Curious About the Cosmos

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Category: Department News

Published: Wednesday, September 11 2024 06:24

For the last four years, Aneesh Anandanatarajan has kept a running list of “big questions” about the universe and how it works. He started the list in high school but shows no signs of slowing down in his senior year as an astronomy and physics dual-degree student at the University of Maryland.Aneesh Anandanatarajan

“I am the type of person to ask questions until someone tells me to stop,” Anandanatarajan said. “I have about 40 questions on my list, and I like to return to them to see how I’ve progressed in terms of what I've learned and what I’m interested in.”

One of his early questions—how are electricity and magnetism related?—was written at a time when Anandanatarajan knew little about plasma astrophysics. Now, he’s conducting research in Physics Assistant Professor Sasha Philippov’s lab, where he uses physics-based simulations to study the turbulent environment and complex electromagnetic interactions around supermassive black holes.

While Anandanatarajan loves asking questions, he’s happiest sharing what he learned with others. As the tutoring chair for UMD’s Society of Physics Students, Anandanatarajan has become a physics ambassador while strengthening his knowledge of the subject.Aneesh Anandanatarajan and Othello Gomes

“As a tutor and as the tutoring chair, it has been important to me to know physics well. I want to fully understand where these different concepts and equations come from,” Anandanatarajan said. “One of the things I'm most excited about is sharing physics with other people.”

Virtually hooked

Anandanatarajan has been interested in exotic objects like black holes and neutron stars since middle school, but he didn’t discover this passion in a lab or a planetarium. While watching YouTube one day, he found a channel with buzzy animated videos about popular science topics, including astronomy and physics. A few videos later, he was hooked.

“It captured my interest in more ways than I expected because I didn’t really know much about those subjects before middle school,” he said. “Over time, I watched more videos and realized that astronomy might be something I’d like to learn more about at an academic and professional level.”

Anandanatarajan said he was initially attracted to UMD’s “great astronomy program,” but he was thrilled to learn that he could add a second degree in physics by taking a few more classes. He’s enjoyed learning from professors who are exploring diverse fields of research.

“There are a lot of really great research topics here at Maryland and professors that are doing active research in those fields,” he said. “I’ve had a lot of great experiences with professors that want me to succeed and have pushed me to succeed.”

One of those professors is Philippov, whom Anandanatarajan started working with in spring 2024. Philippov studies high-energy astrophysics through a blend of theory and computer modeling with a focus on the physics of plasmas—hot, ionized gas surrounding black holes, neutron stars and other celestial objects. 

Anandanatarajan is using computer simulations to study how plasmas composed of electrons and positrons interact with other particles in the corona, an extremely hot and highly magnetized region that surrounds black holes, our sun and other space objects. Through a process called annihilation, these interactions can produce gamma rays, a type of radiation that astronomers can study to learn more about the universe.

“The corona is a very mysterious region that a lot of astronomers are very interested in probing,” Anandanatarajan said. “It’s essentially a breeding ground for electromagnetic activity, so we'd like to understand the phenomena that occur in that region because there are a lot of unknowns when it comes to our observations.”

Through this research, Anandanatarajan learned how to run Monte Carlo simulations that predict the probability of different outcomes—a skill that proved useful on other projects, like the up-and-coming study of high-energy particle collisions.

When interests collide

During the spring 2024 semester, a project in Physics Assistant Professor Christopher Palmer’s PHYS 441: “Introduction to Particle Physics” course let Anandanatarajan play an unexpected role in the next Large Hadron Collider (LHC).

During the course, Palmer teamed up with faculty at MIT to give students a front-row seat to discussions involving the Future Circular Collider (FCC), a proposed collider that would push the boundaries of particle physics beyond the capabilities of the LHC. The hope is that an upgraded collider could discover new particles or find evidence that deviates from the Standard Model of physics, which describes the fundamental forces that shape the universe.

Anandanatarajan and other students at UMD and MIT analyzed Monte Carlo simulations to determine how to precisely measure novel processes produced in electron-positron collisions from the FCCee accelerator, the first stage of the FCC.

“Essentially what we wanted to do was characterize different kinematic properties, such as the energy, momentum and angles at which these produced particles came out,” Anandanatarajan explained.

In March, this culminated in a visit to the second annual FCC workshop, where students presented their projects and spoke with leaders in the field.

“We learned a lot about how high-energy physics is conducted and the planning that is needed for a mega collider that may or may not be built 30 years from now,” Anandanatarajan said. “We talked to many different experts in the field who were thankfully friendly and willing to talk to undergrads about these types of topics.”

