Free Astronomy Magazine September-October 2025

34 SEPTEMBER-OCTOBER 2025 ASTRO PUBLISHING tain newborn, massive, Jupiter-like planets, McClure says, “we’ve always known that the first solid parts of planets, or ‘planetesimals’, must form further back in time, at earlier stages.” 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 miner- als that contain silicon monoxide (SiO) and can condense at the ex- tremely 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 kilometre- sized planetesimals in the Solar Sys- tem, which grew to become planets such as Earth or Jupiter’s core, formed just after the condensation by ESO Bárbara Ferreira The dawn of a new solar system “F or the first time, we have identified the earliest mo- ment when planet forma- tion 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 in Nature . Co-author Merel van ‘t Hoff, a pro- fessor 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 begin- ning to form.” This newborn planetary system is emerging around HOPS-315, a ‘proto’ or baby star that sits some 1300 light-years away from us and is an analogue of the nascent Sun. Around such baby stars, astronomers often see discs of gas and dust known as ‘protoplanetary discs’, which are the birthplaces of new planets. While astronomers have previously seen young discs that con-