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Voyage to the world of Le Petit Prince -- What we can learn from asteroids --
Asteroids are 'behind the scene' stars that are 'small but influential'

Many people think that asteroids are like insignificant pebbles existing between the orbits of Mars and Jupiter, and that is true. Although some of these "pebbles" are more than 900 kilometers in diameter, many are actually very small like the home of the Little Prince. It was only relatively recently learned that asteroids exist throughout the solar system. Many small celestial bodies were even found around the orbit of Pluto, the remotest planet, and many asteroids also exist around the Earth. Diagram 1 shows the distribution of asteroids.


The ones close to Pluto's orbit are called the Edgworth Kuiper Belt Objects, which are considered to be the remnants of planetesimals that were created when the solar system was born. The ones near Earth's orbit are called Near Earth Objects (NEO), and they are the focus of our attention in many senses, including the view of a collision with Earth (Spaceguard).


Currently (as of early 2005), there are about 270,000 recognized asteroids, of which less than 100,000 have their orbits accurately measured and identified by designation number. Some 3,100 NEOs have also been identified. Although asteroids are not flashy because they are too small to be seen by the naked eye, they make up the majority of objects in the solar system. In Diagram 2, you can see that the number of identified asteroids has increased every year since the first one, the Ceres, was discovered on Jan. 1, 1801.


There are three aspects of the relationship between asteroids and mankind. Firstly, the study of asteroids is a key aspect of planetary science to help understand the origin of the solar system. The second factor is that asteroids can be the ultimate threat to mankind as they have the potential to cause huge damage to the Earth in a collision, and thirdly, they could be resources should we ever live in space in the future. Hence, asteroids are insignificant objects in space, but very influential for mankind. Like the Japanese proverb says, "A Japanese pepper is small and looks tame but it is actually quite hot".




Diagram 1. The distribution of asteroids in the solar system. Some 50,000 of them are plotted. Computer Graphics by Kota Nishiyama of JSGA.


Diagram 2. The discovery of asteroids between the first identification in 1801 and 2002. Only asteroids which have designation number are displayed here. As of the end of 2002, about 210,000 asteroids had been found, of which about 50,000 are in the diagram. Computer Graphics by Kota Nishiyama of JSGA.

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