Stars twinkle in the night sky, even millions of light-years away, because they are incredibly hot. Planets are much cooler. In between, brown dwarfs are an astronomical enigma: More massive than planets but smaller than stars, they fit neatly into neither category.

Sometimes, astronomers call these objects “failed stars.” But if you fail as a star, can you succeed as a planet? In other words, can a star or a brown dwarf become a planet? It’s an intriguing idea, but for many astronomers, the answer is no. “Stars and planets, just based on the way that they form, are two different things,” said Kovi Rose, a doctoral candidate of astronomy at the University of Sydney in Australia.