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Учени засякоха най-отдалечените досега гравитационни вълни, чийто произход са две сблъскващи се черни дупки на милиарди светлинни години. Галактическият сблъсък, при който двете тела създават вълни във времето и пространството, се е случил на около 3 млрд. светлинни години разстояние и представлява третият път, в който учените успяват да засекат подобен феномен. Наблюдението е направено от Обсерваторията на лазерния интерферометер за гравитационни вълни, към която работи група от над 1000 международни изследователи. И в трите случая на засичане на гравитационни вълни те са били произведени от изключително енергични сливания на двойки черни дупки. В случая на последното засичане двете черни дупки, които са го предизвикали, са образували ново такова тяло с маса близо 49 пъти тази на Слънцето. „Разполагаме с допълнително потвърждение за съществуването на черни дупки с маси, по-големи от 20 слънчеви маси. Това са обекти, за чието съществуване ние не знаехме преди ОЛИГ да ги засече“, заяви Дейвид Шумейкър, учен към Масачузетския технологичен институт. Съществуването на гравитационни вълни е предречено от Алберт Айнщайн през 1916 година в неговата Обща теория на относителността Потвърдено е едва в края на 2015 г. от учени, работещи с данни от обсерваторията LIGO в САЩ. Тогава за пръв път гравитационни вълни бяха наблюдавани на разстояние от 1,3 млрд. светлинни години. Вторият път беше също през декември 2015 г., на разстояние от 1,4 млрд. светлинни години. Третото наблюдение е било направено през януари 2017 г. и е почти два пъти по-старо и два пъти по-отдалечено от първите две. Наблюденията на ОЛИГ се извършват с два идентични детектора, единият от които се намира в Ханфор, Вашингтон, а другият – в Ливингстън, Луизиана. С откриването на гравитационните вълни учените добавиха още едно доказателство към теорията на Алберт Айнщайн за общата относителност от 1915 г.
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北京时候2017年5月31日深夜, LIGO和Virgo科学合作组织进行了一次内部媒体发布会,确认了第三次引力波事务.LIGO讲话人麻省理工学院传授大卫?舒梅克起首颁布发表aLIGO发现了来自两个黑洞并合的新引力波事务GW170104,以及本次新发现引力波事务的根基特征.为此, 《中国科学:物理学力学天文学》特邀LIGO科学合作组清华团队成员李瑾副传授和范锡龙副传授进行了点评,李瑾副传授还对LIGO的新闻发布原稿进行了翻译.关于GW170104,请见官方主页: 以下为点评正文:自aLIGO (advanced LIGO)于2015年初次直接探测到双黑洞并合的引力波事务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务GW151226.这两次探测配合验证了广义相对论预言引力波存在的准确性, 并证实了宇宙中简直存在能在宇宙学春秋内并合的双黑洞系统.此次探测到的引力波事务GW170104是继前两次探测之后, aLIGO又颠末改良后探测到的分歧质量的双黑洞并合事务, 相关的成果颁发在近期的Physical Review Letter 期刊上[1].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规模(此次引力波源相距地球30亿光年). 与前两次探测比拟, 本次探测具有更深远的物理意义.首要表示在以下几方面: 本次观测是从aLIGO经新一轮机能晋升后采集的数据(官方称为O2轮数据)中发现了该引力波旌旗灯号.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日同时记实到了这一旌旗灯号.因为此次的数据质量较好, 系统活络度更高, 是以在O2轮数据起头运行不久就捕捉到了来自如斯遥远距离的引力波旌旗灯号. 第一次观测到双黑洞自旋正标的目的可以与彼此扭转轨道的角动量标的目的纷歧致.这一成果可以用来区分双黑洞的发源模子.从此次观测成果来看, 双黑洞很可能形成于致密的恒星簇中.别的广义相对论预言黑洞自旋会对波形演化发生至关主要的影响.是以, 经由过程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查验广义相对论的动力学预言. 图3 双黑洞环抱,自旋,轨道进动与引力波辐射.图片版权: LIGO科学合作团队 按照广义相对论预言引力波不存在色散现象.因为GW170104从较远的双黑洞系统传布到地球, 这将更利于我们测试引力波是否存在色散.连系前两次探测到的引力波, 此次对色散因子的上限给出了更严酷的限制.今朝的成果与广义相对论预言的零色散很是吻合.引力波科学合作组织仍在不竭拓展其探测收集,同时继续进行着系统进级[2].相信在不久的未来人类能探测到更多的引力波旌旗灯号.这不仅为验证广义相对论供给更多的实例, 还将大大提高人类对宇宙的复合观测能力. 我们等候在aLIGO发布的6个触发旌旗灯号中发现更多有趣的问题. 参考文献李瑾, 重庆大学物理学院副传授(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年时代在LIGO科学团队Ringdown小组中从事数据阐发工作, 2010年获得博士学位.曾获得中国国度天然科学基金帮助.今朝的首要研究范畴有: 引力波探测的数据处置,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传授, LIGO科学合作组清华团队成员.曾获得中国国度天然科学基金帮助.首要研究范畴: 引力波天文学, 引力波数据处置. 