Eddie Gonzales Jr. – MessageToEagle.com – Even the world’s most powerful telescopes have their blind spots. Although NASA’s James Webb Space Telescope (JWST) can peer billions of years into the past, it still struggles to photograph planets orbiting nearby stars. Stars shine so brightly that their glare overwhelms the faint glow of nearby planets.
Left: JWST/NIRCam observation of star 51 Eridani A (51 Eri) in the F430M filter, using the standard KLIP method (Soummer et al. 2012) to subtract the star’s glare. This method could not detect the planet 51 Eri b in the original analysis (Balmer et al. 2025), whose expected location is marked with a dashed circle. Middle: The same observation, but using the new FLIP method (Ferrer-Chavez et al. 2026) to subtract the star’s glare. Astrophysicists obtained a significant detection (>5 sigma) of 51 Eri b. Right: Simulated image of 51 Eri b, highlighting that the planet is detected at its expected location and that the planet signal has the expected morphology. The location of the star 51 Eri is marked with a star symbol. Image credit: Rodrigo Ferrer-Chavez
Now, a Northwestern University-led team of astrophysicists has developed a new computational technique that cuts through the glare — revealing planets previously hidden from view.
By combining physics-based modeling with machine-learning techniques, the new method accounts for tiny imperfections in the telescope that interfere with its ability to detect faint objects. When the team applied their method to existing JWST observations, they improved the telescope’s sensitivity by up to 15 times. After the new method erased glare, it revealed a giant exoplanet in an image where conventional processing simply could not see it.
The advance could enable astronomers to discover smaller, colder, and fainter planets without changing the telescopes themselves.
“Planets are a million times fainter than their stars,” said Northwestern’s Rodrigo Ferrer-Chavez, who led the study. “So, to image exoplanets, we need to remove that glare. That is a tricky problem because even tiny changes in the telescope can affect how that glare appears. Slight shifts or tilts — even on the scale of just a few nanometers — can change the pattern of light. Our method models how light travels through the telescope and accounts for those tiny changes, allowing us to remove the glare much more precisely.”
Ferrer-Chavez is a Ph.D. student in astronomy at Northwestern’s Weinberg College of Arts and Sciences and a member of Jason Wang’s research group. Wang is an assistant professor of physics and astronomy at Weinberg and co-author of the study. Wang and Ferrer-Chavez are members of the Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA).
Hidden in a sea of starlight
Photographing a planet outside of our solar system is a bit like trying to spot a firefly hovering next to a blazing floodlight. Even relatively bright young giant planets can be 100,000 times fainter than their host stars.
Background image: The Gemini Planet Imager discovered 51 Eri b in 2014. At 2 Jupiter masses, it is the coolest and lowest-mass imaged exoplanet to date, making it the imaged exoplanet most similar to Jupiter. It also orbits in a triple-star system. It orbits roughly 12 au from its main host star, but two low-mass stars 2000 au away are also gravitationally bound (too far to be seen in these images). In monitoring the orbit, we wish to study the history of dynamical interactions 51 Eri b has had with the three stars in the system. The footage uses 5 images taken over 4 years using the Gemini Planet Imager. Over those 4 years, the planet curves toward the star, letting us see the star’s gravitational pull on the exoplanet. Image credit: Jason Wang (Caltech)/Gemini Planet Imager Exoplanet Survey – CC BY 4.0
To tackle this challenge, telescopes like JWST use specialized instruments called coronagraphs, which block out starlight to detect faint objects. But blocking the star isn’t enough. Some starlight still seeps through, producing a hazy pattern that can obscure planets. So, astronomers then use image-processing techniques to remove the remaining glare.
“For the past 20 years, astronomers have tackled this problem by observing a different star and using its image as a reference,” Wang said. “Then, they subtract that reference image from the original observation to remove the unwanted glare to reveal faint planets that otherwise might be hidden.”
Taking the wobble out of the picture
The problem is no telescope can stay perfectly still. Nearly imperceptible changes in the telescope’s physical structure alter patterns of scattered starlight. As a result, the reference image never perfectly matches the actual observation. Even the slightest mismatch can leave behind just enough glare to hide a faint planet.
