LIGO and Virgo Detect Gravitational Waves from Neutron Star Collision for the First Time


Guenakh Mitselmakher, 352-871-1663;

Stephen S. Eikenberry, 352-514-7632;

Imre Bartos, 917-455-6264;

David Tanner, 352-318-3985


Neutron stars are dead stars collapsed into the densest form of matter known to humans, with a teaspoon of neutron star matter weighing a billion tons, and their collision creates a swath of galactic debris. Decades ago, stargazing scientists formed plans to detect signals from this debris. Now, in the new era of aptly named “multi-messenger astronomy,” two international projects have achieved this goal: On August 17 of this year, the Laser Interferometer Gravitational-Wave Observatory (LIGO)’s two U.S.-based interferometers and the Virgo Collaboration’s Italy-based interferometer detected for the first time gravitational waves — ripples in space-time traveling at the speed of light — from the collision and subsequent merger of two neutron stars. The detection occurred just three days after yet another “chirp” from colliding black holes.

This is LIGO’s fifth significant detection of gravitational waves from a catastrophic cosmic event, but the first detection from a kilonova. The Aug. 14 and 17 chirps were the first for Virgo. LIGO sent an alert to about a hundred observatories around the world, sparking a six-hour hunt for light and other emissions within a banana-shaped band of cosmic signals from the event. At an unprecedented scale of international, interdisciplinary collaboration, 60 observatories confirmed that the ripple of gravitational waves were indeed from a kilonova. A broad range of so-called cosmic messengers (gravitational waves, gamma-rays, X-rays, light, radio waves) have been recorded from the collision, marking the beginning of what astronomers refer to as “multi-messenger astronomy.”

Gravitational waves carry information on the acceleration of heavy objects, such as what occurs during the merger of two neutron stars or black holes. In this case, they told scientists that the neutron-star merger occurred about 120 million light years from Earth, closer than scientists’ previous expectations. The discovery was almost simultaneous with a sharp burst of gamma rays observed by two orbiting satellites, Fermi and INTEGRAL.

Neutron star mergers were one of the original motivations for constructing the LIGO detectors, an endeavor that began half a century ago and became the biggest project the National Science Foundation ever funded. In the Advanced LIGO project stage, the interferometers heard the first chirp of gravitational waves from merging black holes in September 2015. The discovery, announced last February, heralded the beginning of gravitational-wave astronomy and earned the LIGO Scientific Collaboration much acclaim.

Scientists in the LIGO Scientific Collaboration, of which UF is a founding member, and elsewhere are using their observations of the neutron-star merger to study the universe as well as the fundamental laws of nature. Currently, gravitational-wave detectors have 232 institutions and about 1600 scientists as members. UF has made key contributions to these studies across the entire scope of the project. Physicists now better understand how extremely energetic photons are produced in outer space. LIGO enables scientists to study the expansion of the universe in unprecedented ways by comparing the observed gravitational waves to what is known about the distant galaxy in which the merger happened more than 100 million years ago. Physicists are also increasing their understanding of how matter behaves at densities greater than that of the atomic nucleus.

UF made seminal contributions to infrared and optical observations of emissions from the debris around the merged neutron stars. Led by Steve Eikenberry of UF Astronomy, UF built the FLAMINGOS2 instrument, a near-infrared imaging spectrograph installed in the Gemini-South 8-meter telescope. FLAMINGOS2 detected the infrared emission 12 hours after the chirp took place and helped confirm the signal, which was characteristic of a kilonova.

In addition, newly appointed UF Physics faculty member Imre Bartos plays a leading role in searches for neutrinos from the merger, probing emission mechanisms at extreme energies. “Neutrinos are notoriously hard to detect, so we use IceCube, a billion-ton detector deep in the ice under the South Pole in Antarctica,” said Bartos. “No extra neutrinos were seen from this event, but even this allows us to set limits on what happened following the merger.”

UF became the third university to join LIGO after Caltech and MIT. The UF-LIGO team in the Department of Physics has spearheaded the design and construction of crucial components of the LIGO observatories and was responsible for the input optics (IO) of both the initial and the Advanced LIGO detectors. The IO is one of the most complex parts of the detector, and many key components were fabricated at UF. Florida also made significant contributions to the optical design of the main interferometer. The team working on these efforts includes Guido Mueller, David Reitze, David Tanner, Paul Fulda, and John Conklin. Hai-Ping Cheng leads the computational effort to reduce thermal noise in the detector.

UF’s Sergey Klimenko and Guenakh Mitselmakher developed the algorithm that discovered the first gravitational-wave signal in LIGO data on September 14, 2015. The UF algorithm is now being used to study the fate of the neutron stars after they merged.

The discovery was published on Oct. 16, 2017 in the Astrophysical Journal Letters (PDF).

