NASA‘s James Webb Space Telescope has resolved a long-standing puzzle in planetary science, confirming a controversial discovery made by the Hubble Space Telescope more than 20 years ago. The Webb telescope’s observations have provided crucial evidence that planet-forming disks in the early universe existed longer than previously thought—something that challenges current models of planet formation.
In 2003, Hubble discovered a massive planet orbiting an ancient star nearly as old as the universe itself. The finding was perplexing because stars of this age, formed from mostly hydrogen and helium, should contain minimal amounts of heavier elements- essential building blocks for planet formation.
According to current models, such stars should have needed more time to form large planets, such as Jupiter. The discovery suggested that planet formation might have occurred much earlier in the universe’s history, but how could planets grow so large with such limited material?
To solve this mystery, researchers turned to the Webb telescope, focusing on stars in a nearby galaxy, the Small Magellanic Cloud, which shares similarities with the early universe due to its lack of heavy elements. Using Webb’s advanced sensitivity and resolution, the team studied the massive, star-forming cluster NGC 346 in this dwarf galaxy—a stellar nursery with a limited amount of heavier elements.
Webb’s observations confirmed the findings made by Hubble in the mid-2000s, which showed that planet-forming disks still surrounded some stars in NGC 346 at an age of 20 to 30 million years—far longer than the conventional wisdom of just 2 or 3 million years.
These results strongly suggested that planets could have had more time to form and grow around these stars, even in the early universe.
Guido De Marchi, lead author of the European Space Research and Technology Centre study, stated, “With Webb, we have a powerful confirmation of what we saw with Hubble, and we must rethink how we model planet formation and early evolution in the young universe.”
The findings challenge existing theoretical models, which predicted that the scarcity of heavier elements would cause planet-forming disks to dissipate quickly in the early universe. Current models suggested that radiation from the star would blow away the disk in less than a million years before the dust could coalesce into planetary bodies.
However, Webb’s observations suggest this process was slower than once thought. The scientists propose two reasons why planet-forming disks persisted longer in environments with fewer heavy elements.
First, radiation pressure from stars in these environments wasn’t as effective at dispersing the disks since the stars only contained about 10% of the heavier elements in the Sun. This slower process would allow the disks to survive longer.
Alternatively, the researchers suggest that stars in such regions might have begun their formation with more significant gas clouds, which would result in bigger, more massive disks. These larger disks would take much longer to dissipate, providing more time for planet formation.
Elena Sabbi, co-investigator of the study, explained, “With more matter around the stars, the accretion lasts longer. The disks take ten times longer to disappear. This has implications for how you form a planet and the type of system architecture that you can have in these different environments. This is so exciting.”
These findings could significantly alter our understanding of how planets form in the early universe and may even offer new insights into the processes that shaped our solar system.
As researchers continue to study the early universe, Webb’s groundbreaking capabilities are expected to answer even more questions about the origins of planets and stars in the cosmos.
Journal Reference:
- Guido De Marchi, Giovanna Giardino, Katia Biazzo et al. Protoplanetary Disks around Sun-like Stars Appear to Live Longer When the Metallicity is Low*. The Astrophysical Journal. DOI 10.3847/1538-4357/ad7a63
