1930 ⟶ Clyde Tombaugh Discovers the Dwarf Planet Pluto

Clyde Tombaugh discovers the dwarf planet Pluto at the Lowel...
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Year
1781
1801
1930
2005
2006

🪐 William Herschel Discovers the Planet Uranus

Amateur astronomer William Herschel discovers the planet Uranus, although he at first mistakes it for a comet. Uranus is the first planet to be discovered beyond Saturn, which was thought to be the most distant planet in ancient times.⟶
William Herschel Discovers the Planet Uranus (1781)
AstronomyPlanetary ScienceSolar SystemDiscoveryTelescopeHerschel18th CenturyScientific Revolution
United KingdomUnited Kingdom

☄️ Giuseppe Piazzi Discovers Ceres, Later Classified as an Asteroid

Italian astronomer Giuseppe Piazzi discovers what appears to be a new planet orbiting between Mars and Jupiter, and names it Ceres. William Herschel proves it is a very small object, calculating it to be only 320 km in diameter, and not a planet. He proposes the name asteroid, and soon other similar bodies are being found. We now know that Ceres is 932 km in diameter, and is now considered to be a dwarf planet.⟶
Giuseppe Piazzi Discovers Ceres, Later Classified as an Asteroid (1801)
AstronomyAsteroidCeresPlanetary ScienceHerschel19th CenturySolar System
ItalyItalyUnited KingdomUnited Kingdom

🪐 Clyde Tombaugh Discovers the Dwarf Planet Pluto

Clyde Tombaugh discovers the dwarf planet Pluto at the Lowell Observatory in Flagstaff, Arizona. The object is so faint and moving so slowly that he has to compare photos taken several nights apart.⟶
Clyde Tombaugh Discovers the Dwarf Planet Pluto (1930)
AstronomyPlanetary SciencePlutoDwarf PlanetClyde TombaughSolar SystemLowell Observatory20th Century
United StatesUnited States

🪐 Discovery of Eris, a Large Body in the Outer Solar System

Mike Brown and his team discovered Eris a large body in the outer Solar System which was temporarily named as (2003) UB313. Initially, it appeared larger than Pluto and was called the tenth planet.⟶
Discovery of Eris, a Large Body in the Outer Solar System (2005)
AstronomySolar SystemErisDwarf PlanetMike BrownKuiper Belt21st Century Science
United StatesUnited States

🪐 International Astronomical Union Redefines Planets, Downgrading Pluto

International Astronomical Union (IAU) adopted a new definition of planet. A new distinct class of objects called dwarf planets was also decided. Pluto was redefined as a dwarf planet along with Ceres and Eris, formerly known as (2003) UB313. Eris was named after the IAU General Assembly in 2006.⟶
International Astronomical Union Redefines Planets, Downgrading Pluto (2006)
AstronomyPlanetary SciencePlutoDwarf PlanetsInternational Astronomical UnionSolar SystemErisCeresDefinition of Planet21st Century Science