The extragalactic background light (EBL) is the sum of the light emitted by sources beyond the Milky Way throughout the history of the universe. While the EBL is present at all wavelengths, at optical wavelengths it is largely sourced by the light from stars and galaxies and is referred to as the cosmic optical background (COB). Direct photometric measurements of the COB provide an important comparison to population models of galaxy formation and evolution. Such measurements therefore provide a cosmic consistency test with the potential to reveal additional diffuse sources of emission. However, the COB has been difficult to measure from Earth due to the difficulty of isolating it from the diffuse light scattered from interplanetary dust in our Solar System, Zodiacal Light (ZL). In this dissertation, I present a pipeline to measure the COB using data taken by the Long-Range Reconnaissance Imager (LORRI) on NASA’s New Horizons mission. Because of New Horizons’ location in the outer Solar System, the ZL is negligible compared to measurements taken from 1 AU. To measure the COB, I characterize and remove structured and diffuse astrophysical foregrounds including bright stars, the integrated starlight from faint unresolved sources, and diffuse galactic light. Dark current and other instrument systematics are also accounted for, including various sources of scattered light. I present a measurement of the COB derived from a set of LORRI images encompassing New Horizons’ journey from the inner Solar System to Pluto and beyond. I discuss sources of systematic error, including astrophysical, calibration, and instrumental sources affecting each foreground component, and put this measurement in the context of other estimates of the COB and EBL.
Library of Congress Subject Headings
Cosmic background radiation--Measurement; Cosmology--Observations
Astrophysical Sciences and Technology (Ph.D.)
Department, Program, or Center
School of Physics and Astronomy (COS)
Symons, Teresa, "The View from 50 AU: Measuring the Cosmic Optical Background with New Horizons" (2022). Thesis. Rochester Institute of Technology. Accessed from
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