Why is Pluto’s surface so cold?

Pluto’s surface is extremely cold primarily due to its immense distance from the Sun. Located in the Kuiper belt, Pluto orbits at an average distance of about 5.9 billion kilometers (3.7 billion miles) from the Sun.12

At this vast distance, Pluto receives only about 1/1,600 of the sunlight that reaches [Earth]. This lack of solar energy results in a mean surface temperature of approximately 40 K (−233 °C, or −387 °F). Because of these frigid conditions, common gases such as nitrogen and carbon monoxide exist on its surface as ices rather than as gases.21