In the most simpliest of terms, Asteroids are rocks of various sizes that orbit the Sun. The majority of asteroids are irregular shaped, Ceres is one that stands out as it circular in nature. They are also referred to as Minor Planets and the I.A.U. site that monitors them is known as I.A.U. Minor Planet Center . Those that come close to Earth are known as Near Earth Objects. Asteroids exist in two main areas around the Sun, the first is the Asteroid Belt between Mars and Jupiter and the second is in the kuiper belt outside the orbit of Neptune. This article is about the belt between Mars and Jupiter. The Kuiper Belt includes the now demoted planet of Pluto to dwarf-planet status. The Asteroid Belt also contains a dwarf planet that is known as Ceres.
The vast majority of the asteroids are between those two planets, however there are some that closer in to the Sun and there are some that are further out. A number of asteroids have had close encounters with the Earth but fortunately, the really big ones haven`t hit for millions of years. An asteroid that does hit the Earths atmosphere is tended to be referred to as a Meteor.
Asteroids and meteoroids were created when the universe was young or as a result of a collision. Some travel through space on a circular journey, others erratically. Those that orbit the Sun between the planets of Mars and Jupiter are commonly referred to as Asteroids. The term Asteroids was coined by Sir William Herschel from the greek asteroeides, aster "star" + -eidos "form, shape". They were discovered after a search was carried out by astronomers who wanted to find out if a theory by Johannes Kepler was correct or not. Kepler predicted that the planets were spaced out according to a pattern of numbers. One of those numbers pointed to a location in space where there was no planet. After searching, the asteroid Ceres was found. One theory is that asteroids are believed to be the remnants of a planet that once existed but was destroyed by the gravititional pull of Jupiter. A second theory has at the beginning of the solar system, debris left over from the creation of the universe bonded together to form planets such as Venus, Mars, Earth and Mercury. However due to Jupiter`s gravitational pull, no planet could form between Jupiter and Mars. Afterwards more asteroids were found whch led astronomers to the conclusion of a asteroid belt containing hundreds of small and large objects. Their paths are erratic, it is believed that one of these asteroids hitting Earth is the cause of the destruction of the dinosaurs.
You`ve also probably seen Farscape episodes such as Bone to be Wild where the crew of Moya hide out in an asteroid field or in the star Wars film Star Wars V - The Empire Strikes Back where the Millenium Falcon hides in an asteroid belt and think asteroids are all close together. The truth is that asteroids are not tightly packed in as they are in the film.
Asteroids fall into three catagories :- 1221 Amor, 1862 Apollo and 2062 Aten. The table below gives a brief description of what they mean.
|Amors||Asteroids which cross Mars orbit but do not quite reach the orbit of Earth. Eros -- target of the NEAR mission -- is a typical Amor.|
|Apollos||Asteroids which cross Earth`s orbit with a period greater than 1 year. Geographos represents the Apollos.|
|Atens||Asteroids which cross Earth`s orbit with a period less than 1 year. Ra-Shalom is a typical Aten.|
The biggest asteroid is Ceres, now classed as a dwarf planet. It is situated between Mars and Jupiter and doesn`t resemble a planet that we would recognise, i.e. a sphere. It is named after the goddess of harvest.
Low, very low, the last asteroid strike that did real damage was the asteroid that killed the Dinosaurs millions of years ago. Our planet is hit constantly by asteroids, they normally burn up on impact. Those that do make it to land are so tiny that damage is minimal. A few people have been killed by an asteroid but I wouldn`t loose sleep over it.
The table below details a number of asteroids whose information is made available from the N.A.S.A. website. Clicking on a link will allow you to see more information and possibly a photo of the asteroid in question. If you want more information on asteroids then visit the NASA site. Some pages when selected will contain a picture of the asteroid, some will contain the path the asteroid takes. If I have not generated a path picture for the asteroid you want, visit the NASA Asteroid Simulater and replace `CERES` with the asteroid you want e.g. Chiron. For some asteroids you will need to enter Number with the Name appended. For the FF asteroid, enter the name 1995FF to get the details.
|Name||Orbital Period||Orbital Eccentricity||Organisation|