Everyone knows which planets have rings: it's Saturn, Neptune, and Uranus. But there's one more you may not be aware of. Jupiter has rings too, although they're so faint it took a spacecraft to find them.
A Dusty Halo
Until 1979, astronomers had no idea that wispy rings of dust and rock particles encircled our solar system's largest gas giant. That's because unlike the rings of, say, Saturn, which are made of relatively large pieces of ice that reflect sunlight, Jupiter's rings are made of miniscule particles of rock and dust—some as small as cigarette-smoke particles—which makes them dark and nearly impossible to see from Earth.
How Many Are There?
Though future spacecraft could learn much more about the rings, as of June 2016 there were four: the main ring, which encompasses the orbits of Adrastea and Metis, two small Jovian moons that are probably the source of the ring's dust; the halo ring, which merges gradually into the main ring on one side and extends halfway toward Jupiter's cloud surface on the other; and two "gossamer rings," which are the faintest of the group and named for the moons from whence they came, Amalthea and Thebe.