Tornadoes have been found on the Sun – almost as big as the Earth and with winds of up to three hundred thousand miles per hour. It is thought they may be a cause of magnetic storms which can disrupt power supplies and computers on Earth.
Magnetic storms are expected to peak in the year 2000 because of a large number of spots on the Sun’s surface. But the “Soho” satellite which found the the tornadoes may be able to warn of the worst of the storms.
Chapter 3
Mercury
Mercury is one of the planets that make up the solar system. It is the closest planet to the Sun. It only takes 88 Earth days to complete one orbit. Mercury has no natural satellite, or Moon, orbiting around it.
Because Mercury is so close to the Sun it can never be very far away from it in the sky as seen from Earth.
Mercury’s surface, like that of Earth’s Moon, consists of craters, plains, valleys, ridges and mountains. These craters are mainly due to the impact of meteorites on the planet’s surface.
Mercury is probably the smallest planet of the Solar System (Pluto may be smaller). Average diameter is about 3,000 miles, which is a little larger than Earth’s moon.
Life cannot exist on Mercury. The temperature on the surface facing the Sun is about 400°C while on the dark side the temperature goes down to -173°C. We came to know a lot about Mercury from the information gathered by the space probe Mariner 10. Mercury takes 59 Earth days to complete one rotation on its axis, which is slower than the Earth’s rotational speed. Mercury has virtually no atmosphere.
Chapter 4
Venus
Venus is the second closest planet to the Sun. Thick clouds cover the whole surface of Venus. In size, Venus is very much like the Earth, 95% of the size of the Earth and its mass is 0.81 of Earth’s. Although in size and structure, there are a lot of similarities, Venus is almost totally unlike Earth in other ways.
Venus has one of the most hostile environments in the Solar System. Its atmosphere contains mostly carbon dioxide, small amount of nitrogen and traces of water vapour, neon and argon. The atmosphere is totally covered by clouds of concentrated sulphuric and hydrochloric acid, sulphur dioxide and liquid and solid sulphur. Chemical reactions make lightning. The carbon dioxide causes the Sun’s heat to be trapped in a “greenhouse effect”. So the temperature on Venus is 460°C. We know more about Venus now from the information sent out by space probes launched during 1960’s and 1970’s. Venus’s surface is rough with rocks, high mountains and deep basins.
Venus takes 225 Earth days to orbit the Sun once. It takes 243 Earth days for Venus to complete one turn on its axis. Of all the planets in the solar system, Venus comes closest to the earth. Another fact is that, compared with the other planets in the solar system, Venus rotate backwards, that is, from east to west. Venus can be seen from the Earth with the human eye. It is often called the “Morning star” or “Evening star”.
Chapter 5
Earth
Earth is the third planet from the Sun. The Earth is the only planet we know of that can support life. It has oxygen in its atmosphere and water in its oceans, both of which are essential for life. And, of all the planets in the solar system, the Earth is at just the right distance from the Sun to neither be too hot nor too cold. Land makes up less than a third of the surface of the earth; more than two thirds is the water in the oceans. All our oxygen has come from plants. The Earth’s insides consist of layers of rock that surround a core made of iron and nickel.
The Earth is not perfectly round and bulges at the equator. The north and south pole are about 13 miles nearer to the Earth’s centre than is the equator.
The Earth spins around once on its axis in 23 hours 56 mins 4.09 seconds. So the actual rotation is 4 minutes less than the full 24 hour day. The Earth orbits around the Sun once in 365¼ days. The spinning of the Earth on its own gives us night and day; the side of the Earth turned towards the Sun has daylight while the opposite side has night. The length of daytime and nightime changes during the year, giving us the seasons. The daytime is longer in summer than in winter. The reason for summer and winter is that the Earth’s axis ‘of rotation’ is tilted at an angle of 23° and always points in the same direction towads Pole star. When the north pole is tilted towards the Sun, the Northern Hemisphere is having its summer. The same thing happens in reverse in the southern hemisphere.
The speed of the Earth spinning is gradually getting slower. 370 million years ago in the Devonian period a day lasted only 22 hours.
The Earth’s orbit around th Sun is oval in shape. So the distance the Earth is from the Sun changes slightly as it follows the orbit. It varies between 90 million and 94.5 million miles. The speed of Earth in its orbit is about 19 miles per second.
