Scientists observe first verified neutron star collision

Scientists using the Dark Energy Camera have captured images of the aftermath of a neutron star collision, the source of LIGO/Virgo’s most recent gravitational wave detection

A team of scientists using the Dark Energy Camera (DECam), the primary observing tool of the Dark Energy Survey, was among the first to observe the fiery aftermath of a recently detected burst of gravitational waves, recording images of the first confirmed explosion from two colliding neutron stars ever seen by astronomers.

Scientists on the Dark Energy Survey joined forces with a team of astronomers based at the Harvard-Smithsonian Center for Astrophysics (CfA) for this effort, working with observatories around the world to bolster the original data from DECam. Images taken with DECam captured the flaring-up and fading over time of a kilonova — an explosion similar to a supernova, but on a smaller scale — that occurs when collapsed stars (called neutron stars) crash into each other, creating heavy radioactive elements.

This particular violent merger, which occurred 130 million years ago in a galaxy near our own (NGC 4993), is the source of the gravitational waves detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO) and the Virgo collaborations on Aug. 17. This is the fifth source of gravitational waves to be detected — the first one was discovered in September 2015, for which three founding members of the LIGO collaboration were awarded the Nobel Prize in physics two weeks ago.

This latest event is the first detection of gravitational waves caused by two neutron stars colliding and thus the first one to have a visible source. The previous gravitational wave detections were traced to binary black holes, which cannot be seen through telescopes. This neutron star collision occurred relatively close to home, so within a few hours of receiving the notice from LIGO/Virgo, scientists were able to point telescopes in the direction of the event and get a clear picture of the light.

“This is beyond my wildest dreams,” said Marcelle Soares-Santos, formerly of the U.S. Department of Energy’s Fermi National Accelerator Laboratory and currently of Brandeis University, who led the effort from the Dark Energy Survey side. “With DECam we get a good signal, and we can show how it is evolving over time. The team following these signals is a well-oiled machine, and though we did not expect this to happen so soon, we were ready for it.”

The Dark Energy Camera is one of the most powerful digital imaging devices in existence. It was built and tested at Fermilab, the lead laboratory on the Dark Energy Survey, and is mounted on the National Science Foundation’s 4-meter Blanco telescope, part of the Cerro Tololo Inter-American Observatory in Chile, a division of the National Optical Astronomy Observatory. The DES images are processed at the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign.

Texas A&M University astronomer Jennifer Marshall was observing for DES at the Blanco telescope during the event, while Fermilab astronomers Douglas Tucker and Sahar Allam were coordinating the observations from Fermilab’s Remote Operations Center.

“It was truly amazing,” Marshall said. “I felt so fortunate to be in the right place at the right time to help make perhaps one of the most significant observations of my career.”

The kilonova was first identified in DECam images by Ohio University astronomer Ryan Chornock, who instantly alerted his colleagues by email. “I was flipping through the raw data, and I came across this bright galaxy and saw a new source that was not in the reference image [taken previously],” he said. “It was very exciting.”

Once the crystal clear images from DECam were taken, a team led by Professor Edo Berger, from CfA, went to work analyzing the phenomenon using several different resources. Within hours of receiving the location information, the team had booked time with several observatories, including NASA’s Hubble Space Telescope and Chandra X-ray Observatory.

LIGO/Virgo works with dozens of astronomy collaborations around the world, providing sky maps of the area where any detected gravitational waves originated. The team from DES and CfA had been preparing for an event like this for more than two years, forging connections with other astronomy collaborations and putting procedures in place to mobilize as soon as word came down that a new source had been detected. The result is a rich data set that covers “radio waves to X-rays to everything in between,” Berger said.

“This is the first event, the one everyone will remember,” Berger said. “I’m extremely proud of our entire group, who responded in an amazing way. I kept telling them to savor the moment. How many people can say they were there at the birth of a whole new field of astronomy?”

Adding to the excitement of this observation, this latest gravitational wave detection correlates to a burst of gamma rays spotted by NASA’s Fermi Gamma-ray Space Telescope. Combining these detections is like hearing thunder and seeing lightning for the very first time, and it opens up a world of new scientific discovery.

“Each of these — the gravitational waves from merging neutron stars, the gamma ray burst and the optical counterpart — could have been separate groundbreaking discoveries, and each could have taken many years,” said Daniel Holz of the University of Chicago, who works on both the DES and LIGO collaborations. “In less than a day, we did it all. This has required many different communities working together to make it all happen. It’s so gratifying to have it be so successful.”

