This thesis discusses the structure of gas and dust in protoplanetary disks around young stars, in which the planets are formed, using ALMA (Atacama Large Millimeter/submillimeter Array)... Show moreThis thesis discusses the structure of gas and dust in protoplanetary disks around young stars, in which the planets are formed, using ALMA (Atacama Large Millimeter/submillimeter Array) observations. Primary targets of this study are the so-called 'transition disks', with a central cavity in the dust disk. A possible explanation for the presence of this cavity is the recent formation of a young planet which has cleared its own orbit. ALMA can for the first time zoom in onto the structure of both gas and dust and answer this question. The thesis presents the first ALMA observations of cold molecular gas and dust in transition disks. These data show that millimeter-dust grains are concentrated in a 'dust trap', allowing the dust particles to grow to larger sizes, an important step in the planet formation process. Also, it turns out that gas is still present in the dust cavity of the disks in this study, its structure points indeed towards the planet clearing mechanism. These discoveries form a giant leap in our understanding of planet formation. In the coming years, ALMA will be completed and allow us to see even smaller details in these disks, possibly even the planets itself. Show less
With over 1800 exoplanets detected, we now believe the majority of stars is orbited by one or more planets. If we want to understand the observed abundance and diversity of planetary systems, we... Show moreWith over 1800 exoplanets detected, we now believe the majority of stars is orbited by one or more planets. If we want to understand the observed abundance and diversity of planetary systems, we have to understand their formation history. The first step in the planet-formation process is the collisional coagulation of microscopic dust grains into kilometer-size planetesimals (the building blocks of planetary systems). The goal of this thesis has been to achieve a better understanding of the microphysics that govern this early growth. Show less
