Ex. 10. Fill in the missing words in the sentences below. Choose from the following putting the verbs in the right tense
| approximately celestial bodies impressive spectacle outer reaches | rate mean circle star | evaporate massive (2) luminous | eventually luminosity approach |
1. A star cannot avoid being … because of the energy generated in the conversion of its hydrogen into helium.
2. The Southern Hemisphere does not have the north’s pole star to help navigators, but its skies undeniably represent an …
3. Apart from the stars in the very centre, those in the inner regions of a spiral galaxy … it more rapidly than those in the outer regions.
4. When the comet’s orbit carries it close to the sun, surface ices … into a great head of steam.
5. Mercury feels the sun’s powerful gravity very strongly, and orbits at a breakneck … – which makes it even more difficult to spot.
6. The … distance between the earth and its closest neighbour in space, the moon, is … 384.000 km.
7. Comets come from the … of the solar system, and their parts, when they reach the inner planets, are hard to predict.
8. Astronomers use imaginary lines, similar to latitude and longitude on Earth, to indicate the position of objects in the sky known as …
9. The …, temperature, and size of stars depends on their mass: the heavier the star, the larger and hotter it is and the brighter it shines.
10. Stars live a long time, but they all die … . The reason is simple: they run out of fuel. But the way a star dies, and how long it lives, depends on how … it is. A … like the sun, or one that is less …, lives for billions of years. Born 4-6 billion years ago, our sun now … middle age.
Ex. 11. Choose the best alternative to complete the following sentences.
1. The moon … Earth as it moves around the sun, orbiting our planes like a large artificial satellite.
a) approaches
b) accompanies
c) pulls
2. Planets and their satellites only shine in the night sky because …
a) they are luminous
b) they have “fusion reactors” to make them shine
c) they reflect light form the sun
3. Nowadays we think of a comet as an aggregate of …
a) matter that contains abundant hydrogen
b) ice and snow and mud
c) frozen water, ammonia, methane and some particles of a metallic and stony character
4. The meteor showers that we regularly receive every August scientists believe to be …
a) the remains of a comet
b) atmospheric phenomena
c) asteroid attacks
5. As the comet approaches the sun …
a) the tail shrinks
b) the tail heads back
c) the tail gets longer
6. Different phases of the moon represent the amount of …
a) the luminous surface of it visible to us
b) the illuminated surface of the satellite visible to us
c) the dark surface of the moon visible to us
7. After Uranus was discovered, astronomers realized that the planet … by an unknown gravitational force – perhaps another planet lying farther out, so the next planet Neptune was found.
a) was being divided into tiny particles
b) was being approached rapidly
c) was being pulled slightly off the course
8. The moon’s orbit around the earth is not quite …
a) circular
b) elliptical
c) ecliptic
Ex. 12. What prepositions are missing in the following article?
Here (1) ___ the earth, 93 million mi (2) ___ the sun, a surface 1m2 (3) ___ area exposed (4) ___ the vertical rays (5) ___ the sun receives an average (6) ___ nearly 20 kcal (7) ___ energy/min. Adding (8) ___ all the energy received (9) ___ the earth’s surface gives a staggering total, although this is but a tiny fraction (10) ___ the sun’s total radiation. And the sun has been emitting energy (11) ___ this rate (12) ___ billions of years. Where does it all come (13) ___?
We might be temped to think (14) ___ combustion, for fire is the only familiar natural source (15) ___ energy that seems at all comparable (16) ___ the sun. But a moment’s reflection shows that the sun is too hot to burn; burning implies the combination (17) ___ other elements (18) ___ oxygen to form compounds, but (19) ___ the sun nearly all compounds are decomposed (20) ___ the terrific heat. And even if burning were physically possible, the heat obtainable (21) ___ the best fuels known would be hopelessly inadequate to maintain the sun’s temperature.