The Color and Binarity of (486958) 2014 MU69 and Other Long-Range New Horizons Kuiper Belt Targets

TL;DR

This study used Hubble Space Telescope data to analyze the colors and binarity of eight Kuiper Belt Objects, including the New Horizons target 2014 MU69, finding they are all red and mostly non-binary, with some variability.

Contribution

First to measure the colors and binarity of multiple KBOs including 2014 MU69, providing insights into their surface properties and binary fraction in the Cold Classical population.

Findings

All eight KBOs are red, typical of Cold Classical objects.

No binaries detected at separations >2000 km and Δm ≤ 0.5.

Some objects show potential photometric variability.

Abstract

The Hubble Space Telescope (HST) measured the colors of eight Kuiper Belt Objects (KBOs) that will be observed by the New Horizons spacecraft including its 2019 close fly-by target the Cold Classical KBO (486958) 2014 MU69. We find that the photometric colors of all eight objects are red, typical of the Cold Classical dynamical population within which most reside. Because 2014 MU69 has a similar color to that of other KBOs in the Cold Classical region of the Kuiper Belt, it may be possible to use the upcoming high-resolution New Horizons observations of 2014 MU69 to draw conclusions about the greater Cold Classical population. Additionally, HST found none of these KBOs to be binary within separations of ~0.06 arcsec (~2000 km at 44 AU range) and {\Delta}m less than or equal to 0.5. This conclusion is consistent with the lower fraction of binaries found at relatively wide separations. A few objects appear to have significant photometric variability, but our observations are not of sufficient signal-to-noise or time duration for further interpretation.