Astronomers caught a planet still being built, under a million years old

A planet less than a million years old is still gathering gas and dust from the disk around its star, and astronomers have finally caught it in the act. The world, named Elias 2-24 b, orbits a young star roughly 450 light-years from Earth and carries about as much mass as Jupiter. A team led by Andrea Bernardi, a doctoral candidate at the Universidad Diego Portales in Chile, confirmed the discovery in a study published Wednesday, September 16, in The Astrophysical Journal Letters.

The confirmation closes a debate that had simmered for roughly a decade over a faint point of light nobody could quite explain. It also hands planet-formation theorists a headache, because the object showed up in a place and at a speed their models say a planet should not yet exist.

A planet caught mid-construction, 450 light-years away

Elias 2-24 b sits inside a debris disk full of dust, gas, and chunks of ice and rock still swirling around its host star, according to NASA’s account of the discovery. Material from that disk is actively falling onto the young, Jupiter-mass planet, which occupies a wide gap that its own gravity appears to be carving into the disk. Lucas Cieza, a professor at Chile’s Instituto de Estudios Astrofísicos and a co-author of the new study, said the discovery undercuts the field’s existing models. “Our planet-formation models already struggled to explain the previous record holders for the youngest known planet,” Cieza said, adding that Elias 2-24 b shows those models are “still missing some important processes.”

Most of the roughly 6,000 confirmed exoplanets cataloged so far are billions of years old and orbit close to their stars, largely because astronomers find them by watching a planet cross in front of its star and dim the light reaching Earth. That method, called the transit technique, does not work well on a planet still buried in a young, dusty disk far from its star. Elias 2-24 b was found a different way entirely, and the gap between what most telescopes can detect and what actually exists in space is exactly why it took a decade to confirm.

Archival Keck images and a decade-old puzzle

The trail started roughly ten years ago, when the Atacama Large Millimeter/submillimeter Array in Chile spotted a gap in the dusty disk surrounding the star Elias 2-24. The European Southern Observatory’s Very Large Telescope then detected a faint point of light sitting inside that gap, sparking an argument among astronomers over whether it could really be a planet. Existing formation theories held that a gap that far out, and that early in the star’s life, appeared too soon and too distant for a planet to have already formed there.

Bernardi’s team went looking for the same point of light in the Keck Observatory Archive, a NASA-funded partnership between the W. M. Keck Observatory and the NASA Exoplanet Science Institute at Caltech. They found it in observations taken in 2018 and 2020 using the observatory’s coronagraph, an instrument that blocks a star’s glare so fainter objects nearby become visible. Stitching those two epochs together let the team track the object’s motion over two years and confirm it moved like a planet rather than a camera artifact or a background star. “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.”

Records broken: PDS 70 and WISPIT 2 dethroned

Before Elias 2-24 b, the youngest confirmed planets were a four-way tie: two planets orbiting the star PDS 70 and two more orbiting WISPIT 2, all of them more than 5 million years old. Current formation models predict it takes roughly 5 million years to build a Jupiter-size planet at Jupiter’s own distance from a star, a gap equal to just over five times the distance between Earth and the Sun, and even longer farther out. Elias 2-24 b orbits about 55 times farther from its star than Earth orbits the Sun, roughly ten times farther out than Jupiter sits from the Sun, yet it is already behaving like a fully forming planet at under a million years of age. That timeline is the specific problem Cieza flagged: the models cannot yet explain how a planet gets built that fast, that far from its star.

Bernardi described the confirmation as a product of instruments working in sequence rather than isolation. “We usually hear about telescopes working separately, but this confirmation was possible only by using multiple telescopes together,” he said, crediting the combination of the Atacama array, the European observatory’s telescope, and the archived Keck coronagraph images for finally nailing down the object’s identity.

What comes next: the Roman Space Telescope

NASA’s Nancy Grace Roman Space Telescope launched August 30, 2026, carrying a coronagraph more powerful than the one at Keck. Roman is designed to spot planets in much tighter orbits than Elias 2-24 b’s, including Jupiter-like worlds currently lost in the glare of their stars. Cieza called the discovery “just the beginning of a new era,” arguing that Roman “will take planet hunting to the next level” by making detections like this one far easier to repeat across other young star systems.

Cieza also framed the find in terms of what it reveals about the galaxy’s ordinary churn. New stars and planets form continuously, he said, which means examples of nearly every stage of that process exist somewhere in the sky right now, even though most telescopes still cannot see them. Elias 2-24 b happened to sit at the outer edge of what Keck’s archive could resolve, caught only because two separate observing runs, four years apart, both recorded the same faint point of light in the same place.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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