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 这一成果为新的恒星级黑洞的存在供给有力的证据 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. 激光干与引力波天文台第三次成功捕获到宇宙时空的涟漪-引力波.这项功效将周全开启人类熟悉宇宙的新窗口.与前两次探测到的引力波旌旗灯号(GW150914,GW151226)近似, 本次旌旗灯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构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, 此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科学合作组新被选的讲话人, 麻省理工学院的David Shoemaker传授谈到: “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观测到响应引力波旌旗灯号之前我们所不克不及确定的工作.”LIGO科学合作组是一个拥有一千多名来自世界列国科学家构成的科学合作研究机构, 他们与欧洲的Virgo科学合作组一路进行引力波的结合探测. 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现阶段观测运行时代, 该运行从2016年11月30日起头一向采集数据到2017年夏日竣事.涉及到的两架布局完全不异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天然科学基金(NSF)帮助. 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. 颠末主体进级后的LIGO称为高新LIGO, 即第二代激光干与引力波天文台.在Advanced LIGO在起头第一轮数据观测时代, 就第一次成功捕获到了来自于双黑洞系统融合过程释放的引力波旌旗灯号该旌旗灯号被观测到的时候为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旌旗灯号.第三次于本年1月4日观测到, 定名为GW170104.针对这一成果, LIGO科学合作小组(LSC)配合撰写了一篇论文, 在Physical Review Letters 期刊上颁发. 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刹时释放的引力波.这种引力辐射比宇宙中所有发光星体以及星系在不异时候内的光辐射还要强.比来此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别离为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. 最新的观测成果进一步给出了与双黑洞彼此扭转以及自旋标的目的有关的参数.因为双黑洞系统中的两成员彼此扭转, 同时它们具有自旋, 这如统一对在冰上各自扭转又绕着彼此扭转的溜冰活动员.双黑洞系统中单个黑洞的自旋标的目的有时与两者彼此扭转轨道的扭转标的目的一致——天文学家称之为平行自旋 , 有时它们的自旋与轨道扭转标的目的相反——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, 黑洞可以在任何标的目的上自旋. 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数据无法确定比来观测到的双黑洞的自旋正标的目的是否倾斜, 可是它们可以显示出与彼此扭转轨道活动标的目的是否一致或相反, 而且能供给若何形成这一现象的依据.要想加倍明白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务, 但这些早期的数据可觉得追求双黑洞形成机制供给线索. "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. 作为该论文的首要作者之一的宾夕法尼亚州立大学和加迪夫大学的传授Bangalore Sathyaprakash说: “这是我们第一次有证据表白黑洞可能为反向扭转型, 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. 今朝, 对于双黑洞的形成有两个主流的模子来诠释.在第一个模子中, 处于浓密恒星簇中的黑洞在其生命后期会逐渐堆积到一路.当它们陷入星簇中间后就形成了双黑洞系统.在这种环境下黑洞的自旋可以在任何标的目的. 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. 另一种模子预言双黑洞是同时降生的: 它们形成于双星系统塌缩, 因为最初的双星具有同向自旋是以发生的双黑洞系统应该也具有同向自旋特征.从LIGO最新一次的探测成果来看, GW170104引力波旌旗灯号反映出响应的双黑洞系统具有反向自旋.如许, 貌似前一种模子(致密恒星簇模子)与尝试更相符. "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“比来我们起头收集关于双黑洞系统的真实统计数据.这很有趣, 因为今朝有一些双黑洞系统的形成过程更倾向于另一些理论模子.经由过程近似的引力波观测, 未来我们可以进一步筛选出合理的理论模子. 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. 这项研究能再次经由过程尝试来验证爱因斯坦的一些理论.例如, 研究人员诡计寻找一种称为色散的物理效应, 当天然光进入某种物理介质如玻璃后, 分歧波长的光波以分歧的速度在介质中传布就会发生色散效应.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, 当引力波从波源传布到地球时不会发生近似的色散现象.今朝, LIGO简直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务, 它的发生地址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成果, 更大的距离使我们可以或许更有决定信念地认为爱因斯坦的理论看来是准确的.” “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.” 荷兰国度亚原子物理研究所(Nikhef)的物理学家, 阿姆斯特丹VU大学的传授, Virgo团队讲话人Jo van den Brand暗示: “LIGO探测器的活络度已经达到惊人的水平.我们估计到本年炎天, Virgo, 欧洲激光干与仪, 将扩大结合探测收集, 帮忙我们更好地对旌旗灯号进行定位. 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数据中搜刮宇宙中更遥远处所传来的引力波旌旗灯号.同时, 他们将于2018年年末起头为LIGO的下一次运行进行手艺进级, 届时探测器的活络度将获得进一步提高. "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: “经由过程第三次明白探测到由两个黑洞碰撞发生的引力波, LIGO慢慢成立起摸索宇宙暗中区域的壮大观测能力.固然LIGO对观测双黑洞碰撞发生引力波这类事务比力敏感, 但我们仍但愿未来它能观测到其他类型的天体物理事务, 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: . LIGO由NSF帮助, 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多名科学家经由过程LIGO科学合作组介入该项目具体工作, 包罗GEO.LIGO与Virgo合作, 将别的的280位欧洲科学家结合起来, 获得了包罗欧洲国度科学中间(CNRS), 国际天然科学基金委员会(INFN)和Virgo主体机构及欧洲重力观测站的帮助.其他合作伙伴拜见:.