Progress in Understanding the Diffuse UV Cosmic Background

TL;DR

This paper discusses recent progress in understanding the diffuse ultraviolet background radiation, utilizing Voyager and GALEX observations to identify components not attributable to dust-scattered starlight.

Contribution

It presents new measurements from Voyager and GALEX, including the first data from the outer solar system, advancing knowledge of the UV background's origin.

Findings

Detection of a UV background component beyond Lyman alpha that is not dust-scattered starlight

First measurements from the outer solar system reducing solar Lyman alpha noise

Preliminary confirmation of a non-starlight component in the UV background

Abstract

I report on progress in my ongoing work with Professor Jayant Murthy concerning the origin and nature of the diffuse ultraviolet background radiation over the sky. We have obtained and are reducing a vast trove of Voyager ultraviolet spectrometer observations of the diffuse background shortward of Lyman alpha, including for the first time measurements made from the outermost regions of the solar system, where noise from solar-system scattered (and then grating-scattered) solar Lyman alpha is lowest. Also, we have obtained and are investigating the complete set of GALEX observations of the diffuse ultraviolet background longward of Lyman alpha. Preliminary investigation appears to confirm that longward of Lyman alpha there exists a component of the diffuse ultraviolet background that is not dust-scattered starlight.