Centre for Exoplanet Science

Star and planet formation

Understanding processes involved in the formation and evolution of stars and planets.

It is quite likely that processes that operate during the earliest stages of star formation play a crucial role in both the formation of the star itself, and in the formation of planets and planetary systems.   When a protostellar system is very young, it is quite likely that the surrounding disc will be reasonably massive, relative to the mass of the central protostar.  As such, it becomes susceptible to the growth of a gravitational instability that can produce spiral density waves, much like those seen in spiral galaxies.

Self-gravitating spirals density waves
Image from a simulation of a young protostellar system showing the presence of self-gravitating spiral density waves in the protostellar disc.

These spiral density waves almost certainly play a key role in driving mass onto the central star, but they may also be important for planet formation itself.  They may aid grain growth, by enhancing the local dust density and, if the system is sufficiently unstable, they may collapse to directly form planetary mass bodies, possibly explaining the wide orbit, gas giant planets that we are starting to directly observe.

What makes this particularly exciting, is that the Atacama Large Millimeter/submillimeter Array (ALMA) now has the resolution and sensitivity to probe this very early stage of star formation and is starting to produce results suggesting that very young protostellar systems do indeed have spiral structures in their surrounding discs. 

The centre is involved in research to try and understand this early phase of star formation, how it might influence the subsequent formation of planets, and how observations of such systems will inform our understanding of both star and planet formation.  With the advent of ALMA, the next few years may see a significant enhancement in our understanding of the earliest stages of star and planet formation and, hence, this is a research area that will be a focus for the Centre for Exoplanet Science.