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Comets and Asteroids

  • Comets and Asteroids Along with the Sun, the planets and their moons, several other objects made up of small pieces of rock, metal and ice are also a part of the solar system. These objects are asteroids, comets and meteors. Quick Q’s: 1. What are sungrazers? Some comets crash into the Sun or get so close to it that they break up into tiny pieces. Such comets are called sungrazers. 2. Where are asteroids found in the solar system? Most asteroids are found in a region between Mars and Jupiter, which is known as the asteroid belt. 3. Do asteroids have moons? The asteroid Ida has a tiny moon, Dactyl. This was discovered by the spacecraft Galileo in 1993. 4. When will Halley’s Comet be seen again? Halley’s Comet takes about 76 years to complete one orbit around the Sun, so it is expected to be seen again in 2061. 5. Why does a comet have a tail? A comet is made up of ice and other material. As it nears the Sun, these materials heat up. Solar wind and pressure from the Sun’s radiation push them outwards to form a tail that always points away from the Sun. Q Are asteroids planets? A When the solar system was formed, some fragments of rock were left spinning in space. These huge space rocks that orbit the Sun are called asteroids. Like other planets, asteroids are also made of metals like iron and have moons. Some of them are called minor planets. Q Are asteroids dangerous? A An asteroid can be thrown off its orbit by the gravity of larger planets, or if it comes too close to another asteroid. Once it is off its orbit, the stray asteroid often strikes the surface of other planets and moons. This causes widespread destruction and creates huge craters. In fact, some scientists think that an asteroid struck Earth about 65 million years ago, causing the extinction of the dinosaurs. Q Are shooting stars really stars? A Shooting stars are actually pieces of burning rock called meteors. A meteor is formed when a piece of debris in the solar system, called a meteoroid, enters the Earth’s atmosphere. As the meteor rubs against the air in the Earth’s atmosphere, it gets hotter and hotter until it burns up in a streak of light. 22 Asteroid belt Most of the asteroids in our solar system can be found in a belt between the orbits of Mars and Jupiter. A meteor We can see a meteor without a telescope when it enters the Earth’s atmosphere. Sometimes, a number of meteors are seen within a very short period of time. They leave a streak of light, which disappears very quickly. This is called a ‘meteor shower’, also known as ‘meteor storm’

    Do meteors ever fall on Earth? A Sometimes small fragments of a meteor, called meteorites, crash on to the surface of the Earth. Some are so big that they make craters where they fall. Many meteorites have been found on the Earth’s surface. The best known of these is the Barringer Impact Crater in Arizona, USA. This crater was created by an iron meteor that fell on the Earth about 50,000 years ago. The meteor was almost 40 metres (130 feet) in diameter and slammed into the surface at a speed of about 11 kilometres per second (6.8 miles per second), creating a crater that was more than a kilometre wide.

    The great Siberian explosion On 30 July 1908 people living near Lake Baikal in Siberia saw a strange bluish light travel across the sky, followed by a loud explosion and shockwaves that knocked people off their feet. The explosion took place near the Stony Tunguska River and was probably caused by a meteor. It flattened about 80 million trees. The meteor may have broken up about 10 kilometres (6 miles) above the Earth’s surface, so it did not leave a crater.

    Where do comets come from? A Comets originate in two different areas of the solar system. Comets from the Kuiper Belt beyond Neptune are called short-period, since it takes them less time than other comets to go around the Sun. Comets from the Oort Cloud take as long as 30 million years to complete one orbit and are therefore called long-period comets. There are about a trillion comets in the Oort Cloud. The Oort Cloud itself is at the edge of the solar system, almost a quarter of the way from the Sun to the next star, Proxima Centauri.

    The Barringer impact crater in the USA was created by a meteorite impact 50,000 years ago


    Regular visitor Halley’s Comet orbits around the Sun once every 76 years, and is the most famous comet in human history.

    Try these too… The Sun (10–11), The Planets (12–13), Humans in Space (24–25), Earth’s Atmosphere (26–27), Scientific Revolution (150–151), Forces and Motion (190–191)