This event also provides a completely new and unique way to measure the present expansion rate of the universe, the Hubble constant, something theorized by Holz and others. Just as astrophysicists use supernovae as “standard candles” (objects of the same intrinsic brightness) to measure cosmic expansion, kilonovae can be used as “standard sirens” (objects of known gravitational wave strength).

LIGO/Virgo can use this to tell the distance to these events, while optical follow-up from DES and others determines the red shift or recession speed; their combination enables scientists to determine the present expansion rate. This new kind of measurement will assist the Dark Energy Survey in its mission to uncover more about dark energy, the mysterious force accelerating the expansion of the universe.

“The Dark Energy Survey team has been working with LIGO for more than two years, refining their process of following up gravitational wave signals,” said Fermilab Director Nigel Lockyer. “It is immensely gratifying to be on the front lines of a discovery this significant, one that required the combined skills of many supremely talented people in many fields.”

The Dark Energy Survey recently began the fifth and final year of its quest to map an area of the southern sky in unprecedented detail. Scientists on DES will use this data to learn more about the effect of dark energy over eight billion years of the universe’s history, in the process measuring 300 million galaxies, 100,000 galaxy clusters and 3,000 supernovae.

Six papers relating to the DECam discovery of the optical counterpart are planned for publication in The Astrophysical Journal. Preprints of all papers are available here: https://www.darkenergysurvey.org/des-gravitational-waves-papers.

“It is tremendously exciting to experience a rare event that transforms our understanding of the workings of the universe,” said France A. Córdova, director of the National Science Foundation (NSF), which funds LIGO and supports the observatory where DECam is housed. “This discovery realizes a long-standing goal many of us have had — that is, to simultaneously observe rare cosmic events using both traditional as well as gravitational-wave observatories. Only through NSF’s four-decade investment in gravitational-wave observatories, coupled with telescopes that observe from radio to gamma-ray wavelengths, are we able to expand our opportunities to detect new cosmic phenomena and piece together a fresh narrative of the physics of stars in their death throes.”

 

 

The Dark Energy Survey is a collaboration of more than 400 scientists from 26 institutions in seven countries. Funding for the DES Projects has been provided by the U.S. Department of Energy Office of Science, U.S. National Science Foundation, Ministry of Science and Education of Spain, Science and Technology Facilities Council of the United Kingdom, Higher Education Funding Council for England, ETH Zurich for Switzerland, National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign, Kavli Institute of Cosmological Physics at the University of Chicago, Center for Cosmology and AstroParticle Physics at Ohio State University, Mitchell Institute for Fundamental Physics and Astronomy at Texas A&M University, Financiadora de Estudos e Projetos, Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, Conselho Nacional de Desenvolvimento Científico e Tecnológico and Ministério da Ciência e Tecnologia, Deutsche Forschungsgemeinschaft, and the collaborating institutions in the Dark Energy Survey, the list of which can be found at www.darkenergysurvey.org/collaboration. 

Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatory, is operated by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation.

Fermilab is America’s premier national laboratory for particle physics and accelerator research. A U.S. Department of Energy Office of Science laboratory, Fermilab is located near Chicago, Illinois, and operated under contract by the Fermi Research Alliance LLC, a joint partnership between the University of Chicago and the Universities Research Association, Inc. Visit Fermilab’s website at www.fnal.gov and follow us on Twitter at @Fermilab.

The DOE Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

 

Professor Steven Lund of Michigan State University has been named the new director of the U.S. Particle Accelerator School (USPAS). His four-year renewable term begins on Dec. 1. He will succeed Professor William Barletta of the Massachusetts Institute of Technology, who has been director since 2006.

The USPAS is recognized as the nation’s premier training program in accelerator science and engineering. USPAS started in 1981 and convenes twice a year to offer a broad range of graduate-level accelerator science and engineering courses in an intensive-school format. Training and documentation produced by the sessions has been recognized for excellence and has had a profound positive impact on the field. All business and activities of the school are coordinated by the director and the USPAS office at the U.S. Department of Energy’s Fermi National Accelerator Laboratory.

“I am delighted about this appointment and eager to continue the outstanding work of the USPAS in educating current and future accelerator scientists and engineers,” Lund said. “It is a great honor to be selected, and I look forward to guiding the school to continued success.”

Lund has been a professor at MSU since 2014 and currently serves on both the Director’s Advisory Council and the Curriculum Committee for the USPAS, working with Director Barletta to coordinate school programs in the community interest. Lund’s position at MSU is at the Facility for Rare Isotope Beams (FRIB), and his focus is theoretical accelerator physics, emphasizing analytic theory and numerical modeling. He also teaches graduate courses in accelerator physics and advises students.

