Saturn is, of course, famous for its rings, but in our solar system there are actually four planets with ring systems of one size or another. Every gas giant in our solar system has a ring that is to say, right now the evidence suggests that everygas giant could have a ring. As mankind begins to look directly at the planets of the universe outside our own solar system, any universal rule of that sort will be vitally important. Now, astronomers are gearing up to start countinggas giants outside our solar system, as a new technique allows identification ofplanetary rings from light-years away.

The technique is as simple as could be, and could even be applied to existing readings to get new information outofold studies. Right now, planets are identified mostly by looking at the change in luminosity of their parent star when the planet moves between that star and the Earth; these readings are called transits. The silhouette is recorded as a rather abstract graph, and if the graph shows thata planet blocks more light from itsstar than it ought to, given predictions for its size, there are two basic possibilities: Either your predictions were wrong in some way, or the objects apparent size is expanded somehow say, withrings.

The researchers want to go back at look at numerous results that earlier studies discarded as false positives tosee whether they might have been planets encircled by rings. If they find that their work can explain historical results more accurately than current theory (or at all), astronomers might end up buildinga list of previously abandoned celestial bodiesto revisit.

Ringed exoplanets came to prominence recently, as a so-called super-Saturn was found with rings many times the size and mass of Saturns (artists rendition at top of page). The actual identity of J1407b is not quite known, however; it could be a dwarf star, and the rings still-forming planets. Additionally, while this method can provethe existence of rings, it cant prove the non-existence of them. In other words, just because this technique doesnt see an expansion in the transit readings, doesnt mean there arent rings. All it really means is that if there are rings, they must be quite thin.

The light-blocking effect changes based on the angle of the rings to the Earth.

Thus, this techniquecant be used in any case where astronomers cant get a second size reading by adifferentmethodof measurement than transit. Without that second measurement, theres no way to tell if the planets transit is blocking more light than it ought to.

Why should astronomers care about rings, specifically? Firstly, because they couldprovide a window into the past of whicheversolar system we end up finding them within. Rings can be very diverse in their makeup and, more importantly, often let a fair amount of light through. Astronomers are great at working with partially blocked light just recently, insight into planetary atmospheres and ever weather patterns was gleaned from light leaking around the edges of a distant planet.

Rings are also often associated with moons. Ancient moon-planet collisions are one possible source of planetary rings, but moons also sometimes enforce the edges and details of a planetaryring. By orbiting in asimilarplane tothe ringsthemselves, a large body like a moon can sweep up any small particulate matter simply by running into it. So far there have been no exo-moons found, but perhaps a ringed system could alert astronomers to a good potential candidate.

Exo-planetologyis undoubtedly the fastest-growing area of astronomy. The Kepler planet-hunter was NASAs very first attempt at finding planets by their transit signatures, and it found thousands. Now, the next generation transit finder, the Transiting Exoplanet Survey Satellite (TESS, is preparing to launch in 2017 and continue that quest. If exo-rings do end up being a major source of interest for astronomers, TESS is specifically the satellite that will be used tocapture them.

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The next frontier in planet science: exo-rings