MSU gravitational physicist awarded grant to observe black hole collisions


Credit: MSU photo illustration by Kelly Gorham

BOZEMAN – A Montana State University researcher of extreme gravity who was recently appointed to leadership positions in two prestigious gravitational physics organizations has received a grant to test Einstein's theory of general relativity using observations of colliding black holes.

NASA awarded $815,000 to Nicolas Yunes, associate professor in the Department of Physics in MSU's College of Letters and Science, and physicist Emanuele Berti, professor at the University of Mississippi.

Yunes and Berti will collaborate on a three-year project designed to study the capabilities of a future space-based gravitational wave detector called the Laser Interferometer Space Antenna, or LISA, which is scheduled to launch in 2034 by the European Space Agency in partnership with NASA.

Once launched, LISA will collect information about the gravitational waves produced when black holes collide. The data could help scientists better understand the nature of the universe and Einstein's theory of gravity through direct observation of the aftermath of these collisions.

In preparation of the launch, Yunes and Berti will use the grant to determine how well LISA can test general relativity with colliding black holes and with extreme mass ratio inspirals. An extreme mass ratio inspiral, or EMRI, is the orbit of a relatively small black hole around a much heavier one that gradually decays due to the emission of gravitational waves.

"At the center of each galaxy, we believe, there is a powerful black hole that's millions of times more massive than the sun–these are very dense objects," Yunes said. "These galaxies move, and sometimes they collide with each other. Observing the gravitational waves produced during these mega-collisions will help us understand whether Einstein was right in these extreme environments."

The analysis has to be done far in advance of LISA's launch date, Yunes said, because tools needed to analyze LISA's data and test general relativity have to be ready for when the data begins to trickle in.

"The analysis we will do with this grant will help us and other scientists in the community to develop and invent these tools," he said.

The three spacecraft that make up the LISA detector will be launched in an equilateral-triangle configuration with sides roughly 1.25 million miles long–nearly five times the distance from Earth to the moon.

Each satellite will carry instruments capable of detecting tiny gravitational waves generated far beyond the Milky Way galaxy.

Space-based instruments, such as LISA, operate at much lower frequencies than Earth-bound gravitational wave detectors, enabling them to detect tiny ripples in the space-time fabric–gravitational waves–that were produced billions of years ago during the collision of distant galaxies.

The first direct detection of gravitational waves was made in 2015 using the Earth-based Laser Interferometer Gravitational-wave Observatory, or LIGO. The work surrounding that detection, which won a Nobel Prize, confirmed portions of Albert Einstein's theory of general relativity hypothesized 100 years earlier.

Yunes said that the data LISA gathers could challenge or confirm previously unexplored portions of Einstein's famous theory.

"In addition to massive black holes at the centers of galaxies, there are also tons and tons and tons of small black holes," Yunes said. "When they fall into any large one, the small ones act as tracers of the space-time geometry. We can ask lots of interesting questions about physics in such extreme environments."

He said this information will either reveal new physics or confirm Einstein's general theory of relativity. It might point to something different, in the way the first detection of gravitational waves has opened the door to new research.

Yunes, who co-founded MSU's eXtreme Gravity Institute in 2015 with MSU gravitational physicist Neil Cornish, recently received two appointments that allow him to help guide the future of gravitational wave science.

In December, NASA appointed Yunes as co-chair of the Gravitational Wave Science Interest Group of the Physics of the Cosmos Program through 2020. He was also appointed co-chair of the Fundamental Science Working Group of the International LISA Consortium.

"That's quite exciting," Yunes said. "Those are quite coveted positions. As chair of these committees, we will organize LISA science as it concerns fundamental physics, evaluate proposals and put them in context to ultimately provide advice to NASA about research to possibly pursue in the future."

Those latest appointments add to earlier awards Yunes has earned during his career.

In 2013, the National Science Foundation awarded its CAREER award to Yunes. The CAREER award is the NSF's most prestigious honor to support outstanding scientists who haven't yet received tenure. In 2015, he won The Young Scientist Prize, the most prestigious award for young scientists conducting gravitational research. In 2017, he received the MSU Fox Faculty Award for Outstanding Research, Scholarship, Creativity and Mentorship.

Yves Idzerda, head of MSU's Department of Physics, called Yunes a "rising star" among MSU faculty who not only attracts grant funding but also can communicate "those unnerving ideas about the theory of relativity, particularly black holes and extreme gravity, to any audience."

"As a member of the MSU eXtreme Gravity Institute, he has used art, poetry and dance to share his insights of these exotic objects," Idzerda said "He is an asset for this department and a wonderful colleague."


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