8th Class Science Stars and the Solar System Artificial Satellites

        Artificial Satellites

Satellites are the objects orbiting a planet. For example the Moon, which is a natural satellite. Artificial satellites are those which are put into orbit by man. The first artificial satellite was Sputnik 1, launched by the Soviet Union in 1957. At present there are thousands of satellites orbiting the Earth at various heights. Satellites are of different types. The communication satellites is used to relay telephone, messages, radio and television signals. It is such a satellite, which have made it possible for us to see on TV, live cricket and tennis matches being played in any parts of the world. Earlier one had to wait till the recorded version or forthe news in the paper. Some artificial satellites carry instruments, that gather and send back information about the earth and its surroundings. This information is of immense value for weather forecasts, scientists, military planners, farmers and fishermen, just to name a few. Satellites can provide ecologists with detailed images of every square meters of the earth's surface for study.

      Today we can easily access any part of the world on our computer, sitting at our home, through internet. This was not possible in the early part of 19th century. It made possible only after artificial satellites are launched into the space. The first artificial satellite launched into the space by any nation was______.

(a) Sputnik 1

(b) INSAT-A    

(c) INSAT-A1

(d) INSAT-A2

(e) None of these

Answer: (a)

Explanation

The first artificial satellites was launched by USSR in the space. It was Sputnik I.

         Before 1957, communication was a very difficult task. This problem has been solved by launching satellites into the earth's orbits. What is the name of the satellite, which is used for weather forecasting purpose?

(a) Communication satellites

(b) Geostationary satellites

(c) Polar satellites

(d) Geosynchronous satellites

(e) None of these

Answer: (b)

Explanation

The satellites, which is used for weather forecasting is Geostationary satellites.

         Asteroids

The asteroids are the small heavenly bodies that revolve around the Sun, between the orbit of Mars and Jupiter. They are also called small planets and are made up of rocks of various sizes. The biggest asteroids is hundred kilometers in diameter, whereas the smallest ones are only few hundred meters in diameter. There are millions of such small and big asteroids orbiting the Sun. Sometime these asteroids collide with each other, break into small pieces and form meteoroids. The largest asteroid by far is 1 Ceres. Its diameter has been 974 km and has contained about 25% of the mass of all the asteroids combined together. The next largest is 2 Pallas, 10 Hygiea and 4 Vesta, which are between 400 to 550 km in diameter. All the others are less than 340 km.

            Comets

These are the small celestial bodies, which revolves around the Sun. They are made up of gas and dust. As they come near the Sun, a long tail start glowing and becomes visible to us. This tail is visible because of the Sun light falling on it. It spreads millions of km. Thus, comets are collections of gas and dust, which appears as a bright ball of light in the sky with long glowing tail. They are generally smaller than the asteroids and are also considered as the member of the solar system, revolving around the Sun as the planet. They take very long period to revolve around the Sun. For example, the Hally's Comets takes almost 76 years to complete on revolution. It was last seen in 1986 and is expected to be visible in year 2062. The famous Bayeux Tapestry is 1066, depicts the Hally Comets. As of today 878 comets have been discovered and their orbits are roughly calculated. Of these 184 are periodic comets having period less than200 years. Others are also periodic, but their orbits have not been well defined. The comets are also called dirty snowballs or icy mud balls, as they are the mixture of ice and dust.

           Meteors

These are the celestial bodies, formed by the disintegration of comets and asteroids, whose size varies from tiny grains to big boulders of several hundred tons. They revolve around the Sun in their orbits. As they revolve around the Sun, they are considered as the member of the solar system. When these meteoroid enter the earth atmosphere, they become a burning ball of fire and are called the meteors or shooting stars. They are seen as a bright streaks of light in the night, for a moment across the sky. The main difference between the star and the shooting star is that, the stars have their own light, but the shooting stars produce light by burning of its particles. Most of them burn completely on entering the earth atmosphere. Those, who do not burn completely and land on the earth surface, are called meteorites. The meteorites are mainly made up of rocks and metals. Every year, thousands of meteorites fall on the earth surfaces at different places.

         There are millions of celestial bodies in the solar system. The small celestial bodies which revolve between the orbit of Mars and Jupiter are called asteroid. What is the name of the largest asteroid?

(a) Vesta

(b) Pallas

(c) Ceres

(d) Hygiea

(e) None of these

Answer: (c)

Explanation

The name of largest asteroid is Ceres.

       The periods of the comets are not found to be same. They vary between 100 to 1000 years. How many comets are there, whose period are less than 200 years?

(a) 124

(b) 154

(c) 164

(d) 184

(e) None of these

Answer: (d)

Explanation

The number of comets whose period is less than 200 years is 184.

• It is believed that the Sun loses around 4 million tones of weight every second.
• The universe expands from the Earth, since at least 10 billion light years and are still expanding.
• The distance between one edge to the other edge of the milky way is about 100,000 light years.
• If the Sun becomes a black hole, it would be only few Km across, but it might swallow the Earth.
• The planet would explode, if the gravity do not hold the materials together.

• The stars are the celestial bodies, which have the light of their own.
• Stars also have a definite life span.
• The distance of stars is measured in light years.
• Stars appear to move from east to west.
• Constellations are the groups of stars, which form a definite pattern.
• Asteroids, comets and meteors are the small heavenly bodies, which revolve between the orbits of Mars and Jupiter.
• The natural satellites of the earth is moon.
• Venus is the brightest planet.
• Pluto is no more considered to be a planet.
• Artificial satellites are used for telecommunications and weather forecasting purpose.