BEST IELTS Academic Reading Test 460

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IELTS ACADEMIC READING TEST 460 – PASSAGE – 1

IELTS ACADEMIC READING TEST – 460

READING PASSAGE – 1

The Layers of the Sun

Consider the earth, the moon, and all the other planets in our solar system. Think about the mass that all those objects must have when they are all added together. Counter-intuitively, added all together they account for only 0.2% of the total mass of the solar system. The sun makes up the remaining 99.8% of all the mass in the solar system! The sun is the center of the solar system and the largest object in the solar system. Our sun is a star that provides light and heat and supports almost all life on Earth.

The sun is a sphere, but unlike the earth and the moon, it is not solid. Most atoms in the sun exist as plasma, or a fourth state of matter made up of superheated gas with an electrical charge. Our sun consists almost entirely of the elements hydrogen and helium, and because the sun is not solid, it does not have a defined outer boundary. It does, however, have a definite internal structure. There are several identifiable layers of the sun:

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The core is the innermost or central layer of the sun. The core is plasma, but moves similarly to a gas. Its temperature is around 27 million degrees Celsius. In the core, nuclear reactions combine hydrogen atoms to form helium, releasing vast amounts of energy in the process. The energy released then begins to move outward, towards the outer layers of the sun.

Just outside the core is the radiative zone, which has a temperature of about 7 million degrees Celsius. The energy released in the core travels extremely slowly through the radiative zone. Particles of light called photons can only travel a few millimeters before they hit another particle in the sun, are absorbed and then released again. It can take a photon as long as 50 million years to travel all the way through the radiative zone.

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Surrounding the radiative zone is the convection zone. Here, hot material from near the sun’s center rises, cools at the surface, and then plunges back downward to receive more heat from the radiative zone. This movement helps to create solar flares and sunspots. These first three layers make up what we would actually call “the sun”. The next three layers make up the sun’s atmosphere. Of course, there are no solid layers to any part of the sun, so these boundaries are fuzzy and indistinct.

The visible surface of the sun is known as the photosphere. This is the region of the sun that emits sunlight. It’s also one of the coolest layers of the sun—only about 6700°C. Looking at a photograph of the sun’s surface, you can see that it has several different colors: oranges, yellow and reds, giving it a grainy appearance. We cannot see this when we glance quickly at the sun as our eyes can’t focus that quickly and the sun is too bright for us to look at for more than a brief moment.

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Looking at the sun for any length of time can cause blindness, so don’t try it! Sunlight is emitted from the sun’s photosphere. A fraction of the light that travels from the sun reaches Earth. It travels as light in a range of wavelengths, including visible light, ultraviolet, and infrared radiation. Visible light is all the light we can see with our eyes. We can’t see ultraviolet or infrared radiation, but their effects can still be detected. For example, sunburn is caused by ultraviolet radiation when you spend too much time in the sun.

The chromosphere is the zone about 2,000 kilometers thick that lies directly above the photosphere. The chromosphere is a thin region of the sun’s atmosphere that glows red as it is heated by energy from the photosphere. Temperatures in the chromosphere range from about 4000°C to about 10,000°C. Jets of gas fire up through the chromosphere at speeds up to 72,000 kilometers per hour, reaching heights as high as 10,000 kilometers.

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The outermost layer of the sun, and the outermost part of its atmosphere, is called the corona. It is the sun’s halo or “crown”. It has a temperature of 2 to 5 million degrees Celsius and is much hotter than the visible surface of the sun, or photosphere. The corona extends millions of kilometers into space. If you ever have the chance to see a total solar eclipse, you will be able to see the sun’s corona, shining out into space.

To conclude, in the sun’s core, nuclear fusion reactions generate energy by converting hydrogen to helium, and the rest of the sun is heated by the movement of this energy outward from the core. Light energy from the sun is emitted from the photosphere, and it travels through space, and some of it reaches the earth. The sun is the source of almost all the energy on Earth and sunlight powers photosynthesis, as well as warming and illuminating our Earth.

IELTS Academic Reading Test

Questions 1-4

Label the diagram below with the names of the layers of the sun. Choose NO MORE THAN TWO WORDS from the reading passage for each answer.

Questions 5-9

Complete each sentence with the correct ending A – I from the box below. Write the correct letter A – I in boxes 5-9 on your answer sheet.

NB not all letters will be used.

5. The vast majority of the total mass of the solar system is accounted for by…

6. There is no fixed outer edge …

7. The core produces energy which…

8. Our planet only receives…

9. One kind of light emitted by the sun, which…

A. can be seen in the photosphere, is a form of superheated gas.

B. is extremely hot and used to create hydrogen.

C. is invisible to humans, can damage our skin.

D. moves at a very slow pace through the area surrounding it.

E. a small proportion of the light which the sun emits.

F. sunspots, which are the third layer of the sun’s atmosphere.

G. the biggest single object in the solar system, which is the sun.

H. the planets and their moons.

I. to the sun due to the fact that it is mostly made of gas or plasma.

Questions 10-14

Do the following statements agree with the information provided in passage 1?

True – if the statement agrees with the information

False – if the statement contradicts the information

Not Given – if there is no information on this

10. The interior of the sun is composed of a mixture of only two elements.

11. The movement of matter back and forth between the radiative zone and the area that surrounds it gives rise to surface features like solar flares.

12. If a person were to stare at the sun for a long time (while using equipment to protect the eyes), they would be able to see that most of the surface of the sun is not yellow.

13. Light travels faster through the chromosphere than it does through the radiative zone.

14. Nearly all the energy on our planet is produced originally by means of a nuclear reaction.

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