No one knows exactly how far the universe can go when it comes to making stars, because the James Webb Space Telescope has now found an object only twice the mass of Jupiter — so small that it cannot become a star.
Discovered in IC 348, a young star-forming region about 1,000 light-years away, these brown dwarfs are born like stars: massive clouds of gas and dust begin to collapse under their own gravity. But because they cannot grow large enough, they never sustain the hydrogen fusion that powers a normal star at their core.
That is where things get strange. Around one of the lightest objects found, there are signs of a disk — meaning we are looking at something close to planetary mass, possibly surrounded by a structure capable of forming new planets. In other words, the universe may not be limited to making planets around stars. It may even be able to start the origins of new worlds around objects of planetary mass.
This discovery blurs the line between stars and planets far more than we imagined. On one side are giant stars that produce their own light. On the other are planets orbiting stars. In between are these strange objects that can be called neither fully star nor fully planet. Nature does not care about our categories; it simply follows the laws of physics.
Perhaps the most interesting thing in the universe is not the discovery of a new planet, but the fact that we still cannot draw a clear line determining when a planet stops being a planet and when a star begins to be a star — because every time Webb looks, it shows us that the universe is not made of the neat categories we imagine.