Study: Refractory solid condensation detected in an embedded protoplanetary disk (DOI: 10.1038/s41586-025-09163-z)
An international research team, including members with ties to the University of Michigan, has witnessed the earliest moments to date of planets beginning to form around a star beyond the sun.
This finding marks the first time a planetary system has been identified at such an early stage of formation and opens a window to the past of our own solar system.
This newborn planetary system is emerging around the young star HOPS-315, which sits some 1,300 light years away from Earth. Around such young stars, astronomers often see discs of gas and dust known as protoplanetary discs, which are the birthplaces of new planets.
Using the JWST space telescope and the Atacama Large Millimeter Array, or ALMA, in Chile, the researchers observed signs of dust and gas coming together to form solids. These solids then bind together, growing first into planet seedlings called "planetesimals" that then grow over time into planets.
"This process has never been seen before in a protoplanetary disc-or anywhere outside our solar system," said Edwin Bergin, co-author of the new study and a U-M professor of astronomy.
Although researchers have observed discs with young planets in them before, they've never witnessed the actual birth of planets. They did, however, know what they should be looking for to finally capture the first moments of a planet's existence.
"We've always known that the first solid parts of planets, or planetesimals, must form further back in time, at earlier stages," said Melissa McClure, lead author of the study and an assistant professor at Leiden University in the Netherlands. McClure also earned her doctorate at U-M in 2015.
Now, researchers representing eight institutions from five countries have combined the powers of JWST and ALMA to take "a picture of the baby solar system," said co-author Merel van 't Hoff, who began the project as a postdoctoral researcher at U-M and is now an assistant professor at Purdue University.
"This system is one of the best that we know to actually probe some of the processes that happened in our solar system," she said of the HOPS-315 system.
In our solar system, the very first solid material to condense near Earth's present location around the sun is found trapped within ancient meteorites. Astronomers age-date these primordial rocks to determine when the clock started on our solar system's formation. Such meteorites are packed full of crystalline minerals that contain silicon monoxide, or SiO, and can condense at the extremely high temperatures present in young planetary discs.
Over time, these newly condensed solids bind together, sowing the seeds for planet formation as they gain both size and mass. The first kilometer-sized planetesimals in the solar system, which grew to become the Earth and Jupiter's core, formed just after the condensation of these crystalline minerals.
In 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 newborn star in its gaseous state as well as within crystalline minerals, suggesting it is only just beginning to solidify.
"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, HOPS-315's disc provides a wonderful analogue for studying our own cosmic history. 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.
The minerals were first identified using the JWST, a joint project of NASA, the European Space Agency and the Canadian Space Agency. To find out where exactly the signals were coming from, the team observed the system with ALMA, an international observatory in Chile's Atacama Desert operated by the National Radio Astronomy Observatory, the European Southern Observatory and the National Astronomical Observatory of Japan.
