Sharper views of 78 infant-star disks in the Ophiuchus cloud reveal crisp rings and spirals—gravitational fingerprints of emerging planets—just a few hundred thousand years after the stars ignite.
By reprocessing ALMA’s archival data at triple the prior resolution, astronomers spotted these patterns in 27 disks, 15 of them newly identified. The discovery pushes planet formation’s starting line far earlier than once thought, showing newborn worlds grow alongside their stars while gas and dust are still plentiful.
Early Signs of Planet Birth
Astronomers have uncovered surprising evidence that planets may start forming much earlier than previously believed, while their stars are still in the process of being born. Using sharper, more detailed images created with advanced techniques, researchers have reanalyzed archival radio telescope data and discovered clear signs of planet formation in the swirling material around very young stars. These findings offer exciting new clues about when and how planets like Earth begin to take shape.
Planets form inside vast disks of cold gas and dust that surround baby stars, known as protostars. These disks, called protoplanetary disks, are where the building blocks of planets slowly come together. While the forming planets themselves are too small and faint to see directly, their gravity can sculpt the surrounding material into rings or spirals. Until now, scientists weren’t sure how early in the star’s life these patterns appeared, mainly because so few disks are close enough to be observed in detail.
Reanalyzing ALMA Archives for Hidden Clues
To find out more, a team led by Ayumu Shoshi of Kyushu University and the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA) turned to previously collected data from the ALMA (Atacama Large Millimeter/submillimeter Array) radio telescope. They applied improved image processing techniques to reexamine 78 protoplanetary disks in the Ophiuchus star-forming region, about 460 light-years from Earth. Thanks to these enhancements, more than half of the resulting images reached a level of detail more than three times better than before.
Rings and Spirals Show Planets Grow Fast
The new high-resolution images show ring or spiral patterns in 27 of the disks. Of these, 15 were identified for the first time in this study. Combining this new sample with pervious work for a different star-forming region, the team found that the characteristic disk substructures emerge in disks larger than 30 au (astronomical units, one au = 149,597,870,700 m, the distance between the Earth and the Sun) around stars in the early stage of star formation, just a few hundred thousand years after a star was born.
This suggests that planets begin to form at a much earlier stage than previously believed, when the disk still possesses abundant gas and dust. In other words, planets grow together with their very young host stars.
Reference: “ALMA 2D super-resolution imaging survey of Ophiuchus Class I/flat spectrum/II disks. I. Discovery of new disk substructures” by Ayumu Shoshi, Masayuki Yamaguchi, Takayuki Muto, Naomi Hirano, Ryohei Kawabe, Takashi Tsukagoshi and Masahiro N Machida, 22 April 2025, Publications of the Astronomical Society of Japan.
DOI: 10.1093/pasj/psaf026
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