Astronomers have confirmed the discovery of Elias 2-24 b, a planet less than 1 million years old, making it the youngest known planet to date. The Jupiter-sized world is still orbiting within its natal disk of gas and dust, providing scientists with a rare opportunity to observe the process of planet formation in real time.
The discovery was detailed in a study published September 16 in The Astrophysical Journal Letters. The research team was led by Andrea Bernardi, a doctoral candidate at the Universidad Diego Portales in Chile. Located approximately 450 light-years from Earth, the system serves as a “time machine” for researchers to explore what the solar system may have looked like billions of years ago.
Challenging Planet-Formation Models
The existence of Elias 2-24 b challenges existing theories regarding how quickly giant planets can form. According to current models, forming a Jupiter-sized planet at roughly Jupiter’s distance from the Sun—just over five times the Earth-Sun distance—takes about 5 million years. Giant planets forming at greater distances are expected to take even longer.
Elias 2-24 b orbits its host star at a distance approximately 55 times the distance between Earth and the Sun, yet it has already reached a mass comparable to Jupiter in less than 1 million years. Lucas Cieza, a professor at the Instituto de Estudios Astrofísicos in Chile and co-author of the study, stated that existing models were already struggling to explain previous record holders—two planets orbiting PDS 70 and two orbiting WISPIT 2, all of which are more than 5 million years old. Cieza noted that Elias 2-24 b suggests current models are still missing important processes.
The results provide support for the “core accretion” formation model, in which a solid core grows large enough to rapidly draw in surrounding gas to build a gas giant’s atmosphere. Researchers believe Elias 2-24 b is currently being observed during this brief and decisive evolutionary phase.
A Multi-Telescope Detection Process
The confirmation of the planet solved a decade-long mystery. Roughly 10 years ago, the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile identified a gap in the young star’s dusty disk. Subsequently, the European Southern Observatory’s Very Large Telescope (VLT) in Chile detected a faint point of light within that gap.
To verify the discovery, Bernardi’s team utilized the Keck Observatory Archive, a NASA-funded partnership between the Keck Observatory and the NASA Exoplanet Science Institute at Caltech/IPAC. The team examined archived observations of seven young stars captured by a coronagraph, a tool that blocks intense starlight to reveal fainter nearby objects. In the Elias 2-24 system, they located the same faint point of light in observations from 2018 and 2020.
By stitching these observations together and analyzing the object’s motion, the researchers determined it behaved as a planet orbiting the star rather than a background star or an imaging defect. Bernardi emphasized that the confirmation was only possible by using multiple telescopes together.
Future Research and Capabilities
The discovery highlights the value of astronomical archives, demonstrating how new processing techniques can reveal data in images collected years earlier. The team now intends to more precisely measure the planet’s temperature, mass, atmosphere, and accretion rate.
While Elias 2-24 b is at the current limit of telescope detection, Bernardi noted that new instruments, such as NASA’s Nancy Grace Roman Space Telescope, which launched in August, should make such detections easier in the future.