THE STRUCTURE OF THE EARTH
The Earth is made up of a surface “crust” the thickness of which ranges between 4 to 44 miles. The crust covers a thick layer of heavier material called the “mantle,” which is 1,780 miles deep until it reaches the “core” which occupies the remaining 2,158 miles to the centre of the Earth.
The Earth’s crust is made up of lighter material than the mantle. There are two kinds of crust. One kind, the “oceanic crust,” lies under oceans and seas, while the other, the “continental crust”, forms the continents. The temperature increases about 30°C for every km deeper into the crust. The core is heavier than that of the mantle and unlike the mantle, is fluid, at least in its outer part. The inner core is probably solid.
Most people think that the Earth and the other planets formed at around the same time, millions of years ago.
Our nearest neighbour in space is the Moon. It circles the Earth keeping the same face pointed towards us. The Moon has no atmosphere to keep the temperaure constant like the Earth so its temperatures range from scorching heat to sub-zero temperatures.
The Moon does not emit its own light. We can see it since it acts like a huge mirror, reflecting sunlight. The Moon is the Earth’s natural satellite. There are many moons/natural satellites circling the other planets of the solar system.
Chapter 6
Mars
Mars is the fourth planet from the Sun and is the next beyond the Earth. Mars is a small, dry planet with a red, rocky surface. It has two tiny moons, called Phobos and Deimos.
Mars has one of the most interesting and varied terrain of any of the terrestrial planets. Olympus Mons is the largest mountain which is 370 miles across and rises about 15 miles high which is about 3 times the height of Mount Everest. This is one of many extinct volcanoes found in Mars. A giant canyon called Valles Marineris which is 2,500 miles long, 90 miles wide and 5 miles deep is present just south of the Martian equator. Strong winds that cause violent dust storms are quite common on Mars.
There is evidence on the surface of Mars that there were lakes, rivers and even oceans, but they are now long gone. Mars can be seen from the Earth with the human eye.
Mars is about half the size of the Earth. Like Earth, Mars has seasons. It has North and South poles covered with white ice caps of frozen carbon dioxide. The Martian day is about 24½ hours and a Martian year is 687 Earth days which is almost the double of an Earth year. The thin atmosphere on Mars is mostly made up of carbon dioxide and a little bit of nitrogen and argon. It’s average temperature is -23°C
Mars has been known since prehistoric times and is sometimes called the red planet.
Scientists still talk about whether life ever existed on Mars. Many space probes have been sent to study Mars. The most recent one was Mars Pathfinder which landed on Mars in 1997 and sent some interesting pictures to Earth.
“Sojourner”rover on Mars 1997
Chapter 7
Asteroids
Astronomers think that there are millions of asteroid in the solar system, ranging in size from a small planetary moon to a tiny object the size of a boulder. Experts who have examined light reflected from asteroids believe that most of them are made of a stone material mixed with metal such as iron and nickel. Asteroids found farther out from the Sun may be made of rock and ice.
The greater majority of asteroids travel around the Sun between the orbits of Mars and Jupiter. Astronomers used to think that they were the remains of a planet that blew up, but it is now thought that they have always been like this. Is not likely that any planet ever formed between Mars and Jupiter because of the strong gravitational influence of Jupiter, the largest planet in the solar system. This gravitational pull would have pulled apart any planetary material that might have collected there.
Chapter 8
Jupiter
Jupiter is the largest of the nine planet that travel around the Sun. It has 16 moons. Ganymede is the largest moon, which is larger than Mercury. Belts of swirling gas clouds cover its surface which is made of a mixture of liquids and gases. It is a cold planet, surrounded by thin ring shaped bands of dust.
Jupiter is the fourth brightest object in the sky (after the Sun, Moon and Venus). It has also been known since prehistoric times.
Jupiter is the first of the gas planets. The gas planets do not have solid surfaces. What we see are the tops of the clouds of these planets. Scientists think that Jupiter has a solid core about the size of the Earth, around which there is a region of liquid hydrogen. This is in turn surrounded by a deep atmosphere.
