Pluto, once considered the ninth planet, is now classified as a dwarf planet. It resides in the Kuiper Belt, a doughnut-shaped region of icy bodies beyond Neptune. Despite its reclassification, Pluto holds many unique and fascinating characteristics.

Its Heart-Shaped Feature

Perhaps the most famous feature of Pluto is Tombaugh Regio, a large, bright, heart-shaped region on its surface, named after Clyde Tombaugh, the astronomer who discovered Pluto.

• The left side of the "heart" is Sputnik Planitia, a vast, nitrogen-ice-filled plain that is one of the largest known glaciers in the solar system.
• Sputnik Planitia is relatively young, suggesting geological activity on Pluto continues to this day.

The Icy and Rocky Composition

Pluto is primarily composed of ice and rock. The surface ices include:

• Nitrogen (N₂)
• Methane ($\text{CH}_4$)
• Carbon Monoxide (CO)

These ices sublime (turn directly into gas) when Pluto is closer to the Sun, forming a thin, temporary atmosphere. When it moves farther away, the atmosphere likely freezes and falls back to the surface.

An Extreme Orbit

Pluto's orbit is highly eccentric (not perfectly circular) and inclined relative to the plane of the other planets.

Pluto spends about 20 years of its orbit closer to the Sun than Neptune. 

System of Moons

Pluto has five known moons, forming a complex system. The largest and most famous is Charon.