Astronomers have confirmed the youngest planet ever found: a Jupiter-size world less than a million years old, still wrapped in the disk of gas and dust that is assembling it. Named Elias 2-24 b, it orbits a young star about 450 light-years from Earth and is the first planet caught this close to its own birth.

The previous record was a four-way tie — two planets orbiting the star PDS 70 and two orbiting WISPIT 2 — all more than 5 million years old. Elias 2-24 b is at least five times younger, and it breaks the timeline that planet-formation models have used to explain how giant worlds assemble.

The confirmation came out of an archive rather than a new telescope. A team led by Andrea Bernardi, a doctoral candidate at Universidad Diego Portales in Chile, searched NASA-funded observations of seven young stars taken with the coronagraph at the W. M. Keck Observatory in Hawaii — an instrument that blocks a star's glare so that fainter objects beside it become visible. In images of Elias 2-24 captured in 2018 and 2020, they found the same faint point of light. By tracking how it moved over time, the researchers ruled out an imaging artifact or a background star and confirmed it as a planet. The results were published September 16 in The Astrophysical Journal Letters.

The object had been a decade-old puzzle. The Atacama Large Millimeter/submillimeter Array had spotted a gap in the dust disk around Elias 2-24 — the kind of gap a massive body carves as it orbits — and the European Southern Observatory's Very Large Telescope saw a faint point of light inside it. Astronomers doubted the reading, because their models held that building a Jupiter-size planet takes about 5 million years, and longer still farther from the star. Elias 2-24 b sits roughly 55 times farther from its star than Earth is from the Sun, about ten times Jupiter's distance.

"Our planet-formation models already struggled to explain the previous record holders," said Lucas Cieza, a professor at the Instituto de Estudios Astrofísicos in Chile and a co-author of the study. "Elias 2-24 b shows us that even our best planet-formation models are still missing some important processes."

Most of the roughly 6,000 confirmed exoplanets are billions of years old and orbit close to their stars, because planets still buried in dust are nearly impossible to detect directly. That blind spot is starting to close: NASA's Nancy Grace Roman Space Telescope, launched August 30, carries a more advanced coronagraph that should be able to find planets in tighter orbits.

Sources: NASA Science, ScienceDaily, Mashable, The Astrophysical Journal Letters