Which planets apart from Saturn have rings?

Super Saturn with a gigantic ring system

The exoplanet J1407b, 430 light years away, is surrounded by a ring system two hundred times larger than that of Saturn. Gaps between the rings also indicate the existence of several moons orbiting Super-Saturn. This is shown by observations made by a research duo from the Netherlands and the USA. According to the scientists in the “Astrophysical Journal”, other moons are likely to form in the ring system around the young giant planet.

Artist's impression of the Super-Saturn J1407b

“For decades, astronomers have suspected that planets like Jupiter and Saturn were surrounded by extensive disks of gas and dust in their early days, in which satellites form,” explains Eric Mamajek from the University of Rochester. "This is the first time we get a glimpse of the formation of moons within a radius of several million kilometers around a planet." J1407b orbits a 16 million year old star with a mass similar to that of our sun. Therefore, the formation of planets and moons at this star is probably not yet complete.

Mamajek found J1407b three years ago using the SuperWASP automatic search program. The planet gave itself away because, seen from the earth, it passed in front of its star and weakened its light in the process. In contrast to other transits of exoplanets, the star's light flickered strangely over a period of 56 days. Together with his colleague Matthew Kenworthy from the Leiden Observatory, Mamajek now provides an explanation for this phenomenon: the planet is surrounded by a system of 37 rings with a diameter of 120 million kilometers, which absorb up to 95 percent of starlight.

"That shows us that there is a lot of matter there that satellites can form," says Mamajek. The ring system contains about a hundred times the mass of the Earth's moon. A large gap in the ring system at a distance of 61 million kilometers from J1407b is also particularly noticeable. Mamajek and Kenworthy suspect that an almost earth-sized moon moves its orbit in this gap. According to the researchers, the entire system is probably in a transition phase from an original circumplanetary disk, in which moons are formed, to a ring system formed by moons similar to the rings of Saturn.