The Bruno Rossi Prize, given by the High Energy Astrophysics Division (HEAD) of the American Astronomical Society (AAS) in honor of significant contributions in high-energy astrophysics, was presented this year to the Neutron Star Interior Composition Explorer (NICER) team. The awardees, which include Haverford’s John Farnum Professor and Professor of Physics and Astronomy Andrea Lommen and Research Associate Wynn Ho, were recognized for development of NICER “and the revolutionary insights it is providing about the extreme environments of neutron stars and black holes, including the first precise and reliable measurement of a pulsar’s mass and radius from detailed modeling of its pulsed waveform."  

“I feel really excited and proud to be on the team,” said Lommen. “It's a really important acknowledgment of the contributions we've made to science, and it feels great.”
 
NICER is an X-ray telescope launched on a SPACEX rocket in June 2017 that now lives on the International Space Station, providing high-precision measurements of neutron stars— objects containing ultra-dense matter at the threshold of collapse into black holes. Lommen is chair of the mission’s High-Precision Timing Working Group, which means she leads a team of colleagues from NASA, the Naval Research Lab, the National Institute of Standards and Technology, and several academic institutions to research timing of x-ray pulsars with sub-microsecond precision. Ho works in three different groups: the Lightcurve Modeling Group, which performs the work of measuring pulsar masses and radii that the Rossi Prize cites, the Magnetars and Magnetospheres Working Group, which analyzes NICER data of pulsars and magnetars for various purposes such as for gravitational wave searches, and the Search Working Group, which uses NICER data to look for new sources.

“The story of this team goes back a long way and involves a lot of failed proposals,” said Lommen. “An early version of the mission was proposed unsuccessfully to NASA around 2005, and then again in 2008, and then finally the version we proposed in 2011 was successful. After many years developing and building the instrument, [we] launched and deployed the instrument on the International Space Station in 2017. I tell my students all the time that it's really important to fail. …I always thought that people who won these big awards were uber-smart and maybe even super-human, but I bet they all have similar stories—a bunch of failures and then a really great success.”
 
That’s not the only lesson Lommen’s students have learned. They have been involved in analyzing data from the NICER mission since she started at Haverford in 2017. Many of them have also published their findings with her. One publication, co-authored with Jack Crump ’23, Sergio Montano ’21, Jess Zeldes ’22, Elizabeth Teng ’20, and Samantha Berry BMC ’22, detected red noise for the first time in an x-ray pulsar. Another, co-authored with Dom Rowan ’20, Lauren Lugo ’21, Elizabeth Spano ’21, and Zaynab Ghazi BMC ’22, characterized the pulsars they were observing: spectra, timing, pulse-shape. Seniors Nathaniel Ruhl, Noah Schwab, and Romana Hladky recently had a paper accepted for publication by the American Astronautical Society in which they show that the NICER X-ray data can be used as a method of space navigation.
 
“We also contribute to the publications of other working groups,” said Lommen. “For example, two former Haverford students, Reilly Milburn ’19 and Sergio Montano ’21, are co-authors on one of the papers to which the Rossi Award citation referred. Their paper helped measure the radius of the neutron star for the first time.” 
 
Though the NICER mission has already contributed so much to the understanding of pulsar size and timing—Lommen’s first article using NICER data back in 2019 provided such precise pulsar timing that it already met the NICER mission requirement—there is still much to do. Future plans include further work on space navigation and additional red noise detection in pulsars.
 
NICER “was accepted as an 18-month mission,” said Lommen, “but we’re going on five years and hoping to get another three.”