This experience initially felt disparate from his other projects, but Anandanatarajan realized that electron-positron collisions and large Monte Carlo simulations play an important role in astrophysics, too. After he earns his undergraduate degree, Anandanatarajan plans to continue studying astrophysics in a Ph.D. program that will allow him to keep asking—and answering—those big questions he’s carried with him for years.

Until then, he looks forward to spending his senior year sharing his passion with anyone willing to listen. He has several ideas for the Society of Physics Students—including a possible YouTube channel, harking back to his initial inspiration—to get students more engaged in physics.

“Making people excited about physics has always been a passion of mine,” he said. “I feel like I enjoy physics more than the average person, so I want to share those feelings with others and show them all of the cool things that physics has to offer.”

In Memoriam

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Category: Department News

Published: Wednesday, September 11 2024 05:24

It is with much sadness that the Department of Physics announces the passing of several members of our community.

• Melanie Knouse Cline, a coordinator in the Maryland Center for Fundamental Physics (MCFP), died on June 3, 2024.
• Robert Dewar, a former postdoctoral associate, died on April 5, 2024.
• Robert Goldstein, an alumnus, died on Sept. 4, 2024.
• Charles Hussar, an alumnus and donor, died on March 30, 2024.
• Verne Kauppe (B.S., '71), who worked in multisensor and microwave remote sensing, died on September 8, 2024.
• William Kuperman (Ph.D., '72), former Director of the Marine Physical Laboratory of the Scripps Institution of Oceanography,  died on June 30, 2024. 
• Ernest Madsen (B.S. and M.S.), a medical physicist at the University of Wisconsin, died on August 24, 2024.
• Martin Vol Moody, an experimentalist working on gravitation, died on August 18, 2024.  
• Robert L. Parker, (Ph.D.,'60) who worked in metallurgy for the U.S. government, died on April 21, 2024.
• Joseph Perez (Ph,D., '68), former head of the Auburn University Physics Department, died on July 25, 2024.
• Edward "Joe" Redish, an acclaimed researcher and Professor Emeritus, died on August 24, 2024.
• Paul Richardson, a physicist with the U.S. Bureau of Mines, died on May 29, 2024.

UMD Physicists Advance NASA’s Mission to ‘Touch the Sun’

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Category: Research News

Published: Wednesday, September 11 2024 05:24

Those who say there’s “nothing new under the sun” must not know about NASA’s Parker Solar Probe mission. Since its launch in 2018, this spacecraft has been shedding new light on Earth’s sun—and University of Maryland physicists are behind many of its discoveries.

At its core, the Parker Solar Probe is “on a mission to touch the sun,” in NASA’s words. It endures extreme conditions while dipping in and out of the corona—the outermost layer of the sun’s atmosphere—to collect data on magnetic fields, plasma and energetic particles. The corona is at least 100 times hotter than the sun’s surface, but it’s no match for the spacecraft’s incredible speed and carbon composite shield, which can survive 2,500 degrees Fahrenheit. Last year, the spacecraft broke its own record for the fastest object ever made by humans. Parker Solar Probe (courtesy of NASA)

This engineering feat was built to solve solar mysteries that have long confounded scientists: What makes the sun’s corona so much hotter than its surface, and what powers the sun’s supersonic wind? These questions aren’t just of interest to scientists, either. The solar wind, which carries plasma and part of the sun’s magnetic field, can cause geomagnetic storms capable of knocking out power grids on Earth or endangering astronauts in space.

To better understand these mechanisms, the Parker Solar Probe will attempt its deepest dive into the corona on December 24, 2024, with plans to come within 3.9 million miles of the sun’s surface. Researchers hope its findings will help them predict space weather with greater accuracy and frequency in the future.

James Drake, a Distinguished University Professor in UMD’s Department of Physics and Institute for Physical Science and Technology (IPST), is helping to move the needle closer to that goal as a member of the Parker Solar Probe research team.

“This mission is what's called a discovery mission, and with a discovery mission we can never be sure what we're going to find,” Drake said. “But of course, everybody is most excited about the data that will come from the Parker Solar Probe getting very close to the sun because that will reveal new information about the solar wind.” 

Reconnecting the dots

Drake and Marc Swisdak, a research scientist in UMD’s Institute for Research in Electronics & Applied Physics (IREAP), have been involved with this mission since its inception. The researchers were asked to join because of their expertise in magnetic reconnection, a process that occurs when magnetic fields pointing in opposite directions cross-connect, releasing large amounts of magnetic energy.

Before the Parker Solar Probe, it was known that magnetic reconnection could produce solar flares and coronal mass ejections that launch magnetic energy and plasma out into space. However, this mission revealed just how important magnetic reconnection is to so many other solar processes. 

