In a cosmic breakthrough, scientists using the James Webb and ALMA telescopes have caught a rare glimpse of a planetary system in its earliest moments — as hot mineral crystals first begin to solidify around a young star called HOPS-315, 1300 light-years from Earth.
This is the first time astronomers have observed the very beginnings of planet formation beyond our Solar System, offering a remarkable parallel to how Earth and its planetary siblings once emerged. The discovery reveals a dusty disc of gas turning into the seeds of future planets — a stunning look back in time to our own origins.
Discovery: Planet Formation Caught in the Act
For the first time, an international team of scientists has identified the precise moment when planets begin to take shape around a star beyond our Sun. Using observations from the Atacama Large Millimeter/submillimeter Array (ALMA), a telescope in which the European Southern Observatory (ESO) plays a key role, along with data from the James Webb Space Telescope (JWST), the researchers spotted the earliest traces of planet-forming material. These tiny specks are made of hot minerals that are just starting to cool and solidify. This discovery marks the earliest stage of planetary system formation ever recorded and offers a rare glimpse into what may have happened in the early days 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,” says Melissa McClure, a professor at Leiden University in the Netherlands and lead author of the new study, published today in Nature.
Co-author Merel van ‘t Hoff, a professor at Purdue University, USA, compares their findings to “a picture of the baby Solar System”, saying that “we’re seeing a system that looks like what our Solar System looked like when it was just beginning to form.”
This video zooms into HOPS-315, a baby star where astronomers have identified gas condensing into solid minerals for the first time.
A Star Like Our Early Sun
The young star at the center of this discovery is known as HOPS-315. Located about 1300 light-years from Earth, it is considered a “proto” or infant star and is thought to resemble what the Sun may have looked like in its earliest stages. Surrounding such stars are swirling discs of gas and dust, known as protoplanetary discs, where planets begin to form. While astronomers have previously observed massive, Jupiter-sized planets already present in some of these discs, McClure notes that the solid building blocks of planets, known as planetesimals, must start forming even earlier.
In our own Solar System, the first solid substances to form near the Sun’s current position are preserved inside ancient meteorites. These rocks allow scientists to estimate the timing of the Solar System’s formation. Meteorites are filled with crystalline minerals containing silicon monoxide (SiO), which can condense from gas at the extremely high temperatures found in young protoplanetary discs. Over time, these crystals clump together, growing in size and mass, eventually becoming the raw material for planets. The first kilometer-sized planetesimals, which would go on to form planets like Earth or the core of Jupiter, emerged shortly after these minerals began to solidify.
The blue jet is moving towards us, and the red one is moving away. Observations taken with the James Webb Space Telescope (JWST) show signatures of SiO moving at about 10 km/s. The SiO jets seen in this ALMA image move about 10 times faster though. This means that the slow-moving SiO must be located in a small area around the star, about the size of the asteroid belt around our Sun, too small to be seen in this image.
Also, the abundance of gaseous SiO measured in the jet seen with ALMA is lower than expected. Since the composition of the jet should be similar to that of the disc from where the jet emerges, this means that some of the gaseous SiO in the disc is condensing into solid material.
Credit: ALMA(ESO/NAOJ/NRAO)/M. McClure et al.
Birth of Planet-Forming Solids
With their new discovery, astronomers have found evidence of these hot minerals beginning to condense in the disc around HOPS-315. Their results show that SiO is present around the baby star in its gaseous state, as well as within these crystalline minerals, suggesting it is only just beginning to solidify. “This process has never been seen before in a protoplanetary disc — or anywhere outside our Solar System,” says co-author Edwin Bergin, a professor at the University of Michigan, USA.
These minerals were first identified using the James Webb Space Telescope, a joint project of the US, European and Canadian space agencies. To find out where exactly the signals were coming from, the team observed the system with ALMA, the Atacama Large Millimeter/submillimeter Array, which is operated by ESO together with international partners in Chile’s Atacama Desert.
This animation illustrates how hot gas condenses into solid minerals around the baby star HOPS-315. At the beginning, we see molecules of silicon monoxide which then condense into solid dust grains. The video then zooms out to reveal an actual image of HOPS-315 taken with the Atacama Large Millimeter/submillimeter Array (ALMA), in which ESO is a partner. This image shows different molecules blowing away from the star: carbon monoxide in orange and silicon monoxide in blue. Credit: ESO/L. Calçada/ALMA(ESO/NAOJ/NRAO)/M. McClure et al.
Echoes of the Asteroid Belt
With these data, the team determined that the chemical signals were coming from a small region of the disc around the star equivalent to the orbit of the asteroid belt around the Sun. “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,“ says co-author Logan Francis, a postdoctoral researcher at Leiden University.
Because of this, the disc of HOPS-315 provides a wonderful analogue for studying our own cosmic history. As van ‘t Hoff says, “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 provides astronomers with a new opportunity to study early planet formation, by standing in as a substitute for newborn solar systems across the galaxy.
ESO astronomer and European ALMA Programme Manager Elizabeth Humphreys, who did not take part in the study, says: “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.”
Reference: “Refractory solid condensation detected in an embedded protoplanetary disk” by M. K. McClure, Merel van’t Hoff, Logan Francis, Edwin Bergin, Will R. M. Rocha, J. A. Sturm, Daniel Harsono, Ewine F. van Dishoeck, John H. Black, J. A. Noble, D. Qasim and E. Dartois, 16 July 2025, Nature.
DOI: 10.1038/s41586-025-09163-z
The team is composed of M. K. McClure (Leiden Observatory, Leiden University, The Netherlands [Leiden]), M. van ’t Hoff (Department of Astronomy, The University of Michigan, Michigan, USA [Michigan] and Purdue University, Department of Physics and Astronomy, Indiana, USA), L. Francis (Leiden), Edwin Bergin (Michigan), W.R. M. Rocha (Leiden), J. A. Sturm (Leiden), D. Harsono (Institute of Astronomy, Department of Physics, National Tsing Hua University, Taiwan), E. F. van Dishoeck (Leiden), J. H. Black (Chalmers University of Technology, Department of Space, Earth and Environment, Onsala Space Observatory, Sweden), J. A. Noble (Physique des Interactions Ioniques et Moléculaires, CNRS, Aix Marseille Université, France), D. Qasim (Southwest Research Institute, Texas, USA), E. Dartois (Institut des Sciences Moléculaires d’Orsay, CNRS, Université Paris-Saclay, France.)
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