Astrophysicists at West Virginia University are making breakthroughs in their research, from searching for and detecting gravitational waves to calculating the mergers of black holes. See how some of our scientists are finding new frontiers in space.
Chasing stars
Maura McLaughlin is co-director of the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) Physics Frontiers Center. The Center includes scientists from more than 40 U.S. and Canadian institutions. McLaughlin and her colleagues search for ripples in spacetime called gravitational waves.
Named to Nature’s “Ones to Watch” list for 2019, McLaughlin expects that NANOGrav will soon detect gravitational waves created by supermassive black holes at the cores of merging galaxies.
“We haven’t made a detection yet, but we’re really on the brink and expecting to make a detection over the next few years,” McLaughlin said.
The first detection will likely be of the background noise due to many galaxy mergers, she explained. That data will provide basic parameters about merging galaxies and test predictions of Einstein’s theory of general relativity. Then, the team can transition to multi-messenger astrophysics, where they detect single sources of gravitational waves and individual galaxy mergers and also observe them with electromagnetic telescopes.
Gravitational waves will be detected through timing an array of ultra-precise millisecond pulsars, or rapidly rotating neutron stars, with large radio telescopes. The influence of gravitational waves on Earth creates a unique signature in the pulses’ times of arrival.
McLaughlin and NANOGrav are supported by a team of about 200 high school students from across the U.S. working to discover pulsars with the Green Bank Observatory in Green Bank, West Virginia. The students in the Pulsar Search Collaboratory have discovered seven pulsars, so far.
“NANOGrav is timing this array of pulsars distributed across the sky, and our sensitivity is linearly proportional to the number of pulsars we time. If we double our number of pulsars, we double our sensitivity,” McLaughlin said. “The students are looking for pulsars to add to this array. They are not directly searching for gravitational waves or doing gravitational wave science, but the work they are doing is really important. The experience is also meaningful for them because they realize that they are part of the collaboration with people from all over the world.”
Students in the Pulsar Search Collaboratory may also enroll in an online WVU High School ACCESS class, where they attend weekly online discussions, analyze data from diagnostic plots and attend virtual observation sessions.
The students are invited to WVU every year for a two-day event where they learn about STEM opportunities on campus, tour labs and present their research. The young researchers can also attend a weeklong camp at the Green Bank Observatory in July each year. They get hands-on experience with the Green Bank Telescope and other smaller telescopes on-site.
“The outstanding work being done by NANOGrav and the Pulsar Search Collaboratory are two great examples of the ongoing, close collaboration between WVU and Green Bank Observatory,” said D.J. Pisano, interim chair of the Department of Physics and Astronomy. “Our continuing partnership gives WVU students and faculty unique access to the largest fully-steerable radio telescope in the world that enables high-impact science and provides meaningful educational experiences to people in West Virginia and around the world.”
Calculating colliding black holes
Since the discovery of gravitational waves by the Laser Interferometer Gravitational Wave Observatory (LIGO) collaboration in 2015, collaboration member and WVU faculty member Sean McWilliams has been on the search for a new way to calculate the waveform produced by two merging black holes.
Scientists usually interpret the signals from gravitational waves by comparing them to computer simulations. Now, McWilliams has created an exact mathematical formula to explain the signals, providing a more accurate method for the calculations and interpretations.
This discovery is more than three decades in the making.
“For a while, it’s been a puzzle. For 30 years, researchers were trying to simulate with supercomputers what happens when two black holes collide. Most theorists expected that the gravitational waves from these mergers would go a little crazy at the end, and do all sorts of crazy, zig-zaggy stuff,” McWilliams said. “But the simulations showed that the signal stayed nice and smooth. That got me thinking.”
The models that LIGO use are all based on the simulations, but an understanding of the merger signal had been lacking. Also, LIGO showed that while the models have been sufficient so far, they had reached the limit of the previous models they were using, so future events would be limited by the modeling accuracy, McWilliams explained.
“The computers were identifying a simplicity that we didn’t anticipate would be there,” McWilliams said. “The simulations were right, but when you do a numerical simulation and you get an answer, you don’t get the explanation of why the answer looks the way it does. With this model, we can calculate exactly what the answer is under a certain set of assumptions, and the answer agrees extremely well with the simulations and reinforces this new physical picture.”
Hear from Maura McLaughlin and her team of high school researchers in episode nine of Sparked, WVU Magazine’s podcast.
Glossary
- Low-frequency waves: These gravitational waves happen long term, often over decades. They are caused by galaxies in the process of merging. While they haven’t been detected yet, the NANOGrav team, including the Eberly College’s Sarah Burke-Spolaor, Duncan Lorimer, Maura McLaughlin and Sean McWilliams, are on the hunt and expect to make a detection in the next few years.
- High-frequency waves: These gravitational waves occur in a short timeframe and on a small scale. They are generated when two black holes collide to form a larger black hole. The waves have been detected by the LIGO collaboration, including the Eberly College’s Zach Etienne and Sean McWilliams.
- NANOGrav: The North American Nanohertz Observatory for Gravitational Waves is a collaboration of scientists from more than a dozen U.S. and Canadian institutions whose goal is to detect gravitational waves using pulsars. The Eberly College’s Maura McLaughlin, Sarah Burke-Spolaor, Duncan Lorimer and Sean McWilliams are members, along with six postdoctoral fellows, 10 graduate students and about six undergraduate students.
- LIGO: The Laser Interferometer Gravitational Wave Observatory is a national facility for gravitational wave research with collaborators from more than 80 universities and other research organizations around the world. The Eberly College’s Sean McWilliams and Zach Etienne are members, along with three graduate students.
Green Bank Observatory
In July 2019, the National Science Foundation formally announced plans to continue operating the Green Bank Observatory.
The NSF signed a “Record of Decision” for the observatory on July 26, located in Green Bank in Pocahontas County. The decision acknowledges that the facility will remain open, with a plan that sees reduced funding from the federal agency but partnerships with new stakeholders. In recent years, the NSF had discussed divesting from the facility.
At the Eberly College, a total of 10 astronomy faculty work closely with the Green Bank Observatory both for research and education. More than a dozen physics and astronomy graduate students also use the Green Bank Telescope in their research.
“WVU has a longstanding and thriving partnership with the Green Bank Observatory,” said Fred King, vice president for research at WVU. “It has been key to elevating the profile of WVU to an international leader in astronomy and astrophysics research. Of equal importance is that it has provided us with a platform to excite secondary school students about science while training and developing the scientists of tomorrow.”
The NSF issued its decision following an environmental impact analysis and input from the public and the scientific community. The agency has urged the observatory to build partnerships with federal, academic and private collaborators to help offset operating costs traditionally provided by the NSF.
The observatory is currently operated by Associated Universities, Inc., a Washington, D.C.-based nonprofit research management corporation.