Text С. The last man to discover a planet

Clyde Tombaugh, a young American research student, made the last discovery of a planet while working in 1930 at the Lowell Observatory, Arizona State College. This planet is Pluto, the ninth one in order of distance from the sun, 3,670 million miles away.

Although Tombaugh, who was 26 at the time, was the first astronomer to see Pluto, its existence had been suspected by Percival Lowell, builder of the observatory at Flagstaff, Arizona. Lowell began searching for the planet in 1905, the year before Tombaugh was born. He observed that there was a difference between the predicted and actual positions of Uranus, and this led him to conclude that there must be another planet. His final calculations about "Planet X" were published in 1914, but he had still not found the planet when he died two years later.

Another American, W.H. Pickering, took up the search, concentrating on the irregular movements of the planet Neptune. He saw a clue in the movement of comets, which seem to be attracted by large planets. There were 16 known comets whose paths took them millions of miles beyond Neptune, which is 2,811 million miles from the sun, and Pickering was convinced that they were being attracted by a still more distant planet.

In 1919 yet another hunt was begun by Milton Humason at Mount Wilson Observatory, Pasadena, California. Instead of mathematical calculations, Humason tried photography. He took two pictures of a series of stretches of the sky, with a gap of one or two days between exposures. In such photographs stars stay still, but planets change position.

When Tombaugh discovered Pluto, it became clear that Humason had photographed the planet twice. Once it had been masked by a star, and the second time its image had coincided with a flaw in the photographic plate. The main difficulty in the search had been that Pluto was extraordinarily faint. Pickering formed the opinion that it was not Lowell's Planet X, but that a huge planet remains to be discovered.

I. Read the text ‘The last man to discover a planet’. Name all the people who tried to prove the existence of the ninth planet.

II. Choose the correct answer.

1. The last man to discover Pluto was …

a) P. Lowell

b) M. Humanson

c) C. Tombaugh

2. The first astronomer to see the ninth planet was …

a) W.H. Pickering

b) M. Humason

c) C. Tombaugh

3. Clyde Tombaugh was born in …

a) 1905

b) 1906

c) 1914

4. Percival Lowell began searching for a new planet in...

a) 1914

b) 1919

c) 1905

III. Write out of the text sentences with the infinitive. Define its forms and functions. Translate the sentences.

IV. Make a written translation of the text ‘The last man to discover a planet’ using a dictionary.

V. Learn to speak about great scientists exploring the Universe. Make use of the following articles.