGO are needed to say anything definitive about the spins of binary black holes, but these early data offer clues about how these pairs may form. This image shows a numerical simulation of a binary black hole merger with masses and spins consistent with the third and most recent LIGO observation, named GW170104. The strength of the gravitational wave is indicated by elevation as well as color, with blue indicating weak fields and yellow indicating strong fields. The sizes of the black holes are doubled to improve visibility. Credit: Image Credit: Numerical-relativistic Simulation: S. Ossokine, A. Buonanno (Max Planck Institute for Gravitational Physics) and the Simulating eXtreme Spacetime project Scientific Visualization: T. Dietrich (Max Planck Institute for Gravitational Physics), R. Haas (NCSA) This is the first time that we have evidence that the black holes may not be aligned, giving us just a tiny hint that binary black holes may form in dense stellar clusters, says Bangalore Sathyaprakash of Penn State and Cardiff University, one of the editors of the new paper, which is authored by the entire LSC and Virgo Collaborations. There are two primary models to explain how binary pairs of black holes can be formed. The first model proposes that the black holes are born together: they form when each star in a pair of stars explodes, and then, because the original stars were spinning in alignment, the black holes likely remain aligned. In the other model, the black holes come together later in life within crowded stellar clusters. The black holes pair up after they sink to the center of a star cluster. In this scenario, the black holes can spin in any direction relative to their orbital motion. Because LIGO sees some evidence that the GW170104 black holes are non-aligned, the data slightly favor this dense stellar cluster theory. We're starting to gather real statistics on binary black hole systems, says Keita Kawabe of Caltech, also an editor of the paper, who is based at the LIGO Hanford Observatory. That's interesting because some models of black hole binary formation are somewhat favored over the others even now and, in the future, we can further narrow this down. The study also once again puts Albert Einstein's theories to the test. For example, the researchers looked for an effect called dispersion, which occurs when light waves in a physical medium such as glass travel at different speeds depending on their wavelength; this is how a prism creates a rainbow. Einstein's general theory of relativity forbids dispersion from happening in gravitational waves as they propagate from their source to Earth. LIGO did not find evidence for this effect. It looks like Einstein was right—even for this new event, which is about two times farther away than our first detection, says Laura Cadonati of Georgia Tech and the Deputy Spokesperson of the LSC. We can see no deviation from the predictions of general relativity, and this greater distance helps us to make that statement with more confidence. The LIGO instruments have reached impressive sensitivities, notes Jo van den Brand, the Virgo Collaboration spokesperson, a physicist at the Dutch National Institute for Subatomic Physics (Nikhef) and professor at VU University in Amsterdam. We expect that by this summer Virgo, the European interferometer, will expand the network of detectors, helping us to better localize the signals. The LIGO-Virgo team is continuing to search the latest LIGO data for signs of space-time ripples from the far reaches of the cosmos. They are also working on technical upgrades for LIGO's next run, scheduled to begin in late 2018, during which the detectors' sensitivity will be improved. With the third confirmed detection of gravitational waves from the collision of two black holes, LIGO is establishing itself as a powerful observatory for revealing the dark side of the universe, says David Reitze of Caltech, executive director of the LIGO Laboratory. While LIGO is uniquely suited to observing these types of events, we hope to see other types of astrophysical events soon, such as the violent collision of two neutron stars.
还是双黑洞并合! https://www.ligo.caltech.edu/news/ligo20160615 此次探测到的双黑洞并合事件被称之为 The Boxing Day event. The Boxing Day event differed from the LIGO's first gravitational wave observation in some important ways, however. 1.The gravitational wave arrived at the two detectors at almost the same time, indicating that the source was located somewhere in a ring of sky about midway between the two detectors. Knowing our detector sensitivity pattern, we can add that it was a bit more likely overhead or underfoot instead of to the West or the East. With only two detectors, however, we can't narrow it down much more than that. This differs from LIGO's first detected signal (GW150914, from 14 September 2015), which came from the 'southeast', hitting Louisiana's detector before Washington's. 2.The two merging black holes in the Boxing Day event were less massive (14 and 8 times the mass of our sun) than those observed in the first detection GW150914 (36 and 29 times the mass of our sun). While this made the signal weaker than GW150914, when these lighter black holes merged, their signal shifted into higher frequencies bringing it into LIGO’s sensitive band earlier in the merger than we observed in the September event. This allowed us to observe more orbits than the first detection–some 27 orbits over about one second (this compares with just two tenths of a second of observation in the first detection). Combined, these two factors (smaller masses and more observed orbits) were the keys to enabling LIGO to detect a weaker signal. They also allowed us to make more precise comparisons with General Relativity. Spoiler: the signal agrees, again, perfectly with Einstein’s theory. 3.Last but not least, the Boxing Day event revealed that one of the initial black holes was spinning like a top! – and this is a first for LIGO to be able to state this with confidence. A spinning black hole suggests that this object has a different history –- e.g. maybe it 'sucked in' mass from a companion star before or after collapsing from a star to form a black hole, getting spun-up in the process.
