15810 Arawn

Arawn is moving in a relatively eccentric orbit entirely beyond the orbit of Neptune. With a semi-major axis of 39.4 AU, it orbits the Sun once every 247 years and 6 months (90,409 days). Its orbit has a perihelion (closest approach to the Sun) of 34.7 AU, an aphelion (farthest distance from the Sun) of 44.1 AU, an eccentricity of 0.12, and an inclination of 4° with respect to the ecliptic. In April 2016, its rotation period of 5.47 hours was determined. == Quasi-satellite dynamical state and orbital evolution ==

In 2012 Arawn was hypothesized to be in a quasi-satellite loop around Pluto, as part of a recurring pattern, becoming a Plutonian quasi-satellite every 2 Myr and remaining in that phase for nearly 350,000 years. Measurements made by the New Horizons probe in 2015 increased the accuracy of calculations of the motion of Arawn. These calculations confirm the general dynamics described in the hypotheses. However, whether this motion means that Arawn should be classified as a quasi-satellite of Pluto remains debated, because Arawn's orbit is primarily controlled by Neptune with only occasional smaller perturbations caused by Pluto. ==Origin==

Arawn is moving in a very stable orbit, likely as stable as Pluto's. This suggests that it might be a primordial plutino formed around the same time Pluto itself and Charon came into existence. It is unlikely to be relatively recent debris that originated in collisions within Pluto's system or a captured object. == Observation ==

Arawn is currently relatively close to Pluto. In 2017 it was only 2.7 AU from Pluto. More observations were made in April 2016. Between 7–8 April 2016, New Horizons imaged Arawn from a new record distance of about 111 million kilometres, using the LORRI instrument. The new images allowed the science team at Southwest Research Institute (SwRI) in Boulder, Colorado, to further pinpoint the location of Arawn to within 1000 kilometers. The new data also enabled calculation that its rotation period is about 5.47 hours. File:PIA205891994 JR1newhorizons.gif|April 2016 observations of Arawn by New Horizons File:New Horizons KEM Trajectory.png|Trajectory of New Horizons and other nearby Kuiper belt objects, with as Arawn. File:1994_JR1_orbit_2015.png|Orbit of Arawn near Pluto Arawn occulted a star on 25 August 2022. == See also ==