1. What sort of star is the sun?
The sun belongs to a family of about 100,000 millions old stars in our Galaxy. Some are much hotter than the Sun, while others are cooler. Some are much larger, and some are smaller. The Sun is a very ordinary star, and there are millions of other stars like it.
2. How hot is the Sun?
The sun is the hottest and brightest at its centre, where the temperature is believed to be about 15 million degree centigrade. By the time this heat has worked its way to the surface, it has fallen and decrease to 6000 degrees about four times as hot as a steel furnace. There are many more stars that are hotter than the sun.
3. What is Sunspot?
A sunspot is a dark area on the suns brilliant surface. It appears dark because it is cooler, and so gives out less light sunspots are particularly common every 11 years or so, and this is known as the sunspot circle.
4. What is the suns corona?
The corona is often called the suns atmosphere but is not at all like our own atmosphere. It has a temperature of a million degrees centigrade and is a million times thinner than air. The brilliance of the sun hides it from view except during the total eclipse.
5. What types of Galaxy are there?
No two galaxies look exactly alike, but there are three main kinds. Some are irregular, with no particular slope, others are spiral, with trailing arms of stars and nebulae. The commonest are elliptical, like a smooth swarm of stars.
6. What is the age of the Universe?
The galaxies in the universe appear to be expanding away from each other. If we work backwards, we find that they were close together between 15,000 and 20,000 million year ago.
7. Which is the nearest galaxy to our own?
Our galaxy’s closest neighbour is the large Magel panic cloud which is about 150,000 light-years away. It is only one third the diameter of our galaxy and contains only a tenth of as many stars.
8. What causes Aurorae?
At about 200 kilometres above the earth’s surface, the air is very thin and its atoms are widely scattered. Tiny electric particles from space, known as electrons, can penetrate the air at this height. If one strikes an atom, a flash of light is given out. An aurora is a glow caused by countless millions of these flashes, produced when the sun is very active.
9. What are solar prominences?
A prominence is a fountain of glowing gas rising up from the sun’s surface. Some prominences escape into space, but most last for a few hours or days, and then fall back into the sun.
10. When did the first man fly in space?
The Soviet cosmonaut Yuri Gagarin made the first orbit of the Earth on 12 April 1961, in a Vostok spacecraft. The trip lasted 108 minutes, and he landed in a field within ten kilometres of the planned descent point.
11. When did the space shuttle make its first flight?
The first space shuttle launch took place on 12 April 1981, using the space shuttle Columbia which was only a test flight, it made 36 orbits of the earth during its 54 hours stay in space. It took off exactly 20 years after the first orbital flight by Yuri Gagarin to the space. The main problem encountered during the maiden flight was the loss of some of Columbia’s 29,000 heat resistant tiles. In January 1986 Challenger blew up shortly after takeoff, killing the crew of seven.
12. Why were the asteroids formed?
The asteroids consist of countless thousands of tiny planets left over from the solar system’s early history when the sun and the planets were being formed.
13. Why are giant planets gaseous?
The sun and the planets of the solar system were formed from a huge cloud of gas and tiny solid particles about 4600 million years ago. Most of the gas was hydrogen. Small planets such as the Earth lost a lot of hydrogen into space, but the giant planets kept all of theirs.
14. Why do comets appear unexpectedly?
Most comets take thousands or even millions of years to go around the sun, and their orbits are so elongated or eccentric’ that they travel from beyond Pluto. Very few become bright enough to see until they are as close as Mars. This is why some comets appear without warning every year. Some comets pass close to the sun every few years. The famous Halley’s Comet, which has a period of 76 years, has been observed regularly since 239 B.C. Comet. West, which was visible in daylight in 1976 will not return to the sun for about a million year.
15. Why do meteors occur?
A meteor is a streak of light high up in the atmosphere. It occurs when a tiny solid object, smaller than a marble, plunges through the air at a speed of many Kilometres per second. The body is burned up by friction, leaving a white-hot trail.
16. Why do the eclipses of the sun occur?
A solar eclipse can be seen only at New Moon when the Moon is between the earth and the sun. On average, a total eclipse is seen from the same site every 350 years.
17. Why is the setting sun red?
The earth’s atmosphere is like a pale red filter and makes all the light coming from space turn slightly reddish but an object which is very low in the sky has to shine through much more air than one high in the sky. This means that its light penetrate through more of this red filter and its tint is deeper.
18. Why does the sun keep shining?
Even the tiniest object you can see with a microscope contains millions of atoms. Each atom contains much tinier particles still. Inside the sun atoms are being pulled to pieces and put together again in a different way. This gives out heat and keeps the sun shining
19. How do stars twinkle?
Out in space, stars do not twinkle. But when their light passes through the Earth’s atmosphere, it is made to flicker by the hot and cold ripples of air. You can see the effect by looking at a distant view over a hot road in summer, or across a bonfire.