“Over the past 35 years the USPAS has developed a program filling a critically important role in the training and education for the national laboratories that use accelerators as research tools,” said Rod Gerig of Argonne National Laboratory, chair of the USPAS Director’s Advisory Council. “Those of us who represent the national laboratory and university community want to thank the outgoing director, Dr. William Barletta, for his service to USPAS over the past 11 years. Also, we have enjoyed and benefited from working with Dr. Lund on the USPAS Director’s Advisory Council, and now look forward to working with him as the USPAS director as we move forward in carrying out this important mission.”

Accelerators are a key driver of discovery science and industry and are central to the discovery missions of the U.S. DOE Office of Science. The USPAS collaboration includes seven U.S. DOE Office of Science laboratories, one U.S. DOE National Nuclear Security Agency lab and two universities. (See full list below.)

“Over its 35-year history, the USPAS has welcomed students of all levels of expertise and in many cases introduced them to the science of particle accelerators,” said Jim Siegrist, associate director of the U.S. DOE Office of Science for the Office of High Energy Physics. “I look forward to Steven Lund continuing this great tradition.”

The USPAS offers a continually updated curriculum of courses ranging from fundamentals of accelerator science to advanced physics and engineering concepts. The school is intended not only to meet the needs of national laboratories, but also to educate people on the many uses of particle accelerators in other fields, including industrial and medical applications.

“Fermilab is proud of its work with USPAS and eager to continue that work with Steven Lund at the helm,” said Fermilab Director Nigel Lockyer. “With thousands of particle accelerators in use around the world for dozens of different applications, teaching students the basics of accelerator technology is more important now than ever.”

MSU is developing its own world-class particle accelerator. FRIB will be a new scientific user facility for the Office of Nuclear Physics in DOE’s Office of Science. Under construction on campus and operated by MSU, the heart of FRIB is a high-power superconducting linear accelerator that will accelerate heavy ions to half the speed of light. FRIB will enable scientists to make discoveries about the properties of rare isotopes, supporting a community of currently 1,400 scientists.

FRIB is presently under construction—slated for completion by 2022—with first portions currently undergoing commissioning. Lund’s research aims to identify, understand and control processes that can degrade the quality of the particle beam.

“Steve is an outstanding researcher and a passionate educator, both of which will serve him well in his new position,” said Thomas Glasmacher, FRIB Laboratory director. “I am pleased he was selected and know he will excel in this new role.”

Before arriving at MSU in 2014 to work on FRIB, Lund held a joint appointment at Lawrence Livermore National Laboratory and Lawrence Berkeley National Laboratory working on physics issues associated with the transport of beams with high charge intensity, design of accelerator and trap systems, large- and small-scale numerical simulations of accelerators, support of laboratory experiments, and design of electric and magnetic elements to focus and bend beams. Lund received his Ph.D. in physics from MIT in 1992.

“The U.S. Particle Accelerator School has educated next-generation accelerator physicists and engineers for decades and through that made sure that we can build ever better accelerators and develop new important technologies,” said Norbert Holtkamp of SLAC National Accelerator Laboratory, a member of the USPAS Institutional Board. “SLAC wants thank Bill Barletta for his strong leadership during his tenure and we look forward to seeing Steven Lund implement his compelling vision. We also thank MSU and FRIB for their strong continued support.“

The USPAS collaboration includes Argonne National Laboratory, Brookhaven National Laboratory, Fermi National Accelerator Laboratory, Lawrence Berkeley National Laboratory, Oak Ridge National Laboratory, SLAC National Accelerator Laboratory and Thomas Jefferson National Accelerator Facility, all U.S. DOE Office of Science labs; Los Alamos National Laboratory, a U.S. DOE National Nuclear Security Agency lab; Cornell University and Michigan State University.

Michigan State University has been advancing the common good with uncommon will for more than 160 years. One of the top research universities in the world, MSU pushes the boundaries of discovery and forges enduring partnerships to solve the most pressing global challenges while providing life-changing opportunities to a diverse and inclusive academic community through more than 200 programs of study in 17 degree-granting colleges.

Fermilab is America’s premier national laboratory for particle physics and accelerator research. A U.S. Department of Energy Office of Science laboratory, Fermilab is located near Chicago, Illinois, and operated under contract by the Fermi Research Alliance LLC, a joint partnership between the University of Chicago and the Universities Research Association, Inc. Visit Fermilab’s website at www.fnal.gov and follow us on Twitter at @Fermilab.

