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DIX Planetary Science Seminar

Tuesday, April 20, 2021
4:00pm to 5:00pm
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Online Event
Aida Behmard, Graduate Student, Planetary Science, California Institute of Technology,
Qicheng Zhang, Graduate Student, Planetary Science, California Institue of Technology,

Aida Behmard

Title: How Common is Planet Engulfment?

Abstract: Dynamical evolution ­can cause planets to be engulfed by their host stars. Following engulfment, the stellar photosphere abundance pattern will reflect accretion of rocky material that composes planetary cores by exhibiting refractory enhancements in order of condensation temperature. Multi-star systems are excellent environments to search for such abundance trends because these stars share the same natal gas cloud and primordial chemical compositions to within 0.05 dex. Thus, refractory differences above 0.05 dex that trend with condensation temperature between stellar companions constitute a signpost of planet engulfment. Such observations have been carried out for a few systems, and have occasionally yielded robust engulfment signatures, e.g., Kronos and Krios (Oh et al. 2018), but only a handful targeted systems with known planets. We aim to augment this sample by carrying out a survey using Keck-HIRES of 40 multi-star systems where one star is known to host a planet. The sample of planets hosted by these systems is diverse and includes hot Jupiters, close-in multi-planet systems, and gas giants at a range of orbital periods. Using the Spectroscopy Made Easy tool, we have obtained abundance patterns for each system that can be assessed for possible engulfment signatures. We will present preliminary results from this survey, which will ultimately be used to constrain the prevalence of planet engulfment, examine its role in shaping current planetary system architectures, and investigate possible engulfment-related patterns in stellar and planetary properties.

Qicheng Zhang

Title: Comet C/2021 A1 (Leonard) and Venus
Abstract: A newly discovered long period comet, C/2021 A1 (Leonard), will pass within 0.03 au of Venus this December, and in the process, may dust the planet with meteoroids ejected from the comet many years earlier while it was still far out in the outer solar system. In this presentation, I will introduce the relevant dynamics of the comet's dust tail and the necessary conditions for its meteoroids to become meteors, compare the event at hand with the much closer encounter of comet C/2013 A1 (Siding Spring) to Mars in 2014 and its associated meteor shower, and briefly discuss the potential observability of meteors on Venus and/or their aftermath. I will additionally present recent imagery and spectroscopy that provide a direct look into the current state of the comet as it makes its way in, and subsequently speculate on the physical properties of the nucleus and its potential future activity.

For more information, please contact Aida Behmard by email at [email protected].