Webb Data Reveals Hidden Giant Planet 51 Eridani b After Glare Fix

A gas giant about 11 times the mass of Jupiter has turned up in James Webb Space Telescope images that astronomers had already searched without finding it. The planet, 51 Eridani b, orbits a star around 97 light-years away, and it became visible only after a team at Northwestern University built software that strips leftover starlight out of the pictures, Space.com reported.

The study appeared Nov. 4 in the journal Nature. The researchers say their method beat standard image processing by two to 15 times at picking out faint planets, which could bring more hidden worlds out of telescope archives.

A planet lost in its star’s glare

Ground-based telescopes first found 51 Eridani b in 2015. Later Webb observations of the same system did not show it. The telescope worked fine; light from the host star, 51 Eridani A, simply drowned the planet out.

That problem is common. Even the brightest planets are 100,000 times fainter than the stars they circle, which Space.com compared to spotting a firefly near a lighthouse. Astronomers use a coronagraph, a device inside the telescope that blocks the star’s disk, but some starlight still leaks around it.

For the past 20 years, the usual fix has been to photograph a different star, treat that image as a reference, and subtract it from the target image to remove the glare, according to Northwestern astronomer Jason Wang. The trick has a weak spot. Telescopes shake slightly. On Webb, the cryocoolers that keep the NIRCam camera cold run small motors, and those motors can make the mirrors vibrate. Even tiny vibrations scatter starlight, and the leftover glare can be enough to hide a planet.

How the digital twin of the telescope works

The team’s method is called Physics-based Learning for Imaging Planets, or FLIP. It builds a virtual copy of the telescope, a “digital twin” that simulates how starlight moves through the mirrors and lands on the detectors.

The researchers then tune that model to match millions of tiny imperfections in the real instrument, adjusting it until its output agrees with what Webb actually recorded. With a good match, they can subtract the simulated glare from the real image and see what is left over.

To test the approach, the group went back to existing Webb observations of three star systems. Two of them, HIP 65426 and 51 Eridani, have known planets. The third, TYC 5899, has none, so it acts as a check that the method does not invent planets where there are none. In data Webb collected two years ago, 51 Eridani b came into view.

“This is real data in a real scenario,” Wang said in a statement. He described the planet as science that had been left on the table because astronomers lacked the right analysis tools.

Why it matters for finding planets like Earth

Most known exoplanets are detected indirectly, through their effect on a star’s light or motion. Taking a direct picture of one requires removing nearly all of the starlight, and FLIP improves on the subtraction step that every such image depends on.

The team hopes other astronomers will apply FLIP to archived and future data to find planets still hidden in their stars’ glare. According to Space.com, the approach could help NASA’s proposed Habitable Worlds Observatory, a mission concept meant to photograph Earth-like planets around distant sun-like stars.

Team leader Rodrigo Ferrer-Chavez of Northwestern said no planets like those in our own solar system are yet known around other stars, because current tools cannot see them. “Every time we improve our techniques, we discover new types of planets,” he said. In his view, finding more of them will help scientists learn how planetary systems form and change, and how typical our own solar system is.

What is still unclear

The result so far is a demonstration on a planet that was already known from ground-based observations, along with two comparison systems. It shows FLIP can recover a faint world in Webb data. Whether it turns up planets nobody has seen before will depend on other teams using it on more targets.

Source: Space.com