Dust and gas in the HD 95086 planetary system

In our efforts to understand the formation and evolution of planetary systems and how other planetary systems relate to the Solar System, some of the best systems to study are those where we have detected both a planet (or planets) and a debris disc as the interplay between the two can tell us even more about the system. In this regard, HD 95086 makes an excellent case study. This 17 Myr star hosts both a giant planet on a wide orbit and one of the brightest debris discs known. Using ALMA, we have imaged this system at millimetre wavelengths and high resolution to determine that the disc extends from roughly 100-300 AU, one of the widest discs known. We find that the location of the inner edge can be explained by the effect of the known planet but only if the eccentricity of the planet is >0.26. We also detect a very low level of CO emission, predominantly coming from the South side of the disc. The low CO mass means that it cannot be primordial and marks this as one of only four systems which we know to have second generation gas production. The ratio of gas to dust in this disc allows us to show that the fraction of ices in this system's cometary bodies is similar to that in the Solar System. In addition to the disc we also find two bright, compact sources. The origin of the brightest of these is hard to explain. Processes within the disc that can explain such a large concentration of dust (such as a forming planet, massive collision etc.) would also require or result in a concentration of CO at that location, which is not seen, meaning that it is more likely to be a background galaxy, even though the chances of such a coincident alignment are small.