WHAT ARE FALLING STARS?

WHAT ARE FALLING STARS?
For thousands of years men have looked up at "falling stars" and wondered what they were and where they coem from. At one time it was believed that they came from other worlds.
Today we know that they are not "stars" at all. We call them "meteors." They are small, solid bodies which travel through space, and which may also pass through the earth's atmosphere.
When meteors come within our atmosphere, we can see them because they leave a fiery train of light. This is caused by the heat made by the friction, or rubbing, of air upon their surfaces.
Strangely enough, most individual meteor particles are quite small, about the size of a pinhead. Occasional meteors weigh many tons. Most meteors are destroyed entirely by heat as they pass through the earth's atmosphere. Only the larger meteor fragments over reach the earth. Scientists believe that thousands of meteors fall to earth each day and night, but since most of the earth's surface is covered by water, they usually fall into oceans and lakes.
Meteors may appear in the sky singly and travel in practically any direction. But meteors usually occur in swarms of thousands. As the earth travels in its path around the sun, it may come close to such swarms of meteors, they become fiery hot upon contact with the upper layers of the atmosphere, and we see a "meteors shower."
Where do meteors come from? Astronomers now believe that hte periodic swarms of meteors are the broken fragments of comets. When comets break up, the millions of fragments continue to move through space as a meteor swarm or stream. The swarms move in regular orbits, or paths, through space. Once such swarm crosses the earth's path every 33 years.
When a piece of meteor reaches the earth , it is called "a meteorite." It has fallen to the earth because gravity has pulled it down. Far back in Roman times,in 467 B.C, a meteorites fell to the earth and its fall was considered such an important event that it was recorded by Roman historians!

WHAT IS COMET?

WHAT IS COMET?
At one time, the appearance of a comet caused people to tremble with fear. They believed that comets were evil omens foretelling plagues, wars, and death.
Today, we have a pretty good idea of what comets are, though we still don't have all the answers about them. When a comet first appears, it is seen as a tiny point of light, thoughi it may be thousands of miles in diameter.
This point of light is "the head," or nucleus, of the comet. Scientists think it is probably made of a great swarm of bits of solid matter, combined with gases. Where this matter originally came from is what is still a mystery.
As the comet approaches the sun, a tail usually appears behind it. The tail consists of very thin gases and fine particles of matter that are shot off form the comet's nucleus of the comet is a third portion, known as "the coma." It is a glowing cloud of matter that sometimes reaches a diameter of 150,000 miles, or even more.
Comet tails are very different in shape and size. Some are short and stubby. Others are long and slender. They are usually at least 5,000,000 miles in length. Sometimes they are almost 100,000,000 miles long! Some comets have no tails at all.
As the tail grow , the comet gains in speed because it is nearing the sun, moving toward it head first. Then a curious thing happens. When the comet goes away from the sun, it goes tail first with the head following. This is because the pressure of light from the sun drives off the very small particles from the comet's head to form its tail, always in a direction away from the sun.
As a result, when the comet goes away from the sun, its tails must go first. During its journey away from the sun, the comet gradually slows down and then disappears from sight. Comets may remain out of sight for many years, but most of them reappear eventually. Comets make trip after trip around the sun, but they may require a long time to make a single revolution.Halley's Comet, for example, takes about 75 years to make its trip around the sun.
At present, astronomers have listed almost 1,000 comets, but there must be several hundred thousand comets in our solar system which remain unseen!

WHAT IS THE BRIGHTEST STAR?

WHAT IS THE BRIGHTEST STAR?
Have you ever looked up at the sky and tried to find the brightest star? You amay imagine that the number of stars you can see is countless.
But the most that can be seen without a telescope are about 6,000 stars, and one-quarter of them are too far south to be seen in north America.
Ever since the days of the Greek astronomers, 2,000 years ago, the stars have been divided into classes according to their magnitude or brightness. Until the invention of the telescope, only six magnitudes, or degrees of brightness, were recognized. Stars of the first magnitude are the brightest, and stars of the sixth magnitude the faintest. Stars fainter than the sixth magnitude cannot be seen without a telescope. Today, stars can be photographed with modern telescopes down to the 21st magnitude.
A star of any given magnitude is about two and a half times fainter than a star of the magnitude above it. There are 22 stars of the first magnitude, the brightest stars, and the brightest star of all is Sirius, which has a magnitude of -1.6 . This makes Sirius over 1,000 times brightest than the faintest star that can be seen with the naked eye.
The lower we go down in magnitude, the more stars there are in that class. Thus, there are 22 stars of the 1st magnitude and about 1,000,000,000 stars of the 20th magnitude.

WHAT IS THE MILKY WAY ?

WHAT IS THE MILKY WAY ?
There is probably nothing more mysterious and wonderful-looking in the sky than the Milky way, stretching like a band of jewels from one end of the sky to the other. In ancient times when prople gazed at this spectacle,they were filled with the wonder and beauty of it just as you are.But since they didn't really know what it was, they made up all sorts of strange and beautiful explanations of the Milky Way.
For example, in early Christian times, people thought it was a pathway for the angels,so they could go up to heaven on it. Or they imagined it was an opening in the heaven, so that we here on earth could have a glimpse of the glory that existed beyond.
Knowing the facts about the Milky Way, as we do today, doesn't remove any of the wonder of it. The facts are just as any "made-up" idea!
Our galaxy is shaped rougly like a watch, round and flat. If you could get above it and look down on it, it would look like an immense watch. But we are inside the galaxy,and when we look up we are looking towards the edge from inside the "watch." So we see that edge curving around us. And since there are millions of stars in it, we see it as the Milky Way.
Did you know that there are at least 3,000,000,000 stars in the galaxy? And here is an idea of its size. It takes eight minutes for light from the sun to reach the earth. For light from the center of the galaxy to reach the sun,it takes about 27,000 years!
The galaxy rotates about its center like a wheel. From our position in it, it takes about 200,000,000 years just to make one revolution!

WHY DID ASTRONOMERS THINK THERE MIGHT BE ?

WHY DID ASTRONOMERS THINK THERE MIGHT BE LIFE ON MARS?

As you know, scientists are now conducting all kinds of experiments to see if life can be found anywhere else in the universe. Naturally, it is easier to explore our own solar system for signs of life than it is to probe outer space. And one of the places where some scientists thought a form of life might have been found is the planet Mars.

Why did they pick Mars? Well, Mars is considered to be a sort of twin of our own planet earth. It is the next planet beyond the earth in distance from the sun. Mars is about half the diameter of the earth and it rotates around the sun in just under two years. But Mars has a day that is almost equal in length to our dady here on earth.

In observing Mars, astronomers have noticed certain things that indicate a form of life may be possible there. First of all, Mars has seasons like the earth. In fact, as the seasons change on Mars, there seem to be changes on its surface. The dark areas get stronger in the spring and summer, and the colour changes from bluish-green to yellow. Could this be vegetation?

Astronomers also believe that there is at least a small amount of water vapor in the atmosphere of Mars, and this would be helpful in supporting life. Then, too, in 1887 an Italian astronomer, Giovanni Schiaparelli,reported seeing markings on the surface of Mars that resembled canals. "Could these have been built by Martians in order to carry water from the polar regions to the desert areas?" scientists wondered.

In 1976 two American Viking space probes landed on the surface of Mars. The instruments in the space probes searched the surrounding soil for signs of life and radioed their results back to earth. These results showed that either there are germs in the soil or that the soil is very unusual and not like that on earth. If life does exist on Mars it would be a very simple form of life.