stable in the long term. Such ring systems can be detected for planets observed by the transit method by additional reduction of the light of the central star if their opacity is sufficient. As of 2020, one candidate extrasolar ring system has been found by this method, around HIP 41378 f. Fomalhaut b was found to be large and unclearly defined when detected in 2008. This was hypothesized to either be due to a cloud of dust attracted from the dust disc of the star, or a possible ring system, though in 2020 Fomalhaut b itself was determined to very likely be an expanding debris cloud from a collision of asteroids rather than a planet. Similarly, Proxima Centauri c has been observed to be far brighter than expected for its low mass of 7 Earth masses, which may be attributed to a ring system of about 5 . A sequence of occultations of the star 1SWASP J140747.93-394542.6 observed in 2007 over 56 days was interpreted as a transit of a ring system of a (not directly observed) substellar companion dubbed "J1407b". This ring system is attributed a radius of about 90 million km (about 200 times that of Saturn's rings). In press releases, the term "super Saturn" was used. However, the age of this stellar system is only about 16 million years, which suggests that this structure, if real, is more likely a circumplanetary disk rather than a stable ring system in an evolved planetary system. The ring was observed to have a 0.0267 AU-wide gap at a radial distance of 0.4 AU. Simulations suggest that this gap is more likely the result of an embedded moon than resonance effects of an external moon(s). Visual comparison See also Shepherd moon Circumplanetary disk Circumstellar disk Accretion disk Lists of astronomical objects References External links USGS/IAU Ring and Ring Gap Nomenclature Everything a Curious Mind Should Know About Planetary Ring Systems with Dr Mark Showalter, Bridging the Gaps: A Portal for Curious Minds Physical Chemistry of Evolution of Planetary Systems Gladyshev G. P. Thermodynamics and Macrokinetics of Natural Hierarchical Processes, p. 217. Nauka, Moscow, 1988 (in Russian). Celestial mechanics Articles containing video clips