Astronomers Discover Youngest Known Planet, Less Than 1 Million Years Old

Astronomers have identified a world that is still being born. The planet, called Elias 2-24 b, is less than a million years old—a newborn by cosmic standards—and it orbits a young star 450 light-years from Earth. It is roughly the mass of Jupiter, and unlike the thousands of other confirmed exoplanets that have been catalogued over the past few decades, this one has not yet finished forming. It sits embedded in a swirling disk of gas and dust, the leftover material from which its star itself coalesced, still actively accreting mass and taking shape.

The discovery, published Wednesday in The Astrophysical Journal Letters, breaks the previous record for the youngest known planet by a significant margin. Before this, astronomers had identified four planets that held the title together—two orbiting the star PDS 70 and two around WISPIT 2—all of which are more than five million years old. Elias 2-24 b is at least five times younger than any of them. The finding matters because it offers astronomers a direct window into the earliest stages of how planets actually form, a process that remains poorly understood despite decades of theoretical work.

The researchers, led by Andrea Bernardi, found the planet exactly where theory said it should be: inside a prominent gap carved into the protoplanetary disk. Planets under formation are thought to create these gaps as they orbit and gravitationally shepherd material around them, so detecting a young world sitting within such a void is powerful confirmation that the theory tracks reality. "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."

Confirming the discovery required a methodical approach. Researchers combined archival observations from the W. M. Keck Observatory taken in 2018 and 2020, tracking the object's movement across the sky over time. This allowed them to rule out the possibility that what they were seeing was merely a background star or an artifact of the imaging process—a crucial step when working at the very edge of what current instruments can resolve. The planet is so faint and distant that it pushes existing telescopes to their limits. "Elias 2-24 b is at the limit of what current telescopes can detect," Bernardi noted, "but with new instruments like NASA's Nancy Grace Roman Space Telescope, such detections should become easier."

The discovery has immediate implications for how scientists understand planetary assembly. Lucas Cieza, a professor at the Instituto de Estudios Astrofísicos in Chile and a co-author of the study, pointed out that even the leading computational models of planet formation have struggled to explain the previous record holders. "Elias 2-24 b shows us that even our best planet-formation models are still missing some important processes," he said. The models, in other words, cannot yet account for how a world this massive can come together so quickly. The finding suggests that either planets form faster than theory predicts, or through mechanisms that current models have not yet incorporated.

What comes next is clearer than it has ever been. The Nancy Grace Roman Space Telescope, set to launch in the coming years, will be far more sensitive than existing observatories and should make the detection of young planets routine rather than exceptional. That shift will allow astronomers to build a much larger sample of forming worlds, refining their understanding of planetary birth and the diversity of outcomes it produces. For now, Elias 2-24 b stands alone as the youngest known world, a cosmic infant still wrapped in the nebula from which it emerged.