On Different Wavelengths

Whether it is wavelengths, perspectives, or strategies, Caltech planetary scientist Katherine de Kleer prefers to settle on more than just one.

“It’s exciting whenever a new telescope comes online because you know it’s going to show you things no one has ever seen,” says de Kleer, an assistant professor in Caltech’s Division of Geological and Planetary Sciences. “But it’s really satisfying to make a new kind of observation on a telescope people have been using for 20 years.”

De Kleer uses a diverse range of telescopes to observe planets and their moons at radio, infrared, and optical wavelengths. Her innovative approaches for studying this wide swath of frequencies have helped shed light on the seasonal evolution of planetary atmospheres. De Kleer’s work also has yielded new insights into the fundamental physics of celestial bodies, including her favorite place in the universe: Io, Jupiter’s third-largest moon and the most volcanically active spot in the solar system.

More than Meets the Eye

For centuries, astronomers have peered through optical telescopes to survey the night sky. Just over the past 60 years, however, scientists have invented instruments to monitor the entire electromagnetic spectrum. Myriad objects and events discernable only at wavelengths too short or too long to be seen by the human eye have come into view. Researchers can detect radio waves emitted by stars, the infrared light of interstellar dust, and x-rays that emanate from superheated matter in the eddies of black holes.

“A common approach is to specialize in one type of observation,” de Kleer explains. “But I like to branch out with strategies and experiments using a range of wavelengths. I enjoy the novelty of coming up with creative ways to look at objects humans have been studying for decades–even centuries—and see them in a new light.”

De Kleer and collaborators have used optical and infrared telescopes at the Gemini Observatory and the W. M. Keck Observatory in Hawaii to monitor Io’s volcanic activities for years. In July 2019, they published data gathered over 271 nights between 2013 and 2018, including near-infrared timelines of eruptions at 75 individual volcanoes.

“Let’s say you could use all the most powerful telescopes across all frequencies,” de Kleer posits. “There are many things in the universe that you could look at once and get all the information you need. But with Io, because it’s constantly changing, this isn’t enough; the time domain is really important. You need to look at how things evolve.”

“It’s a great intellectual challenge, to put together a big, coherent story from these tiny little pieces of information.”
- Katherine de Kleer

Earth-based telescopes enable de Kleer to track the intensity of Io’s thermal emissions at different wavelengths, revealing data not captured even by higher-resolution photos of Io taken from space satellites. This new layer of information uncovers variabilities in the composition and temperature of Io’s geological structures.

Enigmatic Nature

In search of rhythms and patterns between Io’s orbital cycles and the waxing and waning of its volcanic eruptions, de Kleer weaves together statistical analyses and physics equations. With this methodology, she is keen to comprehend the enigmatic nature of the universe.

“I want to understand the processes that lead to the diversity of objects in the solar system,” she says. “For example, how do planets or moons that are comparable in size and composition end up so different from one another? It’s a great intellectual challenge, to put together a big, coherent story from these tiny little pieces of information.”

De Kleer traces her inquisitive nature back to her childhood, and she derives great satisfaction from helping others relate to science in a way that inspires them to ask questions of their own. Toward that end, she has conducted astronomy lessons for girls in inner-city middle schools, educated students at science camp, led a physics course for inmates in San Quentin State Prison, and directed outreach activities at science events and music festivals.

In every setting, de Kleer encourages instructors and students alike to share their different perspectives. “That’s one of the things I love about Caltech,” she says. “Students, postdocs, and faculty interact all the time. People are present and engaged, with an openness and curiosity to learn from one another. It’s really special.”


Planetary evolution is a top funding priority for Break Through: The Caltech Campaign. To learn how you can help scientists at Caltech explore the solar system and beyond, contact Ellen Jampol at (626) 395-4374 or ejampol@caltech.edu.

MAKE YOUR GIFT TODAY