Extrasolar Planetary Systems
Dusty debris from extrasolar comets and asteroids
Dusty debris disks or belts exist because comets and asteroids erode over time (mainly through collisions) and deposit huge quantities of fresh dust that orbits a star. The grains are heated by the star and can be detected at infrared wavelengths. Dust grains also reflect light, and typically this appears as a disk-like or ring-like nebulosity surrounding a star.
Extrasolar giant planets
With direct imaging we can discover and characterize very massive planets (Jupiter-mass or greater) that orbit the star beyond a few astronomical units or more. For example, the semi-major axis of beta Pic b shown below is 10 au. It’s mass is roughly 11 times that of Jupiter and its age is 24 Myr. So the planets that we discover are relatively young and ultimately reveal how planetary systems form and evolve.
The key challenge is to suppress as much starlight as possible because debris disks and planets are very faint. For example, the star Fomalhaut can be seen with the naked eye (it’s a first magnitude star) but Fomalhaut b is approximately 24th magnitude in the visible (1 billion times fainter than the star). Over the years I have been surveying nearby stars using the following facilities:
Hubble Space Telescope (HST)
Gemini Planet Imager (GPI)
Atacama Large Millimeter Array (ALMA)