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SESK: Stuff Everyone Should Know · sesk.info/aero-pluto-dwarf-2006

In what year was Pluto reclassified as a dwarf planet?

2006, which left our solar system with eight planets.

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  1. 1930
  2. 2006 ✔
  3. 2015

Why: Pluto was called the ninth planet for decades. In 2006 the International Astronomical Union reclassified it as a dwarf planet, so the count went from nine planets to eight.

Huh, didn't know that: NASA's New Horizons spacecraft flew past Pluto in 2015, the first close-up visit.

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Why did Pluto stay so calm after 2006? It knew it was still a big deal to its fans.
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References

Answer: 2006. Pluto was called the ninth planet for decades. In 2006 the International Astronomical Union reclassified it as a dwarf planet, so the count went from nine planets to eight.

  1. NASA Science: Pluto science.nasa.gov/dwarf-planets/pluto
    the International Astronomical Union reclassified Pluto as a dwarf planet in 2006.
    Checked 2026-10-10.
  2. NASA Science: Planets science.nasa.gov/solar-system/planets
    reduced the solar system census from nine planets to eight.
    Checked 2026-10-10.

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Flying & DronesUnder the 2006 IAU rules, what must a planet do that a dwarf planet has not done?Flying & DronesWhich dwarf planet lives in the asteroid belt between Mars and Jupiter?Flying & DronesWhich planet is both the smallest and the closest to the Sun?

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