Astronomers confirm Elias 2-24 b as youngest known exoplanet

Old Keck images reveal a planet

Andrea Bernardi, a doctoral candidate at Universidad Diego Portales in Chile, led a team that re-examined archival coronagraph observations from the W. M. Keck Observatory in Hawaii. The observations covered seven young stars, each surrounded by a disc of gas, dust and ice. A coronagraph blocks most of a star's glare, letting astronomers capture light from a much fainter object beside it. In the disc around Elias 2-24, the team found a faint source inside a gap.

Earlier observations from ALMA revealed the gap, and the European Southern Observatory's Very Large Telescope later spotted a faint point of light inside it. The open question was whether that point was a planet, an imaging artefact or a background star. Keck images from 2018 and 2020 settled it: the point moved along an orbital path, so it was bound to Elias 2-24.

Bernardi said formation theory predicts planets should sit in gaps because they carve them. "The planets should be found within the gaps, since they are carving them," Bernardi said. "And that's exactly where we found Elias 2-24 b."

Why the age challenges formation models

The study estimates Elias 2-24 b at less than a million years old. NASA described the previous record as a four-way tie between two planets orbiting PDS 70 and two orbiting WISPIT 2, all more than 5 million years old. Martin Cid Magazine cited PDS 70 b alone as the prior benchmark at about 5 million years.

The planet orbits about 55 AU from its star, or 55 times Earth's distance from the Sun. That is about 11 times Jupiter's roughly 5 AU distance. At that separation the disc is sparser and orbital periods are longer. Core accretion is the standard route: dust sticks together into a core, which then captures gas. NASA says forming a Jupiter-sized planet at Jupiter's distance takes about 5 million years, and longer farther out. Elias 2-24 b has had less than a million years.

Cieza said the earlier record holders had already strained those models. "Elias 2-24 b shows us that even our best planet-formation models are still missing some important processes," he said.

One alternative is disc instability, in which an unstable patch of the disc collapses directly. That can happen on a timescale of thousands of years, but it usually produces more massive objects. The boundary between a Jupiter-mass planet and a brown dwarf is where predictions are weakest.

Cieza said the galaxy makes stars and planets continuously, so every stage of evolution exists somewhere, yet most telescopes cannot detect the baby planets.

Mass estimates rely on models

NASA describes Elias 2-24 b as roughly as massive as Jupiter. Notebookcheck reported an estimated mass between 1.9 and 4 times Jupiter's. Its mass has not been directly measured; current estimates derive from luminosity and evolutionary models. Co-author Alice Zurlo said theoretical models "still struggle to reliably predict its mass, entropy, and expected luminosity" for an object at this stage.

The planet is still pulling material from its disc, so the observations catch it mid-growth. One independent uncertainty is the star's own age: the under-one-million-year estimate is anchored to membership in the Rho Ophiuchi cloud, Martin Cid Magazine reported. If the star sits at the older end of that population's age range, the planet's age estimate rises proportionally, and constraining the star's age is as important to the result as further imaging.

What comes next

The study leaves the formation mechanism open: it does not distinguish between disc instability, unusually favorable core accretion, or a process the models have not yet incorporated. NASA's Nancy Grace Roman Space Telescope launched on 30 August 2026. Space.com reported that it carries the most advanced coronagraph ever launched to space, and researchers hope it will allow more direct observations of exoplanets and their atmospheres.

Bernardi said the confirmation took several telescopes working together, and that the new planet sits at the edge of what current instruments can do.

"Elias 2-24 b is at the limit of what current telescopes can detect, but with new instruments like NASA's Nancy Grace Roman Space Telescope, such detections should become easier."