1915 – Pluto is photographed for the first time but is not recognized as a planet.
Years after, in 1930 Clyde W. Tombaugh, considered Pluto as the ninth Planet of the Solar System. At that time he didn't know that actually it is not.
In 1970 after discovering the minor planet 2060 Chiron, scientists considered that maybe Pluto is not a planet.
Why didn't they say anything? Just because, Astrologists asked scientists to keep silence. For years they were creating their astrological calendars, where they described how birth under different planets is possible to change a human's life. They knew that people whom they cheated for such a long time, would protest, and will never believe them any more.
This lasted till 2006, when the International Astronomical Union (IAU)defined the term "planet" for the first time. and Pluto was reclassified like a "dwarf planet"
Thus the Oxford dictionary got a new word "plutoed", which means "to demote or devalue someone or something"