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A Journey with Dust: from Protoplanetary Disks to Planetary Atmospheres and Outflows


Chachan, Yayaati (2022) A Journey with Dust: from Protoplanetary Disks to Planetary Atmospheres and Outflows. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/8dxy-2b79.


Dust in astronomy is often perceived as a hindrance to true characterization of celestial bodies. However, it is the humble dust particles that often run the show in planet formation and evolution. In this thesis, I present four different observationally inspired problems, which span a vast chronological range from core formation to atmospheric escape, and show how dust holds sway over them. In Chapter 2, I demonstrate that protoplanetary disks that are capable of forming giant planets are also capable of hosting close-in super-Earths within the giant planet’s orbit, in line with the observed correlation between the occurrence rates of these two sub-populations. In Chapter 3, I show how dust dynamics and differences in grain properties across the water ice line create a region at intermediate distances where gas accretion is rapid. This might explain the preponderance of giant planets at such distances from their host stars, independently or complementarily to prevalent ideas on where massive cores form. Subsequently, since our understanding of the simultaneous accretion of dust and gas during planet formation remains poor, I argue in Chapter 4 that atmospheric characterization of Neptune-class planets is valuable for advances in this area. In particular, I discuss my efforts to characterize one such planet (HAT-P-11b) that, as a low metallicity Neptune, serves as an instructive challenge for formation models. Finally, in Chapter 5, I substantiate the idea that dust in the form of photochemical hazes must be present in outflowing atmospheres of super-puffs (i.e. planets with super-Earth-like masses but giant planet-like radii) by using the transmission spectrum and bulk properties of the canonical super-puff Kepler-79d.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Planet formation; Exoplanetary atmospheres; Protoplanetary disks; Spectroscopic characterization of exoplanetary atmospheres
Degree Grantor:California Institute of Technology
Division:Geological and Planetary Sciences
Major Option:Planetary Sciences
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Knutson, Heather A.
Thesis Committee:
  • Stevenson, David John (chair)
  • Yung, Yuk L.
  • Blake, Geoffrey A.
  • Batygin, Konstantin
  • Knutson, Heather A.
Defense Date:24 February 2022
Record Number:CaltechTHESIS:02282022-175350847
Persistent URL:
Related URLs:
URLURL TypeDescription adapted for ch. 2 adapted for ch. 3 adapted for ch. 4 adapted for ch. 5
Chachan, Yayaati0000-0003-1728-8269
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:14509
Deposited By: Yayaati Chachan
Deposited On:12 Mar 2022 00:05
Last Modified:02 Dec 2022 19:39

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