Astronomers have confirmed Elias 2-24 b, a planet less than 1 million years old, as the youngest known exoplanet, using data from NASA-funded archives and telescopes like Keck and ALMA. The discovery challenges existing planet-formation models and offers a rare glimpse into planetary birth.
The confirmation of Elias 2-24 b, a Jupiter-mass planet orbiting a star 450 light-years from Earth, marks a breakthrough in understanding how planets form. At less than 1 million years old, it defies previous assumptions about the timeline of planetary development, which suggested such a massive planet could not form so quickly or at such a distant orbit.
A Decade-Old Mystery Resolved
For over a decade, astronomers debated whether a faint point of light detected in the dusty disk of the young star Elias 2-24 was a planet. Initial observations by ALMA in Chile revealed a gap in the disk, and the European Southern Observatory’s Very Large Telescope in Chile later spotted a light source within it. However, current models predicted such a planet could not form so rapidly or far from its star.
Andrea Bernardi, a doctoral candidate at the Universidad Diego Portales in Chile, led a team that re-examined archival data from the W. M. Keck Observatory. By analyzing observations from 2018 and 2020, they confirmed the object’s motion matched that of a planet, not a background star or imaging artifact. 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.
How the Discovery Was Made
The team relied on the Keck Observatory Archive, a NASA-funded resource that preserves decades of astronomical data. By cross-referencing observations from multiple telescopes, they bypassed the limitations of single-instrument studies. We usually hear about telescopes working separately, but this confirmation was possible only by using multiple telescopes together,
Bernardi said.
Keck’s coronagraph, which blocks starlight to reveal faint objects, was critical. Most of the exoplanets we’ve discovered so far have been found using transits, which happen when a planet passes in front of its star,
explained Lucas Cieza, a professor at the Instituto de Estudios Astrofísicos in Chile. Those transits are hard to spot when the planets are still deeply buried in dust or orbiting far from the star.
Challenging Planet-Formation Models
Elias 2-24 b’s existence forces scientists to reconsider their understanding of planetary evolution. Current models suggest forming a Jupiter-sized planet at its distance from the star would take about 5 million years, yet this planet formed in less than 1 million. Elias 2-24 b shows us that even our best planet-formation models are still missing some important processes,
Cieza said.
The discovery also highlights gaps in observational capabilities. The galaxy churns out new stars and planets continuously, so there are many in every stage of evolution,
Cieza noted. That means we can see the entire process in theory, but there is a large gap in what most telescopes can detect. We are mostly blind to these baby planets right now.
What This Means for Future Research
The confirmation of Elias 2-24 b underscores the need for advanced instruments. With new instruments like NASA’s Nancy Grace Roman Space Telescope, such detections should become easier,
Bernardi said.
For now, the find serves as a benchmark. “Our planet-formation models already struggled to explain the previous record holders for the youngest known planet — a four-way tie between two planets orbiting the star PDS 70 and two planets orbiting the star WISPIT 2 — which are all more than 5 million years old,” Cieza said. Elias 2-24 b shows us that even our best planet-formation models are still missing some important processes.
A Glimpse into the Past
Studying Elias 2-24 b offers a rare window into the early stages of planetary formation. Studying this system offers a time machine of sorts for scientists to explore what our own planetary system may have been like billions of years ago,
said Cieza. The planet’s young age and active disk provide data to test theories about how gas giants like Jupiter take shape.