mountain profile Institute for Astronomy University of Hawaii


Maintained by WW

One of the most exciting astronomical developments in the past 15 years has been the discovery and charac­terization of extrasolar planets—planets in orbit around stars other than our Sun, a.k.a. “exoplanets.” Direct detection of gas-giant exoplanets is now becoming possible, opening the door to new avenues of understanding distinct from radial velocity and transit detections.


Planet Formation

Jonathan Williams studies the formation of planets through observations and modeling of protoplanetary disks. Building on a legacy of work with the Submillimeter Array, we use the Atacama Large Millimeter Array (ALMA) to study disk populations in nearby regions with different ages. This allows us to study how disks evolve around stars of different masses. We find that disks are initially massive but appear to rapidly lose mass within a few Myr. This is likely due to the growth of dust grains from millimeters to pebble-sized building blocks of planets. The gas content also evolves, but whether this is due to chemistry or physical loss, is a subject of current research with profound implications for understanding exoplanet composition.

ALMA has shown that protoplantary disks are highly structured, with rings, cavities and spirals commonplace. A likely reason for these features are protoplanets themselves. With high contrast infrared imaging, we are searching for planets within disks. Ultimately, we hope to make direct links between disk properties and the planets that they form. This is the key to understanding the origins of our Solar System.


Infrared image of a giant planet and protoplanetary disk around the young, approximately solar mass star, PDS70. The star is at the center and is masked out in this image for clarity. The bright point source is the planet, with a mass estimated from its luminosity of several Jupiters. The ring of emission is scattered light from the dust particles from the disk. This image is from Muller et al. 2018 and is data taken with the ESO Very Large Telescope. We are currently analyzing ALMA observations of the dust and gas emission from the disk to study its properties and examine the planet-disk dynamical interaction.


Exoplanet modelling


Nader Haghighipour performs simulations of the evolution of extraterrestrial planetary systems, focussing on:

       Protoplanetary migration in newly formed systems

       Protoplanetary orbits around binary stars

       The size of the habitable zone around single and double stars

He also uses ground-and space-based telescopes such as the Keck, Kepler  and TESS telescopes to search for small super-Earths in the habitable zones of their host stars


Two-dimensional snapshots of the evolution of the disk surface
density with embedded planet around the Kepler 38 binary
system.  The inward migration of the planet is also shown