Rebecca Jensen-Clem, an astronomer at the University of California, Santa Cruz, is sharpening ground-based planet hunting by upgrading the Keck Observatory’s vision. Earth’s atmosphere scrambles starlight, creating glare and swallowing key wavelengths, which is why space observatories like the James Webb Space Telescope are so powerful. Jensen-Clem’s strategy is to beat the atmosphere instead, refining adaptive optics so Keck’s 10-meter primary mirror, made of 36 hexagonal segments, can reveal planets hiding beside stars a million to a billion times brighter.
Her lab focuses on extreme adaptive optics, which aims for the highest image quality over a small field of view by tackling disturbances from wind and the primary mirror itself. In April, Jensen-Clem and former collaborator Maaike van Kooten received the Breakthrough Prize Foundation’s New Horizons in Physics Prize for methods with the potential to enable the direct detection of the smallest exoplanets. In July, she was named to a new committee for NASA’s Habitable Worlds Observatory concept, tasked with defining the mission’s scientific goals by the end of the decade.
One advance Jensen-Clem brought to Keck is a Zernike wavefront sensor installed on the primary mirror. The system uses a specialized glass plate to bend incoming light into a pattern that exposes minute misalignments in the honeycomb of segments. A subtle brightness change in a single hexagon flags a hairbreadth positioning error, enabling precise recalibrations that are critical when chasing very faint targets.
She is also improving Keck’s six-inch deformable mirror, which can reshape up to 2,000 times per second to counter atmospheric turbulence but typically lags true conditions by about one millisecond, especially problematic on windy nights. Inspired by a postdoctoral-era paper, Jensen-Clem’s team built predictive software that uses prior measurements and simple algebra to forecast atmospheric changes rather than react in real time. In tests at Keck, the predictive approach produced images of faint exoplanets two to three times clearer than standard adaptive optics, results published in 2022 and central to her prize.
The predictive software was reinstalled in May as a permanent upgrade and has already refocused artificial starlight; the next challenge is proving it on real targets. Astronomer Thayne Currie notes these techniques will be vital for upcoming giants like the Extremely Large Telescope and the Giant Magellan Telescope. Looking ahead, Jensen-Clem’s group is preparing for the European Space Agency’s Gaia data release slated for December 2026, using stellar wobbles to flag candidate systems. With Keck’s new instrument, they aim to directly image those planets and probe their atmospheres and temperatures, deploying every adaptive optics trick to capture worlds once thought invisible.
