The Submillimeter Array

Science: Circumstellar Disks and Planet Formation

At least one in ten nearby Sun-like stars hosts a giant planet. A massive effort is underway to find more exoplanets, determine their key properties, and associate demographic trends with models of their formation. Ultimately the goal is to develop a robust theoretical framework grounded in this growing suite of empirical evidence that explains how different kinds of planets are made. That formation process is intimately tied to the initial conditions in the reservoirs of planet-building material - the circumstellar disks of gas and dust around young stars.

The Submillimeter Array (SMA) has been pioneering millimeter-wavelength resolved observations of these circumstellar disks, continuing to deliver over a decade of fundamental discoveries that have paved the way in understanding the physical (densities, temperatures), material (grain sizes, turbulence) and chemical properties of these environments where planets are born. At the wavelengths probed by the SMA, studies have focused on resolved imaging of continuum (dust) and spectral line (molecules) in these disks.

images of dust Imaging dust in protoplanetary disks: the mass budget and location of planet formation As most protoplanetary disks are believed to be optically thin at these wavelengths, SMA observations are able to measure their dust mass, and this has allowed us to understand the budget of material that goes on to form planets.

Our Galaxy's Center Imaging molecules in protoplanetary disks: the mass and chemical composition of planet-forming gas The SMA allowed some of the first detailed studies of molecular gas in protoplanetary disks. Its high spectral (velocity) as well as spatial resolution allows to precisely locate and study the kinematics of simple molecules like CO.
Other Galaxies Planetesimal belts: relics of planet formation After reaching an age of about 10 Myr, protoplanetary disks are believed to lose the vast majority of their gas and dust, leaving a planetary system with formed gas giants and rocky planet cores.