- How did the IAU's 2006 vote to reclassify Pluto as a dwarf planet provoke such widespread public reaction?
Dwarf Planets and Kuiper Belt
Pluto, Kuiper Belt objects, and dwarf planet science.
- What evidence led Percival Lowell to predict a ninth planet before Pluto was ever seen?
- How did Clyde Tombaugh's method of comparing photographic plates actually reveal Pluto's movement?
- Who proposed the name Pluto and why was it chosen?
- Why was Pluto later reclassified in 2006, after seventy-six years as a planet?
- How did bombarding uranium-238 with deuterons in a cyclotron produce a brand-new element?
- Why did neptunium-238 need to decay before plutonium could be identified?
- Why does plutonium fission more readily under slow neutrons than uranium-235 does?
- Why was the discovery of plutonium kept classified for years after it was made?
- How powerful was the Trinity detonation compared to conventional explosives, and how far did its effects reach?
- What orbital patterns in long-period comets led Jan Oort to propose a distant cometary reservoir?
- Why do astronomers think comets from the Oort Cloud are making their first pass through the inner solar system?
- What perturbs objects in the Oort Cloud into orbits that bring them toward the Sun?
- Why has the Oort Cloud never been directly observed despite being widely accepted?
- How did James Christy spot Charon as a mere elongation on photographic plates of Pluto?
- How did the discovery of Charon contribute to Pluto's 2006 reclassification as a dwarf planet?
- How was Charon originally discovered in 1978, given how hard it was to see separately from Pluto?
- What surface features could astronomers see on Pluto in Hubble's 1994 images?
- How did Chad Trujillo and Michael Brown detect and confirm Quaoar as a trans-Neptunian object?
- Why did Quaoar's discovery suggest the outer solar system was more populous than previously assumed?
- How far is Quaoar from the sun, and how long does it take to complete one orbit?
- Who discovered Eris, and why did its mass relative to Pluto create a classification problem?
- What new definition of 'planet' did the International Astronomical Union adopt in 2006?
- Why did Pluto fail to meet the IAU's new orbital-clearing criterion?
- What three criteria did the IAU's 2006 definition require for something to count as a planet?
- Why did the discovery of Eris and other Kuiper Belt objects force astronomers to formally define 'planet'?
- Which specific criterion did Pluto fail to meet, and why?
- Why couldn't New Horizons slow down to orbit Pluto during its flyby?
- What features did New Horizons find on Pluto that scientists did not expect?
- How long did it take for New Horizons' images to be transmitted back to Earth?
- What kinds of solar system objects were included in the 11,000 newly catalogued bodies?