One of the closest neighboring “star systems” doesn’t contain any stars at all. Instead, it’s a pair of brown dwarfs — objects that aren’t massive enough to shine as true stars, but that are too massive to be considered planets. In this case, though, both objects probably look a lot like Jupiter, the largest planet in the solar system. Luhman 16 is just six and a half light-years away — the third-closest system to the Sun. The two brown dwarfs are so faint, though, that they weren’t discovered until 2013. Observations made since then have shown that the brown dwarfs orbit each other once every 27 years. Both are about the size of Jupiter, but roughly 30 times more massive. They’re also a good bit hotter than Jupiter, so they produce their own light — mostly at infrared wavelengths. Yet they’re cool enough for molecules in their atmospheres to condense. Although we can’t see them, those molecules probably form bands of clouds like those on Jupiter. Some bands are thick, so they’re dark.
