For 85 years after its discovery, Pluto was little more than a dot in a telescope — until 2015, when a piano-sized NASA spacecraft that had traveled more than three billion miles flew past and revealed a world with a 1,000-kilometer heart-shaped glacier of frozen nitrogen and a surface so young it should not exist.

For 85 years after its discovery, Pluto was little more than a dot in a telescope — until 2015, when a piano-sized NASA spacecraft that had traveled more than three billion miles flew past and revealed a world with a 1,000-kilometer heart-shaped glacier of frozen nitrogen and a surface so young it should not exist.

NASA’s New Horizons Explained: NASA’s New Horizons spacecraft, which left Earth nearly two decades ago and has transformed scientific understanding of Pluto, has entered into the longest hibernation period of its journey so far. The probe made history during its 2015 flyby of our most distant planet – or dwarf planet, as it is known today. And since then, the probe has become the most distant spacecraft to ever explore an object in the Kuiper Be…