20. How do stars die?
A star shines by turning its hydrogen into another element called helium. This change gives out heat and keeps the star hot. When its hydrogen fuel runs down, the star begins to die.
21. How big is the Sun?
The sun measures 1,392,530 kilometres across, or 109 times the diameter of the Earth. If the sun were the size of a football, the earth would be only two millimetres across.
22. How are stars formed?
Stars begin their lives as very thin clouds of hydrogen gas. As each cloud shrinks, the centre grows very hot due to the atoms of gas being squeezed together. Eventually, the clouds become so hot that they begin to shine as stars.
23. How is a spacecraft launched?
To escape from the earth, a rocket must travel at 11 km per second. A single craft could not carry enough fuel to reach this speed, it would be too heavy to leave the ground. So a spacecraft has separate stages, which jump clear as the lower ones use up their fuel. Smaller rocket engines may need more stages.
24. How does Rocket Motor work?
On the earth, we usually move by pushing or pull ing against something fixed. But in space, there is nothing to push or pull against, so movement must be a reaction. A bullet fired from a gun kicks the fire backwards. Hot gas leaving a rocket kicks the spacecraft forward.
25. How does a satellite stay in orbit?
To stay in orbit near the Earth, a satellite must travel at about 8 kilometres per second. Once it has gone into orbit, it will remain to circle almost indefinitely. However, if it is less than about 200 kilometres above the earth, the slight dragging effect of the earth’s outer atmosphere will cause it to lose speed and height, and after a few years it may burn up like a meteor.
26. How does a spacecraft return to Earth?
All spacecraft must find a way of slowing down from a speed of many kilometres per second to give the crew, or cargo, a soft touch down. The landing is usually done by parachute, but the space shuttle glides down.
27. How do astronauts breathe in space?
Our air contains several different gases. The most important one is oxygen since this is what we must breathe in order to live. So astronauts have to take an oxygen supply in their cabin and in their spacesuits. Another problem is how to get rid of the waste of carbon dioxide that is breathed out. It can be absorbed by chemicals, but on a very long flight, it would be essential to extract and recycle the oxygen so that it could be used again.
28. How do astronauts speak to each other?
If they are outside the spacecraft or on the Moon’s surface, they have to speak by radio, since sound cannot travel in empty space. However, if they are
in the atmosphere of the cabin, they can talk normally to each other.
29. How does astronaut make Space Walks?
A person can walk only if he is on the surface of a planet where gravity pulls his feet down onto the ground. In space, an astronaut can only float alongside his spacecraft to which he is tied by a safety line.
30. How do we measure the distance to the moon?
The speed of light is very accurately known. It is 299,792 kilometres per second in space. If a light the beam is aimed towards the Moon and reflected back, the distance to the moon can be worked out.
31. How do unmanned space vehicles work?
Several different kinds of unmanned spacecraft have been sent to the moon. Some went into orbit around it and took detailed photographs. Others have landed on the surface and tested the conditions there sending messages by radio to the earth. They have television cameras to let the operators see where they are going. It can start and stop at will, turn corners, and take samples of the lunar dust.
32. How did Apollo get to the Moon?
Apollo which made the first manned landing in 1969, had to travel in stages. First, it was shot up into Earth orbit then it flew to the Moon and went into lunar orbit. The lunar module then descended to the surface, leaving the command module awaiting its return.
33. How did the Apollo astronauts explore the Moon?
The astronauts most important task was to collect samples of the lunar rocks and soil. In the first three missions, they explored by foot. In the last three, they used a lunar rover.
34. How did the Lunar Rover work?
The lunar rover was a four-wheeled buggy driven by electric batteries. Its top speed was about 12 kilometres per hour, and it had enough power to travel about 65 kilometres before its batteries ran down. The last three Apollo flights took a rover.
The rover could carry two astronauts and about 180 kilograms of cargo. It had several cameras and televisions fitted to its frame.
35. How is the space shuttle launched?
The shuttle is launched into space attached to two booster rockets and a huge fuel tank. As it reaches a height of about 43 kilometres, the two booster rockets parachute back to earth. To return, the shuttle fires its engines to head earthwards and glides down.
36. How is the space shuttle used?
The space shuttle is a workshop it carried the space lab into the orbit. Its job is to carry the astronauts, or cargo else both, into orbit around the earth. It can carry or hold six passengers at a time and has a cargo bay 18.3 metres long and 4.6 metres in diameter.
37. Who discovered Jupiter’s Moons?
Galileo Galilei was one of the first people to point a telescope to the sky, making several very in important discoveries. Turning his instrument to the planets he saw that Jupiter has four bright satellites.
