Studying Comets, Meteors & Asteroids
Astronomy is a fascinating area of physics for home school science students of all ages to study. Observing the heavens provides practical experiences, which are often free and very interesting. Following up from observations can lead to exciting research projects and discoveries of the origins of the universe itself. For those that become more interested, buying a telescope and visiting a planetarium can add even more to an already fascinating subject.
Meteors & Shooting Stars
Meteors have recently been in the news, with the medium sized rock that burned through the atmosphere in Russia, and the Geminid meteor shower that flashed across the sky in mid December. Meteors and shooting stars are, in fact, the same thing and have nothing to do with stars whatsoever. Meteors are lumps of rock or metal in space that drift into our atmosphere. As the Earth’s gravity pull them in faster and faster, the heat of friction from the air that they are passing through causes them to heat up and glow. This is where the familiar sight of a shooting star comes from. Our atmosphere usually protects us from smaller meteors as they simply burn up before they reach the ground. If the meteor is made of iron or other metals, it is more likely to be very hard and could reach the ground (possibly creating a crater). If the meteor is made of rock (which is usually softer than metal), it is more likely to explode in the atmosphere due to the tremendous heat and pressure exerted on it from the atmosphere.
The origins of meteors
Most meteors come from an area of space known as the asteroid belt. This belt divides the inner planets of Mercury, Venus, Earth and Mars from the outer planets; Jupiter, Saturn, Uranus and Neptune. These are lumps of rock and metal floating in space in a ring. Occasionally, through collisions and the gravity of the nearby planets, some of these rocks can be pulled out of the ring and descend towards the inner planets. If one of these flies too close to the Earth, then our own gravity may be strong enough to pull it towards us giving us a light show.
Comets are somewhat different to meteors. First, comets are usually made up of a mixture that contains water ice, methane, ammonia and space dust, clustered together in what is commonly referred to as a ‘dirty snowball’. They also originate from a different region of space. Comets often come from another belt of rocks and ice close to the orbits of Neptune and Pluto called the Kuiper Belt. Many of the objects in the Kuiper belt are dirty snow balls that sit in relatively stable orbits about the sun, however because Neptune and Pluto also reside within the Kuiper Belt, they can be displaced by the gravitational attractions of these planets.
If a dirty snowball moves from its orbit and begins moving towards the sun, it can gain speed and become a comet. As it moves towards the inner solar system, it gains speed and develops a tail – or even two. The heat from the sun causes the comet to emit a plume of gas and dust. The dust reflects the sunlight making it visible, but the gas is much more exciting. As the gas is whipped off the comet, it is ionized (its electrons are stripped) causing it to glow in the same way that lightning glows.
This week the comet PanSTARRs is passing by. Find out more about upcoming comets and astronomical events at Coach Cowland Science and watch for further posts of activities related to comets and meteors.