Published: June 02, 2026, 02:01 UTC
Astronomers Discover Planetary ‘Fingerprints’ in Rings Around Stars — A New Way to Weigh Invisible Exoplanets
Date: 2026-06-02
Featured image: An artist’s illustration of a young planet carving lanes through a protoplanetary disk of dust and gas around its host star. Credit: ESO/M. Kornmesser
A team of astrophysicists at the University of Warwick has developed a breakthrough technique that uses the width and brightness of cosmic dust rings to determine the mass of infant exoplanets — even when the planets themselves are completely invisible to telescopes.
The method, described in a study led by researcher Amena Faruqi, lets astronomers effectively “weigh” hidden worlds by reading the subtle patterns they imprint on the protoplanetary disks that birth them. It works across any wavelength and regardless of dust grain size, removing a long-standing obstacle in exoplanet science.
“We’ve long understood that rings could be created from concentrated dust that piles up just beyond the orbit of young, embedded planets,” Faruqi told reporters. “By reading ‘between the rings,’ we have now found a way to reconstruct the masses of the planets that create the rings.”
The researchers successfully validated the technique on the PDS 70 system, a star system located approximately 370 light-years from Earth that is known to host at least two still-forming gas giant planets. PDS 70 is among the most thoroughly studied planetary nurseries, observed extensively with the Atacama Large Millimeter/submillimeter Array (ALMA) — a powerful network of 66 radio antennas in the Chilean desert.
Protoplanetary disks are vast, rotating reservoirs of gas, dust, and planetesimals that surround young stars. Within these disks, planets slowly coalesce over millions of years. As infant worlds grow, their gravity clears out lanes in the surrounding material, creating gaps. Dust piles up at the outer edges of these gaps, forming bright rings visible to telescopes like ALMA.
Until now, however, scientists could see the rings but not easily deduce what kind of planet had sculpted them.
The Warwick team’s insight was to focus on two measurable features of these rings: their width and the location of their peak brightness. By modeling the physics of how dust responds to a planet’s gravitational influence, they found that both parameters encode precise information about the planet’s mass — and crucially, that this relationship holds true regardless of the observing wavelength or the size of the dust grains involved.
This independence is the key advance. Previous attempts to infer planet masses from disk structures were complicated by uncertainty about the composition and grain-size distribution of the dust. Different wavelengths of light reveal different layers of a disk, and larger grains behave differently from smaller ones. By developing a relationship that sidesteps these variables entirely, Faruqi and her colleagues have given astronomers a robust, universal ruler.
“These bright rings are not just beautiful structures — they are essentially planetary fingerprints,” Faruqi said.
The significance extends well beyond the PDS 70 system. Thousands of protoplanetary disks have been catalogd by ALMA and other observatories, and many of them display similar ring-and-gap structures. The new technique could be systematically applied to those disks, enabling astronomers to build a census of exoplanet masses during the earliest stages of their formation.
That is a period of planetary evolution that has remained stubbornly difficult to observe. Most exoplanet detection methods — such as the transit method used by NASA’s TESS mission or the radial velocity method — are best suited for older planets that have finished forming and settled into stable orbits. Young planets are still buried deep within their natal disks, swaddled in gas and dust that blocks direct observation.
“Measuring the mass of a planet that you cannot even see has been one of the great challenges of exoplanet astronomy,” Faruqi noted. “These rings give us an indirect but reliable measurement.”
The study was first reported by Space.com contributor Robert Lea on June 1, 2026, drawing immediate interest from the astronomy community. Several independent researchers not involved in the work have praised the approach for its elegance and practicality.
The technique arrives at a propitious moment. The James Webb Space Telescope (JWST) has been returning unprecedented infrared imagery of protoplanetary disks, and ALMA continues to resolve finer details in radio wavelengths than ever before. Combining these high-resolution observations with the Warwick team’s analytical framework could accelerate the pace of discovery dramatically.
There are limitations. The method is most reliable for relatively massive planets — those in the gas giant regime, roughly the mass of Saturn or larger — that carve clear, well-separated gaps. Smaller, Earth-mass planets produce subtler disturbances that may be harder to disentangle from the general turbulence of the disk. Additionally, the technique works best in disks that are not overly complex, where multiple planets, disk instabilities, or external radiation have not scrambled the ring patterns.
Nevertheless, the scientific payoff is substantial. By applying the technique across a large sample of protoplanetary disks, astronomers could test competing theories of planet formation at scale. Key questions — such as whether gas giants typically form close to their stars or farther out before migrating inward — could be addressed with observational data rather than simulation alone.
The PDS 70 system itself remains a prime target for follow-up. With at least two confirmed protoplanets — PDS 70 b and PDS 70 c — it offers a rare opportunity to cross-check the ring-based mass estimates against direct measurements obtained through other methods.
For now, the University of Warwick team is focused on refining their models and expanding the sample. Faruqi expressed particular excitement about what the method might reveal about planetary system architectures during the first few million years of a star’s life — a formative era that shapes everything that follows.
“Every ring tells a story,” she said. “We are finally learning how to read it.”