Trong tháng tám, đã có một cuộc họp của Ủy ban danh mục của Hiệp hội Thiên văn quốc tế được tổ chức ở Prague. Tôi không thể đi - đặc biệt thất vọng bởi vì tôi đã, trong nhiều năm, một thành viên của Ủy ban đó, và rất thích làm việc với nó. | Chapter 16 The Problem of Pluto Clyde Tombaugh at the blink comparator Credit Lowell In August there was a meeting of the Nomenclature Commission of the International Astronomical Union held in Prague. I could not go - particularly disappointing because I was for many years a member of that Commission and enjoyed working with it. John Mason did attend and on return told us what had been decided. In 1930 Clyde Tombaugh at the Lowell Observatory in Arizona was carrying out a systematic search for a planet moving beyond the orbit of Neptune using a telescope which had been obtained specially for the purpose. The existence of Planet X had been predicted by Percival Lowell founder of the Observatory from slight irregularities in the movements of Neptune and particularly Uranus. It was not long before Tombaugh found a body not far from the position given by Lowell. It was P Moore The Sky at Night DOI 978-1-4419-6409-0_16 Springer Science Business Media LLC 2010 61 62 16 The Problem of Pluto certainly moving far beyond Neptune and was thought to be considerably larger than the Earth. Naturally it was assumed to be a planet and it was named after the God of the Underworld. Conveniently the symbol PL also fitted in with Percival Lowell s name. From the outset Pluto was an enigma. Its orbit was much more eccentric than those of the other planets and was also more highly inclined 17 . Its orbital period was almost 248 years and at perihelion it moved closer-in than Neptune the last perihelion fell in 1989 and between 1979 and 1999 its distance from the Sun was less than that of Neptune though its orbital inclination meant that there could be no chance of collision. More worrying was the revelation that it was not only smaller than the Earth but even smaller than our Moon and Triton the main satellite of Neptune. With a diameter of only 1 444 miles it simply did not fit in with the general pattern of the Solar System. A satellite Charon was found in 1977 its diameter .
