Free Astronomy Magazine November-December 2025

22 NOVEMBER-DECEMBER 2025 ASTRO PUBLISHING B rown dwarfs are more massive than planets but not quite as massive as stars. Generally speaking, they have between 13 and 80 times the mass of Jupiter. A brown dwarf becomes a star if its core pressure gets high enough to start nuclear fusion. [NASA/JPL-Caltech] portant role in the formation of clouds within their atmospheres. De- spite decades of searching, it eluded detection in the atmospheres of our Solar System’s gas giants, Jupiter and Saturn, as well as the thousands of atmospheres scientists have studied on brown dwarfs and gas giants around other stars. This marks the first discovery of silane in any brown dwarf, exoplanet, or Solar System object. The fact that this molecule hasn’t been detected anywhere ex- cept in a single, peculiar brown dwarf suggests something about the chemistry occurring in such ancient environments. “Sometimes it’s the extreme objects that help us under- stand what’s happening in the aver- age ones,” says Jackie Faherty, a researcher at the American Museum of Natural History in New York City and lead author on the paper. Located about 50 light-years from atmosphere suggests that, in very old objects, silicon can bond with hy- drogen to form a light molecule that can reach the upper layers of a gas giant’s atmosphere. But in objects that formed more recently, like Jupiter and Saturn, the silicon bonds with the more readily available oxy- gen, creating heavier molecules that sink deep below the surface layers of the atmosphere, where they are undetectable by our telescopes. The evidence uncovered in The Ac- cident’s atmosphere confirms as- tronomers’ understanding of how clouds on gas giants form, and of- fers critical insight into how primor- dial formation can impact the com- position of a planet’s atmosphere. Additionally, it reveals how a world formed many billions of years ago can look drastically different than a world formed during the dawn of our Solar System. Earth, The Accident likely formed 10–12 billion years ago, making it one of the oldest brown dwarfs ever discovered. The Universe is nearly 14 billion years old, meaning that The Accident formed at a time when the cosmos contained mostly hydrogen and helium, with trace amounts of other elements, including silicon. Over eons, elements like carbon, ni- trogen, and oxygen formed in the cores of stars, meaning that planets and stars that formed more recently possess more of those elements. The presence of silane in The Accident’s !