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28.11.2020 02:48 •  Английский язык

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Discovery of Pluto
Fill in the blanks with the proper words given before the text: carry, constellation, dim, discovered, distant, existence, force, initiated, orbit, search, visible
Pluto was the third planet
to be (1) ___, as opposed to the six planets that had been (2)___ in the sky to the naked eye since ancient times. Its (3)___ had been postulated on the basis of apparent perturbations of the motions of Uranus and Neptune, which suggested that a more (4)___ planet was gravitationally disturbing the two then outermost planets. It is now known that these perturbations were spurious; Pluto’s small mass could not have produced a gravitational (5)___ strong enough to be the source of the peculiar motions. Thus, the discovery was a remarkable coincidence attributable to careful observations rather than to accurate calculations.
The (6)___ for the expected ninth planet was supported most actively at the Lowell Observatory in Flagstaff in the early 20th century. It was (7)___ by the founder of the observatory, Percival Lowell, an American astronomer who had achieved notoriety through his highly publicized claims of canal sightings on Mars.
After two unsuccessful attempts to find the planet prior to Lowell’s death in 1916, an astronomical camera with a 13-inch objective was built specifically for this purpose in 1929, and a young amateur astronomer, Clyde Tombaugh, was hired to (8)___ out the planetary search. Less than one year after he began his work, on February 19, 1930, Tomabaugh found Pluto in the (9)___ Gemini. The new planet appeared as a (10)___ “star” that slowly changed its position against the fixed background stars as it pursued its 248-year (11)___ around the Sun.