This year’s Physics Nobel Prize was awarded to three scientists who were instrumental in the construction of LIGO and the first direct observation of gravitational waves, published last year. This award was given independently of the discovery of the neutron star collision.

LIGO is funded by the NSF and operated by Caltech and MIT, which conceived of LIGO and led the Initial and Advanced LIGO projects. Financial support for the Advanced LIGO project was led by the 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. More than 1,200 scientists and some 100 institutions from around the world participate in the effort through the LIGO Scientific Collaboration, which includes the GEO Collaboration and the Australian collaboration OzGrav. Additional partners are listed at The list of UF senior LIGO members is Guenakh Mitselmakher (PI), David Tanner, David Reitze (LIGO Executive Director), Sergey Klimenko, Guido Mueller, Bernard Whiting, Steve Eikenberry, Hai-Ping Cheng, John Conklin, and Imre Bartos.

The Virgo Collaboration comprises more than 280 physicists and engineers belonging to 20 different European research groups: six from Centre National de la Recherche Scientifique (CNRS) in France; eight from the Istituto Nazionale di Fisica Nucleare (INFN) in Italy; two in the Netherlands with Nikhef; the MTA Wigner RCP in Hungary; the POLGRAW group in Poland; Spain with the University of Valencia; and the European Gravitational Observatory, EGO, the laboratory hosting the Virgo detector near Pisa in Italy, funded by CNRS, INFN, and Nikhef.

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A particularly rewarding role for graduate faculty members is the opportunity to foster the academic and professional growth of our MA and PhD candidates as they transition from being our students to becoming our eventual colleagues. That is, in short, the goal of our graduate program — to form professionals in the fields of Hispanic linguistics and Spanish and Latin American literatures and cultures, who will shape the future of Spanish studies both within and beyond the academy. In so doing, we continue a commitment that can be traced back to the very origins of the University of Florida.

Spanish has been taught at UF since the school’s move to Gainesville in 1806. In the mid 1940s, we began offering graduate-level courses, culminating in the creation of a graduate-degree-granting program in the academic year of 1950-51. On our shelves, we can find the oldest MA thesis on record, Ronald M. Bryant’s “Four Novels of the Cristero Movement in Mexico” (1955), accompanied by the oldest PhD dissertations: Edna Coll’s “Injerto de Temas en las novelistas mexicanas contemporáneas” and Robert R. Morrison’s “Sainthood in the Theater of Lope de Vega” (both from 1963). Painstakingly typed long before the advent of computers and electronic submissions, these volumes provide a physical connection to a rich heritage for our graduate students as they embark on their own research projects and professional development.

The Spanish graduate program is currently comprised of eleven graduate faculty and thirty-five graduate students who work toward their MA or PhD degrees in either Linguistics or Literature and Culture. All of our students are offered appointments as graduate teaching assistants (GTAs) at the time of admission, which provides them with a tuition waiver, a competitive stipend, and free health insurance. The role of GTAs is twofold, as they complete the coursework and other academic requirements of their intended degrees while they teach Spanish classes at the elementary or intermediate level. As demanding as it is, this dual training as instructors as well as scholars is extremely valuable for their competitiveness on the job market. In addition, our graduate students regularly present at academic conferences (including the Symposium of Spanish and Portuguese Studies they organize every year at UF), participate as instructors in our study-abroad programs, and serve as student representatives on various departmental committees. Yet, all curricular considerations aside, what makes this program a truly remarkable endeavor is the inspiring passion for learning and teaching that our graduate students exhibit, as well as the rich cultural diversity they bring to the classroom and the community: more than half of our current TAs self-describe as female and non-white, and the current cohort comes from eleven different countries. Thanks to their dedication and that of the faculty advising them, a seven-decade tradition of Spanish graduate studies at the University of Florida continues to thrive.

portrait of smiling blonde woman
Crystal Marull, PhD

A summer trip to Spain with her high school’s Language Club “changed everything” for Crystal Marull: her desire to be able to return to Spain eventually led her to select Boston University for college. Crystal participated in their study abroad program in Madrid twice as an undergraduate, and she was invited after graduation to serve as the assistant to the director there, leading to a seven-year stay in Madrid.

While working with students in Madrid, Crystal became fascinated with the process of second-language acquisition. She would observe patterns in learning, question what the brain was doing, and wonder which processes were universal and which ones were idiosyncratic. She kept a notebook of her observations and started forming her own questions and hypotheses. This passion led Crystal to begin a doctoral program in Madrid, but bureaucratic entanglements forced her to change plans. At that point, married and celebrating the birth of her daughter Maia, Crystal and her husband decided to return to the U.S. so she could pursue her degree here. Crystal’s son Thomas was born just after her return to the U.S., where she pursued a master’s degree in education and later a PhD in Spanish: bilingualism and second language acquisition. This past spring, shortly after her UF interview, she successfully defended her dissertation on the same day she had labor induced. “From the defense to the hospital, no joke!” she says. Her son Sebastián was born 36 hours later.

