(524366) 2001 XR254

Lore & Background

2001 XR254 was first observed on 10 December 2001 by astronomers David C. Jewitt, Scott S. Sheppard, and Jan Kleyna using the 2.2-meter University of Hawaii reflector on Mauna Kea. It belongs to the dynamically cold population of classical Kuiper belt objects, which have small orbital eccentricities and inclinations, with semi-major axes mainly in the interval 40–45 AU.

The object is a binary system consisting of two components of approximately equal size. Assuming both have the same albedo, the primary is estimated to be about 170 km in diameter, and the secondary about 140 km. The total mass of the system is about 4×10^18 kg, and the average density of both components is about 1 g/cm3. The surfaces of both components appear to have a neutral color.

The satellite was discovered by the Hubble Space Telescope in June 2006. The minor planet was numbered by the Minor Planet Center on 18 May 2019, but as of 2025 it has not been named.

Reader's Guide

2001 XR254 is significant as a binary system in the cold classical Kuiper belt, a region that preserves primitive material from the early Solar System. Its two components of nearly equal size and low density (about 1 g/cm3) suggest a composition similar to water ice and rock, typical of many trans-Neptunian objects. The discovery of its satellite by the Hubble Space Telescope in 2006 provided key data for estimating the system's mass and density. As a numbered but unnamed minor planet, it remains a subject of study for understanding binary formation and the dynamics of the classical Kuiper belt. Its neutral surface color indicates a lack of strong spectral features, consistent with other cold classical objects.

Did You Know?

• 2001 XR254 was discovered on 10 December 2001 at Mauna Kea Observatory.
• The primary is about 171 km in diameter and the secondary about 140 km.