(On the right: Telescope image of Pluto and Charon)After Percival Lowell established his Flagstaff observatory and published three books on Mars, its canals and supposed inhabitants, he turned his attention to the outer planets. Claims were made that just as the motion of Uranus deviated from predictions, that of Neptune did too. Lowell believed those claims, suspected there may exist one more unknown planet beyond Neptune, and started looking for it. Today, with the mass of Uranus better known, calculations and observations are found to fit each other well, removing the need for "Planet X." Lowell died in 1916 without discovering any planet, and others continued to maintain his observatory (it still exists). In 1928 the observatory received drawings of Jupiter and Mars by a young amateur astronomer who had built his own telescopes, Clyde Tombaugh (born 1906); he was offered a job, and continued Lowell's search. He discovered a new trans-Neptunian planet in 1930: it was quite dim, but moved too slowly to be an asteroid. He named it Pluto--the name of the Roman God of the Underworld (Hades to the Greeks), a name which also started with the initials of Percival Lowell.
Index 
(On the right: Telescope image of Pluto and Charon)After Percival Lowell established his Flagstaff observatory and published three books on Mars, its canals and supposed inhabitants, he turned his attention to the outer planets. Claims were made that just as the motion of Uranus deviated from predictions, that of Neptune did too. Lowell believed those claims, suspected there may exist one more unknown planet beyond Neptune, and started looking for it. Today, with the mass of Uranus better known, calculations and observations are found to fit each other well, removing the need for "Planet X." Lowell died in 1916 without discovering any planet, and others continued to maintain his observatory (it still exists). In 1928 the observatory received drawings of Jupiter and Mars by a young amateur astronomer who had built his own telescopes, Clyde Tombaugh (born 1906); he was offered a job, and continued Lowell's search. He discovered a new trans-Neptunian planet in 1930: it was quite dim, but moved too slowly to be an asteroid. He named it Pluto--the name of the Roman God of the Underworld (Hades to the Greeks), a name which also started with the initials of Percival Lowell.