Jupiter and the other gas planets (Saturn, Uranus, Neptune) have very fast winds blowing along the surfaces of the planets. The winds blow in opposite directions to each other causing Jupiter’s surface to have many different colours. The bright colours are probably cause by chemical reactions.
The outer layer of Jupiter may be as cold as -130°C, but near the planets centre the temperature may be well above 25,000°C. This difference of temperature plays a part in making the weather in Jupiter very inhospitable.
Jupiter’s diameter is 11 times that of the Earth and has a mass that is 300 times greater than Earth. It would take more than 1500 Earths to fill up the space occupied by Jupiter. It takes almost 12 years to complete one orbit around the sun and rotates on its axis every 10 hours.
In July 1994, Comet Shoemaker-Levy 9 collided with Jupiter with spectacular results.
Shoemaker-Levy 9 colliding with Jupiter
Chapter 9
Saturn
Saturn, is the sixth planet from the Sun. It is huge, almost as big as Jupiter. Saturn is the second largest planet in the solar system after Jupiter. Bands of clouds circle the planet, giving it a ringed appearance. It has a solid core surrounded by ice and gas.Saturn has more moons than any other planet; astronomers think that it has more than 20 moons, the biggest one, Titan, is larger than Mercury.
Saturn is over 95 times as massive as the Earth, and its volume more than 740 times as that of Earth. Its diameter is 9 times that of Earth. Saturn takes about 29 years to orbit the Sun and it takes over 10 hours to rotate on its axis. The average temperture is -180°C on the surface.
Saturn’s Rings
Jupiter, Saturn, Uranus and Neptune are all surrounded by rings. Saturn has seven separate flat rings that surround the planet in the plane of its equator. The rings consist of millions of particles of all sizes ranging from dust grains to asteroid sized boulders. Scientists are not sure how the rings formed. They may have formed at the same time as the planet, or they may be the remains of a large moon that blew apart.
Chapter 10
Uranus
Uranus is the seventh planet out from the Sun in the Solar System and the first planet to be discovered after the invention of the telescope, by William Herschel on March 13th 1781. Uranus is a strange green-blue world, a little larger than the planet Neptune.
Like Jupiter, Saturn, and Neptune, Uranus is one of the giant gas planets and has rings around it like the other gas planets.
Uranus has 15 moons, 10 of them were discovered by Voyager 2, an american space probe which flew past the planet in 1986. A lot of our present day knowledge about Uranus is based on the information received from Voyager 2. Voyager 2 also confirmed the presence of 10 rings.
Uranus has a rocky core surrounded by water and shrouded by a dense atmosphere of hydrogen and helium. It is extremely cold and its temperature is -213°C.
The axis of Uranus is tilted at 98° to its orbital path so that Uranus’s poles face the Sun for longer periods of time. This means the rings and moons around Uranus are at roughly right angles from the orbit. Uranus takes 86 years to complete an orbit and spins once in 17 hours.
Chapter 11
Neptune
Neptune is the eighth planet of the solar system. Neptune has a blue atmosphere of clouds and gases like hydrogen and helium. It has a rocky core about as large as the Earth. Neptune has three rings and 8 moons. Six of these moons were discoveres by Voyager 2 which flew past Neptune in 1989.
Neptune is the furthest giant planet from the Sun. It has a bluish-green colour. Neptune was first seen by Galle and d’Arret on September 23rd 1846.
Neptune can be seen with binoculars if you know where to look, but you need a large telescope to look at the planet itself.
It travels around the Sun once every 165 years and it takes just over 16 hours for one rotation on its axis. It is also 17 times as massive as the Earth.
Neptune’s upper atmosphere is very cold at about -200°C. It has a stormy weather, with clouds blowing around at a speed up to 900 miles per hour.
Neptune’s existence became known long before it was actually discovered. Its orbit was worked out mathematically from the gravitational effects it had on Uranus.
Chapter 12
Pluto
Pluto is the ninth and last known planet of the solar system. Pluto is the outermost and smallest planet in the solar system. It is also the coldest planet. Pluto has one moon which is almost half its size.
Pluto is smaller than the Earth’s moon.
Pluto was discovered in 1930 by accident. Calculations which turn out to be wrong, predicted a ninth planet based on how Neptune and Uranus moved. Clyde W. Tombaugh did a careful sky survey which found Pluto despite the mistakes in the calculation.