Early Parker Solar Probe data showed that magnetic reconnection was happening frequently near the equatorial plane of the heliosphere, the giant magnetic bubble that surrounds the sun and all of the planets. More specifically, this activity was observed in the heliospheric current sheet, which divides sectors of the magnetic field that point toward and away from the sun. 

“That was a big surprise,” Drake said of their findings. “Every time the spacecraft crossed the heliospheric current sheet, we saw evidence for reconnection and the associated heating and energization of the ambient plasma.”

In 2021, the Parker Solar Probe made another unexpected discovery: the existence of switchbacks in the solar wind, which Drake described as “kinks in the magnetic field.” Characterized by sharp changes in the magnetic field’s direction, these switchbacks loosely trace the shape of the letter S.

“No one predicted the switchbacks—at least not the magnitude and number of them—when Parker launched,” Swisdak said. 

To explain this odd phenomenon, Drake, Swisdak and other collaborators theorized that switchbacks were produced by magnetic reconnection in the corona. While the exact origin of those switchbacks hasn’t been definitively solved, it prompted UMD’s team to take a closer look at magnetic reconnection, especially its role in driving the solar wind.

“The role of reconnection has gone from something that was not necessarily that significant at the beginning to a major component of the entire Parker Solar Probe mission,” Drake said. “Because of our group's expertise on the magnetic reconnection topic, we have played a central role in much of this work.”

Last year, Drake and Swisdak co-authored a study with other members of the Parker science team that explained how the sun’s fast wind—one of two types of solar wind—can surpass 1 million miles per hour. They once again saw that magnetic reconnection was responsible, specifically the kind that occurs between open and closed magnetic fields, known as interchange reconnection.

To test their theories about solar activity, the UMD team also uses computer simulations to try to reproduce Parker observations. 

“I think that one of the things that convinced people that magnetic reconnection was a major driver of the solar wind is that our computer simulations were able to produce the energetic particles that they saw in the Parker Solar Probe data,” Drake said. 

As part of his dissertation, physics Ph.D. student Zhiyu Yin built the simulation model that is used to see how particles might accelerate during magnetic reconnection.

“Magnetic reconnection is very important, and our simulation model can help us connect theory with observations,” Yin said. “I'm really honored to be part of the Parker Solar Probe mission and to contribute to its work, and I believe it could lead to even more discoveries about the physics of the sun, giving us the confidence to take on more projects in exploring the solar system and other astrophysical realms.”

Swisdak explained that simulations also help researchers push past the limitations of space probes.

“Observations are measuring something that is real, but they’re limited. Parker can only be in one place at one time, it has a limited lifetime and it’s also very hard to run reproducible experiments on it,” Swisdak said. “Computations have complementary advantages in that you can set up a simulation based on what Parker is observing, but then you can tweak the parameters to see the bigger picture of what we think is happening.”

‘Things no one has seen’

There are still unsolved mysteries, including the exact mechanisms that produce switchbacks and drive the solar wind, but researchers hope that the Parker Solar Probe will continue to answer these and other important questions. The sun is currently experiencing more intense solar flares and coronal mass ejections than usual, which could yield new and interesting data on the mechanisms that energize particles in these explosive events.

This research also has wider relevance. Studying the solar wind can help scientists understand other winds throughout the universe, including the powerful winds produced by black holes and rapidly rotating stars called pulsars. Winds can even offer clues about the habitability of planets because of their ability to deflect harmful cosmic rays, which are forms of radiation.

“One of the reasons why the solar wind is important is because it protects planetary bodies from these very energetic particles that are bouncing around the galaxy,” Drake said. “If we didn't have that solar wind protecting us, it's not totally clear whether the Earth would have been a habitable environment.”

As the spacecraft prepares for its December descent into the sun, the UMD team is eager to see what the new observations will reveal.

“One of the nice things about being involved with this mission is that it’s a chance to make observations of things that no one has seen before. It lets you go into a new regime of space and say, ‘Alright, we thought things would look this way, and inevitably they don't,’” Swisdak said. “The ability to get close enough to the sun to see where the solar wind starts and where coronal mass ejections begin—and being able to take direct measurements of those phenomena—is really exciting.”

Catching Cosmic Waves

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Category: Department News

Published: Wednesday, September 11 2024 05:24

University of Maryland (UMD) physics Ph.D. student Max Trevor found himself at a crossroads in 2016. Long fascinated by black holes, Trevor studied the enigmatic objects using X-ray astronomy as an undergraduate at the University of Maryland, Baltimore County (UMBC). But as his graduation date grew closer, Trevor wondered how he could take his passion to the next level. 

