Photometric Exoplanet Characterization and Multimedia Astronomy Communication

Open Access
Author:
Cartier, Kimberly Michelle
Graduate Program:
Astronomy and Astrophysics
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
July 09, 2017
Committee Members:
  • Jason Thomas Wright, Dissertation Advisor
  • Jason Thomas Wright, Committee Chair
  • Steinn Sigurdsson, Committee Member
  • Kevin Luhman, Committee Member
  • Jennifer Macalady, Outside Member
  • Katherine Haines Freeman, Outside Member
  • Ronald Gilliland, Special Member
Keywords:
  • Exoplanets
  • Photometric Techniques
  • Search for Extraterrestrial Intelligence
  • Kepler
  • Astronomy Communication
  • Science Writing
  • Atmospheres
  • Transit Follow-up
  • Exoplanet Characterization
Abstract:
The transit method of detecting exoplanets has dominated the search for distant worlds since the success of the Kepler space telescope and will continue to lead the field after the launch of the Transiting Exoplanet Survey Satellite in 2018. But detections are just the beginning. Transit light curves can only reveal a limited amount of information about a planet, and that information is almost entirely dependent on the properties of the host star or stars. This dissertation discusses follow-up techniques to more precisely characterize transiting planets using photometric observations. A high-resolution follow-up imaging program using the Hubble Space Telescope (HST) searched for previously unknown stars nearby the hosts of small and cool Kepler exoplanets and observed a higher-than-expected occurrence rate of stellar multiplicity. The rate of previously unknown stellar multiples has strong implications for the size and habitability of the orbiting planets. Three systems with newly discovered stellar multiplicity, Kepler-296 (2 stars, 5 planets), KOI-2626 (3 stars, 1 planet), and KOI-3049 (2 stars, 1 planet), were characterized in more detail. In the cases of Kepler-296 and KOI-2626, some of the planets lost their previous habitable zone status because of host star ambiguity. Next, the ultra-short period, ultra-hot Jupiter WASP-103b was used as a case study to test for the presence of a stratospheric temperature inversion through dayside emission spectroscopy using HST. WASP-103b’s near-infrared emission spectrum is consistent with an isothermal or thermally-inverted atmosphere and shows no significant broadband water absorption feature. Detection of an anomalously strong “super-Rayleigh” slope in its optical transmission spectrum prompted follow-up transmission spectroscopy of WASP-103b’s atmosphere using the MINiature Radial Velocity Array (MINERVA), which tentatively verified the unexplained “super-Rayleigh” spectral slope. The final follow-up technique for transiting planets presented in this work quantifies the information contained in a sequence of transit depths using a normalized information content metric. The normalized information content metric can distinguish between naturally occurring, regular transits of real exoplanets detected via Kepler (low information content) and simulated artificial beacons whose depth and timing vary in a prime number sequence (high information content). Highly variable transit sequences with natural explanations—as seen with KIC 12557548, for example—can only be distinguished from artificial beacons when observed at a high signal-to-noise ratio (moderate information content) and may otherwise be confused with a more information-rich sequence. This dissertation also presents a review of effective methods for communicating science to various audiences, with specific applications to astronomy. That chapter highlights the necessity of integrating formal communications training into the early stages of a career in astronomy, explains why and how to apply storytelling techniques to astronomy communication, and details specific strategies to apply when using common communication media. Examples are given for effectively communicating astronomy through academic research papers, slides for an oral presentation, and academic research posters, as well as examples of popular science blogs, feature articles, and news stories.