The DOE Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

It was late 1972 and the Meson Lab was just working on its first beam transport. I was a new crew chief, having just joined the lab, and a man named John was my assistant. We were operating from the MS-2 service building with the roaring power supplies. It was about 8 p.m. The Main Ring had just gone down and the Main Control Room gave an estimate of one hour. (Everything only took one hour back then, until they gave the next updated estimate of one hour!)

As I sat and fiddled with the MAC-16 control computer to see what it would do, John sat with his feet propped up on a desk watching “The Honeymooners” TV show starring Jackie Gleason on a small black and white monitor. I looked up to see a gentleman walking towards me wearing a beret and wearing a top coat. He came over and asked what I was doing, and I said I was trying to learn all about the computer. Nowadays it would be called hacking!

I mentioned the ring was down for an hour. He thanked me, turned and walked back toward the door, glancing at John as he walked past. I asked John who the gentleman was, and John just shrugged. “No idea” he said.

When I came in for my shift the next day, my boss, Jim, called me in to his office. He looked at me with a terse smile and said, “Dr. Wilson was happy to see you trying to understand the control system, but for crying out loud, don’t let John watch “The Honeymooners” when the director is there!”

That event was my introduction to Dr. Robert R. Wilson, and I spoke with him numerous times after that.

Paul Czarapata is the deputy head of the Accelerator Division.

Editor’s note: Earlier today, the Nobel committee selected Rainer Weiss and the pair of Barry Barish and Kip Thorne for the 2017 Nobel Prize in physics for their contributions to the Laser Interferometer Gravitational-wave Observatory (LIGO). Barish has a long history with Fermilab, having led the E-21A experiment in the 1970s, which studied neutrinos at very high energies. He has also been at the forefront of the International Linear Collider effort, which Fermilab has contributed to over the past decade. Rainer Weiss, a professor of physics at MIT, has been a collaborator on Fermilab’s Holometer experiment since its inception in 2009. The detection of gravitational waves in 2015 was a landmark discovery, and Fermilab congratulates the winners of the Nobel Prize and the entire LIGO collaboration.

After being passed up for the honor last year, three scientists who made essential contributions to the LIGO collaboration have been awarded the 2017 Nobel Prize in Physics.

Rainer Weiss will share the prize with Kip Thorne and Barry Barish for their roles in the discovery of gravitational waves, ripples in space-time predicted by Albert Einstein. Weiss and Thorne conceived of LIGO, and Barish is credited with reviving the struggling experiment and making it happen.

“I view this more as a thing that recognizes the work of about 1000 people,” Weiss said during a Q&A after the announcement this morning. “It’s really a dedicated effort that has been going on, I hate to tell you, for as long as 40 years, people trying to make a detection in the early days and then slowly but surely getting the technology together to do it.”

Another founder of LIGO, scientist Ronald Drever, died in March. Nobel Prizes are not awarded posthumously.

According to Einstein’s general theory of relativity, powerful cosmic events release energy in the form of waves traveling through the fabric of existence at the speed of light. LIGO detects these disturbances when they disrupt the symmetry between the passages of identical laser beams traveling identical distances.

The setup for the LIGO experiment looks like a giant L, with each side stretching about 2.5 miles long. Scientists split a laser beam and shine the two halves down the two sides of the L. When each half of the beam reaches the end, it reflects off a mirror and heads back to the place where its journey began.

Normally, the two halves of the beam return at the same time. When there’s a mismatch, scientists know something is going on. Gravitational waves compress space-time in one direction and stretch it in another, giving one half of the beam a shortcut and sending the other on a longer trip. LIGO is sensitive enough to notice a difference between the arms as small as 1000^th the diameter of an atomic nucleus.

Scientists on LIGO and their partner collaboration, called Virgo, reported the first detection of gravitational waves in February 2016. The waves were generated in the collision of two black holes with 29 and 36 times the mass of the sun 1.3 billion years ago. They reached the LIGO experiment as scientists were conducting an engineering test.

“It took us a long time, something like two months, to convince ourselves that we had seen something from outside that was truly a gravitational wave,” Weiss said.

LIGO, which stands for Laser Interferometer Gravitational-Wave Observatory, consists of two of these pieces of equipment, one located in Louisiana and another in Washington state.

The experiment is operated jointly by Weiss’s home institution, MIT, and Barish and Thorne’s home institution, Caltech. The experiment has collaborators from more than 80 institutions from more than 20 countries. A third interferometer, operated by the Virgo collaboration, recently joined LIGO to make the first joint observation of gravitational waves.

Editor’s note: This article originally appeared in Symmetry.