Pluto

Pluto is a small, icy world at the edge of the Solar System. It was discovered in 1930 and takes about 248 Earth years to orbit the Sun. It has therefore not yet completed a single orbit since it was discovered, and will not do so until 2178.^[1] During that one unfinished lap it has been promoted to planet, studied, photographed up close and demoted, without ever reaching the end of the year.

Reclassification

In August 2006 the International Astronomical Union decided on a formal definition of a planet. Pluto did not meet it, because it has not cleared its orbit of other objects, and it was reclassified as a dwarf planet.^[2] Pluto, being about five billion kilometres away, was not present for the vote, and has not lodged an appeal. It is the only world ever demoted at a meeting it could not attend.

• Planet: 1930–2006.
• Dwarf planet: 2006–present.
• Orbits completed in either role: none.

Name and heart

The name Pluto was suggested by Venetia Burney, an eleven-year-old schoolgirl in Oxford, after the Roman god of the underworld. Her grandfather passed the idea on to an astronomer, and it was chosen from a shortlist.

When the New Horizons spacecraft flew past in 2015, it found a large, bright, heart-shaped plain of nitrogen ice on Pluto's surface. Many people took this personally.

See also

• Neptune – which finished its first lap in 2011
• Meeting – where it was demoted
• List of things that are cold – where it is well placed
• Asteroid – another thing that was nearly a planet

References

1. Lap, L. (2006). Not Quite Round Yet. Outer Press.
2. Union Minutes (2006). “Item 4: Pluto”. Pluto absent, no apologies.
3. Heart, H. (2015). “It Has a Heart”. Flyby Notes 1: 1.