JWST just found evidence that some “super-Jupiters” may have formed like planets, not failed stars. A distant star system with four super-sized gas giants has revealed a surprise. Thanks to JWST’s powerful vision, astronomers detected sulfur in their atmospheres — a chemical clue that they formed like Jupiter, by slowly building solid cores. That’s unexpected because these planets are far bigger and orbit much farther from their star than models once allowed.
Gas giants are enormous planets made primarily of hydrogen and helium. They may contain dense central cores, but unlike Earth, they do not have solid surfaces you could stand on. In our solar system, Jupiter and Saturn are classic examples. Beyond our neighborhood, astronomers have identified many gas giant exoplanets, some far larger than Jupiter. The most massive of these worlds begin to resemble brown dwarfs, substellar objects sometimes called “failed stars” because they do not fuse hydrogen.
This overlap raises a major question in astronomy. How exactly do these massive planets form? One possibility is core accretion, the same process believed to have created Jupiter and Saturn. In this scenario, a solid core slowly builds up inside a disk of dust and ice, gathering rocky and icy material until it becomes massive enough to pull in surrounding gas. Another possibility is gravitational instability, where a swirling cloud of gas around a young star collapses quickly under its own gravity, forming a large object more like a brown dwarf.
