International researchers have achieved a groundbreaking milestone by pinpointing the moment when planets began to form around a star beyond our Sun. Utilizing the ALMA telescope, in collaboration with the European Southern Observatory (ESO), and the James Webb Space Telescope, scientists have observed the creation of the first specks of planet-forming material: hot minerals just beginning to solidify. This discovery marks the first time a planetary system has been identified at such an early stage, offering a unique glimpse into the past of our own Solar System.
“For the first time, we have identified the earliest moment when planet formation is initiated around a star other than our Sun,” said Melissa McClure, a professor at Leiden University in the Netherlands and lead author of the study published in Nature.
Unveiling the Birth of a Planetary System
This nascent planetary system is forming around HOPS-315, a ‘proto’ or baby star located approximately 1,300 light-years away. It serves as an analogue of the early Sun. Around such stars, astronomers often observe discs of gas and dust known as ‘protoplanetary discs’, which are the birthplaces of new planets. While young discs containing massive, Jupiter-like planets have been observed before, McClure notes, “we’ve always known that the first solid parts of planets, or ‘planetesimals’, must form further back in time, at earlier stages.”
In our own Solar System, the first solid materials to condense near Earth’s current location around the Sun are found trapped within ancient meteorites. These meteorites, rich in crystalline minerals containing silicon monoxide (SiO), help astronomers date the formation of the Solar System. Over time, these newly condensed solids bind together, forming the building blocks of planets as they grow in size and mass. The first kilometre-sized planetesimals, which eventually became planets like Earth or Jupiter’s core, formed shortly after the condensation of these minerals.
Groundbreaking Observations and Techniques
With their recent discovery, astronomers have found evidence of these hot minerals beginning to condense in the disc around HOPS-315. Their results indicate that SiO is present both in its gaseous state and within crystalline minerals, suggesting it is just beginning to solidify. “This process has never been seen before in a protoplanetary disc — or anywhere outside our Solar System,” remarked Edwin Bergin, a professor at the University of Michigan and co-author of the study.
The identification of these minerals was first made possible by the James Webb Space Telescope, a joint project of the US, European, and Canadian space agencies. To determine the exact origin of the signals, the team observed the system with ALMA, the Atacama Large Millimeter/submillimeter Array, operated by ESO and international partners in Chile’s Atacama Desert.
“We’re really seeing these minerals at the same location in this extrasolar system as where we see them in asteroids in the Solar System,” said Logan Francis, a postdoctoral researcher at Leiden University.
Implications for Understanding Our Cosmic Origins
The disc of HOPS-315 provides a valuable analogue for studying our own cosmic history. As Merel van ‘t Hoff, a professor at Purdue University and co-author of the study, explained, “this system is one of the best that we know to actually probe some of the processes that happened in our Solar System.” It also presents astronomers with a new opportunity to study early planet formation, serving as a stand-in for newborn solar systems across the galaxy.
Elizabeth Humphreys, an ESO astronomer and European ALMA Programme Manager who did not participate in the study, expressed her admiration: “I was really impressed by this study, which reveals a very early stage of planet formation. It suggests that HOPS-315 can be used to understand how our own Solar System formed. This result highlights the combined strength of JWST and ALMA for exploring protoplanetary discs.”
Looking Ahead
This research, presented in the paper “Refractory solid condensation detected in an embedded protoplanetary disk” (doi:10.1038/s41586-025-09163-z), opens new avenues for understanding the early stages of planet formation. The collaboration between international telescopes and observatories continues to push the boundaries of what we know about the universe and our place within it.
As astronomers delve deeper into the mysteries of HOPS-315, the insights gained could not only illuminate the processes that shaped our own Solar System but also enhance our understanding of planetary formation across the cosmos. The continued exploration of protoplanetary discs promises to yield further revelations, offering a window into the origins of solar systems both near and far.
