The rooms of the Koshland Integrated Natural Sciences Center are largely empty this summer, due to ongoing precautions related to COVID-19, but that isn’t stopping Haverford’s astronomers from conducting their high-level research. All of the professors in the Department of Physics and Astronomy, including Professor and Department Chair Andrea Lommen, are working with teams of student scientists remotely from their homes around the world and dorm rooms across campus.

Lommen’s research largely deals with searches for gravitational waves using millisecond pulsars—dead stars that spin very fast and are, therefore, used as accurate clocks—and she was part of the team that launched an x-ray telescope, known as NICER (Neutron star Interior Composition Explorer) and installed it on the International Space Station in 2017. Her six summer students, all but one of whom are conducting research using data from NICER, are supported by NASA and the National Science Foundation.

“My work lends itself well to remote research,” said Lommen. “It's not like I could go to the International Space Station before and collect my data in person, and I still can’t.”

To that end, physics majors Nathaniel Ruhl ’22 and Noah Schwab ’22 are working on a “horizon-crossing” experiment using NICER data. Their work uses observations of a black hole undergoing an outburst as it crosses the horizon of the earth.

“If you know the location of the earth, and the location of the black hole, you can use the time-of-crossing as a way to determine where you are in space,” said Lommen. “ In other words, they’re doing space navigation.”

“The ultimate goal of this research is to develop an algorithm to help spacecrafts in orbit determine their spatial location,” said Schwab. This computation-heavy work is appealing to him and Ruhl as both plan to enroll in Haverford’s 4+1 Engineering Program with the University of Pennsylvania.

“The navigational problem is an engineering problem,” said Ruhl, “so I believe working on this problem will help me think differently and help prepare me for engineering, or any scientific job, in the future.”

“This work is ground-breaking, in that the navigation method we are developing is novel,” said Schwab. “Never before have x-rays from celestial sources been used in this manner for navigational purposes. Additionally, we have been able to use this data to confirm characteristics about the atmosphere that have been determined through other scientific means.”

Another group in Lommen’s lab, composed of Sasha Levina ’23 and Mackenzie Tygh ’22, is doing different novel work with the NICER data. They are the first people in the world to ever study the pulse-by-pulse characteristics of pulsars in the x-ray band. They do this mostly by using Python, a programming language, to construct, compare, and inspect the data.

“The importance of my project lies in this: No single, well-defined, and widely accepted pulsar emission mechanism presently exists,” said Tygh. “Consequently, further comprehension of these rapidly spinning, ultra-dense objects through the analysis of their low- and high-energy radiation may shed light on this poorly understood process.”

“So far they've found that the pulsars behaved mostly as we expected they would, but that's a really important thing to know,” said Lommen of the pair. “A collaborator of mine, Kent Wood, who recently retired from the Naval Research Lab said, ‘If a theorist tells you to test something experimentally, you should test it. If a theorist tells you not to bother testing something, because they know how it'll turn out, then you should DEFINITELY test it.’"

Physics major and French minor Sergio Montano ’21 is spending his summer putting the finishing touches on a Lommen Lab manuscript for publication. The paper, which demonstrates how to place limits on the noise in pulsar timing using x-ray data, features Montano and Jesse Zeldes ’22 (who worked in the lab last summer) as first authors.

“Essentially, pulsars are like space lighthouses that emit pulses once per rotation,” said Montano. “At the International Space Station on Earth, NICER receives these pulses, but there is a lot of noise and error in the data since the pulses have to travel a long way to Earth. We want to eliminate all the noise so that we can get a clean signal and detect a gravitational wave, and my job is to detect a certain type of noise in the data classified as ‘red noise.’”

Physics and mathematics double major Charlotte Park BMC ’22 is the one member of the Lommen team not using NICER data for her research this summer. Instead, she is developing a new method for detecting binary black holes in pulsar timing by creating a new mathematical algorithm.

“My usual day consists of writing code, doing math—there are lots of statistics involved!—and reading a bunch of papers and references,” said Park. “This is one of the reasons I love this project, because I get to do all the three things I like—physics, math, and coding!”

Park is also the lab member farthest from Haverford’s campus this summer; she is at home in South Korea. So Lommen wakes up early every morning for a 7 a.m. check in with Park, when it is 8 p.m. her local time.

“The thing that all my students' projects have in common is that they use computer programming extensively to do the analysis,” said Lommen—a good thing, in particular, for remote work. “You can get a computer to spit out large quantities of numbers really quickly, and then the trick is figuring out if those are really the numbers you thought they were. I would say that 75% of my conversations with my students are about how to do ‘sanity checks’ or ‘truth tests’ of the code they're working on.”

Though the students lamented the loss of a collegial, in-person lab environment this summer, they were quick to note that not only did their work not require such a setting, but that Lommen had been diligent about convening the group over Zoom every Wednesday for feedback, discussion, and progress reports. Additionally, each team member checks in daily with Lommen via individual Zoom meetings.

“Professor Lommen’s passion for both her field and her students never ceases to advance my devotion to continue to ask questions and to discover answers about the universe in which we live,” said Tygh. “She challenges us to take risks and to embrace the inevitability of losing our intended course as we continuously confront new obstacles in our attempts to answer greater unsolved problems.”

“I found that I love doing this research, and it is definitely not a linear path,” said Ruhl. “There are many times when we feel lost, but that makes the breakthroughs even more exciting!”