HOUSTON — To Kirby Runyon, a planetary scientist at the Johns Hopkins Applied Physics Laboratory, the small distant object that NASA’s New Horizons spacecraft flew past on the first day of this year reminds him of monkey bread.

For people not familiar with this sweet pastry, monkey bread consists of balls of dough that are piled into a pan. As they bake, the balls combine into a larger whole. It is a structure that may help explain the process that turned bits of dust and gas into planets in the early solar system.

New Horizons traveled some 4 billion miles to take a close-up look at this 22-mile-long world in the solar system’s icy Kuiper belt beyond Neptune; it is officially designated as 2014 MU69 and nicknamed Ultima Thule. Planetary scientists have never been able to do so for an object this distant, a small shard that has been frozen and almost unchanged since it formed 4.5 billion years ago.

Ultima Thule was not as picturesque as New Horizons’ first target — Pluto, in 2015 — but it was full of surprises. The shape turned out to be unlike anything seen in the solar system. It was not just a simple ball, but two objects that at some stage touched and stuck together, like a snowman. Then the scientists discovered that the two lobes of Ultima Thule were not spherical, but more like lumpy pancakes. The larger lobe is also flatter than the smaller one.