Origin of the word
The invention of the word asteroid was originally attributed to William Herschel, the court astronomer for King George III, in 1802. It is now thought more likely that the word was first coined by the son of a friend of Herschel’s, the Greek scholar Charles Burney. Asteroid in Greek means ‘starlike’.
The largest asteroid known is called Ceres. The diameter of the rock is approximately 930 kilometres; about the size of the state of Texas. Ceres orbits the sun once every 4.6 years.
NASA is to use an asteroid close encounter with the Earth in October this year to test our defences against any future threat from one of these large pieces of rock. An asteroid collision with Earth has happened before, and at some point it will happen again. The research is intended to test the world’s detection and analysis systems should such a threat arise.
The programme scientist and NASA lead in the research, Michael Kelley, stated: ‘This time we are adding in another layer of effort, using this asteroid flyby to test the worldwide asteroid detection and tracking network, assessing our capability to work together in response to finding a potential real asteroid threat.’
a mass of rock that moves around in space. Most asteroids are found between the planets Jupiter and Mars, a region of space known as the asteroid belt.
View the full definition in the Macmillan Dictionary.