A Jupiter is the largest planet in the solar system. Its diameter is 88,846 miles (more than 140,000 kilometers), more than 11 times that of Earth, and about one-tenth that of the sun. It would take more than 1,000 Earths to fill up the volume of the giant planet. When viewed from Earth, Jupiter appears brighter than most stars. It is usually the second brightest planet—after Venus. Jupiter is composed of a relatively small core of metal (iron and silicates surrounded by hydrogen). In the depths of the planet the hydrogen is so compressed that it is metallic in form; further from the centre where the inner atmosphere is stretched about 20000 km, the pressure is lower and the hydrogen is in its normal molecular form. The Jovian cloud tops visible from Earth consist primarily of methane and ammonia.There are other elements and compounds lurking in the cloud tops and below which are thought to be responsible for the colors seen in the atmosphere.
How does Jupiter come to form?
B The Origin theory is a mystical problem. In our own solar system inside or around asteroid belt, there are four rocky planets close to the Sun, each formed in the way described follow-Mercury, Venus, Earth and Mars: The first stars which formed from primordial hydrogen and helium produced in the big bang, cannot have had any planets, because there were no heavy elements available from which they could be built up. Planetary systems ore all second-generation (or later) systems. As the parent cloud of gas and dust from which our Solar System was being formed, began to shrink, any rotation it possessed made it spin faster and faster, and as the core of the cloud collapsed to form a star, some of the material from which it was forming was held out from the centre of the cloud by residual spin, and the material settled down into a dusty disc around the young star. Close to a young star, the lightest material in the disc, comprising mainly hydrogen and helium gas, is blown away by the heat of the star and solar radiation. The material left behind is made up of billions of tiny grains of dust that collide and stick together, building up larger lumps. The lumps of matter may be a few millimetres across and are settling into a thinner disc around the star. The process of accretion-lumps growing by sticking together carries on until the original dust grains have become lumps of rock about one kilometre across, similar to the asteroids that orbit in profusion between Mars and Jupiter today. Once the pieces of rock reach this size, they begin to tug on each other significantly through gravitation, pulling them into swarms that orbit around the star together, bumping into one another from time to time. Gravitation pulls the pieces more and more tightly together, with the largest lumps (which have the strongest gravitational pull) attracting more and more material, growing to become terrestrial planets and their satellites.
C Then there is a belt of cosmic rubble (the asteroid belt), a ring representative in many ways of the kind of material from which the inner planets formed. The material in this ring could never settle down to become a planet itself because it is continuously being disturbed by the gravitational influence of Jupiter, the largest planet in the solar system. Beyond the asteroid belt, there are four “gas giant” planets, Jupiter, Saturn, Uranus and Neptune.These are probably typical of planets that form at large distances from their parent star, planets in which the primordial volatile material has been retained, so that even though they may contain a small rocky core, they are mostly made of gas and ices. Beyond the gas giants, at a great distance, comes small, rocky Pluto, an anomaly, and possibly a comet or asteroid, captured and held in a fixed orbit.
D In March 1993, astronomers Eugene Shoemaker, Carolyn Shoemaker, and David H. Levy discovered a comet near Jupiter. The comet was found orbiting planet Jupiter and is believed to have been captured from the Sun around two decades earlier. The comet, later named Shoemaker-Levy 9, probably once orbited the sun independently, but had been pulled by Jupiter’s gravity into an orbit , the diameter of which becomes smaller, around the planet . When the comet was discovered, it had broken into 21 pieces. The comet probably had broken apart when it passed close to Jupiter.
E According to David Levy, a half-mile-wide object should hit the Earth on the average of once every 100,000 years. However, small objects the size of a grain of sand or a piece of gravel hit the Earth each minute. The frequency with which a 100-meter asteroid/comet hits Earth is about once every 100 years. The chances could be higher or lower because these small objects are not easy to see with our telescopes, so their number is not well known. Calculations revealed that the cemetery fragments were on course to collide with Jupiter during July 1994, and that each fragment could deliver an energy equivalent to approximately 500,000 million tons of TNT. The prospect of celestial fireworks on such a grand scale immediately captured the attention of astronomers worldwide! Scientists hoped to learn much about the effects of a collision between a planet and a comet. Astronomers at all the major telescopes on Earth turned their instruments toward Jupiter at the predicted collision times. Scientists also observed Jupiter with the powerful Hubble Space Telescope, which is in orbit around Earth; and the remotely controlled space probe Galileo. which was on its way to Jupiter.
