ALMA Imaging of Circumstellar Disks: Where and When do Planets Form?

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Both stars and planets form out of clouds of gas and dust. Astronomers have recently discovered that a majority of, if not most, stars have planets, but many of these planetary systems look very different than our own Solar System. This investigator has already surveyed hundreds of young planetary systems using the ALMA array of millimeter telescopes. He will continue this work and search high resolution images from the array for signs of planet formation close to the parent stars. A graduate student and undergraduates will be involved in the work. The investigator will build a small radio telescope for use in undergraduate classes. He is also writing a textbook about the gas and dust from which stars form, and regularly speaks to classes at junior high schools.With baselines up to 13 km, ALMA can achieve a remarkable angular resolution of 0.02 arcseconds at a wavelength of one millimeter. This corresponds to radial scales of 1.5 au at the typical distance of nearby star-forming regions. It is now feasible to image disks and measure basic properties at the scales where most planets are found. Most studies to date have focused on the brightest disks to achieve high signal-to-noise ratios. However, the high optical depths in these bright disks prevent us from seeing into the innermost few au where most planets are found to reside. The PI will study fainter disks to investigate disk structure at solar system scales as their emission should not be saturated even in the smallest ALMA beam if they indeed have low masses.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.