As SPS’ Coordinator of Online Courses in Spanish, Crystal is optimistic about these classes and their role in the UF Online degree program. With the recent incorporation of online language coaches from Ecuador, Spain, and Guatemala, UF students get to practice their communicative skills on a biweekly basis in a small group session tailored to the content covered that week. The initial student response to this addition has been overwhelmingly positive, as has their reaction to the use of the VoiceThread application, which allows them to interact with authentic sources asynchronously.

Crystal sees her role as a curator of the language experience, a tour guide who meticulously determines the content, pacing, and interactivity of the journey. She would like to be more involved in guiding the conversation about what learning language online should look like and what technology we need in order to get us there. “Some find this scary,” she notes, but “I find it thrilling!”

Francesc Morales Gigi Marino

Francesc’s dissertation project offers an original blend of historical and literary analysis —within the broader framework of cultural studies — with the purpose of exploring the role played by fictional representations of archaeologists and archaeological work in the development of modern Spanish national identity. Spanish nationalism(s), either in singular or plural, is presently a highly debated topic in the context of Spain’s economic and political crisis as well as that of Europe’s identity crisis. In this regard, Francesc’s research promises to have an important impact in the field of Spanish studies and that of nationalism at large.

Francesc Morales was born in 1980 in Girona, a small city in Catalonia situated in the northeast corner of Spain, between the Pyrenees and the Mediterranean. His parents had migrated from Andalusia in the 1970s, as had hundreds of thousands of others since the 1960s. As a consequence, Francesc grew up speaking Spanish at home and with relatives, while Catalan was the primary language at school and in the streets.

Francesc has always been curious. “Knowing stuff was very important to me,” he recalls … and he absorbed much of that “stuff” through reading a diverse array of works — Lazarillo de Tormes, The Hobbit (Catalan translation), Hungarian folk tales in Spanish, and so on — but also through movies and TV shows, especially British series that were translated into Catalan.

Francesc moved to Florida after spending two years between England and Algeria, where he had his first experience teaching Spanish as a foreign language. Francesc arrived in the United States in 2009 and was accepted into UF’s Spanish and Portuguese Studies Graduate Program in 2010. When he first entered the academic world, he found the traditional definitions of “literature,” especially those based on political, geographical, cultural, linguistic, and generic boundaries, to be somewhat restrictive. Instead, he prefers to think of “literature” as synonymous with “humanities,” or “visually represented knowledge.” Francesc thus pays special attention to the overlaps between literature and the social sciences, the natural sciences, and the visual arts.

This view has led to the interdisciplinary work that is his dissertation, which is titled “Translatio Imperii: Archeology and Nationalism in Spanish Fiction (1868–1935).” It combines almost all of his academic interests: archaeology, politics, biography, cultural history, literature, and philosophy. Francesc plans to graduate with his PhD in May of 2018.

friendly man sitting with composure in front of bookcase
Diego Pascual

Diego Pascual PhD’13 was born in Madrid, Spain, and grew up in Granada. Diego recalls his first reflections about language as “a really cool thing” to observe and to study came while visiting family in Valencia: “It amazed me to see my relatives switch back and forth effortlessly between [Spanish and Catalan]. It amazed me even more that I was able to understand it all.”

These experiences would later fuel his interest in linguistics and his current research on bilingualism. As an undergraduate student at the University of Granada, he took some linguistics courses, but it was during his first years in the U.S. that he delved into the theoretical and applied study of language acquisition. Thanks to the help and encouragement he received from his professors and friends at Northern Illinois University, where he earned his MA degree, Diego decided to pursue his doctorate.

Diego’s first months at UF were intense and challenging, but rewarding as well. He recalls, “I had the opportunity to work with incredible mentors that trained me and helped me to move confidently forward in my career and in life. The training in research, teaching and service that I received while there has been invaluable in my current job.” Beyond the academics, Diego’s fondest memories involve his family and his classmates, most of whom he knows will remain lifelong friends. Even now, sitting in his office in Texas, Diego can close his eyes and remember with joy and happiness the parties, the trips to the beach, and lunch dates at the Plaza of the Americas.

Since he graduated from UF in 2013, Diego has served as Assistant Professor of Hispanic Linguistics and Director of the Spanish Heritage Language Program at Texas Tech University. While he has received both teaching and research awards, he considers his most important achievement to have been able to awaken an interest in research in his own students. “Going to conferences and seeing them present their own work makes me very proud,” he says. “Now I understand what my professors felt. I hope I made them proud.”