Physics 2G

Physics 2G

1. An asteroid is a rock which orbits the Sun

2. The Moon is a natural satellite of Earth

3. Comets are balls of ice and dust

4. Comets have highly elliptical orbits and come from outside of Pluto’s orbit

5. Closest to a star a comet has a stronger gravitational pull, so it speeds up

6. A NEO is a Near Earth Object (asteroid or comet) which may collide with Earth

7. We use telescopes and satellites to monitor NEOs

8. If a NEO is approaching we can launch a rocket containing explosives to break the NEO up

9. Key Processes

   • Asteroids are smaller than planets. They are rocks left over from the formation of the Solar System. Most are found in an ‘asteroid belt’ in orbit around the Sun between Mars and Jupiter
   • The orbits of some asteroids cross the Earth’s orbit. At various times during the Earth’s history, asteroids have hit it. A tremendous amount of energy was released, throwing up billions of tonnes of dust and hot rocks. Together with smoke from widespread fires, this blocked heat and light from the Sun. It changed the Earth’s climate, making it very cold
   • It is thought that an asteroid colliding with the Earth helped to drive the dinosaurs to extinction. Scientists worry that an asteroid could hit again and cause a global catastrophe. The chances of this happening are very small, but the damage caused by a large asteroid would be huge
   • Most asteroids lie in the asteroid belt, between Mars and Jupiter. Jupiter is a very large planet with a very large gravitational field strength. Its gravity stops rocks from coming together to form a planet. Instead, they orbit the Sun as asteroids.
   • Comets are balls of ice and dust in orbit around the Sun. The orbits of comets are different from those of planets - they are elliptical. A comet's orbit takes it very close to the Sun and then far away again
   • The speed of a comet increases as it approaches the Sun. This is because the strength of gravity increases.
   • Comets are often visible from Earth when they get close to the Sun. This is because the Sun’s heat vaporises material from their surface, forming a tail of debris.
   • Asteroid collisions leave craters behind. These are obvious on the Moon, but on the Earth craters are usually eventually weathered away or covered over by natural processes
   • An NEO is a Near Earth Object. Asteroids or comets on a possible collision course with the Earth are NEO
   • NEO's are difficult to observe because they are smaller, and darker, than planets. But scientists are actively observing many NEOs with telescopes. It is possible to calculate the trajectory (path) of an NEO if enough observations are taken over time
   • In order to reduce the threat of NEO's we need to be able to detect the NEO's early. This will prepare us with the knowledge that we need to deal with the threat. To stop a NEO from impacting Earth, deflection must occur. However, in order for this process to happen, we would need years or even decades warning to be able to plan the deflection process