Pluto is the only planet in the solar system that hasn’t been visited by a space craft. Its temperature is usually between -226°C and -253°C. It looks like a star, even through a telescope.
Pluto’s orbit round the Sun is different from the orbit of the other planets. Sometimes Pluto is nearer to the Sun than Neptune. Also, Pluto rotates in the opposite direction from most of the other planets in the solar system. Pluto takes 248 years to complete a single circuit of the Sun and the length of day on pluto is about 6½ Earth days.
Chapter 13
Comets and Meteors
On a clear night, you may see several shooting stars in the space of an hour. A shooting star, or meteor, looks like a point of light which suddenly darts across the sky and disappears. A meteor occurs when a piece of dust from space, called a meteoroid, burns up as it enters the Earth’s atmosphere. As the meteor plummets to earth at a very great speed, friction with the air produces intense heat which leads a bright glow in the sky. Meteors usually burn up about 50 to 60 miles from the Earth’s surface.
Many meteoroids are fragments left over from comets which orbit the Sun. A comet appears as a faint starlike point of light that moves across the sky for a few nights. As it nears the Sun, the comet grows a tail. Then it swings past the Sun and travels away, becoming smaller and fainter. Comets often reappear at regular intervals (every few years) as they travel past the Earth on their orbits.
Comets
A comet consists of a central core, of dust and ice; a cloud of dust and gas around the nucleus called the coma; and one or more tails. Astronomers have observed hundreds of comets and believe that millions of other comets orbit the sun unseen, far beyond the most distant planet.
Comets have an elliptical orbit around the Sun. Comets seen at fairly regular intervals are known as pariodic comets. The best known periodic comet is Halley’s Comet. It becomes visible every 76 years. Its last visit was in 1986. I saw the comet Hale-Bopp in July-August last year. We’ll have to wait another 5000 years to see it again.
Meteors
Meteors may be no bigger than grains of sand or may weigh up to several grams. They come into the Earth’s atmosphere from outer space moving very fast, and the friction of air makes them so hot that they are completely vaporised into gases before they reach the surface of the Earth. They get so hot that they send out light, leaving a glowing trail behind them. When we see a meteor burning up in the atmosphere like this we often describe it as a shooting star.
Halley’s Comet
Chapter 14
Space Flight
Only a few decades ago, stories about space flight were only found in science fiction books. Today spacecraft blast off regularly from the Earth, placing artificial satellites in orbit around the planet and carrying space probes and astronauts into space. Space flight became a reality because of two inventions : the rocket engine, which is the only engine that can work without air (i.e. in the vacuum of space); and the computer which is needed to guide a space craft on its mission. Space craft do many jobs in space. Much of their work consists of launching satellites which have a range of functions such as mapping the Earth or providing communication links between countries. However, the most exciting part of space flight is the exploration of space itself.
Flipped image of Voyager 2 & Uranus
SPACE SHUTTLE
A space shuttle is an aircraft that can also make repeated flights into space.
SPACE PROBES
Space probes leave the Earth and travel out into space. They are equipped with sophisticated cameras and all kinds of equipments that collect information about space, which is beamed back to Earth by radio. Voyager, Pioneer and Galileo are the names of some of the important space probes
Saturn 5 Rocket
SPACE STATION
People can make the longest space flights on board space stations like Mir. This was built by the Soviet Union. This is a large space craft which is in orbit around the Earth for several years. Smaller space crafts carry the supplies and cosmonauts (soviet astronauts) to the space station where they live and work for long periods of time.
Conclusion
Our knowledge about the solar system is still very limited. We have made vast improvements in our knowledge during the last 30 years with the inventions used in space science. The Hubble Telescope, launched in 1991 has given us an insight into the origin of stars + planets, as it can look into distant stars without any interference of atmosphere. I am sure we would learn more about our solar system as we improve in our technology.
Bibliography
Title AUTHOR ISBN
Childrens Britannica (several) 0-85229-237-6
The Dorling Kindersley
Children’s Illustrated Ann Kramer (editor) 0-86318-629-7
Encyclopedia
Teletext (recent information)
Internet:
http://www.hawastsoc.org/solar
