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）：
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+8.4−6.0M⊙ and 19.4+5.3−5.9M⊙ (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, χeff=−0.12+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 880+450−390Mpc corresponding to a redshift of z=0.18+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 mg≤7.7×10−23eV/c2. In all cases, we find that GW170104 is consistent with general relativity.
29Chennai Mathematical Institute, Chennai 603103, India
30Università di Roma Tor Vergata, I-00133 Roma, Italy
31Universität Hamburg, D-22761 Hamburg, Germany
32INFN, Sezione di Roma, I-00185 Roma, Italy
33Embry-Riddle Aeronautical University, Prescott, Arizona 86301, USA
34Albert-Einstein-Institut, Max-Planck-Institut für Gravitationsphysik, D-14476 Potsdam-Golm, Germany
35APC, AstroParticule et Cosmologie, Université Paris Diderot, CNRS/IN2P3, CEA/Irfu, Observatoire de Paris, Sorbonne Paris Cité, F-75205 Paris Cedex 13, France
36Korea Institute of Science and Technology Information, Daejeon 34141, Korea
37West Virginia University, Morgantown, West Virginia 26506, USA
38Center for Gravitational Waves and Cosmology, West Virginia University, Morgantown, West Virginia 26505, USA
39Università di Perugia, I-06123 Perugia, Italy
40INFN, Sezione di Perugia, I-06123 Perugia, Italy
41Syracuse University, Syracuse, New York 13244, USA
42University of Minnesota, Minneapolis, Minnesota 55455, USA
43SUPA, University of Glasgow, Glasgow G12 8QQ, United Kingdom
44LIGO Hanford Observatory, Richland, Washington 99352, USA
45Wigner RCP, RMKI, H-1121 Budapest, Konkoly Thege Miklós út 29-33, Hungary
46Columbia University, New York, New York 10027, USA
47Stanford University, Stanford, California 94305, USA
48Università di Camerino, Dipartimento di Fisica, I-62032 Camerino, Italy
49Università di Padova, Dipartimento di Fisica e Astronomia, I-35131 Padova, Italy
50INFN, Sezione di Padova, I-35131 Padova, Italy
51MTA Eötvös University, “Lendulet” Astrophysics Research Group, Budapest 1117, Hungary
52Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, 00-716, Warsaw, Poland
53University of Birmingham, Birmingham B15 2TT, United Kingdom
54Università degli Studi di Genova, I-16146 Genova, Italy
55INFN, Sezione di Genova, I-16146 Genova, Italy
56RRCAT, Indore MP 452013, India
57Faculty of Physics, Lomonosov Moscow State University, Moscow 119991, Russia
58SUPA, University of the West of Scotland, Paisley PA1 2BE, United Kingdom
59Caltech CaRT, Pasadena, California 91125, USA
60OzGrav, University of Western Australia, Crawley, Western Australia 6009, Australia
61Department of Astrophysics/IMAPP, Radboud University Nijmegen, P.O. Box 9010, 6500 GL Nijmegen, Netherlands
90INFN, Trento Institute for Fundamental Physics and Applications, I-38123 Povo, Trento, Italy
91Università di Roma “La Sapienza,” I-00185 Roma, Italy
92Université Libre de Bruxelles, Brussels 1050, Belgium
93Sonoma State University, Rohnert Park, California 94928, USA
94Montana State University, Bozeman, Montana 59717, USA
95Center for Interdisciplinary Exploration & Research in Astrophysics (CIERA), Northwestern University, Evanston, Illinois 60208, USA
96Cardiff University, Cardiff CF24 3AA, United Kingdom
97Universitat de les Illes Balears, IAC3–IEEC, E-07122 Palma de Mallorca, Spain
98The University of Texas Rio Grande Valley, Brownsville, Texas 78520, USA
99Bellevue College, Bellevue, Washington 98007, USA
100Institute for Plasma Research, Bhat, Gandhinagar 382428, India
101The University of Sheffield, Sheffield S10 2TN, United Kingdom
102University of Southern California Information Sciences Institute, Marina Del Rey, California 90292, USA
103California State University, Los Angeles, 5151 State University Drive, Los Angeles, California 90032, USA
104Università di Trento, Dipartimento di Fisica, I-38123 Povo, Trento, Italy
105Montclair State University, Montclair, New Jersey 07043, USA
106National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
107Whitman College, 345 Boyer Avenue, Walla Walla, Washington 99362 USA
108School of Mathematics, University of Edinburgh, Edinburgh EH9 3FD, United Kingdom
109University and Institute of Advanced Research, Gandhinagar Gujarat 382007, India
110IISER-TVM, CET Campus, Trivandrum Kerala 695016, India
111University of Szeged, Dóm tér 9, Szeged 6720, Hungary
112Tata Institute of Fundamental Research, Mumbai 400005, India
113INAF, Osservatorio Astronomico di Capodimonte, I-80131, Napoli, Italy
114University of Michigan, Ann Arbor, Michigan 48109, USA
115American University, Washington, D.C. 20016, USA
116Rochester Institute of Technology, Rochester, New York 14623, USA
117University of Białystok, 15-424 Białystok, Poland
118SUPA, University of Strathclyde, Glasgow G1 1XQ, United Kingdom
119University of Southampton, Southampton SO17 1BJ, United Kingdom
120University of Washington Bothell, 18115 Campus Way NE, Bothell, Washington 98011, USA
121Institute of Applied Physics, Nizhny Novgorod, 603950, Russia
122Seoul National University, Seoul 08826, Korea
123Inje University Gimhae, South Gyeongsang 50834, Korea
124National Institute for Mathematical Sciences, Daejeon 34047, Korea
125NCBJ, 05-400 Świerk-Otwock, Poland
126Institute of Mathematics, Polish Academy of Sciences, 00656 Warsaw, Poland
127OzGrav, School of Physics & Astronomy, Monash University, Clayton 3800, Victoria, Australia
128Hanyang University, Seoul 04763, Korea
129NASA Marshall Space Flight Center, Huntsville, Alabama 35811, USA
130ESPCI, CNRS, F-75005 Paris, France
131Southern University and A&M College, Baton Rouge, Louisiana 70813, USA
132OzGrav, University of Melbourne, Parkville, Victoria 3010, Australia
133College of William and Mary, Williamsburg, Virginia 23187, USA
134Indian Institute of Technology Madras, Chennai 600036, India
135IISER-Kolkata, Mohanpur, West Bengal 741252, India
136Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126 Pisa, Italy
137Université de Lyon, F-69361 Lyon, France
138Hobart and William Smith Colleges, Geneva, New York 14456, USA
139Janusz Gil Institute of Astronomy, University of Zielona Góra, 65-265 Zielona Góra, Poland
140University of Washington, Seattle, Washington 98195, USA
141King’s College London, University of London, London WC2R 2LS, United Kingdom
142Indian Institute of Technology, Gandhinagar Ahmedabad Gujarat 382424, India
143International Institute of Physics, Universidade Federal do Rio Grande do Norte, Natal RN 59078-970, Brazil
144Andrews University, Berrien Springs, Michigan 49104, USA
145Università di Siena, I-53100 Siena, Italy
146Trinity University, San Antonio, Texas 78212, USA
147Abilene 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（LIGOLivingston 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."
