Planets are believed to form from dust and gas in swirling disks around young stars. Over time, these protoplanetary disks evolve into debris disks—leftovers from planet formation. These older disks, ranging from a few million to billions of years old, have lost their original gas. Instead, their dust is constantly replenished by collisions between rocky objects.
Using powerful telescopes, astronomers have observed dozens of these disks, stretching tens or even hundreds of times the distance from Earth to the Sun. They often show rings, gaps, and hollowed-out regions—possible signs of hidden planets shaping the dust with their gravity. But so far, no planet has been directly seen causing these features, likely because earlier telescopes weren’t sensitive enough.
Now, in a breakthrough study published in Nature, scientists using the James Webb Space Telescope may have spotted such a planet. Orbiting a young star called TWA 7, it’s roughly the size of Saturn. If confirmed, it would be the lightest planet ever directly imaged outside our solar system—and Webb’s first direct planet discovery.
TWA 7 (also known as CE Antilae) is a red dwarf about 6.4 million years old and 34 light-years away. Its disk, seen almost face-on, made it perfect for Webb’s high-sensitivity mid-infrared observations.
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Using the James Webb Space Telescope’s Mid-Infrared Instrument (MIRI), astronomers spotted a faint infrared signal in the debris disk around the young star TWA 7. This signal is located about 50 times farther from the star than Earth is from the Sun—exactly where scientists expect a planet to be if it were shaping the disk’s structure.
The team used a special tool called a coronagraph to detect the signal more clearly to block out the star’s bright light. This allowed them to pick out much fainter objects nearby. With advanced image processing, they removed leftover starlight and revealed the faint source.
They ruled out the possibility that the object—referred to as TWA 7 b—is something from our solar system just passing by. Although there’s a slim chance it could be a distant galaxy, the data strongly suggests it’s a newly discovered planet.
The faint object lies in a gap within one of three dust rings surrounding the star TWA 7, rings that were first seen with ground-based telescopes. Its brightness, color, and position all match what scientists expect from a young, cold planet about the mass of Saturn, thought to be shaping the debris around it.
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“This looks like a strong candidate for a planet influencing the shape of the TWA 7 disk—and it’s right where we expected such a planet to be,” said lead author Anne-Marie Lagrange.
Co-author Mathilde Malin added, “This discovery shows how Webb can help us spot planets similar in size to those in our own solar system—a big leap in understanding how planetary systems form.”
Early results suggest that the faint object, now called TWA 7 b, is a cold, young planet about the mass of Saturn (roughly 100 Earth masses), with a temperature near 47°C (120°F). It’s located in a gap within the star’s debris disk, indicating it may be shaping the surrounding dust through gravitational interaction.
If confirmed, TWA 7 b would be the first directly imaged planet linked to shaping its disk. It might even hint at the presence of a rare “trojan disk”—dust trapped in the planet’s orbit.
Journal Reference:
- Lagrange, AM., Wilkinson, C., Mâlin, M., et al. Evidence for a sub-Jovian planet in the young TWA 7 disk. Nature (2025). DOI: 10.1038/s41586-025-09150-4