F The fragments fell on the back side of Jupiter as viewed from Earth and the Hubble Space Telescope. But the rotation of Jupiter carried the impact sites around to the visible side after less than half an hour. Scientists estimate that the largest fragments were about 0.3 to 2.5 miles (0.5 to 4 kilometers) in diameter. The impacts were directly observable from Galileo, which was within about 150 million miles (240 million kilometers) from Jupiter. However, damage to certain of the probe’s instruments limited its ability to record and send data. The impacts caused large explosions, probably due to the compression, heating, and rapid expansion of atmospheric gases. The explosions scattered comet debris over large areas, some with diameters larger than that of Earth. The debris gradually spread into a dark haze of fine material that remained suspended for several months in Jupiter’s upper atmosphere. If a similar comet ever collided with Earth, it might produce a haze that would cool the atmosphere and darken the planet by absorbing sunlight. If the haze lasted long enough, much of Earth’s plant life could die, along with the people and animals that depend on plants.
G The smaller cemetery fragments plunged into Jupiter rapidly disintegrated and left little trace; three of the smallest fragments, namely T, U and V left no discernible traces whatsoever. However, many of the cemetery fragments were sufficiently large to produce a spectacular display. Each large fragment punched through the cloud tops, heated the surrounding gases to some 20,000 K on the way, and caused a massive plume or fireball up to 2,000 km in diameter to rise above the cloud tops. Some days after collision the impact sites began to evolve and fade as they became subject to the dynamics of Jupiter’s atmosphere. No-one knows how long they will remain visible from Earth, but it is thought that the larger scars may persist for a year or more. The interest of professional astronomers in Jupiter is now waning and valuable work can therefore be performed by amateurs in tracking the evolution of the collision scars. The scars are easily visible in a modest telescope, and a large reflector will show them in some detail. There is scope for valuable observing work from now until Jupiter reaches conjunction with the Sun in November 2004.
Questions 14-17 Choose the correct letter, A, B, C or D. Write your answers in boxes 14-17 on your answer sheet.
14 People believe the origin of planets of inner asteroid belt can be
A somewhat an inaccurate and too broad theory
B a sophisticated mystery though certain speculation has been proposed
C a totally wrong speculation
D totally explained by the theory made
15 When did the planet of Jupiter come to form?
A when there were no heavy elements
B at the same time as the big bang happened
C during the generation of first stars
D when our Solar System was being formed
16 According to the passage, what is true for the “gas giant” planets?
A They are at large distances from their parent star.
B The original volatile material has been lost
C They contain gas and ices core.
D Each is possibly a comet or asteroid, captured and held in a fixed orbit.
17 Astronomers and scientists on Earth stared their instruments toward Jupiter at the predicted collision times mainly because
A hoped to calculate the real risk of the collision between the Earth and a comet.
B hoped to learn unknown knowledge of a collision between a planet and a comet.
C hoped to collect data about the structure of the Jupiter
D hoped to test the powerful Hubble Space Telescope
Questions 18-23 Complete the following summary of the paragraphs of Reading Passage 2, Choose the appropriate letter from A-L and write your answers in boxes 18-23 on your answer sheet.
E 20 years
F 30 years
G 100 years
The comet of Shoemaker is thought to have been orbiting the Jupiter at least for 18 ..……………… The comet probably once orbited the sun independently, but had been pulled by Jupiter’ s 19 ……………….. into an orbit around the planet. When the diameter of orbit becomes 20 ……………….. with Jupiter’s force, it came closer and had broken into 21-pieces. According to David Levy, the possibility with which a 100-meter asteroid/comet hits Earth is about once every 21 ……………….. The chances could be higher or lower and their number is not well determined.
Calculations revealed that the cemetery fragments were on course to collide with Jupiter during July 1994. Finally, the fragments collide into the back side of Jupiter as viewed from Earth and the Hubble Space Telescope. Large explosion from the impacts 22 ……………….. the huge, hot atmospheric gases. And the comet debris gradually expanded into a dark dust of material that 23 suspended for months in Jupiter’s upper atmosphere
Questions 24-26 Filling the table, Choose NO MORE THAN THREE WORDS AND/OR A NUMBER from the passage for each answer