“We try to make telescopes extremely stable, but there are extreme engineering challenges that we haven’t quite solved yet,” Wang said. “There are known causes of instability and unknown causes. Small thermal changes could cause a mirror to expand or contract by a picometer. Telescopes like JWST have cryocoolers to keep the instrument super cold. Those coolers have small motors that can make the mirrors vibrate. So, there are issues like those but also issues that we still don’t understand as we learn how to build these complex telescopes.”
Instead of relying on reference photographs alone, the Northwestern team took a different approach. Their new method, called Physics-based Learning for Imaging Planets (FLIP), creates a “digital twin” of the telescope — a virtual replica that simulates how starlight travels through the telescope’s mirrors and reaches its detectors.
Using computational techniques similar to those used to train AI models, the team fine-tuned millions of parameters in the digital twin to account for tiny imperfections in the telescope, including subtle shifts in position and optical distortions. Rather than using AI to identify planets, the researchers combined their knowledge of the telescope’s physics with powerful optimization tools.
“We used the same computational tools that researchers use to train AI models, but we did not actually use AI,” Wang said. “Because we already know the physics, we don’t need AI to understand what’s happening.”
By repeatedly adjusting the digital twin until it closely matched the telescope’s actual observation, FLIP recreated the unwanted starlight with remarkable precision. The researchers then subtracted that simulated glare from the image.
Revealing a previously hidden planet
To test their approach, the researchers reanalyzed past JWST observations. They examined observations of two stars — HIP 65426 and 51 Eridani — with known planets as well as a third star, TYC 5899, with no known planetary companions.
Across the observations, FLIP consistently outperformed conventional image-processing techniques, improving sensitivity for detecting faint planets by 2 to 15 times. With the increased sensitivity, the team detected 51 Eridani b, a previously discovered giant planet beyond our solar system hidden in two-year-old JWST data. Carbon dioxide in the planet’s atmosphere absorbed light at infrared wavelengths that JWST observes, making the planet’s signal even fainter.
Although astronomers previously discovered 51 Eridani b with ground-based telescopes, conventional image processing could not distinguish it from residual glare at the wavelength JWST uses to study carbon dioxide in planetary atmospheres. When Ferrer-Chavez applied FLIP to the same observations, the planet emerged.
“We showed that we can actually recover a planet that people previously couldn’t see,” Wang said. “This is real data in a real scenario. It was science left on the table because we didn’t have the right tools to analyze the data in the most optimal way.”
The same property that makes a planet harder to detect also can make it more interesting to study. JWST can make sensitive observations at 4.3 microns, where carbon dioxide strongly absorbs infrared light. Detecting features at this wavelength potentially could give astronomers new clues into a planet’s atmosphere and composition.
From giant planets to Earth-like worlds
For now, Ferrer-Chavez and Wang hope FLIP will help astronomers uncover planets previously hidden within existing observations. By removing starlight more precisely, the method also could allow scientists to study planets at different wavelengths to reveal new clues about their atmospheres.
Looking further ahead, FLIP could help shape the next generation of planet-hunting telescopes. NASA’s proposed Habitable Worlds Observatory aims to directly photograph Earth-like planets orbiting distant sun-like stars. To find such small planets, the telescope may need to maintain optical stability at the picometer scale. That’s equivalent to trillionths of a meter or roughly 100 to 1,000 times more stable than JWST.
FLIP offers a potentially different path forward. Rather than relying on engineering solutions to keep a telescope perfectly stable, astronomers might be able to correct for its tiny imperfections.
“We know of no planets around other stars that are like those in our own solar system,” Ferrer-Chavez said. “It’s not that they don’t exist. It’s that we cannot see them. Every time we improve our techniques, we discover new types of planets. By finding more planets, we can better understand how planetary systems form and evolve, and ultimately how typical our own solar system truly is.”
Source – Northwestern University via EurekAlert
Written by Eddie Gonzales Jr. – MessageToEagle.com Staff Writer