2016年2月11日星期四上午10点30分,是一个物理学界值得纪念的日子,美国的LIGO(激光干涉引力波观测站)加上MIT等各处的专家们,在华府召开了新闻发布会,向全世界宣布首次直接探测到了引力波的消息 【1】 。全世界都为之振奋,天文界和物理界的专家们更是激动不已。 1. 引力波是时空的涟漪 牛顿的万有引力定律揭示了引力与万物的关系。而爱因斯坦的广义相对论则将引力与四维时空的弯曲性质联系在一起。物质的质量使得四维时空弯曲,弯曲的时空又影响其中物体的运动,使其运动轨迹成为曲线而非直线。犹如一大片无限扩展的弹性网格以及上面滚动的小球互相影响一样:网格形状因小球重量而弯曲,小球的运动轨迹又因网格的弯曲而改变,见图1a。 图1:弯曲时空和引力波 设想弹性网格上突然掉下一个很重的大铅球,图1b。铅球不仅使得网格的形状大大改变,而且还将引起弹性床的大震荡,就像一颗石子投在平静的水面上引起涟漪一样,铅球引起的震荡将传播到网格的四面八方。 将上面涟漪的比喻用到四维弯曲时空中,便是物理学家们企图探测的引力波。 与电荷运动时会产生电磁波相类比,物质在运动、膨胀、收缩的过程中,也会在空间产生涟漪并沿时空传播到另一处,这便是引力波。根据广义相对论,任何作加速运动的物体,不是绝对球对称或轴对称的时空涨落,都能产生引力波。爱因斯坦在100年之前 【2,3】 预言存在引力波,但是,由于引力波携带的能量很小,强度很弱,物质对引力波的吸收效率又极低,一般物体产生的引力波,不可能在实验室被直接探测到。举例来说,地球绕太阳相互转动的系统产生的引力波辐射,整个功率才大约只有200瓦,而太阳电磁辐射的功率是它的10 22 倍。仅仅200瓦!可以想象得到,照亮一个房间的电灯泡的功率,散发到太阳-地球系统这样一个诺大的空间中,效果将如何?所以,地球-太阳体系发射的微小引力波一直完全无法被检测到。 2.长久的等待 笔者当年博士论文的课题是有关引力波在黑洞附近的散射问题,记得30年前的一次讨论会上,有人提到何时探测到引力波的问题时无人作声,只有约翰·惠勒笑嘻嘻、信心满满地说了一句“快了!”。我当时只知道推导数学公式,对探测引力波的实验一无所知,但惠勒这句“快了”在脑袋中却记忆颇深,也从此关心起引力波是否真正存在的问题。 1993年,传来了两位美国科学家获得诺贝尔物理奖 【3】 的消息。他们便是因为研究双星运动,即两颗双中子星相互围绕着对方公转,而间接证实了引力波的存在。我当时便立即想起了惠勒的话,心想:果然“快了”! 2000年,听说惠勒的一个学生,就是和惠勒一起合作《引力》之书的KipThorne,是加州理工学院的教授,几年前启动了一个叫LIGO的项目,专为探测引力波。1999年10月的“Physics Today”有一篇文章是关于此项目,我看了之后,脑海里又浮现出“快了”。 2007年,在加州偶然碰到一个原来一起在相对论中心的同学,他在某天文台做天体物理,谈及引力波,他也说快了,因为LIGO一年后将要再次升级,升级完成后就“快了”。 2014年,又一次传来探测到引力波的消息 【4】 。 因为普通物体,甚至于太阳系产生的引力波都难以探测,科学家们便把目光转向浩渺的宇宙。宇宙中存在质量巨大又非常密集的天体,诸如黑矮星、中子星、或许还有夸克星等。超新星爆发、黑洞碰撞等事件将会产生强大的引力波。此外,在大爆炸的初期,暴涨阶段,也可能辐射强大的引力波。 2014年传言在哈佛设在南极的BICEP2探测器探测到了引力波,指的并不是直接的接收,而是大爆炸初期暴涨阶段发出的“原初引力波”在微波背景辐射图上打上的“印记”。但是,后来证实这是一次误导,是一次由尘埃物质造成的假“印记”。 直到今天LIGO的发布会,才真正接受到了引力波。当初惠勒的这句“快了”,实现起来也至少花了30年,爱因斯坦就更不用说,已经等待一百年了! 图2:探测引力波的实验设施和结果示意图 美国花费巨资升级的LIGO,是目前最先进的观测引力波的仪器,它的基本原理是使用激光干涉仪,见图2a。从一点发射出两束垂直的激光,利用测量两条激光光束的相位差来探测引力波,见图2c。每束光在传播距离L后返回,其来回过程中若受到引力波影响,行程所用时间将发生改变而影响到两束光的相对相位。