Astronomers have confirmed Elias 2-24 b as the youngest known planet, a Jupiter-size world less than 1 million years old whose unexpectedly rapid formation far from its star challenges leading theories of how giant planets develop.
By yourNEWS Media Newsroom.
Astronomers have confirmed a Jupiter-size planet less than 1 million years old, providing researchers with an unusually early glimpse of planetary development and raising new questions about how massive worlds can form so quickly at great distances from their stars.
The planet, designated Elias 2-24 b, orbits a young star approximately 450 light-years from Earth and remains embedded within the gas and dust left over from its formation. Researchers reported the confirmation in a study published Sept. 16 in The Astrophysical Journal Letters.
Its extreme youth makes Elias 2-24 b the youngest confirmed planet known to astronomers, replacing previous record holders that were already more than 5 million years old.
More unexpectedly, the planet lies roughly 55 times farther from its star than Earth is from the Sun. Existing models generally predict that assembling a Jupiter-size world should take millions of years even at much smaller orbital distances.
“Our planet-formation models already struggled to explain the previous record holders for the youngest known planet,” 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.”
Andrea Bernardi, a doctoral candidate at Universidad Diego Portales in Chile, led the confirmation using observations preserved in astronomical archives rather than relying solely on newly collected telescope data.
Researchers examined observations of seven young stars taken with a coronagraph at the W. M. Keck Observatory in Hawaii. The instrument suppresses much of the overwhelming light produced by a star, allowing astronomers to search for substantially fainter objects nearby.
That capability is particularly important for young planetary systems, where forming worlds can remain obscured within dense disks of gas and dust.
Elias 2-24 had attracted astronomers’ attention long before the new confirmation.
Observations made with the Atacama Large Millimeter/submillimeter Array in Chile revealed a prominent gap within the dusty disk surrounding the young star. Such openings are of particular interest because growing giant planets can sweep material from their orbital paths, leaving gaps behind.
“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.”
Later observations by the European Southern Observatory’s Very Large Telescope detected a faint point of light inside the gap, raising the possibility that astronomers were looking directly at the object responsible for clearing it.
Confirming that possibility proved difficult.
A faint object appearing near a star can be an imaging artifact, a more distant background source or another astronomical object rather than a planet physically orbiting the system.
Bernardi and her colleagues turned to the Keck Observatory Archive and located observations of the same system collected in 2018 and 2020.
By combining observations separated in time, researchers could examine how the faint object moved relative to Elias 2-24. Its changing position was consistent with an object traveling with and orbiting the star rather than a stationary background source.
The archival evidence allowed the researchers to confirm that the object inside the disk gap was a planet.
The result resolves a mystery that had persisted for roughly a decade while simultaneously creating a larger problem for theories describing how giant planets form.
Under commonly used models, building a planet comparable in size to Jupiter at approximately Jupiter’s distance from the Sun — slightly more than five times Earth’s distance from the Sun — requires about 5 million years.
Planet formation is generally expected to proceed even more slowly at greater distances because the material from which planets grow is distributed over a much larger region.
Elias 2-24 b, however, is located approximately 55 times the Earth-Sun distance from its host star and nevertheless appears to have become a giant planet before its system reached 1 million years of age.
That combination of youth, size and orbital distance is difficult to reproduce using existing formation models.
Scientists develop those models through a combination of physical theories, computer simulations and observations of stars at different stages of development. Young stars surrounded by protoplanetary disks provide some of the most important evidence because those disks contain the raw materials from which planets emerge.
Stars themselves form within large clouds of gas and dust. As matter collapses inward, disks develop around the young stars, while jets can carry away angular momentum and allow additional material to continue accreting.
Within those disks, dust and other material can begin assembling into progressively larger bodies that eventually become planets.
The problem for astronomers is that seeing planets during the earliest stages of that process remains extraordinarily difficult.
“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.”
That observational blind spot has influenced what scientists know about planets outside the solar system.
Approximately 6,000 exoplanets have been confirmed, but most are mature worlds that are billions of years old. Many were found by detecting the small reduction in a star’s brightness that occurs when an orbiting planet passes in front of it.
That transit method has been extraordinarily productive but is less effective for very young planetary systems buried in dust and for planets traveling in wide orbits.
Direct imaging offers another approach, but the enormous difference in brightness between planets and their host stars makes such detections technically demanding.
Elias 2-24 b sits near the limits of what current instruments can observe.
“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.”
The system’s extreme youth gives scientists more than simply another entry in the catalog of known exoplanets.
Because Elias 2-24 b remains surrounded by the material from which planets develop, astronomers can study a planetary system while major parts of the formation process are still unfolding.
That could allow researchers to test competing models against an actual young planet instead of relying primarily on simulations or indirect evidence from gaps and structures within disks.
The observations could also provide clues to conditions that existed during the infancy of Earth’s own planetary neighborhood billions of years ago.
Our solar system no longer retains an easily observable record of every step in its formation. Young systems such as Elias 2-24 therefore function as astronomical snapshots of processes that occurred around the Sun in the distant past.
Astronomers have been studying giant worlds around other stars for decades. One such discovery came in 1997, when Robert Noyes of the Harvard-Smithsonian Astrophysical Observatory and other researchers reported a Jupiter-size planet orbiting Rho Coronae Borealis.
The field expanded dramatically in the following years, particularly after NASA’s Kepler space telescope launched March 6, 2009, to monitor approximately 150,000 stars in the constellations Cygnus and Lyra.
At the time of Kepler’s launch, only 374 exoplanets had been identified during approximately 17 years of discoveries. Thousands have since been confirmed using Kepler and numerous ground- and space-based observatories.
The Nancy Grace Roman Space Telescope is expected to push direct planet observations further.
Roman launched Aug. 30 carrying a more advanced coronagraph intended to demonstrate technologies capable of suppressing starlight with greater precision than many existing instruments.
Although Elias 2-24 b itself travels too far from its star to demonstrate Roman’s full sensitivity advantage, the telescope’s coronagraph is designed to help detect planets in considerably tighter orbits that are currently concealed by stellar glare.
Elias 2-24 b orbits at roughly 10 times the distance from its star that Roman is expected to be capable of probing in appropriate systems.
That improved capability could eventually allow astronomers to find more Jupiter-like planets during formative stages that existing instruments struggle to resolve.
“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.”
For researchers, Elias 2-24 b is particularly important because its existence provides a direct test of assumptions built into current models.
Astronomers now have evidence that at least one giant planet assembled at an unexpectedly early stage and at a distance where conventional formation mechanisms would generally be expected to operate more slowly.
Determining how that happened could require modifications to existing theories or greater consideration of processes that current models do not fully capture.
The planet’s confirmation therefore represents more than a new age record. By revealing a massive world still surrounded by its formative disk less than 1 million years after its star emerged, Elias 2-24 b gives astronomers an opportunity to examine one of the least observable stages in the evolution of planetary systems — and potentially reconsider how quickly planets can be born.
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