38. Who discovered how planets move?
Johannes Kepler 15711630 discovered the true shape of the planets’ orbits around the sun, which are not circles but ellipses. An ellipse has two points within it, each one called a ‘focus’. The sun is situated at one focus, the other one being empty
39. Who discovered Uranus?
William Herschel built the largest telescope of the age 17381822 and discovered the planet Uranus as well as thousands of new objects inside our own galaxy and other galaxies far away.
40. Who was Laika?
Laika, a small Eskimo dog, was the first living thing to be sent into orbit around the Earth. She was launched from the Soviet Union in Sputnik 2 on 3 November 1957.
41. What is Comet?
A comet is an icy body just a few kilometres across orbiting the sun. Particles the size of dust and sand are mixed with the ice. When the comet passes near the sun, the heat turns the ice to gas and the dust pours out into space, making the comet look hazy and perhaps giving it a long tail as well.
42. What is a variable star?
A variable star changes in brightness. Some take a few hours, while others may take many years. Most are swelling and shrinking, becoming brighter and fainter as they do so. Others are pairs of stars, which seem to change in brightness when one passes in front of the other.
43. What is a binary star?
A binary star consists of two stars revolving around each other. The closer they are the faster they revolve. Some binaries take just a few hours to go around once, while others take thousands of years.
44. What are Red Giants and White Dwarfs?
When a star is born, it usually shines steadily for hundreds of millions of years. But eventually, many stars start to puff outwards as a fiery mist. This is the red giant stage. Finally, they shrink into a very hot globe, the size of a planet-a white dwarf.
45. What are Novae and supernovae? Both of these objects are exploding stars, which erupt almost overnight. Several Novae occur our galaxy every year, and some can be seen with
the naked eye.
46 What is a pulsar?
After a supernova explodes, all that is left of a star is a very hot ball of matter a few kilometres across, spinning at a tremendous rate. It sends out a beam of light or radio waves like a revolving searchlight so that it seems to ‘pulse’ on and off. It is called a pulsar,
47. Why can’t we see other solar systems?
The nearest star is over a quarter of a million times as far away as the sun. At this distance, even a large planet would be invisible in the biggest telescope.
48. Why is there life on earth?
All living beings from human beings to bacteria will die if it becomes too hot or too cold, or if there is no air to breathe. No other planet in the solar system has favourable conditions for Earth-like life.
49. Why is there no weight in space?
Weight is the force you feel when the floor, or a chair, stops you from falling towards the centre of the earth. If a hole opened in the ground, you would be weightless while falling down it. This is known as a ‘free fall’. Flying through space everything is in free fall.
50. What is the difference between a planet and a moon? A planet is a dark body orbiting a star. It can only be seen by the starlight it reflects. Almost all the planets in the solar system reflect light from the sun. A moon (or satellite) also shines by reflection, but it revolves around a planet.
51. Why do the moon wax and wane?
The sun can shine (bright) on only one half or hemisphere of the moon. Since it orbits the earth every month, our view of this hemisphere changes. At New Moon, it is turned away from the Earth, and cannot be seen, while at the full moon it is turned towards us. After full, the moon’ waves” or shrinks to invisibility once more.
52. Why is the moon covered with craters?
The lunar craters were probably formed during the first few hundred million years of the moon’s 4500 million year history. They are practically unchanged today because the lunar globe cooled down quickly and preserved them and there is no atmosphere to produce winds and weather, which could have worn these features away.
53. Why is the new moon invisible?
The true new moon lies almost between the Earth and the Sun. The sun is so dazzling that nothing can be seen near it. Also, the night hemisphere of the moon is turned towards the earth.
54. Why is there no life on the Moon?
The life forms that are familiar to us need air and water, as well as protection from some dangerous rays sent out by the sun. The moon has no atmosphere, no water on its surface, and it is completely exposed to space. Also, the temperature of atmosphere at midday is higher than that of boiling water.
55. Why is Mars a dead world?
The two Viking spacecraft which reached the planet in 1976 and examined its surface did not find any sign of life. They also discovered that the temperature is always below freezing point, and the atmosphere is thin and unbreathable.
56. Which planet spins the fastest?
Jupiter, which is the largest of the planets in the Solar System, spins on its axis in the shortest time, only 9 hours and 50 minutes.
57. Why is Mars red?
This red dusty material covers to the planet’s surface and in sometimes blown into huge dust in of the reason storms.
58. Why is Venus so hot?
Although it is always cloudy, enough sunlight breaks through to heat, the ground during its four-year ‘day’.
59. Why is it difficult to see mercury?
These appearances are known as ‘elongations’. At eastern elongation, it is low in the western sky after sunset. At western elongation, it rises in the dawn sky. At these times it looks like a star.
60. What is the Milky Way?
This band is caused by distance stars, which cannot be separated with the by the naked eye.
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