A Research Programme on the Dynamics of Discs and Planets

The first bona fide planet orbiting a sun-like star outside of the solar system was discovered by a team of Swiss astronomers in 1995. Since this time, teams of international scientists have collectively discovered in excess of 350 extrasolar planets. Most of these planetary systems have very different architectures to the Solar System, raising many questions about how these planets formed and evolved. It is believed that planets form in the discs of gas and dust that are observed around young stars - so-called protostellar discs. Although there are significant uncertainties, a basic picture of planet formation has emerged. The first stage involves coagulation of small dust particles within the disc, which stick together when they collide to form larger pebbles. This process continues until larger bodies, with sizes approximately 10km, are formed. These bodies are called planetesimals, some of which are able to grow at a rapid rate through collisions with other planetesimals to form planets. At large distances from the central star, where the temperature in the protoplanetary disc falls to low values, water and other volatile compounds condense out of the gas to form ice grains. This has the effect of substantially increasing the amount of solid material, and allows very big solid planetary objects to form which can attract a large amount of gas from the disc to become gas giant planets, similar to Jupiter and Saturn. In the warmer inner regions of the disc, ice grains cannot form and so smaller rocky planets such as the Earth and Venus are expected to form. There are many theoretical uncertainties associated with each stage of the planet formation process described above, and the Isaac Newton Institute in Cambridge is hosting a four-month research programme aimed at solving some these outstanding theoretical problems. Most of the leading international researchers in this are will be attending the programme, providing a very exciting opportunity for making significant progress in understanding how planetary systems form and evolve.