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| Sunday, 14 November 2004 |
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Junior Observer |  |
| News Business Features Editorial
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Asteroids
Just as there are giant planets in the Sun's family such as Jupiter and Saturn, there are also 'dwarf' planets. These small planets are called asteroids. Asteroids are rocky or metallic objects with round or irregular shapes, most of which orbit the Sun in the asteroid belt between Mars and Jupiter. A few asteroids approach the Sun more closely. None of the asteroids have atmospheres. These asteroids lie in a location in the solar system where there seems to be a space between the planets. There are about 40,000 known asteroids that are over one kilometre in diameter in the asteroid belt. About 3,000 asteroids have been catalogued and there are many more smaller asteroids. Asteroids range in size from tiny pebbles to about 578 miles (930 km) in diameter. Sixteen of the 3,000 known asteroids are over 150 miles (240 km) in diameter. Some asteroids even have orbiting moons. Ceres is the largest of the asteroids. It was the first asteroid ever discovered by the Italian astronomer Giuseppa Pizzi on January 1, 1801. Ceres is about 578 miles in diameter. Asteroids can be pulled out of their solar orbit by the gravitational pull of a planet. They would then orbit that planet instead of orbiting the sun.Astronomers theorise that the two moons of Mars, Phobos and Deimos are captured asteroids. The chances of an asteroid colliding with Earth are very small. But some do come close to earth. The asteroid belt The asteroid belt is a doughnut shaped concentration of asteroids orbiting the sun between the orbits of Mars and Jupiter, closer to the orbit of Mars.Most asteroids orbit from between 186 million to 370 million miles from the sun. The asteroids in the asteroid belt have a slightly elliptical orbit. The time for one revolution around the Sun varies from about three to six Earth years.The strong gravitational force of the planet Jupiter shepherds the asteroid belt, pulling the asteroid away from the Sun, keeping them from careening into the inner planets. ############## China's manned space flights China's second manned space flight will orbit the Earth for five days with two astronauts on board in a mission scheduled for next year. Last year's Shenzhon V orbited the Earth for 21 hours with astronaut Yang Liwei remaining in his seat in the return capsule of the three module craft for the entire mission. The unmanned spacecraft Shenzhou III (Divine III) landed in Mongolia after a week-long mission, in April. |
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