LAUREL, Md. — Ultima Thule, an icy world 4 billion miles from the sun, looks like a big snowman.

At a news conference on Wednesday, scientists working with NASA’s New Horizons mission released several images that the spacecraft took as it flew by on Tuesday, New Year’s Day.

Planetary scientists have never before seen a close-up of a body like Ultima Thule. It is likely a fragment that coalesced more than 4.5 billion years ago and which has remained in the deep freeze of the solar system’s Kuiper belt ever since.

If it is indeed a pristine planetesimal, a building block of the planets, studying it will offer clues to how Earth and its neighbors formed.

On Tuesday, scientists released a blurry picture of this small world, also known by its official designation 2014 MU69, taken before the flyby from a distance of half a million miles. It sort of looked like a fuzzy bowling pin then.