Astronomers have confirmed the youngest known planet, a Jupiter-size baby world less than a million years old that formed far faster than expected.
Astronomers have confirmed the youngest known planet ever observed, a world less than 1 million years old that is still surrounded by the material from which it formed. Known as Elias 2-24 b, the young planet remains embedded in a swirling disk of gas and dust around its host star.
Its extreme youth is forcing researchers to reconsider how quickly large planets can take shape.
“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,” said Lucas Cieza, a professor at the Instituto de Estudios Astrofísicos in Chile and co-author of a paper detailing the results. “Elias 2-24 b shows us that even our best planet-formation models are still missing some important processes.”
A Planet Hidden Inside a Dusty Disk
In a study published September 16 in The Astrophysical Journal Letters, researchers led by Andrea Bernardi, a doctoral candidate at the Universidad Diego Portales in Chile, examined archived observations of seven stars.
Those stars had previously been observed with the coronagraph at the W. M. Keck Observatory in Hawaii, which partners with NASA under a cooperative agreement. A coronagraph blocks much of a star’s intense light, making it easier for astronomers to search for much dimmer objects nearby.
Each of the seven stars is surrounded by a debris disk filled with dust, gas, ice, and rocky material. Astronomers are especially interested in gaps and other patterns within these disks because such features can signal that planets are forming and clearing paths through the surrounding material.
By suppressing the bright light from the stars, the team searched inside those disks for faint planets that would otherwise be difficult to detect. Planets that orbit stars beyond our solar system are known as exoplanets.
“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.”
Elias 2-24 b has roughly the mass of Jupiter, while its host star lies about 450 light-years from Earth. Because the system is so young, it gives astronomers a rare opportunity to study conditions that may resemble what our own solar system looked like billions of years ago.
Artist’s animation depicting Elias 2-24 b, the youngest exoplanet detected to date, still growing within the disk of gas and dust surrounding its young host star. Material from the disk is actively accreting onto the Jupiter-mass planet, which sits within a prominent gap in the disk, supporting the leading theory of giant planet formation. Credit: W. M. Keck Observatory/Adam Makarenko
Watching a Planetary Construction Zone
Stars form inside vast clouds of gas and dust. After a star is born, leftover material continues orbiting around it in a disk. Over time, particles within that disk can collide, stick together, and grow into increasingly larger objects, eventually producing planets that clear paths through the surrounding material.
Studying that earliest stage is difficult because newborn planets are often hidden behind the very gas and dust from which they are forming.
Most known exoplanets have instead been discovered through the transit method. A transit occurs when a planet crosses in front of its star from our point of view, causing the star’s brightness to dip slightly.
But young planets can be difficult to detect this way. Thick dust can hide them, and planets orbiting far from their stars take much longer to complete each orbit, making transits less frequent.
As a result, the overwhelming majority of the roughly 6,000 currently confirmed exoplanets are billions of years old and orbit relatively close to their stars.
Astronomers therefore build planet-formation models using a combination of theory, computer simulations, and observations of young stars surrounded by disks where planets themselves often remain invisible. Discovering more extremely young worlds like Elias 2-24 b could provide important evidence for improving those models.
“The galaxy churns out new stars and planets continuously, so there are many in every stage of evolution,” Cieza said. “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.”
A Decade-Old Mystery Finally Comes Together
The new confirmation also resolves a question astronomers have been investigating for about a decade.
Earlier observations from ALMA (Atacama Large Millimeter/submillimeter Array) in Chile revealed a gap within the dusty disk surrounding Elias 2-24. Later, the European Southern Observatory’s Very Large Telescope in Chile detected a faint point of light inside that same gap.
The observation immediately raised the possibility that astronomers were seeing a young planet. But the idea was difficult to reconcile with existing models of planet formation.
According to those models, a planet should not have had enough time to grow so large at such a great distance from its star. Current estimates suggest that producing a Jupiter-size planet at roughly Jupiter’s distance from the Sun (which is just over five times larger than the distance of Earth to the Sun) takes about 5 million years. Building such a planet farther away should take even longer.
Yet the mysterious point of light appeared about 55 times farther from its star than Earth is from the Sun, and it already showed signs of behaving like a forming planet.
Archival Observations Confirm the Planet
Bernardi and colleagues turned to the Keck Observatory Archive, a NASA-funded partnership between Keck Observatory and the NASA Exoplanet Science Institute at Caltech/IPAC, to see whether the object appeared in earlier observations.
They found the same faint source in Keck data collected in 2018 and 2020.
By combining the observations and tracking how the object moved over time, the researchers determined that it behaved like an orbiting planet rather than a background star or an artifact created by the imaging process. That evidence allowed the team to confirm the object as Elias 2-24 b.
“We usually hear about telescopes working separately, but this confirmation was possible only by using multiple telescopes together,” Bernardi said. “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.”
Roman Could Reveal Even More Baby Planets
Roman, which just launched Aug. 30, carries a more advanced coronagraph designed to detect planets that are difficult for many current telescopes to separate from the overwhelming glare of their stars.
Using a similar direct imaging approach, Roman could detect planets in considerably tighter orbits, including true Jupiter analogs that existing instruments struggle to see. Elias 2-24 b, by comparison, orbits about 10 times farther from its star.
That improved capability could give astronomers access to a population of young planets that has largely remained hidden and help fill one of the biggest observational gaps in planet formation research.
“This is just the beginning of a new era of discovery,” Cieza said. “It’s incredible that with modern technology, we are actually able to see planet formation in action, and Roman will take planet hunting to the next level.”
Reference: “Searching for Embedded Protoplanets with the Keck/NIRC2 Vortex Coronagraph: Confirmation of a Core-accretion Planet in the Narrow Gap of the Elias 2-24 Disk” by Andrea Bernardi, Alice Zurlo, Lucas A. Cieza, Garreth Ruane, Valentin Christiaens, Anuroop Dasgupta, Greta Guidi, Dimitri Mawet, Dino Mesa, Sebastián Pérez and Jonathan P. Williams, 16 September 2026, The Astrophysical Journal Letters.
DOI: 10.3847/2041-8213/ae9bb6
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