Some possible exoplanets may just be a bit of gas

Nature : Many stars are surrounded by disks of dust that orbit at distances similar to that of Pluto’s from the Sun. Some of the disks harbor rings with well-defined edges. Because the patterns are similar to the effects of shepherd moons in the planetary rings of Saturn and Uranus, astronomers hypothesized that the extrasolar rings were caused by unseen planets. Wladimir Lyra of Caltech and Marc Kuchner of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, propose that a more likely explanation is the presence of gas clouds. They created dust orbit models that included dust–gas interactions, not present in most other models. The results showed that the gas clouds could create identical patterns of dust rings. The influence of gas clouds had been suggested before, but this was the first detailed examination of it. The result calls into question several recent possible exoplanet discoveries and may slow the claims of new discoveries in the future.