A groundbreaking announcement helped Trevor make a decision. In February 2016, scientists working on the Laser Interferometer Gravitational-Wave Observatory (LIGO) project announced that for the first time in history, they detected gravitational waves—ripples in spacetime caused by some of the most violent events in the universe, waves that were caused by two black holes colliding with each other billions of light-years away. For Trevor and many other researchers, the Nobel Prize-winning discovery opened up an entirely new way of observing the universe.

“I had some experience with X-rays at UMBC, which I enjoyed,” Trevor recalled. “But hearing about LIGO’s success made me think that gravitational astronomy was going to be the new hot research area for high-energy astrophysics. At that moment, I knew I had to jump in no matter what.”

Knowing that he wanted to pursue gravitational wave research and LIGO science as a graduate student, Trevor found his perfect match at UMD. Attracted by the Department of Physics’ decades-long legacy of gravitational wave research and its continued influence on the field, he joined the lab of Peter Shawhan—a professor of physics and LIGO principal investigator—in spring 2020. Together, they’re working to detect gravitational waves and improve the quality of the data collected by LIGO to ensure its accuracy for all researchers in the community.  

Shawhan, whose work with LIGO stretches back to his time as a postdoctoral researcher at Caltech in 1999, says that the project has come a long way since the announcement of its initial success.

“Today we can laugh and say, ‘Oh, it’s just another regular binary black hole merger,’ but it was a really big deal the first time we were able to detect one,” Shawhan said. “We’re now in the middle of LIGO’s fourth observational run. Thanks to decades of hard work from across the globe and our efforts here at UMD, we can now observe these events every couple of days.” 

Filtering out the noise, keeping the community connected

Detecting gravitational waves in space is no easy task, even now. To do its job, LIGO requires incredibly sensitive instruments called interferometers, which use laser beams to measure minute changes in distance caused by passing gravitational waves. There are currently two interferometers in the United States—one in Louisiana and another in Washington state—and it’s Trevor’s job to weed through the flood of data these interferometers produce, searching for the telltale signs of a gravitational wave event. 

“I write code that performs data analysis in real time. It basically asks, ‘Is this a gravitational wave, yes or no?’ and it tries to match the data points with known profiles of gravitational waves,” Trevor explained. “After that’s done, it repeats the process with the next batch. All this happens in seconds.”

Although interferometers can capture faint signals that come with faraway colliding neutron stars or merging black holes, the instruments are also prone to catching other waves that may not be involved with the cosmos at all—like nearby earthquakes, moving trains or even local weather. Trevor uses tools like machine learning to correlate these irrelevant waves with potential sources and adjusts the detection code to avoid them. According to Shawhan, Trevor’s work is paving the way for upgrades to the LIGO system for future observational runs. 

“Max’s improvements to the algorithms are especially valuable for detecting signals that are particularly challenging to identify,” Shawhan said. “He’s made it easier to separate out irrelevant noise from signals that are made by massive black holes.” 

Trevor is also a major part of the effort to keep astronomers around the world in touch with LIGO’s latest findings. He’s in charge of operating and running a rapid alert software package called Python search for Compact Binary Coalescences (PyCBC). Any time a potential gravitational wave is detected in space, PyCBC feeds information into a system that sends out rapid alerts to astronomers around the world through NASA’s General Coordinates Network—giving them a chance to turn their telescopes to the right part of the sky and potentially catch any visible light from explosive cosmic events. Thanks in part to Trevor’s efforts, PyCBC sends out an alert about once every three days on average, helping to produce over 120 alerts total since LIGO’s current run began.  GCN diagram

“The data is collected, analyzed and sent out really quickly,” Trevor said. “The astronomy community can get preliminary alerts about a possible event within 30 seconds. Timeliness is essential so that scientists can observe the event right as it’s happening and we can form a better understanding of phenomena like black holes and neutron star mergers. It’s really fulfilling for me to play a part in keeping everyone connected.” 

Since joining Shawhan’s lab, Trevor has made significant contributions to LIGO, co-authoring over 30 highly cited papers on the data gathered by the system. As he nears the completion of his doctoral program at UMD, Trevor hopes to continue his work. He believes that his projects, specifically those focused on identifying extraneous noise sources, will play a role in optimizing the next version of LIGO and bring scientists closer to understanding the world beyond Earth. 

“This current observational run is projected to end in June 2025, which is when LIGO will undergo crucial upgrades and changes to make it even more sensitive than previous iterations,” Trevor said. “I’d like to keep doing my part in helping the project stay alive—and supporting the community that seeks to explain how our universe works.”