Caltech Astronomers Win New Horizons Breakthrough Prize

Professor of Astronomy Mansi Kasliwal (MS '07, PhD '11) and Professor of Astronomy Gregg Hallinan have been named winners of a 2022 New Horizons Prize in Physics, one of several Breakthrough Prizes announced today. Together with former Caltech postdoctoral scholar Alessandra Corsi, now at the Texas Tech University, and Raffaella Margutti of UC Berkeley, the scientists are being honored "for leadership in laying foundations for electromagnetic observations of sources of gravitational waves, and leadership in extracting rich information from the first observed collision of two neutron stars," according to the award citation.

In 2017, Kasliwal, Hallinan, Corsi, and Margutti helped make history with their observations of the first-ever cosmic event to be witnessed in both gravitational waves and electromagnetic, or light, waves. The event, called GW170817, began when two dense stellar remnants, called neutron stars, spiraled together and collided, creating a storm of ripples in space and time, or gravitational waves, that traveled outward in all directions. Some of those waves ultimately reached Earth, where the Laser Interferometer Gravitational-wave Observatory(LIGO) detected their signatures.

Just seconds after the gravitational waves were produced, the neutron star collision resulted in an explosion of matter, as well as light spanning the electromagnetic spectrum, ranging from high-energy gamma rays to low-energy radio waves. Kasliwal's team was one of the first to observe the collision in visible and infrared light, using the National Science Foundation (NSF)-funded Global Relay of Observatories Watching Transients Happen (GROWTH) project, a worldwide network of telescopes that specializes in catching short-lived energetic events such as this. The GROWTH team put together a picture of a cocoon breaking out to explain the rich multi-wavelength dataset.

Around two weeks later, as predicted by models, Gregg Hallinan, who is also director of the Owens Valley Radio Observatory (OVRO), together with Alessandra Corsi and collaborators, began seeing the radio waves created by the event using the Very Large Array, a collection of 27 radio telescopes in New Mexico. These radio observations later confirmed the presence of the cocoon, as well as providing the first direct confirmation that a relativistic jet, consistent with an energetic short gamma-ray burst, was produced by the merger. The collision was also seen by X-ray detecting telescopes.

The observation of celestial events through multiple channels (gravitational waves, visible light, X-rays and radio waves, in this case is known as multi-messenger astronomy, and is a growing field of study.

"It is truly an honor to be awarded the New Horizons Prize in Physics, and to share it with valued colleagues," Hallinan says. "Multi-messenger astronomy is an exciting field undergoing exponential growth, and I am grateful to those who have worked closely with me on this journey, particularly Kunal Mooley, Mansi Kasliwal, Udi Nakar, Samaya Nissanke, Kenta Hotokezaka, Alessandra Corsi, Shri Kulkarni, and Dale Frail."

Kasliwal also highlighted the team-based nature of the work.

"Collaborating with a worldwide network of astronomers—the GROWTH collaboration—and working closely with observatory staff and engineers is inspiring. Mentoring students and postdocs is the biggest perk of my job," Kasliwal says. "Pursuing astrophysics to unlock mysteries of our universe is truly a dream job for me—a passion converted into a profession in a dynamic field where the book is actively being written. Discovering where and how the elements in our periodic table are synthesized is exhilarating."

Each New Horizons Prize, which is intended to honor early-career scientists showing leadership in their field, is accompanied by a $100,000 award. The awards ceremony, televised live, has been postponed until 2022 due to the ongoing COVID-19 pandemic.

To see the full list of 2022 New Horizons recipients and Breakthrough Prize recipients, visit https://breakthroughprize.org/.