如果没有探测到引力波,结果是如图2c上图所示的圆形图案;如果探测到引力波,结果是如图2c下面所示的几个椭圆。干涉臂的长度L越长,测量便越精确。以LIGO为例,双臂长度为4千米,见图2b。 图2d是LIGO结果的示意图,图中可见椭圆。LIGO观测机构拥有两套干涉仪,一套安放在路易斯安娜州的李文斯顿,另一套在华盛顿州的汉福。两台干涉仪都得到了类似的结果,方才能证实的确接收到了引力波。 3.物理研究的里程碑 测量到引力波的意义非凡,首先,这意味着科学家们可以通过它来进一步探测和理解宇宙中的物理演化过程,为恒星、星系、乃至宇宙自身现有的演化模型,提供新的证据,有一个更为牢靠的基础。其二,过去的天文学基本上是使用光作为探测手段,而现在观测到了引力波,便多了一种探测方法,也许由此能开启一门引力波天文学。此外,大爆炸模型,以及黑洞等发射的引力波,都是建立在广义相对论的基础上。如今真正探测到了理论预言的引力波,就能再次证明这个理论的正确性。 这次探测到引力波的波源, 据说是遥远宇宙空间之外的双黑洞系统。其中一个黑洞 36倍太阳质量,另一个29倍太阳质量,两者碰撞并合成一个62倍太阳质量的黑洞。显然这儿有一个疑问:36+29=65,而非62,还有3个太阳质量的物质到哪儿去了呢?其实这正是我们能够探测到引力波的基础。相当于三个太阳质量的物质转化成了巨大的能量释放到太空中!正因为有如此巨大的能量辐射,才使远离这两个黑洞的小小地球上的我们,探测到了碰撞融合之后传来的已经变得很微弱的引力波。 因为波源是两个黑洞。探测到引力波也再一次确认了这两个黑洞是宇宙空间中的真实存在。黑洞物理不仅涉及广义相对论,也与量子理论密切相关,实际上,对黑洞的认识在物理的不同领域中也稍有一些不同。我们至少可以从三个不同的角度来看待黑洞: 数学黑洞,指的是经典引力场方程的奇点解,更是一种数学模型。谈的多是黑洞无毛定理、史瓦西半径、视界,等等数学定义。 物理黑洞,多涉及黑洞的热力学性质,诸如黑洞熵、霍金辐射、信息丢失等,与量子物理关系密切。 天文黑洞,真实观测到的被称为“黑洞” 的天体。 引力波的探测结果以及今后朝这个方向的进一步研究,将有助于深化对黑洞物理性质的认识,还有对两个黑洞碰撞融合过程的研究,也必定得到了大量有用的信息。对黑洞的这 3个方向的深入研究,也许能促成量子理论与引力理论的统一 ,对基础物理学的研究意义将十分重大,有着里程碑的作用 。 PhysRevLett.116.061102.pdf 参考资料 : 【 1 】 B. P. Abbott et al. (LIGO Scientific Collaboration andVirgo Collaboration) , Observation of Gravitational Waves from a Binary BlackHole Merger , Phys. Rev. Lett. 116, 061102 – Published 11 February 2016 http://www.bbc.com/news/science-environment-35524440 【 2 】 Einstein, A.: Näherungsweise Integration derFeldgleichungen der Gravitation. In: Sitzungsberichte der KöniglichPreussischen Akademie der Wissenschaften Berlin (1916), 688–696. 【 3 】 Einstein, A., Rosen, N.: On Gravitational Waves. In:Journal of the Franklin Institute 223 (1937), 43–54. 【 4 】 Overbye, Dennis (17 March 2014). Detection of Wavesin Space Buttresses Landmark Theory of Big Bang. New York Times.Retrieved 17 March 2014.