Dori Blakely

Topic

Detecting Forming Planets with Interferometry and Astrometry

Department of Physics and Astronomy

Date & location

• Tuesday, August 25, 2026
• 8:00 A.M.
• Clearihue Building, Room B017

Examining Committee

Supervisory Committee

• Dr. Doug Johnstone, Department of Physics and Astronomy, University of Victoria (Co-Supervisor)
• Dr. Ruobing Dong, Department of Physics and Astronomy, UVic (Co-Supervisor)
• Dr. Charles Curry, School of Earth and Ocean Sciences, UVic (Outside Member)

External Examiner

• Dr. Anthony Brown, Leiden Observatory, Leiden University

Chair of Oral Examination

• Dr. Theone Paterson, Department of Psychology, UVic

Abstract

Possibly the biggest problem in planet formation research is the lack of directly observed protoplanets, that are still actively forming in protoplanetary disks. Only a handful of these objects have been conclusively detected. This is due to the observational challenge inherent in studying any planet close to its host star, with a significant additional complication due to the presence of luminous and extended disk material. In this dissertation, I will present a data analysis framework for detecting and characterizing protoplanets at the diffraction limit of the leading infrared telescopes. I will show that this framework can be used to not only detect planets, but also distinguish between extended disk emission and planets, at the highest angular resolutions, which has been a challenge in previous works. I will accomplish this by applying these methods to archival VLT/SPHERE data of the protoplanetary disk-hosting system LkCa 15, demonstrating the recovery of an extended disk, at the diffraction limit, which previously had been thought to be multiple protoplanets. I will also apply this framework to another archival VLT/SPHERE dataset of the protoplanetary disk-hosting system HD 100546. In this work, I will present the tentative detection of a point source independently in two epochs, that is consistent with a brown dwarf-mass object. Next, I will apply this framework, including several improvements, to JWST NIRISS AMI data of the known protoplanet-hosting system PDS 70. In this work, I will overcome limitations due to detector effects that had severely limited previous works analyzing JWST NIRISS AMI data to measure precise 4.8 μm photometry of PDS 70 b and c. With these measurements, I will present tentative evidence of infrared circumplanetary disk emission around each planet. I will also present the tentative detection of a previously unseen protoplanet candidate. Finally, I will present a novel method for searching for and constraining the sky-position of protoplanets in protoplanetary disk systems using absolute astrometry. I will present the analysis of astrometry of 11 protoplanetary disk-hosting systems. I will present evidence of astrometric signals consistent with companions (stellar, sub-stellar, or planetary) in 4 out of the 11 systems. From this analysis I will present tentative evidence of an excess astrometric noise, that may bias and/or limit the sensitivity of astrometry data of protoplanetary disk-hosting systems. I will also present Gaia data release 4 (GDR4) simulations of the known protoplanet-hosting systems PDS 70 and WISPIT 2, showing how GDR4 will be sensitive to Jupiter-like protoplanets on Jupiter-like orbits, which could lead to the first dynamical mass measurement of an imaged protoplanet, the first detection of a Jupiter-like protoplanet on a sub-10 au orbit, and the demographics of protoplanets, where the giant planets are predominantly found around evolved stars.