Elias 2-24 b, estimated to be less than one million years old, offers a rare opportunity to investigate how quickly giant planets form.
Astronomers have confirmed an exceptionally young planet approximately 450 light-years from Earth, giving researchers a glimpse of a giant world still taking shape within the gas and dust surrounding its star.
Named Elias 2-24 b, the planet is estimated to be less than one million years old. NASA and the discovery team described it as the youngest known exoplanet when announcing the findings on September 16. The research was published in The Astrophysical Journal Letters.
An international team led by Andrea Bernardi, a doctoral researcher at Universidad Diego Portales in Chile, confirmed the planet by combining observations from the W. M. Keck Observatory in Hawaiʻi, the European Southern Observatory’s Very Large Telescope and the Atacama Large Millimeter/submillimeter Array, or ALMA, in Chile.
The planet sits inside a narrow gap in its star’s protoplanetary disk—the rotating reservoir of material from which planets develop. Such gaps have long been considered possible signs of emerging planets, but identifying the objects responsible is difficult because dust and bright starlight can obscure them.
Earlier observations revealed both a gap and a faint point of light within it. Researchers revisited archival Keck observations from 2018 and 2020, examining the source over time to distinguish a planet from a background star or an imaging artefact. Together, the observations provided the evidence needed for confirmation.
The study places Elias 2-24 b at a projected separation of approximately 55 astronomical units from its star, with one astronomical unit representing the average Earth–Sun distance. By comparing its brightness with models of young planets, the researchers estimated a mass between approximately 1.9 and four times Jupiter’s mass.
That estimate carries an important qualification: it does not account for the effects of material falling onto the planet, which can contribute to its brightness. Its mass therefore remains a subject for further investigation.
The team interprets the findings as supporting core accretion, a leading explanation for giant-planet formation in which a growing solid core eventually gathers a substantial gaseous envelope. According to Keck Observatory, Elias 2-24 b appears to be undergoing a rapid phase of gas accumulation.
Its extreme youth makes the system particularly valuable. A giant planet already present at such an early stage places a demanding constraint on models: they must explain how enough material can assemble so quickly, including at considerable distances from a star. The discovery also strengthens the connection between young planets and the gaps observed in their surrounding disks.
Researchers now hope to obtain measurements that better establish the planet’s atmosphere, temperature, mass and continuing growth. Each could help turn this newly confirmed world into a more precise test of how planetary systems begin.
Sources:
