–  HALLEY’S COMET  –
A comet is an object that travels around the sun leaving a bright trail behind. For more than two thousand years, the return of Halley’s Comet has been observed and recorded on Earth every 76 years.Its 1986 visit, however, was the first time that humans took a close look at its nucleus.

One spacecraft went within a few hundred kilometres of the nucleus. Two Soviet craft, Vega 1 and Vega 2, came within 10,000 km of the nucleus on March 6th and March 9th; and the European Space Agency’s Giotto space probe passed within 600 km of Halley’s Comet on March 14th.

Pioneer Venus Orbiter found that the cloud of gases and dust which make up the tail spread over a region about 20,000,000 km across, 15 times larger than the Sun. Scientists also discovered that the comet was losing about ten metres of material from its surface every orbit, suggesting a lifetime of about only ] ,000 orbits – in about 100,000 years it will disappear.

QUESTIONS

A. Mark the statements as True (T) or False (F).
1. Halley’s Comet was first seen more than 2000 years ago. 2. In 1986, two of the spacecraft which observed Halley’s Comet were from the Soviet Union. 3. The sun measures 20,000,000 km across. 4. Halley’s Comet has a lifetime of about 100,000 years left because it is losing material from its surface every orbit.
B.
1. How often can Halley’s Comet be observed from Earth?
2. What is the tail of Halley’s Comet made up of?

TELESCOPE SITES
Today, telescopes are built at remote sites chosen for the quality of their observing conditions. Such sites are preferred because the sky is dark. Near big cities, the light from the cities causes light pollution, which interferes with the observation of the sky. Higher altitudes are 5 more suitable, since there the humidity is very low and the atmosphere is quite calm.
QUESTIONS
A. Mark the best choice.
1. Line 1, ‘remote’ means .
a) isolated b) crowded c) well-lit d) famous
2. To interfere with (line 4) means to .
a) improve b) help c) protect against d) cause difficulty in
3. Line 5, ‘there’ refers to .
a) in humid areas b) in the sky c) in the atmosphere d) at higher altitudes
B. Mark the statements as True (T) or False (F).
1. Telescopes are built near cities to obtain light from cities for a better observation of the sky.
2. The higher the altitude, the higher the humidity.

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