Webb Telescope Recovers Hidden Giant Planet by Erasing Starlight With a Digital Twin

Astronomers have pulled a giant planet out of James Webb Space Telescope data in which it had been invisible, by building a computer simulation of the telescope and using it to subtract the glare of the planet's star. According to Space.com, the method outperformed standard image-processing techniques by two to 15 times in detecting faint planets.

The team, led by Rodrigo Ferrer-Chavez of Northwestern University, published the work on Nov. 4 in the journal Nature. It hopes other astronomers will adopt the technique to uncover planets that starlight has hidden until now.

Which planet was recovered?

The planet is 51 Eridani b, a gas giant with a mass of about 11 Jupiters that orbits a star roughly 97 light-years away. Ground-based telescopes discovered it in 2015. It did not show up, however, in Webb's observations of the system, even though no one doubts the telescope's capabilities. Light from its parent star, 51 Eridani A, drowned it out.

Why is it so hard to see planets next to stars?

Space.com reported that even the brightest planets are about 100,000 times fainter than their host stars. It compared the task to spotting a firefly near a lighthouse. A coronagraph, a tool that blocks the star, does not stop all of its light.

For about 20 years, astronomers have filled the gap by imaging a different star as a reference and subtracting that image from the target observation, explained Jason Wang of Northwestern. The trick has a flaw: even stable telescopes wobble. Webb's NIRCam instrument relies on cryocoolers with small motors, and those can make the mirrors vibrate slightly. That motion scatters starlight and leaves enough glare to mask a planet.

How does the new method work?

The approach is called Physics-based Learning for Imaging Planets, or FLIP. It creates a digital twin, a virtual replica that simulates how starlight passes through the telescope's mirrors and reaches its detectors. Researchers then adjust the twin to reflect millions of tiny imperfections in the real instrument until it matches what the telescope actually records. The simulated glare can then be removed from the real image.

To check the technique, the team revisited Webb observations of three systems. Two, HIP 65426 and 51 Eridani, have known planets. The third, TYC 5899, has none. Applying FLIP to data collected two years ago brought 51 Eridani b into view.

"We showed that we can actually recover a planet that people previously couldn't see," Wang said, describing it as real data in a real scenario. He called the earlier result science left on the table because the right analysis tools were missing.

Why does it matter?

For general readers, the finding shows that existing observations may still hold planets nobody has spotted. Better software, rather than a new telescope, could bring some of them out. The test was on a planet that was already known, so the result shows the method can recover such a world. It does not yet show a new discovery.

Space.com said the technique could help NASA's proposed Habitable Worlds Observatory, which aims to directly photograph Earth-like planets around distant sun-like stars. Ferrer-Chavez said no known planets around other stars resemble those in our own solar system. In his view, that is not because they are absent but because astronomers cannot see them. He said each improvement in technique has revealed new types of planets, and that finding more of them can help show how planetary systems form and evolve, and how typical our own solar system is.

What comes next?

The researchers hope other astronomers will use FLIP on their own data. Space.com did not report specific follow-up observations or timelines.

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Around Prague, based on reporting by Space.com