Pluto is a dwarf planet of the Kuiper belt, a small icy world with a nitrogen glacier shaped like a heart, a hazy atmosphere and an unusually large moon, Charon.
At a glance
| radius | 1,190 km (0.187 × Earth) |
|---|---|
| distance from the Sun | 39.5 AU (5.91 billion km) |
| sunlight takes | 5.47 hours |
| one orbit | 248 years |
| orbit eccentricity | 0.25 |
| reflects | 52% of the sunlight it gets |
Read off the piece’s own catalogue, the same values it draws with.
About Pluto
Pluto is made of rock and ice, smaller than our Moon, on a tilted, elongated orbit that brings it at times closer to the Sun than Neptune. A resonance with Neptune keeps the two from ever meeting. Clyde Tombaugh found it at Lowell Observatory, and for a long time it was counted as a planet, until the discovery of other similar bodies in the Kuiper belt led astronomers to classify it as a dwarf planet.
The New Horizons spacecraft flew past it and revealed a far more active world than expected. A vast plain of nitrogen ice, Sputnik Planitia, forms the western lobe of the bright heart-shaped region, its surface slowly churning; mountains of water ice rise beside it, and a thin atmosphere of nitrogen hangs over all of it in blue layers of haze.
Its largest moon, Charon, is so large compared with Pluto that the two orbit a point in the space between them, each keeping the same face turned to the other.
What you see in the piece
Pluto is lit only by the faint sunlight that reaches it at the edge of the planetary system, so it is a dim, small disc even close up. From Earth it needs a telescope, and from another star it cannot be seen at all.
Questions
Why is Pluto not a planet any more?
Astronomers found that Pluto is one of many icy bodies in the Kuiper belt and has not cleared its orbit of them, so it was reclassified as a dwarf planet.
How long does Pluto take to orbit the Sun?
Pluto takes 248 years to go round the Sun once, on an orbit more elongated than that of any planet (eccentricity 0.25).