The first high-resolution images of a 33km-high snowman-shaped object that lies 1.5bn kilometres beyond Pluto have been released by Nasa.
The photographs of Ultima Thule, captured by the New Horizons spacecraft, were revealed at a press conference last night.
The dark object is made of two spheres combined to form one celestial object.
Alan Stern, principal investigator for New Horizons, said: "It is only really the size of something like Washington DC and it is about as reflective as garden variety dirt. It's a snowman if it's anything at all.
"I don't think we have stressed enough, so I really want to say, what this spacecraft and this team accomplished is unprecedented.
"We were basically chasing it down in the dark at 32,000mph [50,000kmh]."
The images released so far are "just the tip of the iceberg", he said, adding only 1pc of data stored on the spacecraft has currently been received by scientists.
It will take nearly two years for New Horizons to beam back all of its observations of Ultima Thule.
Among the images the scientists are hoping to receive are "higher-resolution views" and pictures taken when the sun is at a better angle for viewing Ultima Thule.
However the photos that have already been sent back have revealed that its colour is actually red.