Astronomers have pulled a giant exoplanet out of James Webb Space Telescope images in which the world's faint glow had been drowned by its star, Live Science reported. Using a combination of modeling and machine learning, a team led by Northwestern University astronomer Rodrigo Ferrer-Chavez recovered 51 Eridani b, a planet already seen by ground-based telescopes but previously lost in Webb's glare. The results were published Nov. 4 in the journal Nature, in a paper titled "Imaging exoplanets below the telescope stability limit."
"Planets are a million times fainter than their stars," Ferrer-Chavez said in a statement. "So, to image exoplanets, we need to remove that glare." Telescopes like Webb use coronagraphs to block some of that light, in a way the researchers compared to a solar eclipse. Even the best coronagraphs cannot remove all of the glare, and the telescopes themselves move. "Even the most stable telescopes vibrate almost imperceptibly as they collect light," Live Science reported, producing slight mismatches that can be enough to hide even a very large exoplanet.
To address that, the team built a "digital twin" of Webb that virtually recreates how light travels through the telescope's detectors, minus movement-based imperfections. They fine-tuned the replica with physics-based computational models and machine learning techniques similar to those used to train AI. The authors stressed that this is not an AI model. "Because we already know the physics, we don't need AI to understand what's happening," co-author Jason Wang, also at Northwestern, said in a statement. They named the approach Physics-based Learning for Imaging Planets, or FLIP.
The team analyzed data from three stars, including 51 Eridani, about 97 light-years from Earth and already suspected to host a giant planet. With FLIP, 51 Eridani b "popped out from the dataset." The researchers hope the same approach will help pick out even harder-to-spot worlds, especially ones that look more like the planets in our own solar system. In nearly 35 years of exoplanet hunting, most discoveries have been unlike those nearby worlds, in part because larger and more reflective planets are easier to see. "It's not that [solar-system-like planets] don't exist," Ferrer-Chavez said. "It's that we can't see them." The Nature paper lists additional co-authors, including K. L. Bouman, and appears in volume 659 of the journal. The verified claim is a recovery of a known planet from existing Webb data, not the announcement of a newly discovered world.