Turning Down Starlight to Reveal Distant Worlds

Turning Down Starlight to Reveal Distant Worlds
by Clarence Oxford
Los Angeles CA (SPX) Apr 23, 2025

Researchers at the University of Arizona have introduced a breakthrough coronagraph that could make previously invisible exoplanets detectable by suppressing the overwhelming light from their parent stars. This advance may pave the way for imaging Earth-like planets in habitable zones, areas where temperatures could support liquid water and potentially life.

"Earth-like planets in the habitable zone ... can easily be up to a billion times dimmer than their host star," explained lead researcher Nico Deshler. "This makes them difficult to detect because their faint light is overwhelmed by the star's brightness. Our new coronagraph design siphons away starlight that might obscure exoplanet light before capturing an image."

Published in Optica, the team demonstrated that the new coronagraph can reach quantum-optical limits for exoplanet detection. Their setup enabled them to identify the position of synthetic exoplanets much closer to their artificial host star than standard resolution limits would permit.

Deshler added, "Compared to other coronagraph designs, ours promises to supply more information about so-called sub-diffraction exoplanets ... This could allow us to potentially detect biosignatures and discover the presence of life among the stars."

Identifying exoplanets by direct imaging has remained challenging due to their proximity to bright stars and their relatively dim light. While indirect detection methods exist, imaging would yield far richer scientific insights.

With NASA's Habitable Worlds Observatory (HWO) prioritizing exoplanet discovery, the development of effective coronagraphs has become a major focus. Building on new understandings that traditional resolution limits can be circumvented, the Arizona team employed spatial mode sorters to refine light separation.

Each light source in space excites distinct spatial modes, much like different notes on a piano. The researchers used a mode sorter to filter out starlight and an inverse mode sorter to reconstruct the image, allowing exoplanet light to emerge clearly.

"Our coronagraph directly captures an image of the exoplanet ... Images can provide context and composition information that can be used to determine exoplanet orbits and identify other objects that scatter light from a star such as exozodiacal dust clouds," Deshler said.

To test their system, the team built a lab-based star-exoplanet setup with a 1000:1 brightness contrast. By simulating the planet's orbit and capturing images frame-by-frame, they could determine its position at separations previously considered unresolvable.

The researchers are now working to refine the spatial mode sorter to reduce optical crosstalk, a challenge for high-contrast imaging. While manageable in moderate scenarios, exoplanet studies demand exceptional light isolation.

This foundational experiment suggests spatial mode sorting could transform future astronomical instrumentation. Its techniques may also impact other fields like quantum sensing, communications, and advanced imaging.

Research Report:Experimental Demonstration of a Quantum-Optimal Coronagraph Using Spatial Mode Sorters