Subatomic explorer

At the South Pole and Marquette, Dr. Karen Andeen is advancing research and devising new technology that will give scientists insight into the origins of energetic cosmic particles raining down on Earth.

By Sarah Wells

Illustration by Joey Guidone/The iSpot

As a child, Dr. Karen Andeen had a deep love for maps. She would pour over atlases, spin globes around their axes and ponder the adventures of the explorers who mapped them. This curiosity for exploration grew with her into adulthood and turned into a passion to map the universe through the study of high-energy, subatomic particles raining down on Earth at every moment. Understanding where these particles come from in space will help scientists pinpoint where events like supernovas exist and even find new intergalactic phenomena.

“For me, a scientist is an explorer. And that’s what I always wanted to be,” says Andeen, now an associate professor of physics.

For her efforts so far, Andeen received the National Science Foundation’s CAREER grant — awarded to select junior faculty members whose research the NSF views as particularly promising — and she is prepared to make new discoveries as never before.

The grant will provide $870,000 over five years to help Andeen advance research that she’s been pursuing since her doctoral work in the mid-2000s at a facility at the South Pole, called the IceCube Neutrino Observatory, which is designed to detect highly energetic, infinitesimal particles zipping through the cosmos. As part of this grant, Andeen will also have the opportunity to analyze the first data coming from a new astronomical instrument that will soon be operating at the observatory, thanks to a design and construction effort she is now leading.

Dr. Karen Andeen

Andeen is what she likes to call a forensic particle physicist, meaning that she’s interested in tracing back the origins of particles that break apart in our atmosphere and whiz through IceCube’s detectors. While IceCube is specifically designed to look for neutrinos — abundant subatomic particles that are difficult to detect — Andeen says it’s also well positioned to look for her favorite ones: charged cosmic rays.

Cosmic rays are pieces of atomic nuclei — such as protons — that have broken up in space and fly around the universe at high speeds. These particles come in a range of energies. While scientists have traced the origins of a portion of less-energetic cosmic rays to exploding stars (supernovae), Andeen says the origins of rarer, high-energy cosmic rays is uncertain. To better understand where these particles originate, scientists first need to know what kind of particles they are: Are they predominantly hydrogen nuclei (protons)? Are they iron nuclei? Are they something else?  Analyzing and measuring these particles is much easier said than done, but the IceCube Neutrino Observatory is one of the few observatories in the world up to the task.

IceCube has traditionally collected data using two instruments — one on the surface named IceTop and one deep inside the ice named IceCube, like the observatory — but Andeen says the two snapshots that these instruments provide aren’t enough to fully understand the high-energy cosmic ray data coming through the observatory. Instead, she has been leading an international team working to finalize the design and construction of a third instrument, IceAct. IceAct telescopes each contain an array of sensors designed to measure the faint blue light, called Cherenkov light, produced when cosmic rays hit the atmosphere and produce an “air shower” that’s analogous to heavy rainfall cascading off an umbrella.

As a leader of the IceAct team within the IceCube collaboration, Andeen has worked to ensure that the new telescopes are viable in the harsh environment of the South Pole, and that the project has broad support within the collaboration. For her own lab at Marquette, she has focused on projects specifically geared toward undergraduate students: In addition to creating a lot of IceAct’s software, Andeen’s undergraduate students have analyzed aurorae data, tested epoxies for the extreme cold environment, and designed and prototyped a new heating coil to melt ice from telescopes exposed to Antarctica’s brutal cold. Andeen’s former post-doctoral fellow, Dr. Matthias Plum, even had the chance to hand-deliver the new coils to the South Pole just before COVID-19 pandemic lockdown measures were announced.

“The heating coils are working fabulously, and they were almost entirely built and tested by three undergraduate women in our lab here at Marquette.” says Andeen, who emphasizes the importance of providing research opportunities for students from groups historically underrepresented in STEM. “We need to ensure that no students are overlooked when it comes to getting the hands-on experience with hardware and software they’ll need in their future careers.”  

Andeen’s CAREER grant will now help fund the analysis of new IceAct data and development of new analytical techniques and upgrades for the telescopes, in connection with the other instruments of the observatory. Through this work, she hopes to better map the universe and foster a love of this far-reaching inquiry in students from all backgrounds. “Our students are the next generation of explorers,” she says proudly.