Physics and astronomy and astrophysics professor contributes to gravitational wave research

A heavy use of computational tools can help to detect what has yet to be discovered, according to Chad Hanna, professor of physics and of astronomy and astrophysics at Penn State. 
 
Hanna, who started at the University in 2014 and is a Penn State Institute for Computational and Data Sciences (ICDS) co-hire, works in a large research group as part of the U.S. National Science Foundation’s Laser Interferometer Gravitational-Wave Observatory (LIGO). Hanna’s research team, which includes Research Innovations with Scientists and Engineers (RISE) team member Ron Tapia, is working to discover astrophysical events — such as gravitational waves, or ripples in spacetime predicted by Albert Einstein in 1916 — caused by the merger of two black holes or other celestial objects. 
 
“The LIGO observatory measures tiny distortions in space that are caused by the merging black holes,” Hanna said. “We are learning about the universe through measuring these tiny distortions in space. It’s a big effort that requires a lot of people for observations to run sustainably day and night.”  
 
As a group, Hanna and other researchers are using high-performance computing (HPC) to detect gravitational waves with computational methods to identify and match gravitational wave patterns. The team analyzes data in real time, working in shifts to observe gravitational waves as data is collected by LIGO. 
 
“We are driven by knowing that we will almost certainly detect the unknown — new phenomena that we have not yet discovered,” Hanna said. 
 
According to Hanna, many different types of astronomical messengers — signals we can detect from Earth — can come from a single source in space. This idea is called multi-messenger astronomy and involves searching for a variety of messengers, such as gravitational waves, light and neutrinos from neutron stars and/or black holes merging. 
 
“Each observation is ultimately carrying information about a different fundamental force of nature,” Hanna said. “Each messenger is telling you a new piece of information about the system.” 
 
The focus of the project remains on gravitational wave observation, but one of the stretch goals of the research is to use gravitational waves to detect dark matter — the mysterious substance comprising about 27% of the universe that doesn’t interact with light in a detectable way. 

“People only know dark matter exists because of gravitational interactions,” Hanna said. “We know it is there, but we don’t know what it is fundamentally. LIGO observes the universe purely through gravity. It might be a tool to learn more about dark matter.” 
 
One theory is that some dark matter forms black holes, which would require dark matter to interact with itself, according to Hanna. 
 
"We are trying to detect compact objects made from collapsing dark matter,” Hanna said. “Specifically, we are looking for dark matter black holes that are too small to be made from the collapse of normal matter.” 
 
Less than 10 years ago, there were no textbooks that explained gravitational waves with actual observations, according to Hanna. As an undergraduate at Penn State, Hanna began contributing to the LIGO research. 
 
“Now, the observations are a part of the science that we teach at all levels,” Hanna said, noting that his group hosts outreach camps that welcome high school students to learn about gravitational waves, hosted by the Eberly College of Science’s Science-U program.  
 
“It is now becoming a part of the normal educational mission. The broader impact of this research is wonderful to share.” 
 
Penn State has been a part of the LIGO scientific collaboration since its inauguration in 1999, with contributions including the use of a computing facility at ICDS. 
 
“My group develops software and algorithms and conducts analyses that are key results in LIGO papers. There’s a big impact on the community,” Hanna said. “We run a LIGO computing facility within ICDS, and it has allowed for nice partnerships with ICDS that will continue to grow going forward. Because we have specific computing needs, we have to develop our own systems. We have pushed forward several cyberinfrastructure proposals including proposals to fund RISE team members, and proposals to fund storage and proposals to connect Penn State to the Open Science Grid — a national consortium of shared computing resources available for U.S. researchers. It is my intention for there to be benefits from all of our LIGO infrastructure work and for it to be impactful for a bigger audience at Penn State.”