Celestial target of small worlds beyond Pluto

Astronomers ponder the make-up of an oddly shaped Kuiper belt object before Nasa's spacecraft completes a flyby in 2019

Nasa's New Horizons spacecraft is making good progress towards its next target, an elongated mini planet which may actually be two smaller worlds in orbit around one another.

Since New Horizons made the first ever flyby of Pluto, in July 2015, the spacecraft has been heading into the depths of the solar system. This region is known as the Kuiper belt, and, rather like an icy asteroid belt, is the home to a large collection of celestial objects.