Astrophysical Observations with the New Horizons Spacecraft

The New Horizons mission launched on 2006 January 19, and performed the first reconnaissance of the Pluto system in 2015 and of a Kuiper belt object, Arrokoth, in 2019. The spacecraft and powerful suite of instruments are in excellent health as the mission continues through and beyond the Kuiper belt. Currently at 56 au and moving at ~3 au/year, New Horizons is in a unique position to not only continue planetary science work, but also to make significant studies for astrophysics and heliophysics. At this heliocentric distance, contamination by interplanetary, geocoronal, and heliospheric light contributions in the optical and ultraviolet are negligible compared to that seen with Earth-based and inner solar system telescopes. We take advantage of New Horizons’ location and capability to make observations not possible otherwise. We present here the recent and upcoming observations planned by the New Horizons Astrophysics Science Theme Team: Cosmic optical background (COB). The COB can provide critical information on the evolution of galaxies and energy production in the optical over the age of the universe, for which New Horizons is an especially sensitive probe. Using the LORRI optical telescope on New Horizons, we have successfully made proof-of-concept observations that already have identified a highly significant anomalous flux in the COB, which is greater than the received flux from all galaxies. In the coming year, we will make more such observations over several more lines of sight. Cosmic ultraviolet background (CUVB). The CUVB provides information about galactic and extragalactic star formation rates, dust scattering, and interstellar shocks, all of which contribute to CUVB emission. A careful accounting of sources of the CUVB can also constrain or rule out more exotic mechanisms, such as a significant source of extragalactic UV emission not associated with the known population of galaxies. Using the Alice UV spectrograph on New Horizons, we will observe several lines of sight to search for and study these distant signals and their potential sources. Lyman-alpha all-sky maps. We will probe the local ISM via pointed UV spectroscopy of the diffuse background and all-sky Lyman-alpha maps. One 30-degree wide great circle sector has already been mapped, which also identified areas of interest for higher-resolution UV mapping. Completion of the sky maps (except for an avoidance zone centered on the Sun) will be made in the upcoming year.