Elias 2-24b: Youngest Exoplanet Ever Detected May Still Be Growing

Astronomers have confirmed Elias 2-24b, an exoplanet less than 1 million years old. Because of its extreme youth, the giant planet may still be gaining mass from the protoplanetary disk surrounding its host star.

Elias 2-24b orbits a young star approximately 139 parsecs, or 454 light-years, from Earth in the star-forming region of Ophiuchus.

The entire system is an infant on astronomical timescales, with an estimated age of no more than 1 million years. That makes Elias 2-24b considerably younger than other directly imaged protoplanets, including those orbiting PDS 70 and WISPIT 2, which are approximately 5 million years old.

A planet challenging theories of formation

“Our planetary formation models are already struggling to account for the previous record holders for the youngest known planets, a four-way tie between two planets orbiting the star PDS 70 and two planets orbiting the star WISPIT 2, both of which are more than 5 million years old,” said Professor Lucas Cieza, an astronomer at Chile’s Institute of Astronomy.

“Elias 2-24b shows that even our best planet formation models are still missing some important processes.”

About a decade ago, observations from the Atacama Large Millimeter and Submillimeter Array (ALMA) revealed a narrow gap in the protoplanetary disk surrounding Elias 2-24.

The European Southern Observatory’s Very Large Telescope later detected a faint point of light within the gap. Professor Cieza and colleagues used the Keck Observatory’s NIRC2 vortex coronagraph to image Elias 2-24b just inside the disk’s gap.

Based on the planet’s brightness and current models of planetary evolution, the researchers estimate that Elias 2-24b has a mass between 1.9 and 4 times that of Jupiter.

This Keck image of Elias 2-24b was taken on June 21, 2018. Image credit: Bernardi et al., doi: 10.3847/2041-8213/ae9bb6.

Keck telescope captures a difficult-to-see protoplanet

“Elias 2-24b is at the limit of what current telescopes can detect, but new instruments like NASA’s Nancy Grace Roman Space Telescope should make such a detection easier,” said Andrea Bernardi, a doctoral candidate at the University of Diego Portales.

The discovery supports the theory that giant planets can form rapidly through core accretion. In this process, a solid planetary core gathers gas from the surrounding disk. This contrasts with gravitational instability, a more sudden formation process involving the collapse of material.

The gaps and bright dust edges observed in the disk around Elias 2-24 are consistent with predictions that a growing planet can carve a path through the surrounding material.

“Elias 2-24b is the youngest exoplanet ever discovered, so its confirmation has important implications for the timescale of planet formation and the origin of the gaps observed in very young disks,” the astronomers concluded.

Research paper

The team’s paper was published in the September 16 issue of The Astrophysical Journal Letters.

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Andrea Bernardi et al. 2026. “Search for embedded protoplanets using Keck/NIRC2 vortex coronagraphs: Confirmation of core accretionary planets in narrow gaps in the Elias 2-24 disk.” Astrophysical Journal Letters 1009, L3; doi: 10.3847/2041-8213/ae9bb6