Connecting the Pale Blue Dots: Detection & Characterization of Exoplanets with Extreme Precision Spectroscopy

Open Access
Roy, Arpita
Graduate Program:
Astronomy and Astrophysics
Doctor of Philosophy
Document Type:
Date of Defense:
May 23, 2017
Committee Members:
  • Suvrath Mahadevan, Dissertation Advisor
  • Suvrath Mahadevan, Committee Chair
  • Jason Thomas Wright, Committee Member
  • Lawrence William Ramsey, Committee Member
  • Jennifer Macalady, Outside Member
  • Steinn Sigurdsson, Committee Member
  • exoplanets
  • spectroscopy
  • instrumentation
  • radial velocity
Two decades ago, technological advancement aligned with some of mankind’s oldest and most compelling questions to give birth to exoplanet science. Since then, the study of exoplanets, more than any other field of astrophysics, has grown in direct consonance with new instrumentation. Building on the success of instruments like HARPS, Doppler velocimetry is now firmly on the path towards extreme precisions (∼10 cm/s ), driven by the urge to find true Earth analogs. This effort, however, requires severe technical artistry and demands unprecedented performance from both hardware and software. In this dissertation, I present the comprehensive and multifaceted path to extreme precision spectroscopy. We begin with existing spectrographs and the battlefield lessons they offer, focusing particularly on PARAS, an operating workhorse instrument with which I have been deeply involved, achieving ∼1 m/s radial velocity (RV) precision over several months. I then detail the design and development of two new instruments that will achieve unprecedented RV precisions: (a) the Habitable Zone Planet Finder, an upcoming near-infrared instrument for the 10 m Hobby Eberly Telescope, designed to achieve 1-3 m/s on cool stars, and (b) NEID, an extreme precision optical instrument aiming at < 30 cm/s that will be the centerpiece of the NASA-NSF Exoplanet Observational Research (NN-EXPLORE) partnership. I summarize the most challenging sources of measurement error and the hardware solutions we have created, including my work on the invention of an efficient ball lens double scrambler that essentially retires issues of illumination instability. As software architect of these instruments, I also describe the pathways to extreme precision data analysis pipelines, rooted firmly in the heritage of current instruments in the field. Having ensured the exquisite quality of spectra from these instruments, I investigate the presence of insidious false positives that mimic the signatures of exoplanets, and the use of complementary techniques for further vetting of promising candidates. Lastly, I present the long arc towards the future of this field, including the direct detection of planetary photons that will light the way towards our understanding of universal habitability.